Temperature vs Brittle Fracture during Hydrotest
Temperature vs Brittle Fracture during Hydrotest
(OP)
We are performing hydro tests outdoors in Alberta right now. I have been questioned about the effect on strength reduction when testing at lower temperature. I recall seeing a chart or graph where strength reduction was plotted against temperature. Can anyone assist here please??? We don't have an issue with our A333 Gr. 6 it is for hydro testing A106 Gr. B.
Thank you
Johnnyoo
Thank you
Johnnyoo





RE: Temperature vs Brittle Fracture during Hydrotest
Keep A106 above -20F
You should have Charpy Testing results on file tested at the lowest of ambient or design temperature whenever below 0F
RE: Temperature vs Brittle Fracture during Hydrotest
You should know what piping code that you are building in accordance with and what the temperature limitations are for various materials
Most piping codes contain tables with allowable stress levels based on temperature. For A106 materials, ASME B31.1 and B31.3 have the same allowable stress at -20F as 70F.
MJCronin
Sr. Process Engineer
RE: Temperature vs Brittle Fracture during Hydrotest
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Temperature vs Brittle Fracture during Hydrotest
RE: Temperature vs Brittle Fracture during Hydrotest
RE: Temperature vs Brittle Fracture during Hydrotest
RE: Temperature vs Brittle Fracture during Hydrotest
RE: Temperature vs Brittle Fracture during Hydrotest
RE: Temperature vs Brittle Fracture during Hydrotest
RE: Temperature vs Brittle Fracture during Hydrotest
From the many failures ( and hundreds of worker deaths) of the North Sea oil platforms of the 1960's and 1970's it was found that every weld contains at least 2 pre-existing micro-cracks, from the initial weld arc and from breaking the final weld arc. The stress concentration factor at the edge of a crack is roughly 5, and during a hydrotest the average metal is close to yield stress. Insufficient fracture toughness combined with a crack edge stress on the order of 4-5 times yield stress is a formula for failure. In addition to that issue, is the separate issue that many welds are not stress relieved.
So the matter is not so much allowable stress as it is fracture mechanics.
"Whom the gods would destroy, they first make mad "
RE: Temperature vs Brittle Fracture during Hydrotest
The BS British Standard codes of the 1970's incorporated fracture mechanics , which addressed the 1940's failures of the Liberty Ships and the 1960's failures of North Sea Oil platforms . Evidence of the BS fracture mechanics approach can be found in today's EN-12952-3 Annex B, comparison of weld notch factors, and the longstanding European explicit concern regarding weld fracture toughness ( not so explicitly a concern in US codes).
"Whom the gods would destroy, they first make mad "
RE: Temperature vs Brittle Fracture during Hydrotest
For ASME Section VIII, Division 1 pressure vessels, see UG-99(h), which says that
For pneumatic tests, UG-100(c) makes the 30°F (17°C) recommendation a requirement.
RE: Temperature vs Brittle Fracture during Hydrotest
Under specific environmental and stress conditions, methanol-induced intergranular cracking can occur in some pipe steel.
http://www.bst-tsb.gc.ca/eng/rapports-reports/pipe...