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Up Topic Welding Industry / Inspection & Qualification / Hydrostatic test pressure
- - By waqasmalik (**) Date 05-16-2017 13:42
Hello all.

I recently learned that when hydrostatic pressure testing is to be carried out at higher temperatures than room temperatures then formula changes a bit from

Test pressure= 1.5* Design Pressure

Test pressure= 1.5* Design Pressure * Tensile strength at room temperature/ tensile strength  of the material at required test temperature

The question is where exactly in any book or literature i can find the tensile strength of materials at different temperatures? Or should i actually conduct a tensile test at required temperature.

Thanx all in advance.
Best regards
Parent - - By 803056 (*****) Date 05-16-2017 13:52
Good question. Perhaps ASM may have some information on that subject. However, they sell information, they don't give it away.

Short of that, you would have to establish it be testing a statistically significant number of samples.

Best regards - Al
Parent - By welderbrent (*****) Date 05-16-2017 14:55
I would have to check the bookstore for them out again, but, doesn't ASNT have material for hydrostatic testing?  I'll see if I can find what I am thinking I saw.

He Is In Control, Have a Great Day,  Brent
Parent - By waqasmalik (**) Date 05-16-2017 16:06
I check it now. I have ASM handbooks
Parent - - By waqasmalik (**) Date 05-16-2017 16:30
The material is 34CrMo4
Parent - By welderbrent (*****) Date 05-16-2017 16:49
By 'material', I was referring to study material for some of their specialized testing and qualifications.  Leak testing, etc.  I thought they had info on Hydro but I haven't had time to look into it.

Parent - By Joey (***) Date 05-17-2017 01:57
Interesting, what code you are reffering to? ASME VIII Div I states the following:

It is recommended that the metal temperature during hydrostatic test be maintained at least 30°F (17°C) above the minimum
design metal temperature, but need not exceed 120°F (48°C), to minimize the risk of brittle fracture.

The test pressure shall not be applied until the vessel and its contents are at about the same temperature. If the test temperature
exceeds 120°F (48°C), it is recommended that inspection of the vessel required by (g) be delayed until the temperature is reduced to 120°F (48°C) or less.

(g) Following the application of the hydrostatic test pressure, an inspection shall be made of all joints and connections.
This inspection shall be made at a pressure not less than the test pressure divided by 1.3....
- - By 803056 (*****) Date 05-16-2017 17:20
My question is, "Why are you performing the hydrostatic test at a temperature above ambient?"

The typical problem is that the test fluid (water) is at a temperature below ambient and the danger is brittle fracture if the material is thick and experiences increased brittleness at lower temperatures.

What is the test fluid and what temperature is the test to be carried out?

Interesting problem.

Parent - By waqasmalik (**) Date 05-17-2017 01:30
Actually the storage medium in pressure vessel is at higher temperature. Its a 75 degree Celsius storage of some gaseous fluid.
Parent - - By waqasmalik (**) Date 05-17-2017 01:33
Im sorry. Actually i should have said that hydro static testing of a pressure vessel in which storage medium is higher temperature than normal room temperature. In every case, hydro testing will be at normal room temperature but test pressure will change,.
Parent - By 803056 (*****) Date 05-17-2017 01:57
That makes more sense to me now. The hydrostatic test is intended to detect leaks. Care must be taken not to exceed the yield strength of the material. So, testing at room temperature, above the transition temperature of the base metal to mitigate the possibility of brittle fracture.

Best regards - Al
Up Topic Welding Industry / Inspection & Qualification / Hydrostatic test pressure

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