Case study
1. For the following process systems: Build its relevant piping
material class according to ASME B31.3 code provisions,
please demonstrate your answer by the used code/standard
paragraphs NO. and clearly showing each step and specifying
the most commonly used piping items (name, size range, class,
schedule, and material)
System
No.
Material
category
Upset
conditions P/T
1
LTCS+ 3.2 C.A
100 bar / 400 C
2
SDSS (25Cr)
250 bar / 200 C
Solution:
Part 1: (Flanges)
- Reference: ASME B16.5 Tables 2-1.1 to 2-3.19, PFD & MSD
- Input: Material categories per system and upset pressure & temperature per line
- Output: Flanges classes, P-T (rating & value) per class, categorize each line reference
to (Flanges classes + Material categories), tag each line categorize (PMC Tag)
- Result
System No.
Flanges class
P-T Rating
P-T value
1
2
600#
1500#
102.1 bar
258.6 bar
69.4 bar
213.3 bar
part 2: Wall thickness
- Reference: ASME B31.3 (Appendix A Table A-1/M and Table
302.3.4 & Table A-1B),
MSD
- Input: P-T rating & value per PMC Tag, allowable stress per
material category, C.A
- Output: Minimum required thickness per size & PMC Tag
part 3: Schedule selection (SCH Slec):
-
Reference: ASME B36.10 & 19 table
Input: Minimum required thickness
Output: Purchase pipe wall thickness per size & PMC Tag
Results
System No.
Flanges class
P-T Rating
P-T value
1
2
600#
1500#
102.1 bar
258.6 bar
69.4 bar
213.3 bar
For system 1
For system 2
part 4: (Fittings)
- Reference: ASME B16.9 & ASME B16.11 Table 7
- Input: Purchase pipe wall thickness per size & PMC Tag
- Output: Purchase fittings wall thickness per size and classes and this table
for small bore sizes, because the large bore size follow the pipe SCH
Results
System No. Flanges class
SCH
SW
1
2
SCH160
SCH40S
6000#
3000#
600#
1500#
NPT
3000#
3000#
Part 5
- Reference: ASME B 16.48, MSS SP 95, MSS SP 97
- Input: Purchase pipe wall thickness, flanges classes
- Output: Purchase fittings (wall thickness and classes) per size & PMC Tag
- Results
Syste
m No.
Flanges
class
1
600#
2
1500#
SCH
SCH
160
SCH
40S
Line
planks &
gaskets
swage
Thredolet
Sockolet
Weldolet
600#
SCH 160 3000#
6000#
SCH 160
1500#
SCH40S 3000#
3000#
SCH40S
Part 6: (Valves)
Reference: MSD, API 6D, API 600, API 602
- Input: Flanges classes & PMC Tag
- Output: Valves classes
-
Note : Due to the complicity of API valves technology, it has separate program
2. Calculate the test pressure of the two systems for NPS 24”
(system 1) and 3” (system 2), please demonstrate your answer
the used code paragraphs NO. and show the St/S ratio, test
pressure @ (rated pressure value, design pressure value, and
yield strength)
Solution:
-Reference to:
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
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Chapter VI
Inspection, Examination, and Testing
345.4 Hydrostatic Leak Test
345.4.2 Test Pressure
The hydrostatic test pressure at every
Point in a metallic piping system shall be as follows:
(a) Not less than 1.5 times the design pressure.
(b) When the design temperature is greater than the
Test temperature, the minimum test pressure, at the
Point under consideration, shall be calculated using
PT = 1.5 PST/S
Where
P = internal design gage pressure
PT = minimum test gage pressure
S = allowable stress at component design temperature
For the prevalent pipe material
ST = allowable stress at test temperature for the Prevalent pipe
material
If the temperature of carbon steel exceed 300 C
The ratio of St/S will be high.
The pressure test above yield stress causes failure to system,
but we control it by determine the maximum ( Rated pressure
,yield stress )
- System 1 (600#)
A333GR6
When the design temperature exceed the test temperature
Pt = 1.5 PSt/S
St = 20000 psi
S =19900 psi
Pt= 1.5x60x (20000/19900) =94.73 bar
600# rated pressure =1.5 x102.1=153.15 bar
Thickness of 24” =28.007 mm
the yield stress=
The yield stress of A333GR6 with thickness 28.007mm=35000 PSI
The test pressure in the safe zone
System 2 :
We calculate the thickness at 3”
The pressure temperature rating =1500#
The pressure rating =255.3 bar
Super duplex material: A790-S32750
PT = 1.5 PST/S
Where
P = internal design gage pressure
PT = minimum test gage pressure
S = allowable stress at component design temperature
For the prevalent pipe material
ST = allowable stress at test temperature for the Prevalent pipe
material
A790-S32750
P =200 BAR
St=38700 psi
S=38500 psi
The ratio =38700/38500
Pt=1.5x200x(38700/38500)=301.55 bar
1500#The Rated pressure=1.5 x 255.3=382.95 bar
The yield stress at the thickness(11.13mm)= 79770.8 psi
The test pressure in the safe zone