Vessel field pneumatic testing with piping together 1

[jtseng123]

Dear,

We have vessels with welded nozzles for LNG service. Shop has done hydrotested per UG-99(b)and code stamped. Field already welded all pipes to the nozzles and will go through pneumatic testing the entire system since isolation of the piping is not possible. For sure any pre-caution will be taken and follow very strict safety procedures. The question is, can we air pressurize to the original water test pressure per UG-99(b)? or we have to use reduced pressure per UG-100 (1.1x MAWP x stress ratio) ? Will the mechanical warranty be voided ?

 

[A clark]

As I understand it you are testing piping attachment welds that are welded to nozzles on the vessel. I agree with David that these welds are outside the scope of Section VIII. These welds should be tested in accordance with the Code for the piping (if any)and can be done at a reduced pressure. I would recommend the following.

1. Determine what if any piping code should be followed
2. If none perform volumetric examination of the weld.
3. Perform a low pressure leak test, such as a halogen test.
4. I would Article 10 of section V as a guide.

Hope this helps
Allan