engineering

1. 1
Mechanical Design
Conditions for
Equipment and Piping
Systems School
2005-2006

2. 2
Overview
Design Conditions Work Process
• Establish design conditions
philosophy
• Design pressure considerations
• Confirm DP/MOT margins for
equipment
• Create DP/MOT mark-up
• Hold Design Conditions meeting
• Set equipment design conditions
• Develop piping design conditions
– Design Codes
– Short term questions
• Set piping design conditions
Input Docs
PFD
Process
release
H&MB
Go-By Jobs
MOC/MSD/
Alloy mark-up
Index of Piping
Material
Classes
Deliverables
Equipment Design
Data/Connection
summaries. Mark
up analytical
sketches.
P&ID Mark-ups
Line list
Systems
comments on pipe
specs

3. 3
Equipment Design
Conditions
Design Pressure Philosophies
Specific Considerations
Design Pressure Margins
Max. Min. Temperature at Design Pressure
Equipment Connection Summaries

4. 4
Design Pressure Philosophies
The design pressure basis is developed in conjunction with the
Overpressure Protection and Vent Philosophy for each job.
Standard Design Pressure Philosophy
When equipment is protected by a relief device, KBR’s standard
design pressure philosophy is to set the design pressure of the
equipment equal to the highest pressure expected during normal
operation plus the margin required for proper operation of the relief
device. The relief device is sized to protect the equipment during
all upset conditions.
Alternate Design Pressure Philosophy
When equipment is protected by a relief device, KBR’s alternate
design pressure philosophy it to set the design pressure of the
equipment equal to the highest pressure expected during normal
operation and non-fire upset conditions plus the margin required
for proper operation of the relief device. The relief device is sized
to protect the equipment for the fire emergency only.

5. 5
Specific Design Pressure Considerations
1. For Centrifugal pump circuits-
Equipment upstream of control valve or a block valve.
DP = Shut-off head (SEM 1-301)
Equipment downstream of control valve:
DP is determined based on operating factors
2. Refrigeration Systems-
Systems should consider the long term settling out
pressure
3. Equipment discharging to a closed relief system-
No official ‘minimum’ standard design pressure exists.
However, for typical closed discharge systems back
pressure problems usually occur if the minimum
design pressure is less than 50 psig.

6. 6
Specific Design Pressure Considerations
4. Pilot-Operated Relief Valve-
KBR standard practice is to maintain the same margins
as for a conventional PSV. Systems may reduce
margins only with approval of Systems CTE (SEM 1-301
3.2.1).
5. Historically, the low pressure side of heat exchangers
were often designed for a fraction (two-thirds originally,
subsequently modified to ten-thirteenths) of the high
pressure side to take advantage of API recommended
practice concerning a tube failure scenario.
However, KBR’s current interpretation of ASME code,
per SEM 1-303 Section 4.2.1, is that designing for this
fraction of the high side pressure does not alleviate the
need to evaluate the effects of tube rupture on the low
pressure side system. Usually, the tube failure scenario
is not controlling because of the ability to dissipate the
flow into the low pressure system without causing
overpressure.

7. 7
6. KBR normally does not design vessels to withstand vacuum
conditions resulting from improper operation of equipment.
The requirement to design equipment for full vacuum
caused by improper operation must be specified by the
owner. Sometimes protective devices such as vacuum
breakers may be provided to prevent the development of
excessive vacuum in a vessel.

8. 8
Design Pressure Margins
Pressure relief devices require some margin
between MNOP (maximum normal operating
pressure) and set pressure due to the
mechanical characteristics of the device.
Pressure relief valves also require a margin
above the MNOP to account for blowdown
which enables the device to reseat. This is to
prevent leakage or simmering/chattering of
the device.

