water in boiler

[johnp]

is it ok to leave water in the boiler?

[fredrosse]

As long as it is not going to freeze!

Layup of the boiler during periods on non-use can be accomplished two ways:

1. Cold Wet Layup, the boiler is filled totally full of water, preferrably with oxygen removed (steaming the water drives out the oxygen just before layup). The boiler has all its connections shut, so no air/oxygen can get in. If you do not boil the water before layup, there can be some corrosion, but generally not serious if the Ph is kept up to 9-11.

2. Cold Dry Layup, the boiler is completely drained, and then dried so there is NO moisture inside the boiler. This is very difficult to achieve, and takes several hours of work. This layup is approptiate for boilers that will possibly be exposed to freezing weather over the winter season. In large boilers, trays of lime or silica gel are placed inside the boiler to absorb moisture. Other methods include a moderate heat source, and healthy ventilation to dry everything out. A hair dryer blowing thru the boiler (in the bottom, out the top) for several hours will dry out a small boiler, provided all the connections are blown out with compressed air before the drying is started.

3. Simply draining the boiler, with some wetness still inside, perhaps trapped in various connections, etc. is the wost condition to layup the boiler, worse than doing nothing at all after a run. Wetness + Oxygen in the air = plenty of corrosion.

There are previous threads here discussing these methods in detail.

[Lopez Mike]

Fred's comments pretty much sum it up.

The only thing that comes to mind is that an empty boiler is not going to be hurt by a reasonable amount of heat. We do weld on them, after all.

In other words, once you have the boiler open to atmospheric pressure, i.e. the blow down left open as well as anything else you can open up, you can build a fairly significant fire in it without hurting anything. Be reasonable. If you start smelling your wood lagging burning, you have over done it!

If a boiler is heated up to, say, 250-300F, there is not much chance of any water being left behind. To be extra sure, use a shop vacuum to blow air through when this is going on.

For those of you in non-freezing areas, the full boiler with de-airated and high pH. water sounds fine.

There is a simple way to tell when the air is gone from water, It stops simmering. Degassed water doesn't make that simmering sound when initially heated. It goes straight into boiling when it gets up near 212F (100C)

In the lab we often need degassed water and we either heat it or dump it in an ultrasonic cleaner. Either way, the little bubbles that first come off are air, not steam.

Dirty little secret in the lab world is that when we have a container that must not have free oxygen or water vapor in it when stored, we fill it with Propane. Cheaper than dry Nitrogen or MIG gas. No smoking kiddies!

Mike

[Oilking]

I pulled out my NSTM 9510 (Boilers) ,& 9560 (Boiler water testing & treattment) from my BT days 38 years ago to double check my memory. For wet lay up the boilers were filled to to the air cocks with deareated feedwater the level was maintained until cold and then the air cocks closed. If equipped a 5 psi nitrogen blanket was then maintained. The Navy Standard for deareated feedwater is <0.02 PPM disolved oxygen! Under cold conditions sodium sulfite ,not sulfate, can be used as an oxygen scavenger. I'll have to do a bit more research on the application rate, my mind isn't ready work out the chemistry without a second cup of coffee.

Good steaming to all!