ARMACO STANDARD
Upcoming SlideShare
Loading in...5
×

Like this? Share it with your network

Share

ARMACO STANDARD

  • 4,494 views
Uploaded on

Loop Diagram basics

Loop Diagram basics

More in: Business
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads

Views

Total Views
4,494
On Slideshare
4,494
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
336
Comments
0
Likes
2

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Engineering Encyclopedia Saudi Aramco DeskTop Standards Drafting Instrument Loop Diagrams Note: The source of the technical material in this volume is the Professional Engineering Development Program (PEDP) of Engineering Services. Warning: The material contained in this document was developed for Saudi Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Any material contained in this document which is not already in the public domain may not be copied, reproduced, sold, given, or disclosed to third parties, or otherwise used in whole, or in part, without the written permission of the Vice President, Engineering Services, Saudi Aramco.Chapter : Drafting For additional information on this subject, contactFile Reference: AGE10803 N. H. Alahaimer on 874-0876
  • 2. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsCONTENTS PAGES Information Instrument Loop Diagram 1 Ild Symbols And Abbreviations 1 Interpreting Ilds 29 Interpret An Ild For A Pneumatic Instrument Control Loop 37 Interpret An Ild For An Electronic Instrument Control Loop 44 Tracing Current Flow In Control Loops 57 Computer Relays 59 Computer Relay Symbols 59 Instrument Systems 67 Foxboro Spec 200 67 The Honeywell Vutronik Control Loop 83 The Honeywell Vutronik Alarm Card 96 Examples Of Honeywell Cards 100 Honeywell Resistance To Current Converter Card 102 Work Aids 104 Glossary 119Saudi Aramco DeskTop Standards
  • 3. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInstrument Loop DiagramEvery process control loop has an instrument loop diagram (ILD) drawn for it. ILDs givemore information about control loops than any other drawing. Although they are of interestmainly to instrumentation engineers and tech-nicians they are one of the most commondrawings seen in Saudi Aramco.ILD Symbols And AbbreviationsHandout No. 1 (Drawing No. 990-J-36492 Sheets 1 and 2) shows common ILD symbols andabbreviations. Some of them will be described in detail in this module.Orifice Plate. Figure 1 shows the symbol for a flow element orifice plate. Figure 2 shows anorifice plate. H L LINE NUMBER FLOW ELEMENT ORIFICE PLATE MARK NO. BORE CORRECT SIZE NUMBER MUST MATCH BORE SHOWN ON ILD 1.550 ORIFICE PLATE OW FL CORRECT DIRECTION NUMBER ON PLATE MUST FACE UPSTREAM FIGURE I. FLOW ELEMENT, ORIFICE PLATESaudi Aramco DeskTop Standards 1
  • 4. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Orifice Plate(Contd). An orifice plate is placed into a pipeline to cause a pressure differentialbetween its upstream and downstream flow. H and L stand for High and Low. They indicatethe high and low pressure sides of the plate. The difference in pressure is used to indicateflow rate. Pressure differential varies as the square of the flow rate. Therefore, the squareroot of the pressure differential reading is needed in order to obtain the linear value of theflow rate.Process variable measuring devices, such as orifice plates, are sometimes called elements.The mark number, seen in Figure 1, is the identification, or tag, number given to the flowelement. Bore is the size of the hole, in inches, in the orifice plate. The line number is theidentification number of the pipeline.Control Valve. Figure 3 shows the symbol for a control valve. The letter S above the smalltriangle means there is an air supply to open or close the valve. The abbreviation INST meansthat an instrument air signal is supplied to the valve positioner. The positioner is shown bythe square block.The output air signal is shown going to the top of the valve. Therefore, the valve operates byair pushing down onto the diaphragm.The mark number for this valve would be PCV, TCV, LCV, or FCV (for pressure,temperature, level or flow control valve) followed by the loop number.Size rating is the size, in inches, of the valve inlet and outlet bore.A. F. ACTION, sometimes shown only as ACTION, says what the valve will do if there is anAir Failure (AF). The word OPEN or CLOSE will be shown after A.F. ACTION. S OUTPUT INST. LINE NUMBER MARK NO. DIAPHRAGM OPERATED GLOBE SIZE RATING VALVE WITH POSITIONER A. F. ACTION FIGURE 3. CONTROL VALVESaudi Aramco DeskTop Standards 2
  • 5. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Electrical Switches. Figures 4 and 5 show electrical switches. In Figure 4, NO means NormallyOpen. NC means Normally Closed.The letter C on its own means Common. By operating the Hand Switch, C can be connectedeither to NO or to NC.Mark No. is the identification of the switch.In Figure 5, SET AT is the value of the process variable at which the switch will automaticallytrip open or close. The value will be shown in psi, °F, or %, depending on the type of switchused (that is, the type of process variable that is being controlled). The symbol % is oftenused in level control. Level may be given not as a dimension but as a percentage of the vesselcapacity. For example the set point may be 75% to show that the vessel should be kept at75% full. NO OR NC HAND SWITCH C MARK NO. FIGURE 4 LINE OF EQUIPMENT MARK NO. SWITCH ( SINGLE ) MARK NO. SET AT FIGURE 5. LEVEL SWITCH ( SINGLE )Saudi Aramco DeskTop Standards 3
  • 6. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Lamps And Lights. Figure 6 shows the symbols used for lamps and lights. LAMP MARK NO. RED RUNNING LIGHTS GREEN MARK NO. FIGURE 6When a light is not identified by a color, the light will usually be white. The mark numberwill give the number of the instrument loop to which the light is connected.ILD Line Symbols. Figure 7 shows ILD line symbols. Lines may be broken to avoid drawingover equipment or information. The line may then be continued on the other side of theequipment or information. PROCESS LINES INSTRUMENT AIR LINES INSTRUMENT ELECTRIC LINES LINE LINE BREAK CONTINUES INSTRUMENT CAPILLARY TUBES FIGURE 7. ILD LINE SYMBOLSSaudi Aramco DeskTop Standards 4
  • 7. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Air Supply. Figure 8 shows more ILD abbreviations. Those on the left indicate air supply.Those on the right are as stated. D/P DIFFERENTIAL PRESSURE + POSITIVE TERMINAL _ NEGATIVE TERMINAL S AIR SUPPLY AO / AFS AIR OPEN / AIR FAILURE CLOSE A/S AC / AFO AIR CLOSE / AIR FAILURE OPEN H HIGH PRESSURE L LOW PRESSURE EITHER SYMBOL MAY BE USED. GND GROUND FIGURE 8. ILD ABBREVIATIONSElectrical Signal Lines. Figure 9 shows ILD Electrical Signal Lines. RED WHITE WIRE COLORS SHIELDED CABLE BLACK GREY THIS SYMBOL INDICATES A SHIELD FIGURE 9. ILD ELECTRICAL SIGNAL LINESThe wires are color coded to show which wires must be connected to terminal posts.Instrument cables that carry low voltage signals are shielded to prevent outside electricalenergy from interfering with the signals.Saudi Aramco DeskTop Standards 5
  • 8. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Box and Cable numbering. Figure 10 shows box and cable numbering. The Junction Box (JB)or Terminal Box (TB) number is located at the top of the box symbol shown in Figure 10.Connections, called terminal posts, inside the block are numbered. JB OR TB NUMBER TERMINAL NUMBERS SHOWN HERE TERMINAL BOX WITH TERMINALS CONDUIT OR CABLE NUMBER CONDUIT OR CABLE NUMBER SHOWN HERE FIGURE 10. BOX AND CABLE NUMBERINGThe conduit or cable number will be written in the block near the electrical line symbol.Cables are always identified in pairs, or groups of pairs, of wire.Saudi Aramco DeskTop Standards 6
  • 9. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Local Indicators. Figure 11 shows the symbols for Local Indicators. Range means the range ofthe indicator scale.The letters B and E in the Foxboro local indicator symbol give the polarity of the input signal(+ve or -ve). (Foxboro is the name of one of the manufacturers of instruments used by SaudiAramco. Another manufacturer is named Honeywell.) LOCAL INDICATOR MARK NO. RANGE B E + _ FOXBORO LOCAL INDICATOR CONNECTIONS FIGURE 11. LOCAL INDICATORSSaudi Aramco DeskTop Standards 7
  • 10. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Temperature Sensing Elements. Figure 12 shows the symbols for Temperature SensingElements.The Range is usually from zero to the maximum process temperature the ResistanceTemperature Element (RTE) will measure in its loop, for example, 0 to 250°F.Type on the thermocouple symbol identifies the metals in the thermocouple, for example,IRON/CON would mean iron and constantan. EQUIPMENT NUMBER RESISTANCE TEMPERATURE ELEMENT MARK NO. RANGE EQUIPMENT OR LINE NUMBER THERMOCOUPLE TEMPERATURE ELEMENT MARK NO. TYPE FIGURE 12. TEMPERATURE SENSING ELEMENTSTransducer. Figure 13 shows the symbol used for a transducer. The figure shows that thetransducer is changing an electrical input signal to a pneumatic output signal. Other symbolsmay show the transducer changing a pneumatic input to an electrical output. + _ TRANSDUCER MARK NO. FIGURE 13. TRANSDUCERSaudi Aramco DeskTop Standards 8
  • 11. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Transmitters. Figure 14 shows the ILD symbols for Level Transmitters. All foursymbols are very similar and all show the vessel in which the level is being controlled. Notethe symbol for an accumulator, which is shown with the dry leg transmitters. Theaccumulator is used to remove liquid from the dry leg. DRY LEG VESSEL NO. L 1 OUT H N MARK NO. S RANGE SUPPRESSION LEVEL TRANSMITTER WITH AIR SUPPLY ELEVATION CONNECTION ( D / P CELL ) WET LEG 2 H RED VESSEL NO. + L _ GREY MARK NO. RANGE LEVEL TRANSMITTER SUPPRESSION ( D / P CELL ) ELEVATION DRY LEG VESSEL NO. L RED 3 + H _ GREY MARK NO. RANGE SUPPRESSION ELEVATION WET LEG OUT 4 VESSEL NO. H L S MARK NO. RANGE LEVEL TRANSMITTER WITH AIR SUPPLY SUPPRESSION ELEVATION CONNECTION ( D / P CELL ) FIGURE 14. LEVEL TRANSMITTERS WITH D / P CELLSSaudi Aramco DeskTop Standards 9
  • 12. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsAll four transmitter types use differential pressure to measure level. Types 1 and 3 are thesame except that 1 is pneumatic and 3 is electronic. Both use dry legs.Types 2 and 4 are the same except that 2 is electrical and 4 is pneumatic. Both use wet legs.Pressure measurement is sometimes expressed as the height of a column of water. This isbecause a column of water one foot high produces a known pressure of 0.433 psi.Alternatively, a column of water 27.7 inches high produces a pressure of 1.0 psi.We can use this information to convert liquid pressure measurements into liquid levelmeasurements.DP transmitters can be fitted with a biasing spring kit. The spring can be used to adjust orbalance out certain differential pressure readings in order to give us the actual readings werequire. When the bias acts to oppose pressure on the high side, it is called suppression.When it acts to assist pressure on the high side, it is called elevation. An example is shownbelow. 100 WC 15 psig SEAL HIGH LOW LEG SIDE SIDE P1 P2 BIAS 3 psig 0 WC HL P1 P2The pressure of liquid in the seal (or wet) leg is not needed for determining the liquid level inthe tank. Therefore, bias can be applied to balance out this pressure. Because bias in thiscase is assisting pressure on the high side, we have elevation.Saudi Aramco DeskTop Standards 10
