Control valve presentation-CONTROL VALVE AN OVERVIEW

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Control valve presentation-CONTROL VALVE AN OVERVIEW

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Control valve presentation-CONTROL VALVE AN OVERVIEW

  1. 1. NIDHIN MANOHAR The Boss of Control Loop, Final Control Element 1
  2. 2. CONTROL VALVE AN OVERVIEW 2
  3. 3. TODAY’S DISCUSSION CONTENT • WHAT IS A CONTROL VALVE ? • CONTROL VALVE ACTUATOR & ACCESSORIES •STANDARDS APPLICABLE FOR CONTROL VALVE •FLASHING •CAVITATION •CONTROL VALVE SELECTION & INTERCHANGEABILITY •VALVE GLAND PACKING & MATERIAL OF CONSTRUCTION •CONTROL VALVE LEAKAGE CLASS • CONTROL VALVE CHARACTERISTICS • ARDUOUS SERVICE VALVE • NOISE REDUCTIONS PRACTICES 3
  4. 4. WHAT IS A CONTROL VALVE ? CONTROL VALVE This is a device used to modulate flow of process fluid in line by creating a variable pressure drop in the line . Normally the pressure drop is made with respect to the control signal received towards flow condition correction required. 4
  5. 5. WHAT IS VALVE FLOW COEFFICIENT ? VALVE Cv - No. Of US gallon [ USG = 3.7 Ltrs] of water per minute passing through the valve in full open condition with 1 PSI pressure Drop across the valve at 15 deg C temp. So essentially valve Cv is capacity of valve in terms of water which helps us to identify suitable size required for any fluid in any pressure / temp. condition. VALVE Kv - Quantity of water in M3/Hr. at temperature between 5 to 40C that will flow through the valve at a specified travel with a pressure drop of 1 Bar. Kv = 0.856Cv 5
  6. 6. TYPE OF CONTROL VALVE All Control valve can be divided in two category. 1. Sliding stem ( Globe valve) 2. Rotary shaft ( Quarter turn ) Also valves may be further subdivided as shown below BY SHAPE BY INTERNAL BY CHAR. BY GUIDING GLOBE PLUG EQ% TOP BUTTERFLY CAGE LINEAR CAGE ANGLE FULL BALL QUICK OPEN TOP & BOTTOM SLANT SLEEVED PARABOLIC Y TYPE V BALL SINGLE SEAT DOUBLE SEAT 6 BUSH/BEARING
  7. 7. VALVE ACTUATOR Actuator - Mechanism which operates the valve by receiving the control signal. Type of Actuator Pneumatic - Spring Diaphragm Piston Cylinder Electrical - Not discussed Hydraulic- Not discussed 7
  8. 8. VALVE ACTUATOR 8
  9. 9. VALVE ACTUATOR 9
  10. 10. VALVE ACCESSORIES VALVE POSITIONERS PNEUMATIC ELECTRONEUMATIC SMART DIGITAL PROXIMITY SWITCHES INDUCTIVE TYPE PNEUMATIC CAM OPERATED SOLENOID VALVES LATCHING/ NON-LATCHING WITH MANUAL OVERRIDE SIGNAL BOOSTERS PRESSURE VOLUME SIGNAL INVERTERS HANDWHEEL AIR VOLUME TANK 10
  11. 11. CONTROL VALVE STANDARDS ANSI :- AMERICAN NATIONAL STANDARDS INSTITUTE B16.34 :- STEEL VALVES • DEFINES CRITERIA FOR VALVE WALL THICKNESS REQUIREMENTS • DEFINES PRESSURE / TEMPERATURE RATINGS • DEFINE HYDRO-TEST REQUIREMENTS Example :A351 CF8M ( Material :- 316SST; Temp range :- -425 °F to 1500 °F) A216 WCB ( Material :- Carbon Steel; Temp range:- -20 °F to 1000 °F ) B16.37 :- HYDROSTATIC TEST PROCEDURE • DEFINES REQUIREMENT FOR HYDRO-TEST = 1.5 X MWP MWP = MAXIMUM WORKING PRESSURE B16.104 :- CONTROL VALVE SEAT LEAKAGE CLASSIFICATION • ESTABLISHES TEST PROCEDURES AND SEAT LEAKAGE CLASSES API :- AMERICAN PETROLEUM INSTITUTE SPEC 6B :- DEFINES PIPELINE VALVE SPEC 600 :- STEEL GAGE VALVES, FLANGED BUTT WELDING ENDS 11
