Allowable Stress for Hydrotest 2

[hamid.njd]

Dear All

I have a qouestion:

In hydrostatic test calculation, what is the allowable stress reference when considering not 90% of the yield stress?
I checked. It is 1.3 times the allowable stress data that is mentioned in Sec.II-D. But I wanted the reference for it.
Can anybody help me?

Thanks in advance

 

[mk3223]

What's the hydro testing you are applied to?

Or, may see the previous discussion per thread794-475211 for reference,

 

[TGS4]

It depends on your Code of Construction. Which Code are you fabricating to with respect to this question?

 

[GD2]

Hamid,
Like other members pointed out, the hydrotesting test pressure and allowable stress depends on to what code is vessel is constructed. It also depends on whether the vessel will be tested vertical or horizontal and whether you are testing it as a Manufacturer or Owner after installation.
if the vessel is constructed to ASME Sec VIII Div 1, calculate the hydrotest test pressure as 1.3 MAWP x lowest stress ratio (S_T/S) of the pressure boundary parts. There is no max pressure limit given by the code. However, it is always good to check that the primary membrane stress do not exceed 0.95Y_S of any pressure boundary parts.
If you want to test the vessel vessel, you need to check if the shell and the bottom head has the required thickness with the adjusted liquid head. For horizontal testing, this check is not required as it is considered negligible.

GDD
Canada

 

[hamid.njd]

Dear All; Thanks for your answers.

The design Code is ASME SEC. VIII-D1. I know how to calculate the test pressure according to UG-99. But the question is "What is the allowable stress for the hydrostatic test?"
According to the SEC. VIII, the maximum allowable stress for the hydro test is 90% of yield stress. But, normally it is not 90%.
I want to know the reference for allowable stress value in hydrostatic case?

 

[DriveMeNuts]

As written by others, there is no allowable hydro test stress for div 1.
If you use 1.3x design pressure then you are sorted, and therefore there is no need for a stress limit.
If you for some reason do need an upper-stress limit, then take inspiration from another code such as VIII Div 2.

 

[hamid.njd]

If there is so, why does the PV Elite use, for example, 179.3 Mpa for hydrotest allowable stress in SA-516 70 material?

 

[DriveMeNuts]

I don't know. How about rather than being spoon-fed answers, you actually do some research? The PV Elite Manual probably contains your answer.

 

[SnTMan]

hamid.njd, converting units, 179.3 Mpa = 26000 psi = 1.3 * 20000.

One-point-three times the ambient allowable for the material. Programmers lazy short-cut.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[IdanPV]

hamid.njd,

Your statement: "According to the SEC. VIII, the maximum allowable stress for the hydro test is 90% of yield stress." is incorrect.
ASME Section VIII-1 not fully address this issue, what it does state is that "...above to the degree that the vessel is subjected to visible permanent distortion, the Inspector shall reserve the right to reject the vessel..."

Now, if you want to prevent the formation of the "permanent distortion", you shall calculate the stresses caused by the test pressure and make sure it does not exceeded the Yield strength of the material (or 90% of the Yield).

 

[r6155]

@ hamid.njd
You are very confused. Try manual calculations before using computer programs.
I suggest training.

Regards