Maximum hydrostatic test pressure - ASME VIII

[mech8790]

Hello everyone!

Can somebody help me to find if the ASME VIII div 1 code can help in determining the upper limit of the hydrostatic test pressure for a can or head? I have read UG-99 and I am not sure if this is out of scope of ASME VIII.

Regards!

 

[david339933]

There is no upper limit. UG-99(d) "...This division does not specify an upper limit for hydrostatic test pressure....".

 

[mech8790]

That's right, but you can't apply any test pressure you want, can you?

 

[david339933]

UG-99 states minimum test pressures only. You can certainly go higher...as stated in UG-99(d). But if the vessel shows "visible permanent distortion, the inspector shall reserve the right to reject the vessel."

 

[mech8790]

Is there any way to calculate how high I can go?

 

[david339933]

For what purpose?

 

[mech8790]

Good question! Let's say it is imposed by a client and there is a reason to do it.

 

[CuMo]

Calculate the maximum allowable working pressure for the component using 90% of material yield strength at ambient temperature.
This should be your maximum allowable test pressure.
However the straight flange (cylindrical shell portion) might govern this value so make sure you account for both (dish & cylinder).
I wouldn't push it this far if not necessary.

 

[TGS4]

Unless your client specifies a criteria, use your good engineering judgement. 90% of room temperature engineering yield in a general membrane categorization is often used by many organizations. If you don't know better/different, that's a good place to start.

 

[mech8790]

Hi!

Thank you for your reply! I have used in my calculations the material yield strength from the table 1A, section II part D. Is the value listed in this table with embedded factor of safety from table 1-100, mandatory appendix(2/3 of Sy)which is only 66% of the yield strength?

 

[TGS4]

Nope. It's the actual minimum specified engineering yield.

 

[mech8790]

Are you sure? Mandatory appendix 1 is the basis for establishing stress values in tables 1A & 1B. Sy is the specified minimum yield strength at room temperature. In the table 1-100, column yield strength we can read 2/3Sy value. I agree whith you that this is the actual specified engineering yield, but the material itself in reality is stronger.

Anyway, can I use this value of the yield strength in my calculations? Someone told me that the maximum allowable stress at the room temp. should be used instead.

 

[r6155]

I think that the intention of your client is the special test in UG-99 (c).

Regards
r6155

 

[TGS4]

Ok. You have me completely confused about what you're doing. Yield stress is obtained from Table Y-1, although the room temperature yield is also listed in Table 1A.

The allowable stress is used for design. And although there is no limit in VIII-1 for the test pressure, many owners specify some fraction of room temperature yield in the general membrane stress.

Do you have any mentoring or technical oversight at your work? Sounds like you need some? Have you ever obtained training on the Code?

 

[mk3223]

Typically for the process improvement or upgrade, the alternative option is to reuse the existing vessels for the process conditions higher than the current design. In this case, one may check it with the allowable pressure condition with an established safety factor by Code. You may push it to the 90% of the yield strength if you have a good reason for it, and of course, by taking a potential risk.
IMO, there is no need to go over this limit since no one, both Engineer and Client, will take the responsibility for it.

 

[r6155]

mk3223
We are talking about new pressure vessel.

Regards
r6155

 

[mech8790]

All my work is checked by a third party body so don't worry TGS4. I am just looking for some answers here, on the forum, cause I would like to know the other's people point of view.

 

[KevinNZ]

"existing vessels for the process conditions higher than the current design"

Does mean you using a high pressure test to change the design pressure of the vessel?