Hello all,
I'm looking for a bit of advice/help with the above problem.
I'm looking at a fuel gas line with two valves (different flow ratings) in parallel, upstream flow meter (0 to 40 MMSCFD), upstream pressure of 500 to 1000 psi, and downstream pressure feedback.
Instrumentation on flow meter and downstream pressure. Valve actuators 4-20 mA.
Gas fired devices downstream.
There are 12 gas fired generators downstream, of which approximately 5 units can be run on the primary valve (Valve A). When generator 6 through 12 are brought online, gas demand will increase and the second valve should begin to open, in order to meet the flow demand. As a generator is removed from service, the flow decreases, and Valve B should close off until pressure is back under control.
I assume that the primary valve will be fully open with 6 or more generators running, and the secondary valve will 'take up the slack'.
I've looked at one loop to control both valves based on pressure, two loops (one for each valve) controlling on pressure, two loops with an override on the secondary based on flow being above 12.3....
I just seem to be having a mental block at coming up with the right solution. Any and all thoughts and comments welcome here....
I'm looking for a bit of advice/help with the above problem.
I'm looking at a fuel gas line with two valves (different flow ratings) in parallel, upstream flow meter (0 to 40 MMSCFD), upstream pressure of 500 to 1000 psi, and downstream pressure feedback.
Instrumentation on flow meter and downstream pressure. Valve actuators 4-20 mA.
Gas fired devices downstream.
Desired control is:
Valve A controls downstream pressure to 375 psi.
Once fuel rate exceeds 12.3 MMSCFD, Valve B (higher rated flow characteristics) begins to open.
Pressure of 375 psi should be maintained.
Valve A controls downstream pressure to 375 psi.
Once fuel rate exceeds 12.3 MMSCFD, Valve B (higher rated flow characteristics) begins to open.
Pressure of 375 psi should be maintained.
There are 12 gas fired generators downstream, of which approximately 5 units can be run on the primary valve (Valve A). When generator 6 through 12 are brought online, gas demand will increase and the second valve should begin to open, in order to meet the flow demand. As a generator is removed from service, the flow decreases, and Valve B should close off until pressure is back under control.
I assume that the primary valve will be fully open with 6 or more generators running, and the secondary valve will 'take up the slack'.
I've looked at one loop to control both valves based on pressure, two loops (one for each valve) controlling on pressure, two loops with an override on the secondary based on flow being above 12.3....
I just seem to be having a mental block at coming up with the right solution. Any and all thoughts and comments welcome here....