9. 9
Design Pressure Margins
Vessels that operate at pressures greater than
atmospheric (Non-Boiler Code)(ASME VIII)
If protected by a pressure relief valve: MNOP =
Maximum Normal Operating Pressure
MNOP + 5 psi (DPmin < 50 psig)
MNOP * 1.1 (50 < DPmin < 1000 psig)
MNOP * 1.07 (DPmin > 1000 psig)
If protected by a pressure relieving device other than a
pressure relief valve (rupture disk, etc):
Minimum design pressure = Maximum value of
MNOP * 1.1
MNOP + 10 psi
MNOP * (margin recommended by vendor)

10. 10
Design Pressure Margins
Vessels that operate at atmospheric pressure up to
a maximum of 2.5 psig
- Design per API 650
- DP = MAWP calculated by Vessel Mechanical or
tank vendor (not set by Systems)
Large storage vessels that operate at pressures
greater than 2.5 psig but less than or equal to 15
psig
- Design per API 620
- If protected by a pilot operated relief valve:
DP = Maximum value of:
MNOP + 0.5 psi
MNOP * 1.1

11. 11
Design Pressure Margins
Surface condensers in steam service
DP = 15 psig and FV
Cooling water side of exchangers
DP = Maximum value of:
MNOP * 1.1
Cooling water pump shut-off pressure
Use 150 psig and full vacuum minimum design
pressure for exchanger sides in cooling water service
because of possible transient conditions.

12. 12
Design Pressure Margins
All other exchangers
If protected by a pressure relief valve, Design Pressure =
MNOP + 5 psi (DPmin ≤ 50 psig)
MNOP × 1.10 (50  DPmin ≤ 1000 psig)
MNOP × 1.07 (DPmin  1000 psig)
If protected by a pressure relieving device other than a PRV
(i.e. rupture disk), Design Pressure =
Maximum value of:
MNOP × (Margin recommended by vendor)
MNOP + 10 psi
MNOP × 1.1

13. 13
Design Pressure Margins
Machinery
Systems does not set design pressures for machinery.
Systems only provides the input information used by the
machinery group in determining the design pressure for
that equipment.

14. 14
Determine Equipment Design Conditions
The recommended method for developing design
pressures is to mark up a copy of the PFDs with
proposed pressure relief device locations and
equipment design pressures. Thus, an overall view
is developed of the potential relief scenarios, the way
equipment is protected from overpressure, and the
equipment design conditions.

15. 15
Effect of PRV Location on Design
Pressure
What is design pressure?
REACTOR
MNOP = 1200
MNOP(1.1)=1320
PROCESS
COOLER
MNOP=1100
MNOP(1.1)=1210
MIXER
MNOP=1000
MNOP(1.1)=1100
OXIDISER
MNOP=900
MNOP(1.1)=990
SURFACE
CONDENSER
MNOP=800
MNOP(1.1)=880

16. 16
PRESSURE
(PSIG)
LOCATION
SET PRESSURE OF
RELIEF VALVE
INDICATES DESIGN
PRESSURE
MNOP
MNOP + 10%
O
O O
O
O
1300
1200
1100
1000
900
800
O
Effect of PRV Location on Design Pressure

17. 17
Maximum & Minimum Temp at Design Pressure
• Systems is responsible for specifying the
maximum temperature [Tmax] coincident with
the design pressure for equipment design
– Equipment containing liquids at their bubble point:
• Maximum temperature will be the boiling point at
design pressure
– Maximum temperature must consider process
upsets and allowance for control variation.
– When specifying maximum temperature, be aware
of flange ratings (Tmax, DP cannot exceed flange
rating).
– Minimum operating temperature at design
pressure is provided if the lowest operating
temperature is below the minimum design ambient
temperature

18. 18
Depressuring Conditions
• Applicable in light hydrocarbon services
• Equipment can be depressurized and thereby auto
refrigerate to temperatures lower than the minimum
ambient design temperature
• Coincident temperatures and pressures from 80% of
design pressure down to atmospheric
• Used to determine MDMT ( minimum metal design
temperature)

19. 19
Design Data and Connection Summary
Systems is responsible for communicating equipment
design data and connecting line data to other work
groups. This information is normally provided on the
Design Data and Connection Summary.
Types of Equipment Connection Summaries
• Vessel Design Data and Connection Summary
• Exchanger Design Data and Connection Summary
• Furnace Connection Summary

