plugs, caps, flanges for hydrostatic pressure test

[MWinczewska]

is there recomendation for the material type for plugs to pressure testing of the welded pipe line made by super duplex material and carbon steel with inconel clad. a specialy with thinking om contamination aspect. Recomendations in standars such as ASTM. if yes where can if find this in standards?

 

[metengr]

There is no requirement to use like for like materials on the pressure retaining part for plugs or blanks. For hydrostatic testing, material used for plugs or blanks must be designed to provide adequate strength at temperature (in this case the required minimum temperature) because after the hydrostatic test they will be removed and even possibly re-used. So, there is no hydrostatic testing standard that requires use of a specific material for plugs, caps and flanges.

Selection of a specific material type from one of the ASME B16.XX specifications or similar standards is based on engineering judgment. If you are attaching plugs or blanks by welding consideration should be given to provide enough base material to allow complete removal of the plug without affecting the pressure part base material.

 

[metengr]

Just to clarify - (in this case the required minimum temperature), this refers to the minimum hydrostatic test temperature.

 

[MWinczewska]

thanks for the answer metengr. Why is it minimum temp. not the maximum? sorry if this is stupied question I just dont know a lot about the pressure test. I'm asking about the contaminations from the carbon steel pressure plugs on stainless steel line. I know that the line have to be cleaned after pressure test. but any way what is the best practice in such a case...

 

[metengr]

MWinczewska;
I added the comment because when you select the material using a standard like ASME B16.5 or other, you need to know both pressure and temperature. Typically, I use the minimum temperature for the hydrostatic test. That is it.

 

[MWinczewska]

ok. thanks

 

[OGMetEngr]

Carbon steel contamination of duplex and other stainless steels should be removed by a pickling or passivation product. I would take a read of ASTM A380 (pickling and passivation) or of A967 (passivation). Passivation using nitric or citric acid may be sufficient, but if the contamination and corrosion is extensive, or if other contaminants other than iron are present, pickling using e.g. - nitric/hydrofluoric acid may be required. Look at the ASTMs as they detail all of this.