Vacuum Breakers

dyoung9121

Is it normal to put vacuum breakers on the main steam line and on the steam header. Wouldn’t a main vent be a better option?

Jamie Hall

No and yes. But not on the header -- the main vents belong on the outer ends of the steam lines (one pipe and many two pipe) or on the dry returns (most vapour systems and some two pipe with crossover traps). They don't accomplish anything at the header.

dyoung9121

Okay so I have a 2 pipe with crossover f&t’s. Half way down the steam main there is a vacuum breaker but it looks like there may have been a vent there originally. Then on the header there is also a vacuum breaker so I guess what I’m asking is can I swap those breakers for main vents?

Jamie Hall

Yes you can -- but keep in mind that they won't speed up steam delivery to any part of the main downstream from them.

Are the crossover F&Ts working properly? They are very much not my preference for crossovers -- a thermostatic (like a radiator) and a water seal have much more venting capacity -- but it is what it is. Do you have plenty of venting on the dry returns at the boiler?

dyoung9121

Jamie, we just replaced all the f & t ‘s and there are plenty of old vents on the dry return but we are replacing them as well as all them are way over 10 years old

EBEBRATT-Ed

If you have crossover traps and vents on the dry returns then you should only need 1 vent at the end and may not need that depending where the cross overs are located. I would keep 1 vacuum breaker

dyoung9121

Thanks for the responses. I am going to keep the breakers cause I was trying to find ways of speeding up the venting but I think I’ll do that with the main vent at the end of the steam main