Location of diverter valves and LN vaporizers
Location of diverter valves and LN vaporizers
(OP)
I have a client that has an existing liquid nitrogen tank and a single vaporizer.
They are wanting to go to 24/7 so are wanting to put in a second vaporizer and a 3 way diverter valve to alternate the vaporizers.
The question we are considering is whether the diverter valve should be on the liquid side, making it a cryogenic valve or on the gas side, making it a gas valve.
All the set ups i have seen has the valve on the liquid side.
Would there be any problems with putting the valve on the gas side?
A side issue is the client wants the valve to be electropolished. The gas side valves can be electropolished, but I cannot find any cryogenic valves that are electropolished. They can be cleaned to Class 100 cleanliness, but not electropolished.
They are wanting to go to 24/7 so are wanting to put in a second vaporizer and a 3 way diverter valve to alternate the vaporizers.
The question we are considering is whether the diverter valve should be on the liquid side, making it a cryogenic valve or on the gas side, making it a gas valve.
All the set ups i have seen has the valve on the liquid side.
Would there be any problems with putting the valve on the gas side?
A side issue is the client wants the valve to be electropolished. The gas side valves can be electropolished, but I cannot find any cryogenic valves that are electropolished. They can be cleaned to Class 100 cleanliness, but not electropolished.





RE: Location of diverter valves and LN vaporizers
RE: Location of diverter valves and LN vaporizers
We are designing the system to have one vaporizer offline for 6-24 hours so, even though the piping is insulated, the cryogenic liequid will likely vaporize in the piping upstream of the offline vaporizer. I am concerned the expanding gas will force its way into the inlet pipe of the on line vaporizer. I don't know if this is a problem, but I would prefer to keep any vaporized gas in the vaporizer or downstream of it.
Am I being overly cautious?
RE: Location of diverter valves and LN vaporizers
RE: Location of diverter valves and LN vaporizers
RE: Location of diverter valves and LN vaporizers
So there is on concern with two phase flow in the upstream piping or is that considered acceptable?
RE: Location of diverter valves and LN vaporizers
Regarding putting 2 in parallel, the problem with that is that as frost covers the vaporizer fins, it acts as an insulator and eventually can cover a very large portion of the vaporizer. I've seen vaporizers covered more than half way in a gigantic ice ball. Putting 2 in parallel without a diverter can help but it means the vaporizers are only going to defrost and shed all that insulating ice if the entire system goes down. Hence the need for 2 separate vaporizers with a diverter.
RE: Location of diverter valves and LN vaporizers
RE: Location of diverter valves and LN vaporizers
RE: Location of diverter valves and LN vaporizers
The system will be under 24/7 operation.
Should I be concerned?
RE: Location of diverter valves and LN vaporizers
The cryogenic valve by Sharpe specifically says they've provided a relief hole in the ball and stem slot to accommodate the potential of trapped liquid. Get the cryogenic valve and I'd suggest warning your equipment supplier about the hazards of ball valves in cryogenic service.
I could also recommend Worcester valves for this application. We've used their valves extensively.
RE: Location of diverter valves and LN vaporizers
Looking at the cut sheet, it appears the only time there would be trapped liquid is if we used the valve for shut off. We have cryogenic valves on the tank for this so we would not be using the diverter valve for that purpose. We are also specifying the actuator to use 180 degree turns.
I also have looked at the Worcester/Flowseerve valves. The contractor/supplier submitted Sharpe.
RE: Location of diverter valves and LN vaporizers