Gasket used in hydrotest 3

[Deccocwb]

Some gaskets specified in mechanical design is very expensive and I´m looking for a low cost solution for gaskets to be used in ordinary hydrotest for ASME VIII div 1 vessels. Could I use a gasket, different from that specified in mechanical design, only to perform the Hydrotest?

I think, if I use a different gasket but specified for the hydrotest pressure and compatible with the vessel's flange, it will be ok! Since the hydrotest is performed in controlled area and short time...

 

[SnTMan]

Deccocwb, most often the service gaskets are used for hydro (the customer often insists) and the unit is not broken afterwards.

In cases where it is necessary to open a bolted joint after hydro, a hydrotest gasket may be used in place of a service gasket, and I have had this situation exist on a recent job. Following reassembly, some means is needed to test the affected bolted joint, and it is often done with a relatively low pressure air test.

For this type of situation it is good to get buy-in from the customer and especially the AI.

Regards,

Mike

 

[dig1]

My only comment with this is that I have seen a very soft (forgiving)gasket used for hydro and it does not leak but when the unit is placed in service with a harder gasket the unit does leak.

This is more of a case with specially fabricated flanges (in the case I am referencing it was fabricated rectangular flanges) where the surfaces were not machined properly and the softer gasket conformed to the irregularities and the required service gasket did not.

Typically, I specify that the hydrotest gaskets be equalivent to the services gaskets, especially when fabricated flanges are used (in addition to make sure there is proper tolerancing on the flange).

While this can be perceived as expensive it really isn't when you are on a shutdown replacing a piece of equiment and you are starting back-up and the connection/attachment point starts leaking.

 

[SnTMan]

dig1, good point, it is important to match somewhat the characteristics of the two gaskets used, so the hydro gasket is a reasonable substitute for the service gasket.

Regards,

Mike

 

[Apakrat]

Back in my days of hydrostatic testing of cross country pipelines and facilities, all gaskets, including seals of gate valves, pig launcher settings, etc. had to withstand a pressure test exceeding pipe yield point, plus holding of that pressure with no loss, for a minimum of 24 hours.

Only welds at the pipeline tie-in joints, were not tested.

Have found and replaced failed valves up to and including 36" ID. Never had a valve manufacturer to dispute of refuse to pay for cost of replacements, when presented documentation.

Sure is hard for me to understand concern of a few cents of cost in the price of a gasket, over the potentials of a gasket failure that may cause loss of life, period!


At 74th year working on IR-One2 PhD from UHK - - -