Vacuum breaker for a relief line?

[Dacosta]

Hello out there

Do I need a vacuum breaker for a relief line? If so then why?

I have a two-stage ammonia system with a diffusion tank. My lowest temperature is –40ºF (10psia) but the relief valve is on the discharge of the booster compressor (45 psia). The relief line is 4” sch 40 steel, it is about 80ft (105ft equilivent) run from the farthest relief valve to the diffusion tank. Outlet of the relief line is 30ft under the water in the diffusion tank.

Any thoughts on this?

Thanks

Dan

[keepitcool]

Does it have an Emergency Control Firemans box also? If not it is not possible to suck water into your system. If it does than you should consider drilling a small hole on the pipe that goes to the bottom of the tank and into the water bath. Drill it inside the diffusion tank but above the water level. That way if you have a relief valve lift the small amount of gas released from your hole will go out the relief stack. I have seen people suck water into their system through a Firemen's box. It is not that hard if you don't know what you are doing and monkey with the valves inside the Emergency Control Box. Ask your boss to keep his hands off!