need help identifying threads

[packmule]

Recently had to replace steam jet nozzles on evaporator train at a paper mill recovery boiler. Of course, one out of six nozzles gaulded while we were attempting to unsrew it. Needless to say the internal threads were slightly damaged after we finally removed the nozzle. The solution to this interuption appeared simple-- go to machine shop and get tap to clean up threads. One problem, the major dia. of the threads on the nozzles measure .808 inches, or 20.5mm. I haven't bothered checking the pitch yet because I realized instantly we had an odd size and there's probably not one in the entire state. Couldn't find anything in Machinery Handbook on threads this size. Could this be special made to this application only? The nozzles screw into sch. 80 pipe and have 150 lbs. of steam going thru. Any ideas?

 

[deanc]

How bad is it? Does it have a seal? Have you contacted the original supplier?

Can you recut to a standard thread? Can you cut off and replace?

If you get in a pinch, sit down at bench and hand work them out, awl, Dremel, bent files. Been there before.

 

[europipe]

Maybe it's acc. ISO standard.
It looks like M24x2.0 to me but I'm not sure.
Is the pitch 2mm?

Greetings

 

[rmw]

If you can get access to the nozzle you can weld it to the steam chest. It will be a dissimilar metal weld but that shouldn't be rocket science around a paper mill.

Your danger in trying to repair the threads is that you don't get a tight joint and a seal where the nozzle attaches to the steam chest. Then you get wire drawing of the threads and leakage of the motive steam into the suction chamber adding to the jet's load.

Once you weld the nozzle when it wears out you have to replace the entire steam chest, but in a pinch, what the heck. Many people who don't like threaded nozzle designs take new jeta apart and weld the nozzles anyway.

rmw

 

[packmule]

Thanks to everyone for your responses. The threads turned out to be 1/2-14 NPSM (national pipe straight threads for mechanical joints) We found a tap locally and clean up the threads and welded a bead around the nozzle for safe-keeping. Thanks again.

Greg