Re: natural gas black pipe unions
Posted by keith the steamfitter on January 01, 2004 at 23:24:06:
In response to Re: natural gas black pipe unions
: does one use thread sealant on the face of a union / the large threading nut? I know the two small pieces that thread onto both ends of the black pipe obviously do receive thread sealant.

the first thing that you have to realize, it that the compound used, generally a pro-dope type product, is a lubricant, the seal is provided by the pitch of the threads and proper threading of the pipe. it IS certainly a good idea to 'dope' the face of the union prior to installing the face and collar. the brass is much softer than the steel and it will allow proper seating. another rule of thumb i use, never, NEVER use a 150lb union. for the sake of a few dollars, invest in a 300lb union for the simple fact you will have less leaks and/or problems. the money you spend on the union will be saved in ever having to go back a fix it.

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