Hydrostatic test
Could someone give me some guidance on hydro test pressure, Im looking at sect, VIII div 1 Under UG-99 Standard Hydro test. (b) vessels designed for internal pressures shall be subject to a hydro test pressure which every point in the vessel is at least 1.3 times the maximum allowable working pressure to be marked on the vessel multiplied by the lowest ratio (for the materials being used) of the stress value S for the test temp on the vessel to the stress value S for the desighn temp (see UG 21).
Im not sure I understand this portion….. multiplied by the lowest ratio (for the materials being used) of the stress value S for the test temp on the vessel to the stress value S for the design temp (see UG 21).
Id like to know if someone can clearify how I come up with the test pressure…please give an example if possible?
How is this calculation done, and how do I determine what the maximum would be?
MDK

Mike,

Write down Stest (at the test temperature) and Sservice (at the service temperature). Divide them, so you get a number >=1. Do it for each detail of pressurised stuff. Choose the smallest number. Multiply this number by your MAWP and by 1.3. That's your (minimum!) test pressure value. Clear now?

_________________
Konrad Anikiel

Write down Stest (at the test temperature) and Sservice (at the service temperature).
Could i have a bit more detail on these numbers and where i get them from?
What would be the max is there a calculation for max?
MDK
Also can i get an opinion on this
#150 flange required 30bar- hydrotest & #600 flange required 110bar-hydrotest; if both are connected in a same piping spools have i to test at lower or higher pressure (code of construction B31.3)
thks
MDK

S (at test Temp) and S (at service/ design temp) are allowable stresses at Test Temp and Service/ design temperature respectively.

Please refer ASME Sec II, part D for allowable stresses of material.

Piping Spools with different pressure ratings shall have different design pressure and therefore required to be hydrotested at different test pressure. Such piping spools are therefore required to be hydrotested separately.

If flange ratings are different due to some other reason such as piping spec break (design pressure is same), hydrotest shall be based on design pressure of piping spool and not on flange with higher rating.

Regards

Mike

Lets take an example

A pressure vessel is has MAWP 6 barg, and 325 deg C as design temperature. MOC is SA 516 Gr. 70.

Hydrostatic pressure = 1.3 x MAWP to be marked on the vessel x lowest ratio of the stress value S for the test temperature on the vessel to the stress value S for the design temperature

Now stress value at hrdrotest temperature = 138 MPa. ( Vessel will be hydrotested at ambient temperature)
Stress value at design temperature = 132 MPa. (Note that it is the stress value at design temperature, and not the operating temp)
For these values, refer ASME Sec II Part D, Page 16, Table 1A

= 6 x 138/132