  • 13. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Transmitters (Contd). Figure 15 shows how a differential pressure transmitter is used tomeasure level in a vessel open to the atmosphere.Atmospheric pressure acts on the top of the water and also on the low pressure side of the DPcell. Therefore, the difference in pressure between the high and low sides of the cell is equalonly to the pressure exerted by the water level.Example: If the DP cell senses a pressure differential of 10 psi it means that the level of wateris 10 x 27.7 inches. OPEN TANK LEVEL MEASUREMENT AIR PRESSURE LOW PRESSURE HEIGHT WATER SIDE VENTED TO ATMOSPHERE H L FIGURE 15. LEVEL MEASUREMENT USING A DP CELLSaudi Aramco DeskTop Standards 11
  • 14. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Transmitters (Contd). Figure 16 shows how a DP transmitter measures level in a closedvessel. 200 TANK PRESSURE 200 DRY LEG WATER 100 H L DP CELL FIGURE 16. LEVEL MEASUREMENT USING DP CELLIn order to obtain a differential pressure that depends only on the liquid level, the pressure ofthe tank atmosphere must be cancelled out. This is done by connecting the low side of the DPcell to the top of the tank. This connection is called a dry leg.Saudi Aramco DeskTop Standards 12
  • 15. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Transmitters (Contd). Figure 17 shows why wet legs are sometimes used. AIR 200 200 WET LEG WATER 100 H L DP CELL FIGURE 17. LEVEL MEASUREMENT USING DP CELLThe atmosphere in a tank may carry vapor from the liquid. If a dry leg DP cell is being used,some of the vapor will condense in the leg. After a time, liquid at varying levels could collectin the leg. This would cause differential pressure readings that do not represent only theheight of liquid in the vessel.Saudi Aramco DeskTop Standards 13
  • 16. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)To overcome this problem the wet legs are made to a known height, then filled with liquid.Because the liquid level in the leg is constant, the pressure it exerts on the low side of the DPcell is constant. This pressure can be taken into account when reading differential pressure.Figure 17 shows that it is possible for the low side pressure to be greater than the high sidepressure. DP cells are always connected with their high side to the vessel.Temperature Transmitters. Figure 18 shows the symbols for Temperature Transmitters. Rangegives the temperature range of the transmitter, for example 0 to 250°F. EQUIPMENT OR LINE NUMBER RED + _ GREY TEMPERATURE TRANSMITTER. MARK NO. THERMOCOUPLE WITH INTEGRAL RANGE ELECTRONIC mV / mA CONVERTER EQUIPMENT OR LINE NUMBER RED + _ GREY TEMPERATURE TRANSMITTER. RESISTANCE TEMPERATURE DETECTOR MARK NO. WITH RTD / mA CONVERTER RANGE FIGURE 18. TEMPERATURE TRANSMITTERSSaudi Aramco DeskTop Standards 14
  • 17. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Pressure and Flow Transmitters. Figure 19 shows two kinds of transmitters, one for pressure andone for flow. The difference is in the connection to the process. Pressure measurementrequires only one connection. Flow measurement requires two connections; one for the highpressure side of the orifice plate, and one for the low side. EQUIPMENT OR LINE NUMBER RED + _ GREY PRESSURE TRANSMITTER MARK NO. RANGE OUT IN S FLOW TRANSMITTER WITH AIR MARK NO. SUPPLY CONNECTION RANGE FIGURE 19Note that the flow transmitter has two input lines (on the left). This is because the flowtransmitter is using differential pressure.Range will show the calibrated range of each transmitter. Examples would be: • 0 - 100 psi (for pressure transmitter) • 0 - 100" W.C. (inches water column) - [for flow transmitter]Saudi Aramco DeskTop Standards 15
  • 18. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Controller. Figure 20 shows the ILD symbol for a controller. IN OUT CONTROLLER S MARK NO. SET POINT P. BAND RESET DERIVATIVE ACTION FIGURE 20. ILD CONTROLLER SYMBOLThe meaning of the terms shown on the controller are explained below.Mark No. identifies the process variable or loop number which is being controlled.Set Point is the process variable value to which the controller has been set. It is the valueneeded for efficient and safe operation. The set point setting can be altered by the operatorwhen necessary.P Band means proportional band. This is a setting which determines the amount the variablemeasurement must change from the set point for the control valve to move through 100% ofits travel. For example, suppose the total travel of a control valve is 6" (that is from fullyclosed to fully open is a travel of 6"). If a total deviation of the process variable from setpoint is also 6" (that is 3" below set point to 3" above set point) then the P Band is 100%(because a 6" movement of the variable causes a 6" movement of the valve).Note that the controller has a constant pressure air supply. The output of this supply dependson the input being received from the transmitter (which signal depends on the process variablemeasurement).Saudi Aramco DeskTop Standards 16
  • 19. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Control. Figure 21 shows a level control system. The valve is fully closed when thelevel is 3" above its set point. It is fully open when the level is 3" below its set point.Therefore, the level must travel through its full range in order to move the valve through100% of its travel (6"). Therefore, P (Proportional) Band is 100%. 1.5 FEET 1.5 FOOT 200 % 100 % 50 % PB PB PB 6 VALVE 6 FLOAT MOVEMENT MOVEMENT VALVE A SPAN 3 SET POINT 3 ZERO VALVE B FIGURE 21. LEVEL CONTROL SYSTEMSaudi Aramco DeskTop Standards 17
  • 20. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Control (Contd). Figure 22 shows the arrangement for a P Band of 50%. A totaldeviation from the set point of 3" causes a 6" movement of the control valve. The P Band is,therefore, 50%. 2 FEET 1 FOOT 200 % 100 % 50 % PB PB PB 6 VALVE 3 FLOAT MOVEMENT MOVEMENT VALVE A 1.5 SET POINT 1.5 VALVE B FIGURE 22Saudi Aramco DeskTop Standards 18
  • 21. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Control (Contd). Figure 23 shows the arrangement for a P Band of 200%. A total setpoint deviation of 12" causes a 6" movement of the control valve. 1 FOOT 2 FEET 200 % 100 % 50 % PB PB PB 6 VALVE 12 FLOAT MOVEMENT MOVEMENT VALVE A SPAN 6 SET POINT 6 SPAN VALVE B FIGURE 23. PIVOT TO THE LEFTSaudi Aramco DeskTop Standards 19
  • 22. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Control (Contd). Reset may have a time value next to it. Reset is used with proportionalcontrol to return a variable back to its set point. (Reset is also sometimes called Gain.)For example, Figure 24 shows a stable process. The level is at set point and 50 gpm isentering and leaving the tank. WATER IN 50 GPM MAXIMUM LEVEL SET POINT MINIMUM LEVEL WATER OUT 50 GPM FIGURE 24. STABLE PROCESSSaudi Aramco DeskTop Standards 20
  • 23. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Control (Contd). If for some reason the flow leaving the tank increases to 60 gpm thelevel will fall. The float will then cause the control valve to open and input flow will increase.However, the valve cannot adjust until after the level has deviated from set point. Hence, anew stable condition may exist which is not at set point, as shown in Figure 25. Thedifference between the new level and the set point is called offset. WATER IN 60 GPM OFFSET SET POINT WATER OUT 60 GPM FIGURE 25. STABLE BUT OFFSETSaudi Aramco DeskTop Standards 21
  • 24. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Control (Contd). Reset is used to help the proportional control to bring the variable backto set point. It does this by sending an extra signal to the control valve. The signal adjusts thecontrol valve until set point is reached. Then the reset signal stops.The reset mechanism is part of the controller. It has a scale on which different times can beset, for example from 0.1 to 50 minutes. A setting of 0.5 means that the control valve will beadjusted every 0.5 minutes until set point is reached.Derivative also may have a time value next to it. It is usually used only in TemperatureControl Loops. Derivative is sometimes called Rate Action or Integral.Derivative is necessary because proportional plus reset control may take a long time to correcttemperature deviations from set point. Derivative action is concerned with how fast atemperature is changing from set point.If temperature is deviating only slowly from set point, the controller will make only smalladjustments to the control valve. Derivative action senses the speed of the changeimmediately the change begins (unlike reset, which responds after the change has occurredand caused offset).If the rate of change is high, derivative immediately causes a large adjustment to be made tothe control valve to bring the temperature under control.Derivative action stops when the temperature stops changing.The derivation mechanism is also a part of the controller. It uses the same kind of time scaleas the reset unit.Action will have Direct or Reverse next to it. Direct means that if the input signal to aninstrument is increased, the output signal from the instrument will also increase. Reversemeans that if the input signal increases, the output signal decreases.Saudi Aramco DeskTop Standards 22
  • 25. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Indicating Controller. Figure 26 shows the symbols used for an indicating controller. They arethe same as for a basic controller except that a scale range for the variable will be given.Scales may be linear or square root.Linear scales are used for those process variables which change in direct proportion tochanges in instrument output signals, e.g. level, temperature, pressure. Flow measurements,however, are taken from differential pressure readings at an orifice plate. Differentialpressure changes in proportion to the square of the flow rate. Therefore, the square root of thedifferential pressure must be found (or extracted) from a differential pressure signal in orderto find the flow rate. This is why some scales are square root. IN OUT S MARK NO. SET POINT INDICATING P. BAND CONTROLLER RESET DERIVATIVE ACTION SCALE RANGE IN ( IND. CONTROL ) OUT ( MANUAL CONTROL SET UNIT ) MARK NO. S INDICATING CONTROLLER SET POINT WITH MANUAL CONTROL UNIT P. BAND RESET DERIVATIVE ACTION SCALE RANGE FIGURE 26. INDICATING CONTROLLERSSaudi Aramco DeskTop Standards 23
  • 26. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Panel-Mounted Indicator. Figure 27 shows the symbol for a panel-mounted indicator. Rangegives the range for the indicator scale. IN INDICATOR ( 1 TO 3 POINTERS ) MARK NO. RANGE FIGURE 27. PANEL MOUNTED INDICATORStrip Chart Recorder. Figure 28 shows the symbol for a strip chart recorder. Mark numbersand Range are given for each pen.If more than one instrument loop is being recorded, additional input line symbols are addedfor each loop. Notes may be given to explain more about the symbols.GND, L1 and L2 mean Ground, Line 1 and Line 2, respectively. IN GND L1 L2 MARK 1 ST. PEN RANGE 1 ST. PEN RECORDER ( 1 TO 3 PENS ) MARK 2 Dn. PEN RANGE 2 Dn. PEN MARK 3 Dr. PEN RANGE 3 Dr. PEN FIGURE 28Saudi Aramco DeskTop Standards 24
