Field Test Pressure

[dbday]

Hi,

Can anyone tell me how to work out the Field Test Pressure for an ASME VIII Div 1 pressure vessel.

I know how to work out the shop test pressure, but am not sure if shop and field test pressures are really one and the same thing.

Thanks

 

[vesselfab]

shop test is in horizontal position

field test is corroded condition and in vertical position.

Static head on lower sections of tower have to be considered.

But the real danger is skirt on a tall tower that is not originally designed to be full.

 

[MrTank]

vesselfab,

are you stating that in general, shop tests are done in horizontal position? How come compress allows shop testing in vertical position and checks if all parts/components are under the allowable stresses including hydrostatic pressure?


-MechCiVAero

“I have not failed. I've just found 10,000 ways that won't work.”
-Thomas A. Edison

 

[metengr]

Field test could imply a pressure test on an in-service vessel. In this case, the original code of construction hydrotest would not apply.

Field test could also mean a code required hydrostatic test on a new vessel installed in the field. Which one applies, in-service or new construction?

 

[jtseng123]

dbday,
For vertical tower, you shall work backward :
1. Calculate test pressure per code formula, say 400 psig ( don't worry about vertical position or horizontal position).
2. Get the static head from face of flange of top nozzle to face of flange of bottom nozzle in vertical position, say 100 psig.
3. wow, now you have total of 500 psig. Check flange rating table, the test pressure shall not exceed 1.5x rating pressure. If it exceeds, you have to change the flange one class higher. You will need to check many bottom nozzles.
4. Alright, the nozzle problem taken care of so far, now you completely meet code requirements, and fulfill many project specification requirements that vertical vessel shall be designed for future hydrotest in vertical and corroded condition.
5. Now work backward: The test pressure in horizontal position for a vertical tower shall be = 500 psig from point 3 - static head in horizontal position, say 15 psig = 485 psig. This is the test pressure must be read from pressure gauge at shop in horizontal position. You will be sleeping well now.
6. For sure your skirt and foundation must be designed for hydrotest weight with reduced wind /seismic loads per many project specifications around the world.

Commercial program will check stresses at all components, and give you warning sign if exceeding 90% of the yield for carbon steel.