  12. 12. CONTROL VALVE STANDARDS NACE :- NATIONAL ASSOCIATION OF CORROSION ENGINEERS NACE MR-01-75 • DEFINES SULFIDE STRESS CRACKING RESISTANCE MATERIAL • MATERIAL COMPLY TO NACE STANDARD ARE CARBON STEEL WITH HEAT TREATMENT SST 302,304,316,17-4PH ALLOY STEEL MONEY, HASTELLOY C • MATERIAL NOT SUITABLE FOR NACE ENVIRONMENT IS CAST IRON 12
  13. 13. CONTROL VALVE STANDARDS ISA :- INSTRUMENT SOCIETY OF AMERICA • DEFINES STANDARDS FOR CONTROL INDUSTRY Example :VALVE SIZING EQUATIONS. NOISE PREDICTION TECHNIQUE CONTROL SIGNAL 3 - 15 PSIG, 6 - 30 PSIG OSHA :- OCCUPATIONAL SAFETY AND HEALTH ACT DEFINES CRITERIA FOR PERMISSIBLE DURATION FOR EXPOSURE OF NOISE LEVEL 13
  14. 14. SHELL REFERENCES Control Valves –Selection , Sizing and Specification • DEP 32.36.01.17- Gen July 1987 & • Basic Process control & Instrumentation Shell M114-1999 • Shell Best Practice –[Ref Process Measurement and Control Devices –Shell Canada Ltd Standard 16-1.2] 14
  15. 15. CONTROL VALVE LEAKAGE Control Valve Leakage This is basically the fluid which passes through the valve when the valve is fully closed. This value however should not be considered as the valve Cv at NIL Opening. So this leakage shall depend on the contact of valve plug & seat with the seating force applied for holding the plug over the seat. 15
  16. 16. CONTROL VALVE LEAKAGE Maximum Leakage ANSI/FCI 70-2 Test Medium 0.5% valve capacity at full travel Class II 0.1% valve capacity at full travel Water / Air Class III 0.01% valve capacity at full travel Class IV 0.0005ml/min/psid/in. port dia Class V Water Bubbles per Port dia. mL per Min. Min. Class VI 1 1 - 1/2 2 2 - 1/2 3 4 6 8 1 2 3 4 6 11 27 45 0.15 0.30 0.45 0.60 0.90 1.70 4.00 6.75 Air 16 Pressure and temperature Service DP or 50 PSID whichever is lower at 10 to 52deg C Service DP at 10 to 52deg C Service DP or 50 PSID whichever is lower at 10 to 52deg C
  17. 17. VALVE CHARACTERISTICS Equal % flow. Linear - Rate of change of flow due to change of valve travel is proportional to earlier - Rate of change of flow is same to rate of change of valve travel Quick Open - Full capacity attaining without change of travel after initial opening On/Off suction - Used mainly as Isolation valves (Pump and ESD valves) 17
  18. 18. TRIM AND CAGE DESIGN 1. CHARACTERISING FLOW • Linear Cage • Quick Opening Cage • Equal Percentage Cage • Modified Equal percentage flow 2. NOISE ABATEMENT 3. ANTI CAVITATION 18
  19. 19. CHARACTERIZING FLOW BY CAGE TYPE 19
  20. 20. CHARACTERIZING FLOW 100 Quick Opening Li Cv % Design Cv 80 r ea n 60 40 20 a Equ l% 0 0 20 40 60 80 % Valve Travel 20 100
  21. 21. VALVE SELECTION PROCESS FOLLOWED IN RELIANCE • If valve sizing does not give warning of cavitation, flashing or Noise level ( >85dBA) then select standard trim valve. • If valve sizing gives warning of cavitation, flashing or Noise level ( >85dBA) then select arduous service trim valve. Example:- For cavitation select CAVITROL III stage 1 to 5 valve or CAVITROL 4 valve. For noise select WHISPER I ,III or WHISPERFLO valve trim. • Select the suitable Approved vendor suiting the product . Example:- ABB - Introl design or CCI - DRAG design. • In case of very high DP ( DP*100/P1 > 50%) or Noise select ABB or CCI valves. Example:- Compressor Anti - surge control valves - CCI- DRAG design. 21