20. 20
Purposes of Equipment Connection
Summaries
1. To advise piping design and vessel mechanical of
the sizes and specifications for piping connecting to
equipment.
2. Provide size and rating of utility nozzles (vents,
drains, steam out, etc.)
3. Convey mechanical design conditions to
mechanical groups
– Design Pressure
– Maximum operating temperature
– Minimum operating temperature (if required)
– Depressuring conditions (used for MDMT)
– Alternate design conditions (must be coincident)

21. 21

22. 22
Piping Design
Conditions
Determination of Design Pressure and
Temperature
Piping Line List
Piping Line List Generation
Design Codes

23. 23
Determination of Design Pressure and
Temperature
• Design temperature
Fluid temperature during the most severe condition
expected during operation or upset (SEM 1-602,
Sections 3.2 and 4.0)
• Design pressure
Non pumped piping systems (SEM 1-602, Section
6.1)
Design pressure should be the design pressure of
the vessel to which the piping is attached plus the
static head of the liquid at the lowest point of the
piping.

24. 24
Determination of Design Pressure and
Temperature
Pumped piping systems
– Centrifugal pump ( SEM 1-602, Section 6.2.2)
The piping design pressure from the pump discharge through the
last downstream block valve should be the greater of (1) or (2) below:
(1) Dp = max suction pressure ( during pump shutoff)
+ max static head ( at pump nozzle)
+ shutoff differential
(2) Dp = max suction press (Suction vessel at its max. relieving
pressure)
+ max. static head ( at pump nozzle)
+ normal pump differential
– Positive displacement pump ( SEM 1-602, Section 6.2.3)
In general, discharge piping is protected by a relief valve. The relief valve
should be set with sufficient margin on top of the operating pressure of
the discharge pipe. Margin will vary based on the type of positive
displacement pump.

25. 25
Line List components
• Design Pressure and Temperature
– These are defined as the coincident conditions that
produce the highest stress in the pipe.
– Used by Piping Design (isometrics), Systems (wall
thickness calcs, pipe spec selection) and Piping
Mechanical (stress analysis).

26. 26
Line List components
• Test Medium / Test Pressure
– Almost always hydrostatic. Consult with the work group leader for lines
that may be pneumatically tested or for services where a leak test is
permissible. Test pressures are calculated by the line list program based
on the ASME code. Test pressure information is used by Piping Design
(isometrics), Piping Engineering, Civil (pipe support loads) and by
Construction and Plant Services groups (field pressure testing).
– Hydrotest Pressure
• ASME B31.3 (Per SEM 1-302, Section 5.1)
• ASME B31.1 (Per SEM 1-302, Section 4.2)
– Pneumatic Test
• ASME B31.3 (Per SEM 1-302, Section 5.3)
• ASME B31.1 – Not Allowed

27. 27
Line List components
• Piping Material
– The design conditions of the line shall be used in
selecting the piping material ( also called piping
class).
– The metallurgy section of the Chief engineer’s office
alloy mark-up determines the use of special or alloy
piping in respect to factors such as corrosion, erosion,
and hydrogen attack.
– The pipe class selected shall be based on using the
most economical piping material that will resist the
limiting conditions of the service.

28. 28
Line List components
• Schedule (wall thickness)
– Taken from the piping class, this is based on the
coincident pressure and temperature limits set for
the class
• Flexibility Temperature
– Defined as the extreme highest (or lowest) temp
the pipe will experience after installation. Not
necessarily coincident with design pressure; can
be induced by environmental considerations (e.g.
solar radiation temp). Used by Piping Mechanical
(stress analysis, thermal displacement)

29. 29
Line List components
• Insulation Temperature / Thickness & Paint Class
( SEM 1-602, Section 10)
– Insulation thickness is based on the operating
temperature and pipe size specified and reported
by the program as a look up feature.
– The paint class is also determined by the program
and based on the max. normal operating
temperature. Selection must also take into
account the flex temperature.( SEM 1-602, Section
3.6)
– Otherwise, they are taken from the V-Class
Summary (for paint codes and insulation codes
based on operating conditions and materials of
construction) or client specifications.

