Insp nspe ect ction ion Proc roce edur dure e 01-SAIP-02
31 May, May, 2004
Retirement Thickness of In-Plant Piping Document Responsibility: Inspection Department
Saudi Saudi Aramco Aramc o Desk DeskTop Top Standards Standards Table Table of Cont ents 1 2 3 4 5
Scope............................... Scope............................................. ........................... ................ ... 2 Purpose................................ Purpose.............................................. .......................... ............ 2 Applicable Documents........................... Documents................................... ........ 2 Definitions........................... Definitions........................................ .......................... ............... 2 Calculation Procedure.............................. Procedure................................... ..... 3
Appendix I – Retirement Thickness Determination Tree............... T ree............................ .................. ..... 5 Appendix II - Typical Example of Calculation Procedure........................... Procedure............................. 6
Previous Issue: 31 December , 2000 Next Planned Update: 1 June, 2009 Revised paragraphs are indicated in the right margin Primary contact: contact: Supervisor, IEU on phone 874-6604 874-6604
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Document Responsibility: Inspection Dept. Issue Date: 31 May, 2004 Next Update: 1 June, 2009
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2
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01-SAIP-02 Retirement Thickness of In-Plant Piping
Scope 1.1
This SAIP establishes criteria for determining retirement thickness for INPLANT metallic piping designed per ASME B31.3.
1.2
Some corrosion patterns, such as pitting, may require additional considerations. For evaluation of this type of corrosion, contact the Inspection Department / Operations Inspection Division.
1.3
The structural retirement thickness' in this SAIP do not pertain to buried piping. The requirement for retirement thickness of buried piping is based on pressure / temperature design only.
1.4
This SAIP is intended to establish a standardized methodology by Saudi Aramco inspection personnel in the implementation of inspection programs within Saudi Aramco facilities. The SAIP shall not be included in purchase orders or contract documents issued to outside agencies.
Purpose 2.1
The objective of this SAIP is to specify the basic requirements of calculating the retirement thickness of in-plant carbon steel piping. This thickness may be dictated by either hoop stress at design pressure and temperature or by structural limitations.
2.2
The criteria for retirement thickness, as established by this SAIP shall be used in the preparation of Safety Instruction Sheets (SIS) (refer to SAES-A-005 and SAES-L-125.
Applicable Documents 3.1
Saudi Aramco References Saudi Aramco Engineering Standards
3.2
SAES-A-005
Safety Instruction Sheet
SAES-L-125
Safety Instruction Sheet for Piping and Pipelines
SAES-L-310
Design of Plant Piping
Industry Codes and Standards American Petroleum Institute API STD 574
Inspection of Piping, Tubing, Valves, and Fittings
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Document Responsibility: Inspection Dept. Issue Date: 31 May, 2004 Next Update: 1 June, 2009
01-SAIP-02 Retirement Thickness of In-Plant Piping
American Society of Mechanical Engineers ASME B31.3
Process Piping
American Society of Mechanical Engineers ASME SEC VIII
4
Rules for Construction of Pressure Vessels
Definitions 4.1
tm =
The Minimum Required Wall Thickness in inches, including the corrosion allowance.
Commentary Note: It should be noted that there is a terminology difference between ASME B31.3 and ASME SEC VIII. The t in ASME B31.3 includes the corrosion allowance. The t in ASME SEC VIII excludes the corrosion allowance. m
m
4.2
t
=
1.
The Retirement Wall Thickness in inches, which is the greater of: Pressure Design Thickness. or
2.
Minimum Structural Thickness (tstr ) required to withstand the stresses imposed by the weight of the line and its contents.
4.3
c
=
Corrosion Allowance in inches (based on corrosion rate and next inspection).
4.4
The relationship between the retirement wall thickness (t) and the minimum required wall thickness (tm) is as follows: t = tm - c
or
tm = t + c
tm = retirement thickness as per ASME
5
Calcu lation Procedur e The retirement wall Thickness (t) of piping shall be equal to the greater of the values: 1.
calculated in paragraph 5.1 or
2.
designated in paragraph 5.2, table 1, as shown below:
5.1
Pressure Design Thickness
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Document Responsibility: Inspection Dept. Issue Date: 31 May, 2004 Next Update: 1 June, 2009
01-SAIP-02 Retirement Thickness of In-Plant Piping
The thickness required for design pressure, in accordance with the following Barlow's equation of ASME B31.3: t
=
PD (2SE)
Where: P =
Internal Design Pressure (psig). For critical piping as defined in SAESA-005, the design pressure is given in a Safety Instruction Sheet (SIS). If no SIS is available, other sources of design parameters are: •
•
•
5.2
Name plate of connected fixed equipment, such as pressure vessels or pump performance curve pressure at zero flow with the pump located at or lower than the elevation of the subject pipe. Relief valve settings. Other plant drawings, such as Process and Instrument Drawings (P&ID's), Process Flow Diagrams (PFD's), or line designation tables.
D =
Actual Outside Diameter of pipe in inches. From Table 1 API STD 574.
E =
Longitudinal Weld Joint Quality Factor as specified on Table 302.3.4 of ASME B31.3 or Table A-1B of ASME B31.3.
S =
Basic Allowable Stress (psi) for metals at design temperature, from Table A-1 of ASME B31.3.
Minimum Structural Thickness (Tstr ) The minimum structural wall thickness (tstr ) required is determined from Table 1 in SAES-L-310 section 10. In Appendix 1D: Pipe Actual Outside Diameter Table 1 API STD 574.
31 May, 2004
Revision Summary Revised the” Next Planned Update”. Revised Structural thickness to align with SAES-L-310 and reissued with editorial changes.
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Document Responsibility: Inspection Dept. Issue Date: 31 May, 2004 Next Update: 1 June, 2009
01-SAIP-02 Retirement Thickness of In-Plant Piping
APPENDIX I RETIREMENT THICKNESS DETERMINATION TREE
D: Pipe Actual Outside Diameter
P: Internal Design Pressure
t =PD/(2SE) Barlow's Pressure Design Formula ASME B31.3
S: Basic Allowable Stress Table A-1 ASME B31.3
Thickness Based on Structural Thickness From Table 1 SAES-L-310
E: Weld Joint Quality Factor ASME B31.3 Table 302.3.4
The Larger of the Two Values
Retirement Thickness (t)
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Document Responsibility: Inspection Dept. Issue Date: 31 May, 2004 Next Update: 1 June, 2009
01-SAIP-02 Retirement Thickness of In-Plant Piping
Ap pen di x II – Ty pi cal Exam pl e of Calc ul ati on Proc edu re Calculate the retirement wall thickness (t) for the following pipe: Nominal Diameter = 8 Inches (Actual OD = 8.625") Internal Design Pressure (P) = 500 psi Design temperature = 300°F Material = Carbon steel, API 5L Grade B, Seamless. Flange Rating = 300# 1.
Thickness required for pressure/temperature design: From Table A-1 of ASME B31.3 S = 20,000 psi E =1 (Seamless) t = PD/2SE = 500 (8.625)/2(20000) (1) = 0.108"
2.
From SAES-L-310 Table 1, the minimum structural wall thickness (tstr ) is 0.10" The retirement wall thickness (t) for this pipe is limited by the pressure design requirement and is 0.108".
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