  22. 22. VALVE SELECTION PROCESS S t a n d a r d M a te r ia ls : C a rb o n s te e l W C B C a rb o n s te e l N A C E S ta in le s s s t e e l 3 1 6 o r 3 1 6 L S t a n d a r d R a t in g s : A N S I r a tin g c la s s 1 5 0 A N S I r a tin g c la s s 3 0 0 A N S I r a tin g c la s s 6 0 0 Is it s ta n d a a r d m a te ria l No Y es Is it s ta n d a r d fla n g e r a tin g No Y es S p e c ia l v a lv e d e s ig n a n d a p p lic a t io n re f D E P 3 2 .3 6 .0 1 .1 7 S ta n d a rd T e m p . R a n g g e 0 deg. C + 420 deg. C Is te m p e r a tu r e w ith in g s ta n d a rd ra n g e Y es No S e v e r e S e rv ic e : C h o k e F lo w C a v ita t io n N o is e a b o v e 8 5 d b A O x y g e n s e r v ic e Is it s e v e r s e r v ic e L o w te m p e ra tu re s e r v ic e H F s e rv ic e E th y le n e o x id e s e r v ic e V a c u u m s e r v ic e H P s te a m s e r v ic e H y d r o g e n s e r v ic e C h lo r in e s e r v ic e Y es No S ta n d a r d v a lv e d e s ig n a n d a p p lic a tio n . R e f D E P 3 2 .3 6 .0 1 .1 7 A ll S e c tio n e x c e p t 6 and 7 22
  23. 23. POPULATION OF CONTROL VALVES AT RELIANCE JAMNAGAR. Based on above criteria RIL complex has following Installed quantity of valve • • Fisher direct supply ( Through Bechtel ) :1800+ valves. • Fisher package supply valves :800+ •Masoneilan package supply : 180 + • ABB UK direct supply :150+ • CCI USA direct supply :40+ • Fisher Gulde package supply : 190 + • Linde Mepag package supply : 120 + •Copes Vulcan package supply : 50 + •Keystone Biffi direct supply : 300 + •Neles Jamesbury direct supply : 630 +23
  24. 24. VALVE INTERCHANGEABILITY • Body pressure rating and certification ( e.g. IBR ) • End connection ( Ex:- Screwed or welded flange connection ) • Valve Size and type. • Trim Size - Cv • Leakage classification • Body and trim material and certification ( e.g. NACE ) • Plug and cage characteristics. • Actuator bench setting / spring range. • Actuator action ( AFC/ AFO ) • Process temperature ( For gland packing and body - trim material ) 24
  25. 25. Flow Path through a Control Valve - Analogy Minimum Geometrical Flow Area Streamlines Contract as Flow Approaches Restriction Vena Contracta (Minimum Flow Area) 25
  26. 26. Variation in Pressure and Velocity P1 Pressure Variation ∆P Velocity Variation P2 Valve Outlet Valve Trim Inlet Trim Exit Vena Inlet Contracta 26
  27. 27. Pressure Recovery ∆P Low Recovery High Recovery Valve Outlet Valve Trim Inlet Trim Exit Vena Inlet Contracta 27
  28. 28. FLASHING Flashing : The formation of vapor bubbles in liquid flow streams at vena contracta. As liquid passes through a restriction (vena contracta) in a control valve the liquid velocity increases and liquid pressure decreases. And if the pressure at this point falls to or below the vapor pressure of the liquid, vapor bubbles form in the flow stream. Flashing results if this pressure remains below vapor pressure of liquid. When a liquid flashes into vapor, there is a large increase in volume. Due to increase in volume velocity will increase and hence high velocity will erode the surface. Flashing damages can be identified by smooth polished appearance of eroded surface. Flashing damages is usually at or near seat line of the valve plug and seat ring. Vapor pressure :- The pressure at which liquid begins to vaporize. 28
  29. 29. FLASHING DAMAGE ( Tag no. 241FV040 ) 29
  30. 30. FLASHING DAMAGE ( Tag no. 241FV040 ) 30