  • 27. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Two-Purpose Instrument Devices. Figure 29 shows the ILD symbols for two components of aloop combined into one.The top output signal goes to a level transmitter or controller. The bottom output signal goesto a final control element, such as a control valve. OUT VESSEL NO. IN LEVEL TRANSMITTER / OUT CONTROLLER S WITH AIR SUPPLY CONNECTION ( DISPLACER ) TRANSMITTER CONTROLLER MARK NO. MARK NO. RANGE SET POINT AND P BAND RESET FIGURE 29. TWO - PURPOSE INTRUMENT DEVICESSaudi Aramco DeskTop Standards 25
  • 28. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Level Transmitter/Controller. Figure 30 shows the symbols used to denote a transmitter or acontroller. In each case, the appropriate information blocks would be filled in and the otherblocks left blank. EQUIPMENT OR LINE NUMBER OUT PRESSURE TRANSMITTER OR CONTROLLER WITH AIR SUPPLY CONNECTION IN S MARK NO. RANGE SET POINT TRANSMITTER P BAND MARK NO. RESET RANGE OR DERIVATIVE ACTION EQUIPMENT OR LINE NUMBER OUT TEMPERATURE TRANSMITTER OR CONTROLLER WITH AIR SUPPLY CONNECTION IN S MARK NO. RANGE SET POINT TRANSMITTER P BAND MARK NO. RESET RANGE OR DERIVATIVE ACTION FIGURE 30. LEVEL TRANSMITTER / CONTROLLERSaudi Aramco DeskTop Standards 26
  • 29. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Three-Way Solenoid Valve. Figure 31 gives the symbol for a three-way solenoid valve. Thissymbol is usually connected to the symbol for the final control element. Most solenoid valvesare not very large. They are commonly used to shut off instrument air supply to controlvalves. SOLENOID OPERATED THREE - WAY VALVE ENERGIZED P-A P A DEENERGIZED A - E E MARK NO. FIGURE 31.Saudi Aramco DeskTop Standards 27
  • 30. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsILD Symbols and Abbreviations(Contd)Three-Way Valve Operation. Figure 32 shows the normal operation of a three-way valve. Whenthe coil is energized, air flows to the control valve actuator without interruption.When the solenoid coil is de-energized (which is what happens when the Emergency ShutDown (ESD) button is pressed) the three-way valve closes. This blocks the flow of air to thecontrol valve. At the same time, the 3-way valve allows the air which is operating the controlvalve to vent to the atmosphere. This causes the control valve to close. AIR TO AIR FROM SUPPLY ACTUATOR SUPPLY ACTUATOR P A P A E E ENERGIZED DEENERGIZED P - PRESSURE A - ACTUATOR E - EXHAUST FIGURE 32Saudi Aramco DeskTop Standards 28
  • 31. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRETING ILDSHandout No. 2 (Drawing 461-J-NA-942815) is a simplified ILD. The Title Block, shown inFigure 33 below, identifies the loop that is on the drawing.It is Flow Control Loop 101 (FC-101). The block says that FC-101 is part of a crude oilpipeline at Berri-3 Plant, Ras Tanura, The Plant Number is 461.The index letter, J, is the standard index letter for Instrument Loop Diagrams.The Reference Drawing Block gives the drawing numbers of P&IDs and InstrumentInstallation Schedules on which FC-101 can be found.Reference is also made to the drawing numbers of Rack Power Distribution (Rack Pwr Dist.)and ILD PC-301.Saudi Aramco DeskTop Standards 29
  • 32. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRETING ILDS (Contd)Handout No. 2 shows that the ILD is divided into four parts: FIELD, FIELD JUNCTIONBOX, CONTROL ROOM PANEL REAR and CONTROL ROOM PANEL FRONT. (Largejunction boxes are sometimes called Marshalling Boxes.)When reading an ILD, it is usual to start at the sensing element. In Handout No. 2, this is anorifice plate, as shown in Figure 34.Note: The Figures given inside the circles are for this module reference only. They do notappear on an actual ILD. 7 4 NA - 942815 461 J 61845 REV. NO. SHT DRAWING NO. PLANT NO. INDEX JOB ORDER NO. FIELD 8 E-9007 6 7 5 4-20 m ADC 4 9 MARK NO. FT - 101 RANGE 0-100WC 2 H L 10 - P - 145 - 1A1 3 MARK NO. FE - 101 1 BORE 6 ILD SENSOR AND TRANSMITTER FIGURE 34Saudi Aramco DeskTop Standards 30
  • 33. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRETING ILDS (Contd) The mark number (which is the same as a tag or identification number) of the At 1 flow element is 101 (that is, FE-101). The BORE of the flow element is 6" (that is, the hole through the orifice plate is 6" diameter). 2 H and L show on which side of the orifice plate high and low pressures are sensed. 3 The pipeline is 10" pipe and the pipeline number is 10"-P-145-1A1. 4 The Mark Number for the Flow Transmitter is 101 (that is, FT-101). The pressure measuring range of the transmitter is 0-100" water column (WC). 5 Auxiliary process lines take high and low pressure to the flow transmitter. 6 This is an electrically operated flow transmitter, as shown by the electric signal lines . 7 The electrical signal lines are shielded all the way from the transmitter to the next loop component. 8 E-3007 is the identification number of the electrical signal line cable. Electronic loops use standard instrument signals of either 4 to 20 mA or 10 to 9 50 mA, direct current. The drawing shows that 4-20 mA DC is being used.Saudi Aramco DeskTop Standards 31
  • 34. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRETING ILDS (Contd)Figure 35 shows the JUNCTION BOX and CONTROL ROOM PANEL REAR instrumentsignal wire line connections.(1) Shows JUNCTION BOX-200 (J.B. 200). The left side cables come from the flow transmitter and enter Terminals 1 and 2. Terminal 3 is used to ground the shielding on the signal line.(2) C-8101 identifies the signal line cable coming from JB 200.(3) J. B. 320 is located behind the control room panel, that is, panel rear.(4) CC-517 identifies the wire cable from JB 320 that goes to Flow Recorder (FR-101) on the Control Room front panel.(5) The wire line symbol shows a connection between Terminals 12 and 13. This is done in order to complete a circuit.Saudi Aramco DeskTop Standards 32
  • 35. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRETING ILDS (Contd)Figure 36 gives information about control panel instruments.Saudi Aramco DeskTop Standards 33
  • 36. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRETING ILDS (Contd)(1) These are the incoming signals from JB 320.(2) This is the ILD symbol for a three-pen recorder.(3) Mark No. 1st Pen is for flow recorder FR-101. 0-10 Ã identifies the part of the strip chart which is recording the flow in loop 101. The square root sign (Ã) shows that a square root scale is being used.(4) The 2nd Pen is recording the pressure in control loop PC-301. The range 0-100 refers to the part of the strip chart that is recording pressure. The note symbol, 2 , refers to the reference drawing in the Legend block.(5) These are incoming signals from JB 320 to flow indicating controller, FIC-101.(6) This is the basic ILD symbol for an indicating controller.(7) These are the outgoing symbols from FIC-101.(8) CC-518 identifies the cable between the FIC-101 and JB 320.Saudi Aramco DeskTop Standards 34
  • 37. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRETING ILDS (Contd)Figure 37 below shows again the wiring terminations In the junction box and rear panels.(Reference should be made to the ILD as a whole.)(1) The outgoing signals from FIC-101 go to the same JB 320 as do the incoming signals to FIC-101. Different terminals in JB 320 are used for the incoming and outgoing signal wires.(2) C-8101 is the same cable that has the incoming signal lines.(3) This is JB 200. It has the signal lines from the flow transmitter, FT-101. It also has the outgoing signals wired to terminals 5 and 6.(4) E-1115 identifies the signal cable wires from JB 200 to the field instruments.Saudi Aramco DeskTop Standards 35
  • 38. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRETING ILDS (Contd)Figure 38 below shows the field-mounted instruments which complete the control loop. MARK NO. FTd - 101 1 3 S 2 4 S 6 10- P - 145 - 1A1 MARK NO. FCV - 101 SIZE RATING 10 GLOBE 5 A. F. ACTION CLOSE FIGURE 38. ILD TRANSDUCER AND CONTROL VALVE(1) These are the signal lines from JB 200.(2) This is the symbol for a transducer. Mark No. identifies it as Ftd-101.(3) The transducer changes the incoming electrical signal to an outgoing pneumatic signal.(4) This is the basic ILD symbol for a control valve.(5) The information block shows that the control valve is Flow Control Valve FCV-101. It is a 10" globe valve. A.F. Action Close means it will close if there is an air failure.(6) This is the pipeline number. It is 10" pipe, line number S-145.Saudi Aramco DeskTop Standards 36
  • 39. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR A PNEUMATIC INSTRUMENT CONTROL LOOPFigure 39 shows a simplified section of a P&ID. Control Loop number 113 is controlling thelevel of tempered water in the surge drum 139-D-211.Saudi Aramco DeskTop Standards 37
  • 40. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR A PNEUMATIC INSTRUMENT CONTROL LOOP(Contd)The level in the drum is sensed by the level transmitter, LT-113. The transmitter sendspneumatic signals to a level indicating controller, LIC-113, and to two level switches LS-113A andLS-113B.In turn, LIC-113 sends pneumatic signals to a level control valve, LCV-113. If the level inthe drum goes low, the signals cause the control valve to open. This allows more make-upwater to flow into the drum. If the level goes high, the signals cause the valve to close. Thisreduces the make-up water flow rate.The level switches are connected to high and low alarms (XA-3-32 and XA-3-33). Theswitches are set to operate if the drum level goes dangerously high or dangerously low. Theyare operated by the pneumatic signals coming from the level transmitter. The 3 refers to therow number on the control panel. The 32 and 33 respectively refer to the column numbers.They give the locations on the control panel where the alarms can be found.Figure 40 shows how the level control loop would look on an ILD.The ILD is shown in sections in Figure 41 through 44Saudi Aramco DeskTop Standards 38
  • 41. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR A PNEUMATIC INSTRUMENT CONTROL LOOP(Contd)Saudi Aramco DeskTop Standards 39
  • 42. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR A PNEUMATIC INSTRUMENT CONTROL LOOP(Contd)Figure 41 is the ILD symbol for the level indicating controller LIC-113. The range is from 0-100. Because it is a level controller, the scale range is a percentage. Levels are usuallyindicated as a percentage of the vessel capacity. 0 to 100, therefore, is the range fromcompletely empty to completely full. Note the triangle and letter S to indicate air supply.Saudi Aramco DeskTop Standards 40
  • 43. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR A PNEUMATIC INSTRUMENT CONTROL LOOP(Contd)Figure 42 is the symbol for a level transmitter. The symbol ÆP/P means that the differential,pressure (ÆP) sensed by the transmitter is sent to the loop controller as a pressure (P). It willbe sent as a pneumatic pressure signal of 3 to 15 psi.The figure shows that the transmitter senses the differential pressure at equipment number139-D-211. This is the surge drum shown on the P & ID.Saudi Aramco DeskTop Standards 41
