B31.3-2008 Hydrostatic test pressure limitation

[timsch]

In this code, I see a requirement for Hydrostatic Testing of piping systems that the test pressure be 1.5X the design pressure.

I am puzzled by section 345.2.1 "LIMITATIONS ON PRESSURE" that states the following:
(a) Stress Exceeding Yield Strength. If the test pressure
would produce a nominal pressure stress or longitudinal
stress in excess of yield strength at test temperature, the
test pressure may be reduced to the maximum pressure
that will not exceed the yield strength at test temperature.
[See paras. 302.3.2(e) and (f).]

345.2.1a seems to void the previously stated 1.5X pressure test requirement. Please correct me if I am misinterpreting this.

 

[jte]

You are not misinterpreting.

All the Code is saying is that if the hydrotest pressure as calculated at 1.5x would potentially damage the system, then don't do it. No sense in requiring a test which would be expected to fail the system.

jt

 

[BigInch]

Its not voiding the other clause; its simply a limitation to it's applicability. This clause also says, "may", so it leaves the option open.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[timsch]

Thank you for the responses. I am just somewhat baffled by an engineering standard that is not somewhat firm regarding a safety factor, especially considering the wording in 345.4.2 Test Pressure:

Except as provided in para.
345.4.3, the hydrostatic test pressure at any 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
82
under consideration, shall be calculated by eq. (24).

If the 50% SF were a recommendation, I would have expected slightly different wording. I am still getting familiar with the ASME standards, and in light of this, I don't think I will ever forget the hilarious "Always, Sometimes, Maybe, Except" acronym explanation that I saw in a post on this forum recently

 

[BigInch]

The 1.5 is not a safety factor. It is a proof that a safety factor of 50% exists.

b) is just normalizing the design conditions to standard conditions.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[timsch]

Agreed - 1.5 is not a safety factor in itself.