  31. 31. CAVITATION Cavitation : The formation and subsequent collapse of vapor bubbles in liquid flow streams. As liquid passes through a restriction in a control valve the liquid velocity increases, while the liquid pressure decreases. The pressure reaches a minimum at a point called the vena contracta, and if the pressure at this point falls to or below the vapor pressure of the liquid, vapor bubbles form in the flow stream. Downstream of the vena contracta, flow area increases, velocity de-creases, and pressure increases. If this recovered pressure is sufficient to raise the pressure above the liquid vapor pressure, the vapor bubbles will collapse. The collapsing bubbles generate significant noise and vibration, and can mechanically attack pipe walls and valve components. Cavitation damages can be identified by rough and pitted surface. Cavitation damage may extend to the downstream pipeline if that is where the pressure recovery occurs. Phenomenon of Cavitation is experienced in CV and PUMPS 31
  32. 32. CAVITATION P1 ∆P P2 PV PVC’ Valve Outlet Valve Trim Inlet Trim Exit Vena Inlet Contracta 32
  33. 33. CAVITATION DAMAGE 33
  34. 34. CAVITATION CONTROLS •SYSTEM DESIGN 1. LOCATION OF VALVE 2. CASCADING •MATERIAL SELECTION HARDEN MATERIAL, LIKE 17-4 pH, 440C, 420SST HT AND 316/COLMONOY 6 / ALLOY 6 34
  35. 35. CAVITATION CONTROLS • ANTI - CAVITATION PRODUCTS • CCI DRAG DESIGN, UP TO 380 BAR PRESS. DROP. • FISHER CAVITROL - III DESIGN CAVITROL - III WITH 1 STAGE- UP TO 99 BAR. CAVITROL - III 2-3 STAGES- 99 TO 207 BAR. CAVITROL -4 , ABOVE 200 BAR, SIZE LIMIT 2” TO 6”. • ABB INTROL DESIGN 35
  36. 36. CAVITATION CONTROLS :- FISHER CAVITROL DESIGN CAVITROL - III CAVITROL - III STAGE - 2 STAGE - 3 36
  37. 37. CAVITATION CONTROLS :- FISHER CAVITROL DESIGN CAVITROL - 4 37
  38. 38. CAVITATION CONTROLS :- ABB INTROL DESIGN INTROL CAGE 38
  39. 39. CAVITATION CONTROLS :- CCI DRAG DESIGN CCI DRAG CAGE 39
  40. 40. CAVITATION CONTROLS :- CCI DRAG DESIGN 40
  41. 41. CAVITATION CONTROLS :- CCI DRAG DESIGN 41
  42. 42. CHOKED FLOW Choked flow :Formation of vapour bubbles in the liquid flow stream cause a crowding condition at the vena contracta which tends to limit flow through the valve. If valve pressure drop is increased slightly beyond the point where bubbles begins to form, a choked flow condition is reached. With constant upstream pressure, further increase in pressure drop will not produced increased flow through the valve. 42
  43. 43. NOISE FUNDAMENTALS Noise :- A random mixture of sound pressure waves of various amplitudes and frequency. Which people do not like to hear. Sound Wave :- A pressure wave with a fixed frequency and amplitude traveling through a medium. Unit of Noise :- dBA ( Decibels )= 20 Log( Existing sound pressure level / 0.0002 microbars ) Source of valve noise: • Mechanical Noise :- It produces high mechanical stress - fatigue failure of vibrating part. Mechanical noise can be solved by improved design to suppress vibration by good guiding and rugged construction. • Vibration of valve components :- This is due to lateral movement of valve plug relative to guide surfaces. The sound level produce normally will have frequency less then 1500Hz and is describe as metallic rattling. • Fluid impingement upon the movable of flexible part ( Metallic chattering ) • Components resonates at its own natural frequency ( single tone 3KHz to 7KHz) • Hydrodynamic Noise :- It is due to cavitation. It is because of implosion of vapor bubbles and is relatively low. 43
