Smith mills 4500 steam mud drum nip

hot1

Anyone ever changed a leaking mud drum nip on mills 4500 steam boiler?
Have repair nip. Just haven't done it before.

EBEBRATT-Ed

Yes. I have done lots of them.

Are you changing the nipple or just the gasket? Usually just the gasket leaks.

1. If changing just the gasket

a. Drain boiler, back off on nut. But before backing off the nut clean the threads on the nipple above the nut with a wire brush and put some penetrating oil on the threads above the nut. Then back off the nut as far as you can. Then scrape off the old gasket and clean up the gasket surface. There is a washer under the nut use the old one over if it is ok. Install a new "split" gasket. The split gasket comes with a string. Wrap the string around the gasket and tie an overhand knot. Then tighten the nut down on the gasket until the gasket squishes out to the same diameter as the washer. Don't over tighten. Fill the boiler and check for leaks. If the gasket leaks just snug, it enough to stop the leak. If you have to replace the metal washer remove the old washer by cutting it...tin snips usually work and install a split washer. It comes with a brass rivet. Drop the rivet in the hole (do not crimp the rivet it just sits in the hole) Then tighten nut as above.

b. Replace the entire nipple

a. You will need a split nut, a split washer and rivet, a half coupling (male x female) and a nipple

Cut the old nipple with a sawzall above the nut. Leave enough room to get a pipe wrench on the nipple coming out of the boiler section. Put a pipe wrench on the nipple near the boiler section. An 18" wrench with a cheater pipe is your best bet. Just try and break the nipple loose from the boiler section, that is the tough part. Once you get it to move stop and make another cut in the nipple and remove about 1" section of the nipple. If the nipple will not come out get a cutting torch and cut it out.Now remove the loosened nipple from the boiler section. Then put your wrench on the nut and back the nut off. The lower section of the nipple may come out with the nut or you may have to wrench it out after the nut is off. The threads in the drum are a running thread and usually come out fairly easily.

Clean up the threads in the section and in the drum. Clean up the gasket surface. If the gasket surface is pitted a little you can resurface it with a hand grinder. If its pitted clean and grind as best you can and put "pro poxy" on it and grind it smooth after it cures.


Put the running thread (of the new nipple) into the drum all the way. Make male x female coupling into the section with tape and dope. Tape and dope the upper end of the nipple and make it into the half coupling.

Then put the split gasket, split washer & rivet and split nut on the nipple and tighten as above.


If you have a lot of nipples leaking, then it's usually better to drop the drum buy cutting all the nipples and reinstalling new nipples instead of repair nipples.


Good luck. Takes some patience and finesse. Not the easiest job.

retiredguy

@EBEBRATT-Ed Good explanation. The worst replacements were when you could not get the nipple out of the boiler section and you had to use a cutting torch.

ScottSecor

We did on a total of about eight boilers, haven't worked on a mud drum nipple in over twenty years. Not sure we made money on any of them. Very labor intensive, and often done while kneeling in a puddle of dirty boiler water. The advice above is solid and spot on. All I can offer is make sure you give yourself plenty of time, likely double of what you assume it will take.

Mad Dog_2

Give a range or do T & M...Dont take a beating.  It can't be rushed as the boys said.  Mad Dog 🐕 

EBEBRATT-Ed

Smith boilers used to be made in Westfield, MA which is only 10 miles from me. Back in the 70s when I started and before they had a pretty much 100% lock on the boilers that were installed around here. I would say over 80% of all the schools had Smith boilers,

So I have replace a lot of nipples,

If the mud drums had a lot of sludge from not being maintained we would drop the drums and clean and repaint the drums and go back in with all new nipples.

2 guys working like a dog in most cases it would take a day to drop a drum clean it up and a day to reinstall. (depending on the number of sections)

Leaning in over the drum with a cutting torch cutting out an overhead nipple while getting showered with sparks isn't my idea of fun anymore.

If I remember the nipples were made from xtra heavy pipe.

The other problem with dropping the drum was you had to put a threaded rod through the boiler to hold the sections in position so they wouldn't move, If the sections spread a little and soot and insulation material filled the gap when you put the drums back the holes would not line up. Then you have a horror show.

They also made split welded repair nipples for the top drums which were another issue..

hot1

Got that mud drum nip on Smith 4500 steam boiler changed. Three hours and some skinned knuckles. Ended up plugging the section. A piece of the nipple boss on the section pealed off and took out the first three starter threads. The nip was screwed into the section about a quarter inch and I thought I could chase the threads in the section and screw the repair nip in deep enough where it wouldn't leak. That worked for a couple of turns of the repair nip, then another piece of the section boss pealed off. No recovering from that so decided to plug the section. In general the nip came out of the section bottom relativity easy. Thank God for WD40!
Now the nip from steam drum to section had to come out. Oh boy, more potential for disaster. Scrambled up on top of her, threw the four footer on it, and didn't it crush the darn thing. Ended up cutting slots in the header portion of the nip and tried to peal it out of the steam drum, but couldn't get enough angle on the saw z all to get inside the nip. So got very lucky and was able to spin the nip out with my chisel by folding in the tabs where I had tried to slot the nip and hitting the chisel with my three pounder. Not very interested in doing any more of these!

retiredguy

As @EBEBRATT_Ed wrote, replacing these nipples, gaskets, even boiler sections is not rocket science but it can be a horrible job. If you do enough of them it becomes just another job. In the western half of Pa where we operated I got very good at all Smith work. I do not know how many of these I replaced but it was a lot. Now that you got the top and bottom nipple out and plugged the drums, you can fire the boiler for a little while until that section melts away. Now you need a new section, so the real fun begins.

hot1

For sure! Thanks for the reply