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Ground union joint

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TheValveLady

Industrial
Jun 6, 2023
6
I did search for this topic, and let me tell you that I got a bunch of political results!

I am inquiring why a Ground Union Joint might be specified in lieu of a standard Union for a mining piping system. I have no data on the operating media or conditions. I only have this description: UNION, THRD, CLASS 3000, GROUND JOINT, STEEL-TO-STEEL SEAT, ASTM A182 GR F316/316L DC, MSS SP-83. Research tells me the ground union has a tapered conical seat, providing a larger sealing surface and that it's common in gas piping systems to prevent leaks of flammable gas. Makes sense but further reading states reliance on ventilation systems for this.

 
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To me a ground joint union (metal to metal machined seat) is standard and if I ordered a MSS SP-83 union I would expect to receive a GJ union. The only other style I am aware of is an O ring type union which relies on an O ring which degrades over time and as I recall is more typically used in a dielectric union (electrical isolation created across the joint).

(Would probably have better luck in the Piping forum)
 
Thanks GBT. In my limited time on the PFF side of things, this is the first I have encountered the GJ.
 
TheValveLady, just as an FYI there is a Valve Engineering Forum.

And, oh yeah, welcome to Eng-Tips :)

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
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