  44. 44. NOISE FUNDAMENTALS Aerodynamic Noise :Highest energy component at same frequency where human ear is most sensitive. Large amount of energy converted to aerodynamic noise. • High intensity noise resulting due to turbulent flow of gas, are due to high relative velocity. This can be classified as non-periodic or random noise with occurring frequency between 1 KHz to 8 KHz. • Valve pressure drop ( Main source ), • Obstruction in flow path, • Valve style , having more flow directional changes, • Degree of turbulence varies with valve style1, • Valve size. 44
  45. 45. PERMISSIBLE EXPOSURE DURATIONS NOISE LEVEL OSHA :- OCCUPATIONAL SAFETY AND HEALTH ACT DEFINES CRITERIA FOR PERMISSIBLE EXPOSURE DURATIONS NOISE LEVEL IN JAMNAGAR COMPLEX MAX. 85 dBA IS CONSIDERED AS A VALVE SELECTION CRITERIA. DURATIO N IN HO URS PER DAY SO UND LEVEL IN DBA 8 90 6 92 4 95 3 97 2 100 1-1/2 102 1 105 1/2 110 1/4 O R LESS 115 45
  46. 46. NOISE CONTROL • PATH TREATMENT • INSULATION OF PIPE • HEAVY WALLED PIPE • SILENCER • SOURCE TREATMENT • VALVE CAGE STYLE ( TRIM ) • WHISPER - I ( DP/P1 <= 0.65 ), Noise reduction up to 18 dBA. • WHISPER - III ( 0.6 <= DP/P1 <= 0.99 ), Noise reduction up to 30 dBA. • WHISPERFLO (NEW DESIGN), Noise reduction up to 10 dBA. • BY INLINE DIFFUSER • BY WHISPER DISK 46
  47. 47. NOISE CONTROL - SOURCE TREATMENT WHISPER - III DESIGN WHISPER - I DESIGN 47
  48. 48. NOISE CONTROL - SOURCE TREATMENT WHISPERFLO DESIGN BY FISHER 48
  49. 49. NOISE CONTROL - SOURCE TREATMENT WHISPER DISK AND IN LINE DIFFUSER DESIGN BY FISHER 49
  50. 50. NOISE CALCULATION SPL = SPL∆P + ∆SPLCG + ∆SPL∆ P/P1 + ∆SPLK + ∆SPLP2 SPL = OVERALL NOISE LEVEL IN DECIBLE ( 1 METER DOWNSTREAM OF VALVE OUTLET AND 1METER FROM THE PIPE SURFACE ) SPL∆ P = FUNCTION OF PRESSURE DROP ACROSS THE VALVE ( MAJOR COMPONENT ) ∆SPLCG = GAS SIZING COEFFICIENT ( MAJOR COMPONENT ) ∆SPL∆P/P1 = RATIO OF PRESSURE DIFFERENTIAL TO INLET PRESSURE ∆SPLK = CORRECTION IN DBA FOR PIPE SIZE AND SCHEDULE ∆SPLP2 = DOWNSTREAM PRESSURE SIMPLIFIED EQUATION ( WITHOUT MUCH LOSS OF ACCURACY ) : SPL = SPL∆P + ∆SPLCG 50
  51. 51. CONTROL VALVE GLAND PACKING 51
  52. 52. CONTROL VALVE GLAND PACKING Temp. Range Common use -73 to 232C Non-Radioactive -40 to 232C All chemicals ( Except Molten alkali) Non radioactive Vacuum Pressure / Vacuum Suitablity for Oxygen /Oxidizing Service Packing material Description Stem friction Split rings of braided composition impregented with Low PTFE Yes PTFE impregented composition No single PTFE V - Ring Solid rings of molded PTFE Low No Double PTFE V - Ring Solid rings of molded PTFE Low Special consideration Required 2 to 4 micro inch RMS valve plug stem finish Split rings of braided, preshrunk PTFE yarn impregented with PTFE; available with copper rings at Low top and bottom of packing box to meet UOP specification 6-14-0 for acid service. - -84 to 232C Vacuum, All chemicals Yes ( Except molten alkali ) -18 to 538C Water, Stem Petroleum products, Radiactive Yes but upto Graphite/ and Non-radiactive 371C Ribbon/Filament nuclear Ribbon style graphite rings and rings of braided graphite fibers with sacrificial zinc washer High Low chloride content ( less then 100ppm) chrome plated stem not necessary for high temperature service 371 to 649C High temperature oxidizing service Solid rings of ribbon-style graphite with sacrificial zinc washers High - Yes Chesterton 324 Ribbon - Style graphite 52
