PetroBob
Chemical
- Dec 23, 2005
- 60
Folks
I'm looking for ideas to solve an urgent design problem. We've been asked to replace an existing small hydrogen control panel with an identical panel (but using swagelok connections for easier maintenance). The panel is used to let hydrogen down from cylinder pressure, through a single stage regulator, and then the H2 is passed through piping out to the plant. H2 supply pressure = 136 barg/2000 psi cylinder pressure (when the cylinders are full), and downstream of the regulator is 10 barg/150 psig (14 barg design pressure). The hydrogen is in pallets of 15 cylinders, which are changed out manually when they run out. The hydrogen is only used intermittently (for a few hours twice a week).
The difficulty arises because this system also needs to deliver sufficient flow when the cylinders are running empty (down to say 12 or 14 barg). This means we end up with a regulator with larger Cv than otherwise would be required (Cv = 0.5). Therefore the regulator failure case gives us a very large relief flow rate.
The existing relief valve is 0.5" inlet and outlet. (Short outlet pipe ~ 2 ft long, venting above the panel which is outdoors). Existing piping downstream of the regulator is 1/2" increasing to 1" a few ft downstream. Our preliminary calc suggests a required relief valve size of 3L4. ie the existing relief and downstream piping are very undersized.
Our panel is physically small (4' x 3'). The client is expecting us to replace like with like. A 4" outlet relief valve could not be supported without significant structural design (and would look daft).
We've brainstormed a few ideas. 2 stage regulator? Orifice plate upstream or downstream of the regulator? These ideas would probably restrict the flow too much for the cylinder-nearly-empty case. Slam shut valves? (Do they exist for high pressure 136 barg?)
Any more ideas to reduce the size of the relief case?
I'm looking for ideas to solve an urgent design problem. We've been asked to replace an existing small hydrogen control panel with an identical panel (but using swagelok connections for easier maintenance). The panel is used to let hydrogen down from cylinder pressure, through a single stage regulator, and then the H2 is passed through piping out to the plant. H2 supply pressure = 136 barg/2000 psi cylinder pressure (when the cylinders are full), and downstream of the regulator is 10 barg/150 psig (14 barg design pressure). The hydrogen is in pallets of 15 cylinders, which are changed out manually when they run out. The hydrogen is only used intermittently (for a few hours twice a week).
The difficulty arises because this system also needs to deliver sufficient flow when the cylinders are running empty (down to say 12 or 14 barg). This means we end up with a regulator with larger Cv than otherwise would be required (Cv = 0.5). Therefore the regulator failure case gives us a very large relief flow rate.
The existing relief valve is 0.5" inlet and outlet. (Short outlet pipe ~ 2 ft long, venting above the panel which is outdoors). Existing piping downstream of the regulator is 1/2" increasing to 1" a few ft downstream. Our preliminary calc suggests a required relief valve size of 3L4. ie the existing relief and downstream piping are very undersized.
Our panel is physically small (4' x 3'). The client is expecting us to replace like with like. A 4" outlet relief valve could not be supported without significant structural design (and would look daft).
We've brainstormed a few ideas. 2 stage regulator? Orifice plate upstream or downstream of the regulator? These ideas would probably restrict the flow too much for the cylinder-nearly-empty case. Slam shut valves? (Do they exist for high pressure 136 barg?)
Any more ideas to reduce the size of the relief case?
