6 replies to this topic

[freeman]

Dear All,

 

I wish to know how to calculate the design pressure and temperature of piping.

 

Are they related to the conditions of upstream or downstream equipment.

 

Thanks.

[Ajay S. Satpute]

Hi,

 

Please refer Norsok standard P-001 (Process design).

 

Regards.

 

Ajay

[breizh]

Consider the resources attached .

 

Breizh

[kkala]

Thanks, Breizh, for the useful 'Piping Classes.pdf' concerning selection of piping materials , as written in the introduction. I have been searching for such a document, as a useful example. It does not specify design pressure / temperature of piping, which is a subject in "NORSOK Process Design P-001.pdf", but it explains how e.g. pipe thickness is selected once pipe diameter and design pressure / temperature have been fixed.
It is also clarified in para 4.1 (seamless pipe) that only A-333 Gr6 is recommended down to -50 oF design temperature (-45.5 oC) out of mentioned carbon steel (CS) pipes, rest reported CS pipes shall be used to -20 oF (-29 oC).
For example, let us try to specify pipe thickness for hydrocarbon condensate, DN=10", design pressure=650 psig - design temperature=300 oF for the project having adopted "Piping Classes.pdf".
Appendix A indicates that suitable class is B01, rating=300 Lb, material=CS, corrosion allowance=1.6 mm, limit  655 psig for 300 oF; fluid symbol=HC (to be used in the line 'name', on line list and PID).
Appendix B says in addition for class B01: Sch40 (for 10" diameter pipe) seamless pipe of  CS A106 B. Flanges and gaskets shall be of  300 Lb rating.
Just to roughly verify  thickness: allowable stress SE=20000 psi (table 10-49), external pipe dia D=10.75 in (table 10-18), design pressure P=650 psig, coefficient y=0.4, t=P×D/(2×(SE+Py))=0.1724 in. Required wall thickness = t+corrosion allowance=0.1724 + 1.6/25.4 = 0.235 in, versus Sch 40 pipe of 0.365 in nominal thickness (Table 10-18) and minimum possible thickness 0.365×(1-12.5%) = 0.319 in (12.5% assumed thickness tolerance). So min thickness of Sch 40 pipe > required wall thickness.
It is noted that above thickness calculation is based on Perry's section "Transport and Storage of Fluids", subsection "Process Plant Piping". Tables in parentheses refer to 7th edition of Perry.
Piping can receive stresses additional to those caused by internal pressure, e.g. compressive stresses due to thermal expansion, due to water hammer, stresses due to bending if piping has individual supports, etc. Detailed stress analysis is responsibility of piping engineer.
Hopefully the example is helpful, comments welcomed.

Edited by kkala, 11 February 2013 - 03:54 PM.

[Art Montemayor]

The query presented by Freeman is how to CALCULATE the design pressure and temperature for piping.

 

The answer is:  YOU DON"T.  Design pressure and temperature are SPECIFIED, NOT CALCULATED.

 

Either you specify them or they are found specified in your Design Basis.  It is that simple.

[kkala]

Indeed, the query would be more precise by "how to specify the design pressure and temperature of piping" and the reference to Norsok standard P-001 is OK for this. It is not easy to be precise using a foreign language.

[Shivshankar]

Freeman,
 
You should refer to ASME B31.3 Process Piping. Charles Becht IV or CASTI Guide to ASME B31.3 by Woods and Bauguley for more details.
 
http://www.psig.sg/D...n of Metals.pdf

 

http://sections.asme...ipingDesign.pdf
 
Regards
Shivshankar

Edited by Shivshankar, 15 February 2013 - 04:27 PM.