API 617 - allowable stresses in casing

[tigny]

Hello,

does anyone know why the allowable stresses in API 617 7th edition:2002 (axial and centrifugal compressors and expander compressors for petroleum, chemical and gas industry) are not equivalent to ASME II part D allowable stresses (I mean 2007 revision)?

I have found a 1999 draft for the 7th (present) revision of API 617 which proposed to use the sames allowables as ASME II part D.

But it didn't make it to the 7th edition.

Does anyone know why?

Has it something to do with the 1.5 times design pressure for the hydrotest, which is now 1.3 in 2007 revision of ASME VIII div 1?
[this corresponds to Tensile stress/4 or /3.5]

Below are excerpts of the current code and the draft's proposed terms.

yours truly,

current terms (7th edition-2002):
2.3.1 .I .1 The allowable tensile stress used in the design of the pressure casing (excluding bolting) for any material shall not exceed 0.25 times the minimum ultimate tensile strength for that material at the maximum specified operating temperature.
For cast materials, the allowable tensile stress shall be
multiplied by the appropriate casting factor as shown in Table 1.2-2.

proposed terms in 2nd draft od 7th edition (may 4 1999)
2.3.1.1 The hoop stress values used in the design of the casing for any material shall not exceed the values given for that material in Section II of the ASME code at the maximum operating temperature.
For cast materials the factors specified in Section VIII Division 1 of the ASME code shall be applied.
Pressure casings of forged steel, rolled and welded steel plate, or seamless piping with welded covers shall comply with the applicable design rules of Section VIII Division 1 OR 2 of the ASME Code.
Manufacturing data report forms, third party inspections, and stamping as specified in the ASME code are not required.
The casing design shall ensure that it is suitable for the maximum allowable working and test pressure (including hydrotest) and for all specified operating conditions. The
design shall include at least 3mm (1/8 inch) corrosion allowance.
Notes: 1. There are no pressure vessel codes applicable to this equipment. ASME
pressure vessel codes specifically excludes rotating equipment.
2. Corrosion allowance may not be needed for stainless material.

 

[pmover]

in the front section of the api-617 std, i believe there should be some reference to whom you can direct your question to within the API organization. if not there, then the information is certainly listed in the API website for the 617 std.

I would recommend directing your question directly to the API committee. btw, i have previous made requests and have received a response within the week.

should you do this, then please post the response from the API committee member - thanks!

good luck!
-pmover