Insulating Steam Mains

Doug Oest

Need some feedback on a job I visited on Monday. Old church with a V906 in a 2 pipe system with Trane drip traps. Since it was fresh in my memory from another old vapor system job I just fooled with, the Trane drip traps made me think was a vapor system. The church was circa 1887!!

To cut to the chase, the symptom is water bouncing severly in the boiler. Now, before anyone says clean the boiler, hear me out. The boiler was cleaned 13 times. I checked with the contractor on his cleaning method and its sound.

My theory is the uninsulated supply pipes that are exposed in the extremely cold crawl spaces under the church are condensing the steam rapidly, causing a temporary vacuum, which makes the water drop about 3-4" in the sight glass when the boiler first starts up.

We lowered the pressuretrol as low as it could go (about 1 psi) since we had about 30" of dimension "B". As the boiler ran and the system got hot, the flucuating water line seemed to calm down. However, most of the water was up in the system - seemed the water line was down about 3-4" in the sight glass. When we shut off the boiler and waited for the condensate to return, it took almost 45 minutes. But it all came back - so I knew it wasn't a leaky return pipe.

There were other things happening too- we had steam coming out of the dry return and a vent was leaking up in one of the foyer areas. There was one trap that was discovered and no one new it was there. Could be why the steam was coming out of the dry return. These items will be addressed and fixed.

Does anyone think that uninsulated pipes can cause this drop in level? I think it can. Couldn't find anything on it in Lost Art so far, I'll keep digging.

Thanks

Jerry_15

Sometimes less is more. The pipes need to be insulated anyway, and could certainly kick up a fuss, but try cutting the firing rate by half, just as an experiment, fdrom a cold start, and check/replace/add main vents. A big main vent right in the boiler room might make a world of difference. A drop like that, and a high sight glass at rest, also point to over firing. You can also reduce the flow on the feed so it won't overfill while waiting for the condensate to return. If the traps are old, just rebuild em all as a matter of course. That may keep you going while you do the other work. Nothing worse than a loud knocking at the door in the middle of a sermon, or better: if you could only time it. Good luck

Doug Oest

Covered the bases

Yep, the guy replaced all the traps except for the one we found the day we were there. He's replacing that one as we speak.

He did try cutting the fire in half basically, but that goes beyond our 20% recommendation in derate- if you go too far down, you'll get flue gas condensation. But it did seem to help a bit. He's firing 3.00 right now and there is supposed to be a 4.00 nozzle in there now (@300 psi). I should have asked him what his stack temp was when he fired at 2.75 gph. I will ask.

He also replaced all the vents and yea, there is a big main vent just before the boiler room... but surprisingly, no water hammer.

Good thought about the down firing. And no doubt, a throttling valve on the condensate pump- it comes on for like 5 seconds and shuts off!!

All good thoughts. I also found a section on the front page of Dan's website called Steam Problems. Under that, there is a section called "the system is producing unwanted vacuum". In there it talks about "the steam pipes are partially insulated". Sounds like that's it to me.


I was also thinking of a slow opening motorized valve to let the steam out slow and bring the temp of the pipes up slow, but I hate zone valves in steam systems. That's a last resort.

I think I'm on the right track with the insulation.

Thanks for your input!

Jerry_15

Sounds like you got it - and definately don't start putting in motorized valves or adding equipment before insulating. Thats high-pressure stuff, you don't want, or need, to go there. Re-porting that burner may come, but for now at least its woikin. Time it from cold start to pressure, that will tell you plenty. Too much boiler, my friend, too much boiler. Good luck