  53. 53. VALVE MATERIAL Essentially material for the valve is valve assembly MOC. Standard material commonly used can be listed as below Valve Body & Bonnet - As per Process Internals - As per Process . Commonly SS316 with or w/o stellite. Valve Gasket - Graphite, Metallic SS 316 or SS 316L Valve Packing - Commonly Teflon Or Graphite Fasteners - B7 or B8M Actuator Yoke - Cast Iron Actuator Spring - Spring Steel Actuator Diaphragm - Nitrile Rubber with fabric reinforcement Accessories - Commonly Aluminum. 53
  54. 54. TECHNOLOGY With the advent of new technology Control Valve has undergone rapid change in terms of change in Internals, Capacity Increase, Guiding, Leakage Class Improvement, Treatment of Noise And Cavitation And Finally DIGITAL. About 30 years back control valves were only available with top guided or top & bottom guided design with asbestos packing and practically no solution available for Hi Pressure drop application leading to Noise for Gas service Or Cavitation for Liquid Service. 54
  55. 55. TECHNOLOGY Now a days we are also having control valve with digital technology, where valve positioner is digital in nature and able to provide PID function at the valve itself. Digital positioner can provide the following apart from acting as interface between controller and valve actuator 1. Provide HART feedback. 2. Can couple with Foundation Fieldbus. 3. Can provide valve diagnostics. 4. Helps in Asset Management. 5. Provide lock, soft alarms and data logging facilities. 6. Can achieve split action, remote calibration etc. 55
  56. 56. Trouble Shooting in Control Valves. T R O U B L E S H O O T IN G M A L F U N C T IO N LE A K AG E A C T IO N C Y C L IC M O T IO N IN S T A B IL IT Y H U N T IN G ( A t a n y v lv o p e n in g ) H ig h S t e m F r ic t io n V IB R A T IO N (N O IS E ) H U N T IN G ( N e a r t o v lv c lo s e p o s n ) O v e r s iz in g To C heck G la n d P a c k in g R educe dP In c re a s e A c tu a to r U s e S m a lle r C v v a lv e F lo w t o C lo s e flo w d ir e c t io n C hange F lo w d ir . A t a n y v lv o p e n in g In c re s e S u p p o rt O th e r s o u rc e F in d P lu g g u id e w e a r & te a r R e p la c e w it h n e w 56 D U LL R E S P O N SE N O T W O R K IN G A t s p e c ific v lv o p e n in g Poor P ip in g C h e c k V lv G u id in g O TH ER S R esonance of V ib r a t io n R esonance N o is e o f v lv p lu g In c re a s e p ip e s u p p o r t C hange p lu g p r o file T h r o t le p u m p d is c h a r g e v a lv e C hange C v v a lu e
  57. 57. Trouble Shooting in Control Valves. T r o u b le S h o o t in g M A L F U N C T IO N A C T IO N C Y C L IC M O T IO N LE A K A G E O TH E R S D U LL R E S P O N S E N O T W O R K IN G T ra v e l N o t s m o o th ( I n b o t h d ir ) S lu r r y / s lu d g e in v lv g u id e A c tu a to r p is t o n r in g w e a r & te a r C hange P is t o n r in g T ra v e l N o t s m o o th ( I n o n e d ir ) G la n d p k g h a rd e n e d L e a k in A c tu a to r d ia p h . C hange g la n d p k g C hange d ia p h . D is s e m b le & C le a n L e a k fr o m A c t. s te m seal C hange s te m s e a l U se dust s e a l b e llo w E n la rg e g u id e r in g b le e d e r h o le P r o v id e fla s h in g p o r t U s e ja c k e te d v lv b o d y U s e ro ta ry o r a n g le ty p e v a lv e 57
