High pressure boiler - wet lay up

Bill Vadakin

I am trying to determine the best way to put one of my boilers out of service for 4 to 5 months but still be able to bring it back on line if needed in a short period of time. I have been told that a "wet lay up" is the best but I am not able to find out the proper way to do this.

Can you help?

Thank you.

Tony Conner

Wet Lay Up...

...means leaving the water in the boiler. It's usually filled right to the boiler stop, and an elevated level of sulphite is maintained. The water level and sulphite needs to be checked at least weekly. It's pretty easy for this to go through the cracks, with vacations and things. Another way is to leave the water at its normal level, but maintain a nitrogen blanket in the steam space. The goal is the same - keep oxygen out of the steam space. If air is present in the steam space, it'll dissolve in the upper layer of boiler water, and cause pitting at the water line.

Unless the shutdown is really short - like a week or two, I'd go for a dry lay up. Drain the water and flush out the boiler. Leave handholes/manholes open. If you have all of the gasket faces cleaned up, and the new gaskets ready, it doesn't take much longer to get the boiler back in service - just the fill time. And there's pretty much nothing to maintain while it's down and empty. When you've re-filled the boiler after having it drained, fire it until you make a little steam, even if you don't really need to. That drives off any dissolved oxygen in the fill water, and minimizes corrosion. You don't necessarily need to bring it right up to operating pressure, just make the water boil, and that gets rid of the dissolved gasses.

George_10

good advice

I agree that it is just as easy to lay up a boiler dry versus wet. I always suggest using a fan to force air through the drained and opened boiler to help dry out all those little cracks and crevices that can remain wet. One thing that I have noticed when laying a boiler up wet, is that when using an oxygen scavenger, it tends to stratify in the boiler. It seems you have more equal chemical distribution when you warm the boiler every so often.
Scott