  • 44. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR A PNEUMATIC INSTRUMENT CONTROL LOOP(Contd)Figure 43 shows the level control valve. 3"-SC-160-IAIA identifies the make-up waterpipeline. This is the line the level control loop uses to control the level in the surge drum.Saudi Aramco DeskTop Standards 42
  • 45. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR A PNEUMATIC INSTRUMENT CONTROL LOOP(Contd)Figure 44 shows the level switches in the control loop. LS-113A is the high level alarmswitch. It is set to open when it receives a 12-psi signal from the level transmitter.LS-113B is the low-level alarm switch. It will open when it receives a 6-psi signal from thelevel transmitter.Figure 40 shows that the switches are connected to alarms XA-3-32 and XA-3-33 on the frontpanel of the control room. The alarms can be seen on windows 3-32 and 3-33Saudi Aramco DeskTop Standards 43
  • 46. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOPHandout No. 3 (Drawing Number J-415-NB-582636) shows an electronic instrument controlloop. Electronic loops are more complicated than pneumatic loops. There are two reasons forthis:• Loop components are both field mounted and located in the control room. Also, the instruments may be great distances away from each other. They must be connected together by electric wires. The wires may pass through one or more junction boxes.• The electric wiring connections between instruments must be done in such a way that complete electric circuits are formed.Saudi Aramco DeskTop Standards 44
  • 47. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)The top of Handout No. 3 shows a pressure control loop, shown again below in Figure 45.The symbol for a control valve can be seen. It has Tag No. PCV-51. It is connected topipeline 4"-5-304-6A1 and has a 20-psig air supply. Fig 45Saudi Aramco DeskTop Standards 45
  • 48. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)Figure 46 shows the symbol for the transducer. You can tell it is a transducer because it hastwo electrical connections, an air supply and a pneumatic output line. The two electric wiresare part of the control loop electric circuit. The current through the transducers varies withchanges in process variable values. Air at a constant pressure of 20 psig is supplied to thetransducer. The output value of the air pressure varies with changes in the transducer current.Hence, electric signals are converted to pneumatic signals.The symbol for a transducer is sometimes drawn as a square, but Foxboro, the companywhich makes the instrument, draw it as a circle.The letters E and B identify the terminal connections inside the transducer junction box. Noteagain that the transducer needs a 20-psig air supply. The symbols shown in Figure 47 are forlocally-mounted air regulators.Saudi Aramco DeskTop Standards 46
  • 49. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)Saudi Aramco DeskTop Standards 47
  • 50. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)Figure 48 shows the symbols for the field-mounted pressure indicator (PI-51) and the field-mounted pressure transmitter (PT-51).The transmitter is shown to be connected to a pipeline identified as 4"-S-305-3A1. Thecircular symbol marked IND shows that the transmitter has an indicator mounted on it.Saudi Aramco DeskTop Standards 48
  • 51. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)Figure 49 shows the field junction box. All the instruments of Loop P-51 are wired into thisbox. The box is identified as ETB3. The number that follows the ETB3 symbol is theterminal number for the wire inside the terminal box.The symbol marked 503 is a shield for the cable coming out of the junction box. It shields thecable from outside electrical interference.Saudi Aramco DeskTop Standards 49
  • 52. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRICAL INSTRUMENT CONTROL LOOP(Contd)Figure 50 shows that the wiring goes from the junction box, through a marshalling box, and toa panel interconnection junction box in the control room.A marshalling box (MB) is simply a big junction box. It is usually located just inside thecontrol room building. It is a collection point for field wiring that comes into the controlroom from many parts of the plant. From the marshalling box, the instrument loop wiring isorganized and routed to various display areas and panels in the control room.The number of marshalling boxes in a plant depends on the size of the plant. Each box isnumbered. Figure 50 shows that on this ILD the marshalling box is MB7. The number thatfollows each MB7 is the terminal number inside the box. There may be hundreds of wires ineach box.Saudi Aramco DeskTop Standards 50
  • 53. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRICAL INSTRUMENT CONTROL LOOP SETFigure 51 shows, at the left, numbered blocks between the marshalling block and the panelinterconnection junction box. These are the individual wire numbers between the boxes.The panel interconnection junction box is located behind the control room panel. It is usuallyclose to the loop controller. A short cable connects the controller to the junction box. Thecable carries a number of wires each insulated from the others. The wires are color coded.Saudi Aramco DeskTop Standards 51
  • 54. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)The panel interconnection junction box symbols are shown in Figure 52.The colors identify wires inside the connecting cable. Each of the lines below the colorsrepresents one wire inside the cable. The letter indicates the connection point on the cableplug. For example, the violet wire in the cable is connected to point F in the cable plug. Youcan also see from the figure that the violet wire is connected to the terminal strip at connectionnumber 5. Figure 53 shows the cable plug.The letters BK at the top of the numbers column identify the terminal strip inside the panelinterconnection junction block. The ILD shows the identification of other terminal strips,such as BH1, EA1 and so on.Saudi Aramco DeskTop Standards 52
  • 55. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)The (+) and (-) signs indicate the polarity of each numbered terminal that is being used.Saudi Aramco DeskTop Standards 53
  • 56. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)Figure 54 shows that there is a 100-ohm resistor connected across terminals 3 and 4 in thejunction box. Resistors are needed whenever an input signal is too high for other instrumentsin the control loop.Saudi Aramco DeskTop Standards 54
  • 57. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)Figure 55 shows the symbol for the pressure controller.The controller needs a 118V 60Hz power supply. FOP No. F3-10 means that the instrumentis located on the Face Of Panel F3, in position 10. On other ILDs the abbreviation BOP(Back of Panel) may sometimes be seen.Saudi Aramco DeskTop Standards 55
  • 58. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR AN ELECTRONIC INSTRUMENT CONTROL LOOP(Contd)Figure 56 shows the recorder and its connections.Saudi Aramco DeskTop Standards 56
  • 59. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsTRACING CURRENT FLOW IN CONTROL LOOPSThe symbol at the bottom right-hand corner of Figure 56 is for a three-pen recorder. Pennumber 2 records pressure values on PR-51. The recorder operates with a 118V, 60Hzsupply.In order to record pressure values, the recorder must be connected to the pressure controlloop. It must receive signals that indicate the pressure values.A study of the ILD, on Handout No. 3, shows that the power to operate the pressuretransmitter, PT-51, is supplied by the pressure controller, PC-51. The controller also operateswith a 118V, 60Hz supply. The ILD shows that a multi-wire cable connects the pressurecontroller output to terminal 1 on terminal strip BK. A wire connects terminal 1 to thepositive side of the pressure transmitter, PT-51. The transmitter acts as a variable resistor. Itsresistance depends on the value of the process variable. Therefore, the current flowingthrough the control loop changes as the transmitter resistance changes. And this change is ameasure of the process variable.From the transmitter, the current flows through the pressure indicator, PI-51. From there itgoes to terminal BK-3. From BK-3 the current flows through a 100- ohm resistor to BK-4. Awire connects BK-4 to BH-6. A wire from the multi-wire cable connects BH-6 to the plug.The ILD shows this connection to be letter H on the plug (a violet colored wire). The currentgoes to operate PR-51.In order for the current to flow, there must be a complete circuit. Therefore, the current thatoperates PR-51 must be returned to its source, PC-51. The ILD shows that this is done byconnecting a wire from the multi-wire cable (a brown wire) to terminal 7 on terminal stripBH. This wire acts as a return wire. It takes the return current from PR-51 to BH-7. A wireconnects BH-7 to terminal 2 on terminal strip BK. A wire from the multi-cable wire isconnected to BK-2. The IDL shows this to be connection U on the plug (a grey color wire).The connection completes the circuit.Saudi Aramco DeskTop Standards 57
  • 60. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsINTERPRET AN ILD FOR A PNEUMATIC INSTRUMENT CONTROL LOOP(Contd)Figure 57 shows the symbol for a panel-mounted alarm. The numbers 1 - 10 identify thelocation of the alarm in the alarm display panel, i.e., Row 1, Column 10.Tracing the wires from the alarm shows that it is connected to the multi-wire cable plug atterminals 6 and 7 on terminal strip EO. Temperature switch TS-54 is connected by the multi-wire cable (connections J and B) to these same terminals. Hence, the current passing throughTS-54 can also pass through alarm XA-1-10. If the supply fails, the switch will trip and setoff the alarm.Saudi Aramco DeskTop Standards 58
  • 61. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsComputer RelaysComputer Relay SymbolsSymbols are used to show Computer Relays on ILDs. Details of other information related tothe relays may also be given. This section of the module covers the symbols and relatedinformation.Manufacturers Symbols. Saudi Aramco uses instrumentation supplied by two manufacturers,Foxboro and Honeywell. Relays supplied by these companies are drawn differently on ILDs.An example is shown in Figure 58. The symbols are for adder/subtractor cards.Saudi Aramco DeskTop Standards 59
  • 62. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsComputer Relays (Contd)Manufacturers Symbols(Contd). Foxboro instruments use the words "adder" or "summer" ontheir cards (from "sum" meaning add).Foxboro summer card output terminals are always the number 2 terminals. Honeywelladder/subtracter card output terminals are always the number 6 terminals.TP (terminal panel) followed by a mark number is used to identify terminals on HoneywellComputer Relays.Handout No. 4 (Drawing No. R84-A-NA-B44995 Sheet 1) is a P&ID for a deethanizersystem. Handout No. 5 (Drawing No. R84-J-NB46327 Sheet 1 A) is the ILD for FlowControl Loop F-010 shown on the P&ID.Saudi Aramco DeskTop Standards 60
