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Ground union joint

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TheValveLady

TheValveLady

Industrial
Joined
Jun 6, 2023
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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)
 
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Thanks GBT. In my limited time on the PFF side of things, this is the first I have encountered the GJ.
 
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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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