Maximum Allowable Surge Pressure per ANSI B31.1 in 1974

[whoowho]

A client has asked me to do some hydraulics calculations on a power plant built in 1974. Client tells me that maximum allowable surge pressure is 120% of maximum allowable operating pressure (MAOP) per the 1974 edition of ANSI B31.1, which governed the design at the time. However, I can't find a copy of ANSI B31.1 going back to 1974 to confirm the statement. Does anyone, know where I can get my hands on a copy of ANSI B31.1 (1974), or can anyone confirm that the MASP is 120% of MAOP for power plant piping constructed in 1974?

 

[rconner]

I’ve noticed noone has responded to your inquiry. While I'm not going to purport any expertise in this code I wonder if one reason for this could be that the specific verbiage/limitation you’ve asked about might not really have been in this code?

However, while I likewise do not have a copy of any earlier code I believe ANSI B31.1 1977 contained the words in Section 102.2.4 Ratings: Allowance for Variation from Normal Operation.

“Either pressure or temperature or both may exceed the design values, if the calculated stress in the pipe wall does not exceed the maximum allowable stress value from Appendix A for the coincident temperature by more than (a) 15 percent during 10 percent of any 24 hour operating period or (b) more than 20 percent during one percent of any 24 hour operating period.”

[Incidentally, while you would have to look at the pertinent table in “Appendix A” for the specific “maximum allowable stress value” and temperature ranges etc. applicable, I think this was at normal temperatures about a fourth of the tensile strength value for some steel pipes at least in 1977.]

 

[rconner]

[oops, I probably should have said, to be a little more precise in my last bracketed sentence, "...about a fourth of the minimum tensile strength requirement."]

 

[whoowho]

Thanks for that info. The content from 1977 version appears to be consistent with verbiage in the 1998 version, which is as far back as I could find. I will have to assume the limits identified in Section 102.2.4 haven't changed since 1974 and ask the client to prove otherwise.

 

[JohnBreen]

All,

I will confirm that wording close to that quoted goes back at least as far as the 1967 edition of the USAS B31.1 Code:

From paragraph 102.2.4 Ratings, Allowance for Variations from Normal Operations

........"Either Pressure or temperature, or both may exceed the design values if the stress in the pipe wall calculated by the formulas using the maximum expected pressure during the variation does not exceed the S-value allowable for the maximum expected temperature during the variation by more than the following allowances for the periods of duration indicated:

(1) Up to 15 percent increase above the S-value during 10 percent of the operating period.
(2) Up to 20 percent increase above the S-value during 1 percent of the operating period"

The "S-values" in the 1967 B31.1 Code were of course were the allowable stresses as provided in Appendix A. For ferrous Materials below the creep range the basis of the allowable stresses was the least value of 25 percent of the specified minimum tensile strength at room temperature or 25 percent of the expected minimum specified tensile strength at temperature or 62.5 percent of the minimum expected yield strength for 0.2 percent offset at temperature.

The 1967 edition of the "B31.1.0-1967" Code (total of 68 pages) marked the time when the B31 Codes for Pressure Piping were broken out into separate sections from B31.1.o through B31.8.0 but before B31.6.0 was issued it was pulled into B31.3.0.

I would have to go down into my basement to get out copies of the B31.1 Code and it addenda prior to 1960 (and prior to the the 1955 B31.1.0 Code and addenda) and to do that I would have to fight a battle with the spiders whose homes would be disrupted by such a quest.

Regards, John