  58. 58. Trouble Shooting in Control Valves. T r o u b le S h o o t in g M A L F U N C T IO N A C T IO N C Y C L IC M O T IO N N o s ig n a l & s u p p ly p r . LEA KA G E D U LL R ES PO N S E N O T W O R K IN G N o s ig n a l p r . s u p p r. a v l O TH E R S N o s u p . p r. S ig n a l p r . a v l P o s n O / P N il A c tu a to r n o t w o r k in g w it h a ir s u p . T r o u b le in a ir s o u r c e T r o u b le in c o n t r o lle r C heck C o n t r o lle r A FR c o n t a m in a t io n C le a n F ilt e r T r o u b le in p o s n p ilo t r e la y C heck S t e m / g u id e g a llin g / ja m m in g D is a s s e m b le & check T r o u b le in e le c t r ic s o u r c e C o n t r o l s ig le a k a g e C heck a ir t u b in g P n t u b in g Leakage C h e c k T u b in g ( m a in ly a ir c o n n .) A c t d ia p h a ir le a k C hange p a rts F o r e ig n p a r t ic le in v lv p o r t D is a s s e m b le & check L e a k a g e fr o m t u b in g A c t d ia p h a ir le a k C h a n g e p a rts T r o u b le w it h A FR C heck AFR S te m B e n d C hange p a rts C heck com p. e le c s o u r c e & M a in a ir t u b in g P o s it io n e r a ir le a k C h a n g e b e llo w o r d ia p h T r o u b le in A c tu a to r C heck A c t S tro k e 58
  59. 59. Trouble Shooting in Control Valves. M A L F U N C T IO N LE A K A G E A C T IO N O TH E R S C Y C L IC M O T IO N D r ift o f a ir s u p p r . T o o m u c h a ir c o n s u m p t io n in o t h e r lin e E n la r g e c o m p re s s o r c a p a c it y H u n t in g o f S ig a ir p r . T r o u b le in A FR C heck A FR C o n t r o l lo o p R e s is t a n c e In s e rt v o l ta n k & r e s t r ic t io n t o a ir s ig n a l lo o p H u n t in g o f V lv s t e m T r o u b le in C o n t r o lle r C heck C o n t r o lle r P o s it io n e r lo o p h u n tin g S h ift in p lu g r e a c t io n fo r c e 59 D e c re a s e d P C heck posn p ilo t r e la y E x c lu s iv e c o m p re s s o r C heck posn p a r t s fr ic t io n H ig h e r s iz e A c tu a to r
  60. 60. Trouble Shooting in Control Valves. M A L F U N C T IO N LEAKAG E O THER S S eat Leak G la n d L e a k V a lv e C lo s e d C o r r o s io n & e r o s io n o f v lv s e a tin g s u r fa c e C o r r o s io n & e r o s io n o f s e a t r in g th r e a d or gasket V a lv e n o t a b le t o c lo s e Leakage th r o ' in n e r v lv b o d y w a ll T o o h ig h d P I n s u ff ic ie n t p k g n u t t ig h t G a llin g o n g u id e o r p o r t R e m a c h in e & L a p s e a t s u r fa c e C hang e seat & seat gasket T a c k w e ld d e fe c t a r e a R educe dP C heck s e a t d e s ig n C h a n g e v lv body In c re a s e A c tu a to r s iz e Pkg Lub m is s in g C h e c k fo r F o r e ig n p a r ts Change s e a t & p lu g T ig h t e n p kg . n ut R e m a c h in e g a llin g p o r t io n P r o v id e lu b o r c h g p k g . W e a r & te a r of pkg C hange pkg D a m a g e o f s te m s u r fa c e C h a n g e p a rts o r r e m a c h in e U se dust seal b e llo w s C o r r o s io n /e r o s io n of seat gasket s u r fa c e 60 E x a m in e p a r t M O C C hange gasket R a n g e a b ilit y n a r r o w e d because of c o n t r o l p o s itio n changed C o r r o s io n / e r o s io n o f p lu g o r S . r in g C h a n g e s e a t r in g o r p lu g
  61. 61. T HA NK Y OU 61

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