  • 63. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsComputer Relays (Contd)Manufacturers Symbols(Contd). The ILD on Handout No. 5 shows that Honeywell relayinstruments are being used.The ILD shows that the following instruments are to be found in the field (that is, out in theplant area). • Flow Transmitter, FT-010 NOTE: On this ILD the mark • Flow Element, FE-010 numbers also include the Plant • Flow Indicator, FI-010 number (R84). • Flow Transducer, FTd-010 • Flow Control Valve, FCV-010It also shows that the following instruments are found on the front of Control Panel CP-R84-101. • Flow Recorder, FR-010 • Flow Totalizer, FQI-010 • Flow Indicating Controller, FIC-010Note that the flow indicator, FI-010, has a (non-linear) square root scale. This is because theindicator is connected in series with the flow transmitter, FT-010, and the transmittersdifferential pressure signals have not yet passed through the square root extractor.The auxiliary rack section shows that there are three Computer Relays being used. These are: • FY-010A - a multiplier/divider card • FY-010B - a square root extractor • FQ-010 - a flow integrator card.Saudi Aramco DeskTop Standards 61
  • 64. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsComputer Relays(Contd)Computer Relay Symbols (Contd). Note that the function of the relays is shown at the top, asshown in Figure 59.The square root sign (Ã) indicates a square root extractor. The multiplication sign (X)indicates a multiplier/divider card which is performing multiplication. (If a division sign ( )were above the relay, the card would be performing a division function.) The integral sign (_)indicates an integrator card.Saudi Aramco DeskTop Standards 62
  • 65. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsComputer Relays (Contd)Computer Relay Symbols(Contd). Figure 60 shows where the other information about the relayswas obtained from the ILD.Saudi Aramco DeskTop Standards 63
  • 66. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsComputer Relays (Contd)Computer Relay Symbols(Contd). A study of the ILD (Figure 60) shows the symbol 2 10-TT-016-12The arrow enters the multiplier card at terminal number 8.10-TT-016 tells us that a temperature transmitter, TT-016, is sending a signal to the multipliercard. The 12 tells us that a wire from terminal 12 on the transmitter is connected to terminal 8on the multiplier.The number 2 in the box refers us to the Reference Drawings given on the right-hand side ofthe ILD. 2 refers to ILD NB-B46327, sheet 35.This kind of information is characteristic of ILDs. They show where an input signal comesfrom and, if necessary, will make reference to another ILD to show the destination of thesignal.Block number 7, just above TPAI-1, shows that the output from terminal 3 goes to 10TY-010B. The reference drawing section refers to ILD NB-B46327 sheet 29. Sheet 29 is shownin Handout No. 6. (Drawing No. R84-J-B46327 Sheet 29.) It shows that a TYPE Ethermocouple is used to sense the temperature in line 16"-P-1002-3A1. It also shows that a3", globe type temperature control valve is fitted into line 3"-SC-1001-3A1C.The symbols shown at the center of the auxiliary rack section of the ILD are for a computersystem. They are shown in Figure 61.Saudi Aramco DeskTop Standards 64
  • 67. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsComputer Relays (Contd)Saudi Aramco DeskTop Standards 65
  • 68. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsComputer Relays (Contd)Computer Relay Symbols(Contd)Note that the symbol MV/I represents the temperature transmitter TT-10. MV/I means it isconverting millivolts to current. Two input signals are shown entering the transmitter. One isfrom TE-010; the other is from TE-015. Block 3 says that TE-015 is found on Sheet 34.17/C cable, in the Rack Section, means 17 conductor cable. It is a cable containing 17conductor wires. The cables are connected to the control instruments.The ILD shows that lines 7 and 10 out of TPA-2-2 can be traced to the computing relays TY-010A and TY-010B respectively.TY-010A is the signal selector. The symbol above the card (<) is the mathematical symbolfor less than. In this case, the symbol means that the card is a low signal selector. If thesymbol was >, which means greater than, the card would be operating as a high signalselector.TY-010B is the adder/subtractor card. The Greek letter, capital sigma (_) above the cardmeans the sum of. It shows that the card is operating as an adder or subtractor, depending onhow the card is set. If a plus sign (+) is over the card, it means that the card is only adding.The Greek capital letter delta (Æ) or a minus sign (-) is used to indicate a subtractor card.Note that the input signal to terminal 5 on the adder/subtractor card comes from TPA1-1-3.This shows again how ILDs are used to trace electric circuits from one drawing to another.Other connections are shown going to sockets and pins for the computer control of thetemperature.Saudi Aramco DeskTop Standards 66
  • 69. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInstrument SystemsSaudi Aramco uses two control systems that are manufactured as complete units. Thesystems are shown on ILDs. One of the systems is the Foxboro Spec 200 and the other is theHoneywell Vutronic.Foxboro Spec 200Spec is an abbreviation for Simplified Package for Electronic Control. The basicarrangement of the Spec 200 is shown in Figure 62. PROCESS TRANSMITTER I P ALARMS 4 - 20 mA 4 - 20 mA 10 - 50 mA INPUT OUTPUT RTD BUFFER AND CONTROL BUFFER AND THERMOCOUPLE 0 - 10V FUNCTION 0 - 10V SIGNAL 10 - 50 mA SIGNAL mV CONVERSION CONVERSION VOLTAGE BASIC ARRANGEMENT OF A SPEC 200 LOOP FIGURE 62Saudi Aramco DeskTop Standards 67
  • 70. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInstrument Systems(Contd)Foxboro Spec 200 (Contd)The system is a closed loop. The block symbol marked I/P (Figure 63) is used to show Spec200 transducers. These transducers convert current energy (I) to pressure energy (P). I P FIGURE 63Input signals such as 4-20 mA, 10-50 mA, millivolts and ohms can be used by the system.These signals are converted to 0 - 10 Volts DC signals by input signal converters. The 0 - 10V signals are used by rack and panel mounted instruments, such as controllers, indicators,recorders and alarms. Using small voltage signals makes the system safe to work on.All Spec 200 instruments are connected in parallel. This allows components to be removedfrom the loop without breaking up the system. It also means that the same voltage is appliedto all components.Output signal converters are used to send 4-20 mA and 10-50 mA signals to field instruments.The Spec 200 system consists of two areas: the display area and the nest area, as shown inFigure 64.The display area contains the recorders and indicators, and provides all the informationneeded by operators.The nest area contains the circuit cards for the control, computing, input and outputconverters, alarm and conditioning units.Nest units are fitted into sections called racks.Saudi Aramco DeskTop Standards 68
  • 71. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInstrument Systems(Contd)Foxboro Spec 200 (Contd)Saudi Aramco DeskTop Standards 69
  • 72. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInstrument Systems(Contd)Foxboro Spec 200 (Contd)Figure 65 shows the operation of the Spec 200. PROCESS TRANSMITTER 5 VOLTS I P ALARMS 0 - 20 mA 5 VOLTS 4 - 20 mA INTPUT OUTPUT BUFFER AND CONTROL BUFFER AND 0 - 10V FUNCTION 0 - 10V SIGNAL 0 - 50 mA SIGNAL CONVERSION CONVERSION 5 VOLTS 5 VOLTS INPUT SIGNAL DISTRIBUTION FIGURE 65Saudi Aramco DeskTop Standards 70
  • 73. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInstrument Systems(Contd)Foxboro Spec 200 (Contd)Suppose the following: A process control loop is for pressure control; the set point is 15 psi;the transmitter has a range of 0-30 psi; the current range for the transmitter is 4-20 milliamps.From the above it follows that a set point of 15 psi is equal to 50% of the transmitters range.This gives a signal of 12 mA (i.e. 50% of 4-20 mA range). As long as the process pressureremains steady at 15 psi, the transmitter sends a 12 mA signal. When the 12 mA signalreaches the input buffer and signal converter relay card in the nest unit, it is changed to avoltage signal.Spec 200 operates on 0-10 V. Since 12 mA is exactly half the transmitter range, the voltagesignal would also be exactly half its range, that is, 5 V. Therefore, the relay card in theconverter sends a 5 V signal to all other components in the control loop. For example, 5 voltswill be sent to the recorder and this will be seen as 15 psi on the recorder graph.The transducer operates on a milliamp range. Therefore, the voltage signal must be convertedback to an amperage signal before it enters the transducer. This is done by the card in theoutput buffer and signal converter in the nest unit.The Spec 200 cards are used for specific functions. Some of these functions are describedbelow.Saudi Aramco DeskTop Standards 71
  • 74. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsFoxboro Spec 200 (Contd)The Function of the 2AI-I2V Current to Voltage Converter Card. The Foxboro current convertercard Model No. 2AI-I2V is a solid state component located in the nest assembly. 2AI-I2Vstands for: 2 - A Spec 200 component A - Analog signals in and out I - Input instrument I - Current signals in 2 - This is an isolated card V - Voltage signals outThe 2AI-I2V card has only one function. It receives 4 to 20 mA signals from a fieldtransmitter and changes them to 0 to 10-volt signals. These are the signals needed by theSpec 200 system. The voltage output is proportional to the current input.The card can operate with two inputs and two outputs for dual operation. This means that thecard can receive and convert 4-20 mA signals from two transmitters.The input (current signals) sides of the card circuit are isolated electrically from the outputsides (voltage signals). The two circuits are not connected by wires, but the input influencesthe output because it passes through a transformer. This induces a proportional voltage in theoutput side of the transformer coils.Isolated cards are used because they give more protection to the cards. For example, a shortcircuit in the transmitter circuit will not damage the card.If the figure 3 were shown in place of the 2, it would mean that the card was not isolated.The Function of the Controller Card 2AX+45. The Foxboro controller card, 2AX+45, haselectronic circuits that receive the input signals and modify them according to the controlsettings. The card sends an electronic output signal to control a final control element, usuallya control valve.Saudi Aramco DeskTop Standards 72
  • 75. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsFoxboro Spec 200 (Contd)The Function of 2AP+ALM-AR Alarm Card. Alarm cards cause alarms to sound in the plantcontrol room if operating conditions become abnormal.The Foxboro 2AP+ALM-AR is a dual alarm card. That means that it can monitor twodifferent variables at the same time. 2AP+ALM-AR stands for: 2 - Spec 200 component A - Analog signals in and out P - Process component module ALM - Alarm AR - Dual absolute alarm - relay outputThe card can be set to send output signals to two different alarm lights. For example, the2AP+ALM-AR alarm card could monitor pressure for a low condition and temperature for ahigh condition. The card can also be set to monitor both high and low conditions for thesame process variable. It could do this using only one input signal.The alarm card is a solid state function card that slides into a module in the nest unit. Thecard has two single alarm circuits with a common power supply. Each alarm has one input,one set point, and one output. Alarm points are calibrated from zero to 100% of scale.The alarm card receives voltage signals from other function cards, such as a square rootextractor, or a resistance-to-voltage temperature card. It has two relays built into it, one foreach alarm circuit. When the alarm is off, the relays on the alarm card are energized. Therelay contacts are normally open (NO) and this gives a no-alarm condition, as shown inFigure 66. TERMINAL NUMBERS -4 LAMP NC OFF COM - + -2 POWER SUPPLY NO +2 TERMINAL NUMBERS RELAY CONTACTS OPEN FIGURE 66Saudi Aramco DeskTop Standards 73
