Blowdown proceedure

Paul Brown

I've worked with hydronic heat for 15+ years but am new to steam heat. I have a boiler where the water in the sight glass surges and suspect the boiler is dirty. I have found information that I should blowdown the boiler according to the instructions in the boiler installation manual. That is where my problem is. I find no such instruction. How do I blowdown the boiler? Is there a source on-line where it is described? What is the theory behind the proceedure? What is it I am doing (other than making the water level stop surging)? Have I forgotten to ask an important question?

Eager student,
Paul

Dale

How big

Will assume your not on a big CB so there's a few things to do. One is see if the mfg has something in the install instructions. The term 'blow down' like alot of other terms is old and I think relates to the old big steam drum with mud legs at the bottom boilers. If no instructs avail. the idea on a small steamer is to clean the top of the water where the junk floats and blocks the steam. You can put a pipe in the top and a temp ball valve and or better yet find the skim tapping and slowly drain hot water to get the junk out. Then comes the chemicals if that doesn't work.

Paul Brown

More information

Thanks Dale for the reply. I'm dealing with 2 Weil-McClain LGB-9 boilers in a lead/lag set up controlled by a W-M EMCS. The boilers are piped with blowdown pipes at the tap which is described in the instructions as the tap used to "skim" the boiler. My real concern is how much and how often and how long? Do I do it daily (I'm the caretaker for these babies)? Do I just repeat the blowdown proceedure until the surging stops?

Thanks,
Paul

Paul Brown

more info

Thanks Dale for the reply. I'm dealing with 2 Weil-McClain LGB-9 boilers in a lead/lag set up controlled by a W-M EMCS. The boilers are piped with blowdown pipes at the tap which is described in the instructions as the tap used to "skim" the boiler. My real concern is how much and how often and how long? Do I do it daily (I'm the caretaker for these babies)? Do I just repeat the blowdown proceedure until the surging stops?

Thanks, Paul

Dale

Depends

The main thing to me is if and how the chemicals are used. If for some process steam they need alot more blowdown especially if the chemicals are fed batch, if auto feed then less often as long as chems are checked. If these are heating only, I would blow down for 4 weeks in a row and then once a month. I think the bounce of the gauge glass tells alot, if alot of bounce alot more initial skimming. Also, I trust you are blowing down the low water cut offs at least once a week in the heating season. I like to start by slow draining to make sure the lwco cuts off the burner on a leak situation. If you have 2 lwco on each boiler test them separately temp jumping them as you test. I think this should be done (the slow drain lwco test) at least once each season.

Paul Brown

I'll try that

Yes, the each boiler has 2 lwco and they do get cleared and checked routinely for operation. So, all set there. The water is tested regularly for ph and--so far--are in fine shape, though I know chems have been added in the past. I'll try the weekly blowdown as you suggest to control the bounce in the gauge glass.

Thanks.