Drain Vavle / PR safety vavle for the receiver.

We have seen that many a times these valves do leak & the entire NH3 has to be wasted. WE have seen Danfoos Quick Drain valve & is really good. But that comes with a price tag & hence all try & avoid that.

We are trying to put up TWO drain valves so that One shall be always open & other shall be operated for draining the oil etc. in case of eventual leak, atleast we can close the back up valve. Any better idea than this?

Same is the story with Pr Safety valve. There also we get Dual safety valve operating on a similar principal as above. Again any better idea in this concept?

I agree with oil drain valve, you should always put a stop valve before it. Also pipe outlet away so liquid ammonia/oil doesnt spray on/near you.
Dual relief valve you should avoid a stop valve before it , as it is against safety regulations normally. Its a good idea to only have one relief in service, by forward or back seating manifold.
If you have a stop valve before it, there is the danger of it being closed and vessel has no protection (unless you have a lock out procedure).Its unusual for reliefs to leak or vent,as plant/compressor pressure switches should be set 10-15%lower than relief valve setting.

Hello SMPS,

Quick drain valve from danfoss is a good idea in combination with a stop valve.

For the relief valve you can use a bursting disc in fron of it.
Then the valve cannot leak and in an event of overpressure the disc will burst and after that the relief valve will open.

For burting discs we use Rembe from Germany.

Greetings,

Bart.

Dear Bart.
This is a new idea for sure. I shall check up on this as well.

Dear Bart.

Which model you use for NH3 receivers? from Rembe

Hello SMPS,

The model depends on what size it has to be and what pressure it has to be. It's also important is the discholder is compattible with the safetyvalve.
We normally use it in combination with HERL safetyvalves and then we use the KUB type.
Check the site at rembe.de
(in india they are represented by Kilpauk, Chennai
There are also bursting discs from the brand FIKE.
Check the site at fike.com. (they are also in India)

hope this helps.

I concur with the idea to use rupture discs on the main relief valves. If you use high quality discs like Fike or BS&B (ones I have experience with) you can get their rupture pressure certified for very close tolerances. This helps to reduce the weep pressure that can affect relief valves if the pressure happens to get within the pressure range where the relief valves start to simmer (slightly rise off of the valve seat).

Another aspect worth noting also is the use of the maximum design working pressure for vessels. I tend to support higher design pressures to help contain the refrigerant.

The concept of using a back-up service valve in front of the oil drain valve is also very valid. I would bet that more ammonia has been lost because of improper oil draining procedures than just about anything else.

Many thanks for the valuable replies.