  • 76. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsFoxboro Spec 200 (Contd)The Function of 2AP+ALM-AR Alarm Card (Contd. So long as the process variable that the alarmcard is monitoring stays within its set-point range, the relay will stay energized.Imagine that the alarm circuit is monitoring a pressure control loop. The alarm is set to comeon if the pressure goes too high. At this condition, the voltage signal coming into the alarmcard will be at the value for which the alarm card has been set. This will cause the relay to bedeenergized. When this happens the NC contacts close, as shown in Figure 67, and the alarmlight comes on. TERMINAL NUMBERS -4 NC COM - + -2 POWER SUPPLY LAMP ON NO +2 TERMINAL NUMBERS RELAY CONTACTS CLOSED FIGURE 67Saudi Aramco DeskTop Standards 74
  • 77. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsFoxboro Spec 200 (Contd)The Function of the 2AO-V2I V/I Card The Foxboro voltage to current (V/I) card is a solid statecomponent located in the nest assembly. 2AO-V2I stands for: 2 - Spec 200 component A - Analog signals in and out O - Output instrument V - Voltage signals in 2 - This is an isolated card I - Current signals outThe 2AO-V2I card has only one function. It receives input voltage signals from the controllercard and converts these 0 to 10 volts to a 4 to 20 mA output signal. This output signal is sentto a field mounted transducer. The current output is proportional to the voltage input.The Function of the 2AI-P2VR/V Converter Card. The Foxboro 2AI-P2V resistance to voltageconverter card is a solid state component located in the nest assembly. It produces an outputvoltage signal that is proportional to the temperature of a resistance temperature detector(RTD). 2AI-P2V stands for: 2 - Spec 200 component A - Analog signals in and out I - Input P - Platinum resistance bulb 2 - An isolated card V - Voltage outputThe converter card has two inputs and two outputs for dual operation with a common powersupply.Saudi Aramco DeskTop Standards 75
  • 78. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsFoxboro Spec 200 (Contd)The Function of the 2AI-P2VR/V Converter Card (Contd). A resistance temperature detector(RTD) is used to monitor the temperature of a process. The resistance measured by the RTDis sent into the converter card. The card changes the measured resistance from ohms intovolts. The card is calibrated so that the low end of the temperature range corresponds to zerovolts. The high end of the temperature range is calibrated to correspond to 10 volts.Output signals from the converter card can go to a loop controller, a temperature indicator, atemperature recorder, and to an alarm card.NOTE: Some cards may be identified as 2AI-N2V, where the N stands for nickel. RTDsoperate on the principle that some metals increase their electrical resistance when heated.Other abbreviations often seen on Spec 200 cards are: I/P for input O/P for output DS for Distribution ÆP/I means differential pressure (ÆP) input, current (I) output.Saudi Aramco DeskTop Standards 76
  • 79. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsFoxboro Spec 200 (Contd)Nest Unit Card Symbols. Symbols used on Saudi Aramco ILDs for Nest Unit cards on the Spec200 are as shown in Figure 68. Handout No. 7 (Drawing No. 490-J-674433) Shows an ILDwith Spec 200 control. 28 +2 A: (PY - 101A) +4 +1 A: (PY - 101A) B: PY - 102A B: PY - 102A 29 -2 -4 -1 C: C: 30 D: ANALOG INPUT D: REC. DIST. E: 4 - 5 - 3 E: 4 - 2 - / F: 2AI - 13V F: 2AX + DSI NEST UNIT CARD SYMBOLS FIGURE 68Note the word analog on some of the card symbols. This means that the card is operatingwith numbers that are represented by directly measurable quantities, such as voltage,amperage. That is, the numbers are analogous to physical quantities. Compare this withdigital which means that operation is made with numbers and is represented by numbers.Note also the letters A, B, C, D, E and F. These will be given as a legend on ILDs for Spec200. They identify each function of the card in the rack area. See Figure 69. A, B and C tellus the Tag Numbers of the respective loops. D tells us the function of the card. For examplein Figure 68 one card is an analog input card and the other is a recorder distribution card. Etells us the location of the card. For example, 4-5-3 means that the card is in rack 4, nest 5and is card 3. F tells us how to identify the card in a nest unit. For example, 2AI-13V willbe printed on the card near the bottom. LEGEND A : TAG NO. LOOP A B : TAG NO. LOOP B C : TAG NO. LOOP C D : FUNCTION E : LOCATION REF. F : MODEL NO. FIGURE 69. LEGENDSaudi Aramco DeskTop Standards 77
  • 80. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInterpreting Foxboro Spec 200 ILDs(Contd)Handout No. 8 (Drawing No. 490-J-NB-67483) shows a Spec 200 loop ILD. It is for a levelcontrol loop L-360 at Ras Tanura Refinery.Figure 70 shows part of the ILD.The variable being measured is the level in vessel 4900 - 14. The ILD shows (inside thevessel) the high level alarm (HLA) is 3 feet and the low level alarm (LLA) is 1 foot 8 inches.The level transmitter (LT-360) senses the level in the vessel. The ILD shows that thetransmitter output is a pneumatic signal. The signal will vary between 3 and 15 psi. The levelmeasurement is indicated on a locally mounted indicator, LI-360. The same pneumatic signalthat indicates the level value is sent to a transducer, LTd-360A, Model E11GM. The ILDshows that LTd - 360A converts the pressure signals to Milliamp signals (i.e., 3 - 15 psipneumatic signals are converted to 4 - 20mA signals). FIELD MARSHALLING RACK AREA JUNCTION BOX BOX MTC #2 4" - C - 46 - 3AI FIELD LINE NO. TAG LT - 360 MODEL 2500T-2495 RANGE 60 " P/I ETB #6 490D-14 FISHER RED + 23 368 8 -12+ +1 A : LY - 358 +3 HLA LEVEL GREY TRANSMITTER - 24 369 8 -12- -1 B : LY - 360A -3 0 C: +4 LLA +2 D : ANALOG INPUT -4 3 - 0" -2 E : 8 - B6 0 F : 2AI - 13V 1 - 8" TAG LTd. - 360 A MODEL EIIGM 67 FR CAL.RANGE 3 - 15# DATA LOGGING CONNECTOR 8 S 23 TAG LI - 360 LOCATED NEAR IND. 24 MODEL ASHCROFT 1279A LCV - 360 CAL.RANGE 0 - 1000 LDL - 360 FIGURE 70. INPUT CIRCUITSaudi Aramco DeskTop Standards 78
  • 81. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInterpreting Foxboro Spec 200 ILDs(Contd)Tracing the two output wires from LTd - 360A shows that they are connected to terminals +2and -2 on card 2AI - I3V. This card has two inputs and two outputs. The card model numberindicates that the card is not isolated electrically.The 4-20 mA input at terminals 2 is found as an output at terminals +4 and -4 of the card.Figure 71 shows that one pair of wires goes to a data logging connector (Level Data Logging(LDL-360). This is for a computer connection. The computer receives and records the levelsignal, but it does not control anything in the loop.Another pair of wires goes to terminals +1 and -1 on the alarm card 2AP - ALM - A. Theterminals are jumped to terminals +3 and -3. This gives a single input to both alarm circuits(+3B is LS-360 (H); -3 is LS-360 (L) .)One alarm circuit responds to a high level. The other responds to a low level. As long as theprocess level remains between the high and low set points, no alarm will be given. FIELD MARSHALLING RACK AREA NO. 8 JUNCTION BOX BOX MTC #2 ETB #6 23 368 8 -12+ +1 A : LY - 358 +3 24 369 8 -12- -1 B : LY - 360A -3 0 C: +4 +2 D : ANALOG INPUT -4 -2 E : 8 - B6 0 F : 2AI - 13V DATA LOGGING CONNECTOR 8 23 24 LDL - 360 +1 A : LS - 360 (H) +3 -1 B : LS - 360A ( L ) -3 +2 C : +4 -2 D : ALARM -4 E : 8 - E9 +5 F : 2AP - ALM - A -5 -1 TO FY - 360A 1 NB - 674434 +1 FIGURE 71. 2AI - I3V OUTPUTSaudi Aramco DeskTop Standards 79
  • 82. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInterpreting Foxboro Spec 200 ILDs(Contd)Figure 72 shows the outputs. It can be seen on the symbols that terminal 9 refers to the high(H) alarm, and terminal 10 to the low (L) alarm. +1 A: 9: X A -2 -3 (H) +3 -1 B: 10: X A -2 -4 (L) -3 +2 C: +4 -2 D: ALARM -4 E: 8 - E9 +5 F: 2AP - ALM -A -5 +1 TO FY-360 A NB - 674434 -1 +1 A: 9: X A -2 -3 (H) +7 -1 B: 10: X A -2 -4 (L) -7 +2 C: +8 -2 D: ALARM DIST. -8 +3 E: 8 - F10 +9 -3 F: 2AX + DSI -9 +4 +10 -4 -10 +5 +11 -5 -11 +6 +12 TO ALARM -6 -12 RACK 15 FIGURE 72. ALARM CIRCUITTerminals +2 and -2 are for output 1. The wires from terminal 2 can be traced to the alarmdistribution card 2AX +DSI, terminals +9 and -9. This is the high level signal input.Saudi Aramco DeskTop Standards 80
  • 83. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInterpreting Foxboro Spec 200 ILDs(Contd)Terminals +5 and -5 on 2AP - ALM - A are wired to terminals +10 and -10 on 2AX + DSI.These are the low-level input terminals.If there is a high or low alarm, the distribution card will send a signal to Alarm Rack 15,through a standard 2AK cable. The ILD shows that the annunciator XA - 2 - 3 illuminates fora high-level alarm. Annunciator XA - 2 - 4 lights up for a low-level alarm.Figure 73 shows the 2AP - ALM - A card. It shows that input terminals +3 and -3 have twoadditional pairs of wires connected to it. +1 A : LS - 360 (H) +3 -1 B : LS - 360A ( L ) -3 +2 C: +4 -2 D : ALARM -4 E : 8 - E9 +5 F : 2AP - ALM - A -5 -1 TO FY - 360A NB - 674434 +1 TAG LIC - 360 MODEL 230SM LOCATION P10 - 8 SET PIONT P. BAND RESET ACTION REVERSE +1 A : LY - 360 +3 -1 B : -3 +2 C: +4 -2 D : ANALOG CNTRL. -4 E : 8 - D5 +5 F : 2AC + A4 -5 FIGURE 73. CONTROL INPUT CIRCUITSaudi Aramco DeskTop Standards 81
  • 84. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsInterpreting Foxboro Spec 200 ILDs(Contd)One pair goes to a computing relay FY - 360A which can be seen on drawing NB - 674434.The other pair goes to terminals +1 and -1 on the top of controller card 2AC + A4. It is thesetwo connections that provide the O - 10v signal for the controller.The output signals of the control card are +2 and -2 as shown in Figure 74.The O - 10 volt signal enters the voltage to current connector card 2AO - V2I + P + P atterminals +4 and -4. The 4 - 20mA output signals leave from terminals +2 and -2. Afterpassing through the marshalling and field junction boxes, the mlliamp signals enter thetransducer LTd - 360B. The transducer converts the current signals to 3 - 15 psi pneumaticsignals to operate control valve LCV - 360. +1 A : LC - 360 +3 -1 B : -3 +2 C : +4 -2 D : ANALOG CNTRL. -4 E : 8 - D5 +5 F : 2AC +A4 -5 67 FR ETB#6 RED +1 OUT + 25 370 8 -10+ A : LY - 356C +3 S GREY - 26 371 8 -10- -1 B : LY - 360C -3 0 C: +4 +2 D : ANALOG INPUT -4 -2 E : 8 - CI +5 LINE NO. 4 - C - 33 - 3AI 0 F : 2AO - V3I + P + P -5 S 67 FRS TAG LCV - 360 TAG LTd - 360B MODEL 3" MODEL 69TA - I CAL.RANGE AO / AFC CAL.RANGE 3 - 15 PSI FIGURE 74. OUTPUT CIRCUITSaudi Aramco DeskTop Standards 82
