Removing deposits steam boiler

ScottSecor

I did my best to search on this subject but only came up with questionable answers. First of all, we are very familiar with skimming and the using TSP to clean cast iron steam boilers. This particular boiler is a eight section Weil McLain 88, roughly twelve years old. The boiler was installed by others and is not piped ideally, however we found a few serious leaks in crawl spaces that we didn't know existed until recently. We repaired the leaks near the end of the heating season

The boiler needed to be skimmed and cleaned with TSP at least once a month during the heating season for the last year or two. Part of this is due to the improper piping, but that is constant. The minerals in the fresh water make up are almost certainly the cause of the extensive priming and surging after roughly 30 days. Below is a lousy photo (that is not pipe dope at the end of the threads, furthest away) of one of the tappings on the front of the boiler. Appears to be a hard white substance that coats the sections, skim tapping, low water cutoffs, etc. I'm guessing the stuff is about 1/16" thick. We don't large amounts of rust when we dump the boiler or lwco's, no more than typical.



In the past we've rented a sewer jet for use on Smith 28 boilers with decent results for the lower tappings (sometimes referred to as mud legs) to remove large amounts of rust. However on WM 88 boilers there's only one lower port that we could access and I doubt it would be worth the effort. I'm leaning towards a strong mixture of TSP and Caustic Soda, heated to roughly 140 degrees and circulated for 24 or 48 hours with a temporary circulator. I suspect there is a liquid chemical that would work but we're afraid it might damage the elastomer seals and will likely cost more than ten times the amount. We've used muriatic acid years ago for copper coils but I would not think that would work well with cast iron sections and "rubber" seals.

Any suggestions or ideas?

nicholas bonham-carter

Do you have a meter on the makeup water feed, so you know that fresh water intake from leaks has been completely reduced?
Maybe you could fill it with RO water, which would redissolve the calcium scale.—NBC

ScottSecor

Yes, there is a water meter now. Water usage was certainly excessive with the leaks that were undetected for some time. Wild guess would be about ten gallons per day during the heating season, could have been this way for years.

There were no active staff or church members that knew the steam piping (or crawl space) layout. They balked when we offered to examine the entire system and come up with a extensive punch list. Thankfully, an older inactive church member came forward and shared his knowledge, along with the sextant that did not realize floors were not supposed to buckle in closets above crawl spaces (that we didn't know existed).

Maybe RO is the way to go. Would you suggest a one time "shot" to clean the boiler or install a permanent system to continually strip the calcium from the water? Before we do anything, we'll have the water tested.