EFM-520 build thread

Here's my engineering thought on pipe thread sealing. First a threaded joint is just a spiral path to a leak. Mechanical locking of the threads is necessary for the physical strength of joining the pipes. Once you get good thread engagement you've got all the strength you need. Teflon tape just makes it easier to get more turns by reducing friction. In a ideal world with perfect threads and pipe tapers it would seal, and seal uniformly along multiple threads. But it doesn't. So we need a seal. Using the engineering design principle of turning something that's bad into something that good .... The bad is the pressure of the water causing a leak. The good is we can use that same pressure to push on a gasket and make an ever tighter seal. The more pressure the better the seal. That's where the RTV comes in. It's a remarkable material, first developed for the space program by GE's chemical engineers. It stays flexible over all sorts of environmental conditions and maintains those characteristics for 50+ years. Room Temperature Vulcanizing (RTV) silicone in the threads is the gasket. Having in in multiple threads makes redundant gaskets. Each thread where water gets past a void, it pushes on the downstream RTV which is flexible and makes a seal.

Bottom line clean the threads so you get good bonding of the RTV to the metal, use the correct temperature range product and will get a water/air tight seal the first time.

BTY, the principle outlined above is why flat plate domestic how water coils will always leak. It's a dumb design. Water pushes on the thickness of the gasket from the inside, nothing restrains it other than the squeezing of the studs/bolts. The gasket dries out and it leaks. A better design would do away with the flat plate gasket and use an O-ring in a grove. Then when the water pushed on the O-ring it makes the seal tighter and tighter. If you select the right O-ring material, e.g. vition, it would not leak and have long life. Domestic coils that thread into 4" or larger pipe threads provide much better seals against leakage.

I have a question about this subject. I have a cast iron radiator that someone used a sawzall on to get a fitting out. The threads on the opening are cut into. The blade went a little deeper than the thread. The radiator is an 8' wall hung unit. I want to use it in my garage. Will Ultra Black Permatex seal that up or should I use something like JB Weld?

I've had good luck using RTV in a situation like that. In my case the saw blade cut depth was about half the distance between the minor and major root of the thread. I'd suggest you put the radiator union on that end using RTV. Plug it and then pressure test it with garden hose water from the other end. Maybe put a pressure gauge on the air vent tapping. Don't go over 25-30 psi. If it doesn't leak good, just take the union apart being careful not to disturb the cured RTV and install in your boiler piping. If it leaks try again, or another technique. Let the RTV cure for a day or more before pressure testing.

Thanks Yanche, I'll give that a try. In this case the cut doesn/t look like it went to much deeper than the thread.

Just a thought. I've been on jobs where the company that Kevin works for has done all the fittings. Enough joints that the word gazillion would apply. He's right, they don't talk about leaky joints. just a thought. Scott

Thanks scott, I know everybody has there way of doing things and if it works for them then thats great. I have experemented with other methods as well and have found that most anything works with good threads. Its when you have bad threads the thick permetex is the right product to use. I cut my own threads, except on nipples, so I usually dont use that messy stuff. Stoker-Man, thanks for the heads up on the stoker time estament.

Stoker-Man, does the boiler come with stove cement or do I have to get some to set the boiler ? Just want to be prepared when it gets here.

Your boiler will come with everything it needs, except a thermostat and circulator.

One more week, I hope

All:

My EFM 520 boiler arrived today. Here are a few pictures I snapped to show the progress made this morning:







Now I will finish the coal bin and load her up. The rest of the installation will not begin until August 11, 2008. I will snap pictures and post them as it comes together.

On a side note, stoker-man has been extremely helpful with answering my questions posted on this thread as well as my numerous PMs and I can't say enough about Stoker-man's and EFM's commitment to servicing its customers (esp newbies like me).

Manny

Will the bricks under the base allow the ash pit door to close?

Stoker-man:

I just tried the ash pit door and it does appear to close tightly. It is a little difficult to gauge because there is no place to attach the door (yet) it must attach to the front jacket. But, it does close tightly as is. I used 1 1/2 inch concrete blocks and they extend beyond the base of the boiler about 1/2 inch.

Manny

Is that a new unit or a refurbed? I'm just comparing mine to yours. There are some minor differences, round door on mine, the ash door attaches directly to the frame etc.

Bill:

Brand spanking new. I have a tag stating it was manufactured in June, 2008. I can't say for sure, but it does look like the ash bin door attaches directly to something other than the base of the boiler.

Manny

Nice unit. Mine was built in 1959. They look the same other than those few minor differences. I can't wait till this winter.