  • 85. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control LoopHoneywell manufacture a process control system called the Vutronik. It can be used tocontrol a complete system in a plant. The system is made up of five categories, as shown inFigure 75. ACCESSORY EQUIPMENT CONTROL FIELD CONTRX AND EQUIPMENT SYSTEM NONCONTROL STATION ELECTRONIC AUXILIARY UNIT FIGURE 75. VUTRONIK SYSTEMSaudi Aramco DeskTop Standards 83
  • 86. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Electronic Auxiliary Units. Electronic auxiliary components are used for performing monitoringand computing functions. The components are printed circuit cards mounted in a single-cardfile. The cards provide such functions as: ° alarm switches ° square root extraction ° millivolt to current conversion (mV/I) ° resistance to current conversion (Ω/Ι)Saudi Aramco uses single-card files (cases) to house auxiliary cards. The cases are mountedbehind the control panel or in a rack. Figure 76 shows a file case.Input signals are transmitted to the card circuit through a flat flexible circuit and card-edgeselector.Note that the case has a 16-point terminal block for connecting signal wiring.The card receives the input signal and then performs the function for which it was set (i.e.square root extraction, mV to I conversion, etc.). The output signals are transmitted backthrough the edge connector and flexible circuit to the terminal block. Wires transmit thesignals to the control instruments in the field and control room.Saudi Aramco DeskTop Standards 84
  • 87. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Contrx System. Contrx is a plug-in system. It connects the Vutronik display panel instrumentsto the field instruments. The connections are made through termination panels similar to theone shown in Figure 77.Saudi Aramco DeskTop Standards 85
  • 88. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Contrx System (Contd). Signals from field instruments pass from the terminals throughmulticonductor cables to the control room instruments, as shown in Figure 78.Saudi Aramco DeskTop Standards 86
  • 89. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Accessory Equipment. The Vutronik system includes accessories such as power supplies,Zenner barriers and standby control modules.The power supplies provide the voltages for operating Vutronik devices. A Zenner barrier isa connection device that keeps loop current below an unsafe limit. It limits current surges andprevents sparking due to short circuits. Standby control modules can be plugged into a loopto allow a Vutronik controller to be removed without upsetting the process.Field Equipment. Field equipment used on the Vutronik system include: ° Flow measurement instruments ° Pressure measurement instruments ° Level measurement instruments ° Transducers ° Valve positioners ° Control valves.Vultronik transmitters use a 4 to 20mA current loop. Other devices in the system use 1 to5vdc. Therefore, the current signal being used by the transmitters must be converted to avoltage signal.Saudi Aramco DeskTop Standards 87
  • 90. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Changing Current Signals to Voltage Signals. Figure 79 shows a Vutronik terminal block (TPA).Terminal number 4 is the signal common (that is, it is the terminal to which all signals return).You saw earlier that there are eight terminal blocks on a Vutronik termination panel (TPA).ALL number 4 terminals on a TPA are connected together internally. This produces a circuitthat carries a common voltage signal through the TPA (that is, through all eight terminals.) TRANSMITTER 250ž 1 2 3 4 5 6 7 8 9 10 11 12 13 14 +25V PV SC +V -V 1 - 5V LL RL #1 AL #2 RSP DC OUT AL COM AL TPA TERMINAL BLOCK FIGURE 79Saudi Aramco DeskTop Standards 88
  • 91. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Changing Current Signals to Voltage Signals (Contd). Terminal number 1 on each terminal blockis connected to a 25v dc supply. The power supply is not shown on ILDs. Terminal number2 is the process variable input to the controller.A jumper lead is connected across terminals 2 and 3. A 250-ohm resistor is connected acrossterminals 3 and 4. The resistor helps to reduce the 25 vdc to a 1 - 5 vdc potential acrossterminal 3 and the signal common. This arrangement is shown in Figure 80. TRANSMITTER 4 - 20 mA 250ž 1 2 3 4 5 6 7 8 9 10 11 12 13 14 _ + 25 vdc FIGURE 80Saudi Aramco DeskTop Standards 89
  • 92. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Changing Current Signals to Voltage Signals (Contd). Figure 81 is a reminder of what is meant bysignal common. It is the common point on a parallel circuit through which current is returnedto its source. CONVENTIONAL DRAWING UNCONVENTIONAL DRAWING OF CIRCUIT OF CIRCUIT R1 R2 R3 R1 R2 R3 SIGNAL COMMON SIGNAL COMMON FIGURE 81Saudi Aramco DeskTop Standards 90
  • 93. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Changing Current Signals to Voltage Signals (Contd). Return connections from controlinstruments to the signal common at terminal 4 are NOT shown on ILDs.Note the following from Figure 79: Current flows: ° from terminal 1 to the transmitter ° from the transmitter to terminal 2 ° from terminal 2 across the jumper lead to terminal 3 ° through the 250 ohm resistor to terminal 4, the signal common.Remember that Vutronik transmitters operate with 4 - 20mA. If a 4-mA current signal isreceived from the transmitter, then Ohms Law says that the voltage drop across the 250-ohmresistor is 1 volt, since V = IR = 0.004 x 250 = 1 V.If a 20-mA current signal is received from the transmitter, then from 0.020 x 250, there is a 5-v drop across the 250-ohm resistor.4 - 20 mA is the range of current flow through the transmitter. This is proportional to a 1-5 vsignal at the signal common.Figure 82 shows a Vutronik system for level control loop 3010. The system is operating alevel recorder, a level indicating controller and an alarm.Note the symbol [-||-] that is used to denote a switch card.As an example, we will trace the signal that operates the level recorder, LR - 3010.A 25 - vdc power supply producing 4 - 20 mA is connected to terminal 1 on TPAI-2. Thissupply is not shown on the ILDs. (Remember that other connections, such as the internalconnections between all terminal 4 and the return connections from instruments to terminals 4are also not shown on ILDs.)A wire connects terminal 1 on TPAI-2 to the positive side of the transmitter, LT-3010. Theconnection is made through CA-41 and FA-1 on the BACK AUXILIARY RACK, RK-D28-3001-1. From FA-1 the wire goes to TB-E-3007 in the junction box, terminal 1. The wire isshielded and is earthed at terminal 3.Saudi Aramco DeskTop Standards 91
  • 94. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsTracing SignalsSaudi Aramco DeskTop Standards 92
  • 95. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Tracing Signals (Contd). From TB-E-3007 the current goes to the positive side of thetransmitter. The transmitter acts like a variable resistor: the resistance depends on the processvariable measurement it is receiving. Therefore, the current that passes through thetransmitter depends on the process variable measurement.The current flows from the negative terminal of the transmitter, through TB-E-3007 terminal2, FA terminal 2, CA terminal 42 and to TPAI-3 terminal 2.Terminal 2 on TPAI-3 is wired to terminal 2 on TPAI-2. This terminal is jumped to terminal3. Terminal 3 is connected by a 250-ohm resistor to terminal 4. The voltage drop across theresistor will be between 1 and 5 volts, depending on the value of the current which theprocess variable has allowed to flow through the system. But, remember, terminals number 4are connected together, internally, even though this is not shown on the ILD. Therefore, thevoltage across terminals 2 and 4 in TPAI-2 and TPAI-3 is 1-5 v, as shown in Figure 83. 4 - 20 m A FROM TRANSMITTER TPA1- 3 1 2 3 4 5 _ + VOLTMETER WILL V INDICATE 1 TO 5 vdc INTERNAL 250ž CONNECTION TPA1- 2 1 2 3 4 5 + 25 vdc TO TRANSMITTER FIGURE 83. ILD DETAILSaudi Aramco DeskTop Standards 93
  • 96. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsTracing Signals (Contd)Suppose a connection is made between terminal 2 on TPAI-3 and the input of the recorder,and then from the output of the recorder to terminal 4 on TPAI-3. The voltage across therecorder terminals will be between 1 and 5 vdc, proportional to the value of the processvariable. Hence the voltage operating the recorder will be in accordance with the value of theprocess variable.The connections between the terminal blocks and the instruments are made by wires orcables. These connections are not shown on ILDs. The same wires or cables connect theinstruments to terminal 4, the signal common, in order to complete the circuit.The ILD shows that the output signals from the level indicating controller come fromterminals 5 and 6 on TPAI-2. These are the standard terminals used on Honeywell TPAs foroutput signals. (Remember that the output signals of a controller are proportional to the inputsignals it receives from the transmitter. In this case the input signals will be between 1 - 5 Vdc and the output signals will be between 4 - 20 mA DC.)The wire from terminal 5 goes to transducer LTd-3010. The current signal is converted to apneumatic signal to open or close control valve LCV-3010. The negative terminal of thetransducer is connected to terminal 6 of TAPAI-2. This terminal is connected to the negativeterminal of the controller and so completes the circuit.The schematic in Figure 84 shows the circuits we have been discussing.Saudi Aramco DeskTop Standards 94
  • 97. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Control Loop(Contd)Tracing Signals (Contd) LT - 30 10 4 - 20 mA + SIGNAL COMMON - LR - 3010 + 25 vdc 1 - 5vdc POWER SUPPLY 250ž LIC - 3010 SC + - LTd - 3010 4 - 20 mA + - LS-3010-1/ 2 LCV - 3010 FIGURE 84Saudi Aramco DeskTop Standards 95
  • 98. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Alarm CardThe Honeywell alarm card monitors a process variable and trips an alarm if the variable goesbeyond preset limits. The alarm card may trip a circuit to start or stop a pump, open or close avalve, or trip a plants ESD system.The Honeywell dual alarm card has two input circuits. Each input circuit needs a 1 to 5 vdcinput signal.Figure 85 shows a simple illustration of how the alarm card operates as part of an alarmcircuit. ALARM OUTPUT 1A ALARM CIRCUIT 1A INPUT 1 1 - 5 vdc ALARM OUTPUT 1B CIRCUIT 1B ALARM ALARM OUTPUT 2A CIRCUIT 2A ALARM INPUT 2 1 - 5 vdc ALARM OUTPUT 2B CIRCUIT 2B ALARM FIGURE 85. DUAL ALARM CIRCUITSaudi Aramco DeskTop Standards 96
  • 99. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Alarm Card(Contd)Each input has two outputs. Each output is a set of relay contacts. They act as the switch partof the alarm card. Figure 86 shows how a relay operates.A relay is an electrically-operated switch. Figure 86 shows a relay that is normally open. Aspring keeps the relay contacts apart. When current flows through the coil the soft iron corebecomes a magnet. The magnetic force pulls the armature down and the contacts close.When the current stops flowing through the coil, the spring pulls the contacts apart. Nowreturn again to the dual alarm system (Figure 85.) When the input voltage signal goes beyonda preset limit, the relays will operate. They will activate an alarm in the control room.Saudi Aramco DeskTop Standards 97
