Blow-down in vacuum

Fizz

Has anyone had any issues with blow-down of boiler in vacuum? I've been doing it by returning to pressure. Concern for LWCO during vacuuum b-d with air rushing-in. Legitimate concern or not?

ChrisJ

I don't see how you could do a blowdown in a vacuum?

Fizz

That's what I thought, but waited to hear from guys' in the know.
Thanks Chris.

PMJ

You can't do those things in vacuum. I bd the lwco in the brief part of the cycle when there is no vaccum.

Fizz

Thanks PMJ, will try it. I'm amazed that the boiler hasn't required any extra water this season, and the water has been fairly clear. Added benies for vacuum?

EBEBRATT-Ed

If you blow the LWCO down in a vacuum the float will jump up and down risking damage to it. not good

PMJ

Fizz said:

Thanks PMJ, will try it. I'm amazed that the boiler hasn't required any extra water this season, and the water has been fairly clear. Added benies for vacuum?

I think so. Air is the enemy really. It interferes with distribution and it causes corrosion.

gerry gill

I have a customer who has a Dunham vapor vacuum system. The original Dunham air eliminator still is there, and it has a vacuum check on it. If the boiler has recently ran, (like in the last day) you can open the drain valve and nothing comes out. Take the vaporstat off and woosh, out comes the water, as air rushes in via the pigtail. When we service the boiler, thats the only way we can drain it below the ports we wish to open.

As a side note, i asked her how her steam distribution is throughout the house, She perked right up and said 'great!'

PMJ

gerry gill said:

I have a customer who has a Dunham vapor vacuum system. The original Dunham air eliminator still is there, and it has a vacuum check on it. If the boiler has recently ran, (like in the last day) you can open the drain valve and nothing comes out. Take the vaporstat off and woosh, out comes the water, as air rushes in via the pigtail. When we service the boiler, thats the only way we can drain it below the ports we wish to open.

As a side note, i asked her how her steam distribution is throughout the house, She perked right up and said 'great!'

Great to hear there is some natural vacuum still in operation Gerry.

Is there a vacuum gauge on that system to see how much vacuum there is?

gerry gill

You know, i don't think i even looked...but i will next time i go there!

PMJ

gerry gill said:

You know, i don't think i even looked...but i will next time i go there!

Thanks.

It really is a great system. Let a little air out each cycle and sink into vacuum evening out the distribution between cycles. It is what I do and like your customer I think the results are great.