Removing scaling from the inside of the 520 boiler

What is a good product and procedure to remove hard water scale from the 520 boiler?

In some past life I have been intimately involved in descaling a boiler or three.

I cannot say the result was what I wished for. Oh I got a lot of it - but it never all comes out in the time you get - some other sub is always on your heals.

First - open a wash out port and get a sample - take it to your local water specialist where you going to buy the chemical and he will figure out if its mostly silica, or salts -carbonate or sulfate. Purchase a vast amount of the poison he recommends and soak the vessel at the prescribed rate. Heat helps! Jet wash and rod the crud out via the mud legs and repeat. and repeat and repeat

or -- just chamber a round and blow a toe off.

Its likely more cost effective to junk it and replace.

When our shower head gets clogged with water deposits (lime buildup) we just remove it and soak it in white vinegar for 24 hours.
Maybe draining the 520 boiler and filling it with a dilution of water/vinegar would accomplish the same thing?

We used to use sulfamic acid for hard water scaling, but I don't know if it would work in a boiler.

There's a reference in a posting by forum member "mikeandgerry" that may be of help. See post: cast iron or steel boiler?

Mike's post references this document:

http://www.afcesa.af.mil/shared/media/d ... 13-040.pdf

It's a fairly complete document on how to treat boiler water. While it doesn't specifically discuss removing scale it does give you the common chemicals in boiler water. I like Sting's suggestion of getting a chemical analysis of the scale.

Suggest you visit Lehigh University with a sample of your scale and ask for an analysis and chemical recipe for its removal.

stoker-man wrote:What is a good product and procedure to remove hard water scale from the 520 boiler?

The first question that comes to mind is why or how did is scale up in the first place?

The only way to get significate scale in a boiler is to have considerable amount of make up water enter the system. The make up would be needed only from a leak in the system that was left unchecked for considerable time.

If you made up that much water to create scale, that water also had oxygen in it. That oxygen no doubt attacked the metal of the boiler. You may remove the scale and find out you need tube/plate repairs.

I'm with Sting. If the rest of it is in good condition, salvage the stoker, base, jacket, etc. and buy a new pressure vessel.

I'm with sting and steamup, do what you can easily; if it's too nasty, just bite the bullet and get a new pressure chamber. You cannot see the inside of the beast, so if it looks sketchy, it probably is. It's short money to be able to sleep well knowing you won't have any leaks to ever deal with. I've got 1954 to 1998 boilers of many makes, and I've make a 'lawn ornament' of one or two when necessary. It is just not worth the risk to yourself or a friend to take a chance. Coil area replacements are an exception in AA's or EFM's, but still use good common sense.
We pressure wash the things as a first step anyway, and most are in excellent condition, but massive scale is a red flag for me. I don't fancy playing with a chemical bath for a boiler blank either, so safety first when dealing with nasty elements.

If you really think it is worth the effort, here is a tech bulletin on acid cleaning from weil-Mclain.



Note: When soaking or cleaning a boiler, the system must be vented to atmosphere. Otherwise, the gases released during cleaning will build up pressure and cause a dangerous condition such as a blown boiler and flying acid.

The guy who asked me how to do it has probably done something by now, but this will be a great resource for the future.