  • 100. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Alarm Card(Contd)Figure 85 showed that the card provides two separate alarms for each input signal. Thus, forexample, both a high and low alarm can be set for the input from a level transmitter.Handout No. 9 (Drawing No. U54-J-XB-B19079) shows an ILD for level control loop L-020.The alarm card is located on the auxiliary rack RX-454-1. The card is a level switch LS-020A and B.The card receives two 1 to 5 vdc signals from terminals 2 and 7 on TPAI-7. They areconnected to terminals 3 and 5 on the alarm card. The mark number of input 1 is LS-020A.Its alarm settings are 2.1 volts high/1.0 volt low. These are alarms 1A and 1B respectively.Input 2 has a mark number of L-020B. It uses only one alarm setting, which is 3.0 v high.This is alarm 2A.Tracing the connections from the alarms back to the switch card shows that the alarm outputterminals for these three alarms are: Output for Alarm 1A - Terminals 2 and 6 Output for Alarm 1B - Terminals 7 and 8 Output for Alarm 2A - Terminals 10 and 11These connections are made through terminal strips TBC and TBA. Alarm 1A operates XA-1-37 Alarm 1B operates XA-1-43 Alarm 2A operates XA-1-30Saudi Aramco DeskTop Standards 98
  • 101. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsThe Honeywell Vutronik Alarm Card(Contd)Note that alarm circuits 1B is not a complete circuit on the ILD. This is because alarm 1B isalso connected to TBA-78, which is seen to be shown on drawing number XB-B-19078 sheetB. (A study of this drawing shows that alarm 1B is part of the ESD system.)The ILDs will not always show the inputs and outputs on an alarm card. When they are notshown, you must refer to the vendor manual. This gives the inputs and outputs of all thealarms.Note the bracket around terminals 14, 15 and 16. This means that the terminals act as a singleunit case only.A study of the ILD for loop 020 shows that when the level transmitter LT-020 senses a lowlevel in U54-D-052 the light in window panel 1-43 on the control room panel will come on.When the level is high the light in window 1-37 will come on. (Note that terminals 82 and 83on TBA are jumped together to form a complete circuit.)SummaryAlarm cards can be used to monitor any process variable. The mA output from anytransmitter is converted to 1 to 5 vdc and used to operate the cards. The cards can monitortwo different variables at the same time. Both input signals are independent of each other.Each set of output contacts on the card can be set at high or low alarms.Saudi Aramco DeskTop Standards 99
  • 102. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsExamples of Honeywell CardsHoneywell mV/I Converter Card. The Honeywell mV/I converter card is mounted in asingle card file. The card has two separate converter circuits. It can be used in two differentloops at the same time. Each output is 4-20 mA.Figure 87 shows an ILD for a temperature control loop.A thermocouple (Type J) measures temperature in the field. The thermocouple developsmillivolt signals, the values of which depend on the temperature measurement. Wires carrythe mV input signal to input number 1 on the mV/I converter card, TY-304. Note that theinput terminals are on the card, not on the card file terminal strip. The ILD shows that theconverter is in the auxiliary rack in the control room.The card converts the mV signal to a 4-20 mA signal. The output of TY-304 is shown to beat terminal 12. The 250-ohm resistor on TB 1 converts the mA output signal to 1-5 vdc.Remember that the power supply and some connections are not shown on ILDs. Theseinclude the internal connections that link all terminals number 4 together, and the wire orcable connections that take the 1-5 vdc signal to the control instruments.The 1-5 vdc signal goes to TR-304 (Recorder). The same voltage also exists across terminals3 and 4 on TB 2. From these the voltage is sent to TI-304 (Indicator).Saudi Aramco DeskTop Standards 100
  • 103. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsHoneywell mV/I Converter Card (Contd)Saudi Aramco DeskTop Standards 101
  • 104. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsHoneywell Resistance to Current Converter CardFigure 88 shows a temperature control loop in which a Resistance Temperature Detector(RTD) is used to measure temperature. The RTD is a variable resistor. Its resistance changesaccording to changes in temperature.TY-305 converts the resistance signal to a 4-20 mA signal. The 250 ohm resistor on TB 7causes a voltage drop of 1-5 vdc. This voltage is used by TR-305 and TI-305.Saudi Aramco DeskTop Standards 102
  • 105. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsHoneywell Resistance to Current Converter Card (Contd)Figure 89 show an ILD using square root extractor card, SQ-301. The operation of the circuitis similar to those already discussed.Saudi Aramco DeskTop Standards 103
  • 106. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDSILDs use standard symbols to depict various control instruments. These symbols, taken fromSaudi Aramco Standard Drawing numbers 990-J-AD-036491, 990-J-AB-36492 and 990-J-AB-36493 are shown below:Saudi Aramco DeskTop Standards 104
  • 107. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) 01500H H L LINE NUMBER FLOW ELEMENT : MARK NO. ANNUBAR TYPE 01500E PD / T LINE NUMBER FLOW INSTRUMENT: PD : POSITIVE DISPLACEMENT MARK NO. METER. SIZE T : TURBINE METER 01500D PD OR T OUT TRANSMITTER WITH INTEGAL ORIFICE S LINE NUMBER S 01500C INSTR. LINE NUMBER MARK NO. PISTON OPERATED BALL VALVE POSITIONER, SWITCHING VALVES SIZE/RATING AND VOLUME TANK. A.F. ACTION HOOK UP DWG. AB 036560 2Saudi Aramco DeskTop Standards 105
  • 108. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) 001500 OUTPUT S INSTR. LINE NUMBER DIAPHRAGM OPERATED MARK NO. GLOBE VALVE WITH SIZE /RATING POSITIONER A.F. ACTION MOTOR 01500A JUNCTION BOX DIAPHRAGM - OPERATED GLOBE VALVE WITH POSITIONER MARK NO. M CONT. PSTN VALVE PSTN LINE NUMBER MARK NO. SIZE/RATING TYPE NC OR NO C MARK NO. NC OR NO CONT. POS VALVE POS MARK NO. CONT. POS VALVE POS SAFETY SHUT OFF VALVE WITH TWO CYLINDERS AND TWO LIMIT SWITCHES LINE NUMBER MARK NO. SIZE 3Saudi Aramco DeskTop Standards 106
  • 109. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) MARK NO. CONT. POS VALVE POS C NO OR NC SAFETY SHUT OFF VALVE WITH ONE CYLINDERS AND C TWO LIMIT SWITCHES NO OR NC LINE NUMBER MARK NO. CONT. POS VALVE POS MARK NO. SIZE 5 1 4 HAND OPERATED SPRING 3 2 RETURN 4 WAY PILOT VALVE MARK NO. 5 1 4 DIAPHRAGM OPERATED 4 WAY PILOT VALVE 3 2 MARK NO. LINE OR EQUIPMENT MARK NO. C NO OR NC SWITCH ( SINGLE ) MARK NO. SET AT 4Saudi Aramco DeskTop Standards 107
  • 110. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) LINE OR EQUIPMENT MARK NO. C C NO OR NC SWITCH ( DUAL ) NO OR NC MARK NO. SW1 SET AT SW2 SET AT JB OR TB NUMBER TERMINAL BOX WITH TERMINALS RB NUMBER RELAY BOX OR SHUTDOWN SYSTEM CONDUIT OR CABLE NUMBER CHECK VALVE PNEUMATIC TERMINAL 5Saudi Aramco DeskTop Standards 108
  • 111. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd)Saudi Aramco DeskTop Standards 109
  • 112. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) COAX PROXIMITY VIBRATION PICK - UP ELEMENT EQUIPMENT MARK NO. SHIELD MARK NO. RANGE BLACK A RED B GREEN SEISMIC VIBRATION C WHITE PICK - UP ELEMENT D EQUIPMENT SHIELD MARK NO. MARK NO. RANGE MTG. POS. MOTOR J. B. MOTOR OPERATED VALVE M LINE NUMBER MARK NO. SIZE 7Saudi Aramco DeskTop Standards 110
  • 113. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) 1 2 3 7 4 SPEED TRANSMITTER 8 5 WITH INTEGRAL SPEED INDICATOR 9 6 10 MARK NO. RANGE INSTRUMENT PROCESS LINES INSTRUMENT AIR LINES INSTRUMENT ELECTRIC LINES INSTRUMENT CAPILLARY TUBES SPARE IN RECORDER ( 1 TO 3 PENS ) GND. L1 L2 MARK 1st PEN RANGE 1st PEN MARK 2nd PEN DWG. NO. RANGE 2nd PEN MARK 3rd PEN RANGE 3rd PEN 8Saudi Aramco DeskTop Standards 111
  • 114. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) IN CONTROLLER OUT S MARK NO. SET POINT P. BAND RESET DERIVATIVE ACTION INDICATOR ( 1 TO 3 POINTERS IN MARK NO. RANGE IN INDICATING CONTROLLER OUT S MARK NO. SET POINT P. BAND RESET DERIVATIVE ACTION SCALERANGE 9Saudi Aramco DeskTop Standards 112
  • 115. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) IN INDICATING CONTROLLER ( IND. CONTROL ) WITH MANUAL CONTROL UNIT OUT ( MANUAL SET CONTROL UNIT ) MARK NO. S SET POINT P. BAND RESET DERIVATIVE ACTION SCALE RANGE COLOR CODE 1 TERMINAL STRIP WITH 2 CORD SET 3 4 THE TERMINAL STRIP COLOR CODE AND CORD SET SHALL 100 ž 5 TYPICAL BE IN ACCORDANCE WITH 6 VENDOR DRAWINGS. 7 8 9 10 9 CORES TIED BACK INDICATING CONTROLLER IN OUT S MARK NO. SET POINT P. BAND RESET DERIVATIVE ACTION SCALERANGE 10Saudi Aramco DeskTop Standards 113
  • 116. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) CONTROLLER DWG. NO. MARK NO. SET POINT P. BAND RESET DERIVATIVE ACTION INDICATOR ( 1 TO 3 POINTERS ) DWG. NO. MARK NO. RANGE ALARM UNIT DWG. NO. MARK NO. SET POINT EMF / RTD TO CURRENT CONVERTER DWG. NO. MARK NO. RANGE IN RANGE OUT 11Saudi Aramco DeskTop Standards 114
  • 117. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) 10 11 9 12 VIBRATION MONITOR 8 13 SEISMIC TYPE OR PROXIMITY TYPE 7 14 6 15 5 16 4 17 GRND. 3 18 L2 2 19 DWG. NO. L1 1 20 MARK NO. PRE ALARM S. D. SET AT SCALE RANGE MULTIPOINT TEMPERATURE RECORDER MARK NO. RANGE SCALE L1 DWG. NO. L2 GRND. MULTIPOINT TEMPERATURE INDICATOR MARK NO. RANGE SCALE L1 DWG. NO. L2 GRND. 12Saudi Aramco DeskTop Standards 115
  • 118. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) MARK NO. TEMPERATURE MONITOR SCALE RANGE MASTER MODULE NO NC H MARK NO. TEMPERATURE SWITCH SET AT ANNUNCIATOR ALARM ACTION SINGLE SET POINT NO NC MODULE H HI. SET AT TEMPERATURE SWITCH HI. HI. SET AT ANNUNCIATOR ALARM ACTION DUAL SET POINT MODULE NO NC FOR FRONT OF PANEL H MOUNTING. MARK NO. TEMPERATURE SWITCH ANNUNCIATOR ALARM DUAL SET POINT FOR NO HI. SET AT REMOTE RACK NC ACTION C MOUNTING. NO NC C NO HI. SET AT NC ACTION C NO NC C 13Saudi Aramco DeskTop Standards 116
  • 119. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) COMMON ANNUNCIATOR WINDOW TERMINAL ONE COMMON TERMINAL FOR ALL ANNUNCIATOR LIGHTS MARK NO. WINDOW ANNUNCIATOR WINDOW TERMINAL MARK NO. WINDOW PUSH BUTTONS MARK NO. MARK NO. SPEED INDICATOR MARK NO. RANGE HAND SWITCH NO OR NC C MARK NO. 14Saudi Aramco DeskTop Standards 117
  • 120. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsWORK AIDS (Contd) LAMP MARK NO. RED RUNNING LIGHTS GREEN MARK NO. DIODE 1 TELEPHONE JACK 2 MARK NO. 15Saudi Aramco DeskTop Standards 118
  • 121. Engineering Encyclopedia Drafting Drafting Instrument Loop DiagramsGLOSSARYDerivative The name given to the control procedure that is concerned with(or Rate Action): how quickly a process variable (usually temperature) is changing its value.Offset: The difference between the actual value of a process variable and its set point value.Proportional band: The ration, as a percentage, of the deviation of a process variable from set point divided by the amount of control valve stem movement the deviation causes.Reset (or gain): The name given to the control procedure which is designed to bring a process variable back to its set point.Saudi Aramco DeskTop Standards 119