Boiler needs internal descaling?

galileo

I have a 600 thousand BTU steam boiler that was installed about 50 years ago. I flush it out on a weekly basis starting from the highest to the lowest flushing outlet. Last summer, I had my heating contractor install some parts and he mentioned that the boiler should be descaled fro the outside since there was quite a buildup of soot etc just above the gas flues and the back of the boiler. He suggested that he clean the external soot so I gave him the go.
That fall, during boiler startup, I noticed that the lowest flush cleanout was expelling steam with very little water instead of water only. After a few months, that cleanout was exhausting steam only. This was quite unusual but at least the boiler was still working. I decided to have the boiler cleaned out at the end of the heating season chich was this past spring. There are no steam boiler technicians anywhere near me and I attempted to find out if there is a way of descaling the boiler from the inside using some kind of descaling agent. The water in this area has a very high hard water rating.
Question: Not sure if I should attempt to descale the inside of the boiler with some type of solution? And, if so, what would be recommended? If I don't solve this problem I may have no choice but to replace the boiler. Any suggestions would be much appreciated.

Thanks

nicholas bonham-carter

Pictures of your boiler would identify the high and low flushing points.
Generally, the lowest drain point will remove any loose sediment at the bottom of the boiler. If the drain valve has become clogged with sediment, then the valve should be removed, and the tapping cleared out.
There is probably also a low water cut off, whose float chamber needs periodical draining.--NBC

galileo

nicholas bonham-carter

That boiler needs more than a cleaning of the fireside, burners, and flues:
Clean the sight glass, so you know what the water level is.
Verify the 1.5 psi max pressure with a new low pressure gauge, (0-3psi).
I would not do much chemical descaling, without looking at the fireside sections for stalactites of calcium, indicating leaks.
Do an overfill leak test, and let it sit for a day, to check for leaks.
Others here will probably think of more advice.—NBC

galileo

Nicholas, thank you kindly for your suggestions.

nicholas bonham-carter

Let us know how it turns out.—NBC

galileo

Thanks, I will let you know.