30. 30
Piping Line List Generation
• The following line data must be shown on
the P&IDs
– Line number (ID)
– Size
– Class (spec)
– Design Code
– Insulation Temperature
– Insulation Type
– Special Requirements (remarks - optional)

31. 31
Piping Line List Generation
Procedure to generate Line List Report:
• Engineer marks up P&ID with line list
information indicated above and gives to CAD
designer to incorporate.
• Engineer (usually P&ID Coordinator or the
dedicated CAD designer) enters the conditions
for the design codes into Design Code Manager.

32. 32
Piping Line List Generation
• After incorporating the mark-ups, the
designer propagates the P&ID. During
propagation, PDS stores the information into
the database and looks up the insulation
thickness from the tables.
.
• Calculation routines determine the test
pressure and paint code for each line and
also check that the specified design
conditions are within the allowable flange
ratings for the assigned pipe spec. The
routine also produces a Checker’s Report
that lists all problems, errors and warning
messages.

33. 33
Piping Line List Generation
• Once the above routine is complete, the Line
List Report is run. All relevant data from
P&IDs, including remarks, as well as results
from the calculation and look up routine, is
reported in a specified line list format and can
be printed.

34. 34
Piping Line Cell Data

35. 35
Design Codes
• Groups of 3 letters that serve as a reference tag
to data in the database. Each design code has
a defined set of data. Design codes are used as
a shorthand method of assigning the same
design conditions to a multiple set of pipes or
pipe segments.

36. 36
Design Codes
• A design code is defined by the following
components:
– Design Pressure
– Design Temperature
– Flex Temperature High
– Flex Temperature Low (if required)
– Fluid Phase
– Test Medium
– Percentage Full Vacuum (if required)

37. 37
Design Codes
• Usually the letters of a design code have no specific
meaning, with the exception of utility systems where it is
common practice to assign logical letters. Hence design
codes in utility services are assigned a “U” as a starting
letter, followed by a recognizable pair of letters based on
the service. Examples of these are:
– UHS - high pressure steam
– UCW - cooling water
– UPA - plant air
• A block of letters is normally assigned to each process or
utility area for allocation of design codes at the start of a
project.

38. 38
Design Codes
• Ground rules for design codes:
1. One design code cannot be assigned 2 sets of
conditions, however, 2 or more design codes can have
the same conditions.
2. A design code, once assigned, should not be deleted
(since it may have been used by others in a different
area and also because there are plentiful codes
available).
3. Once assigned, the conditions of a design code
should not be changed (for the same reasons indicated
in 2 above).

39. 39
Design Codes

40. 40
Homework
Based upon the following portion of an annotated process
diagram, determine the design conditions.
Also complete a Pipeline Nomenclature, on the enclosed
forms, for all of the lines shown on the process diagram.
Consider these lines to be governed by ASME B31.3 and that
the piping material should be carbon steel.
For reference there is included a V Class Summary (pages 1-
10) which has the Insulation Type Codes defined, the
Insulation Thickness Tables, and the Piping Paint Codes.
Also for reference are two pages of Allowable Stresses from
ASME B31.3. Use the Piping Material Specifications given in
the class handouts.
This homework will be submitted to Instructor

41. 41
Annotated Process Diagram
101-E
101-F
101-J
M
P-106-4"
P-105-4"
102-C
TOWER
P:
3 PSI
P-101-18"
P-102-8"
NORMAL T = 110 F
104-C
P-107-4"
MAX NORMAL TEMP = 451 F
MAX NORMAL
TEMP = 190 F
MAX NORMAL TEMP:
110 F
STATIC
HEAD TO
MAX. LIQ.
LEVEL:
5 PSI
P-103-8"
P-104-6"
STATIC HEAD
TO INLET: 20 PSI
CALCULATED
PUMP SHUTOFF
PRESS: 610 PSIG
CALCULATED MAX.
SUCTION PRESS: 570 PSIG
MAX OPERATING
PRESS: 500 PSIG
@ 200 F
CW
PROCESS
FEED
MP STEAM