5.6. Systems Based on Elastomeric Type Deluge Valves:
The system demands are the same as in above Part 5. However, the manner in which the deluge systems are handled is quite different.
5.6.1. Monitors:
Nodes 12 and 13 have monitors attached to them which have the following data –
k – factor = 2500 (lit/min, bar)
Required flowrate = 5000 (lit/min, bar)
Minimum pressure = 1 barg
Maximum pressure = 20 barg
The monitors normally do not have Elastomeric valves and so they are modelled the same way as before – as nozzles.
As the deluge valves are of the Elastomeric type the flowrates are fixed. So, we cannot model them as nozzles. What we need to do is the following. We can set the flowrates at the deluge systems. The pressure generated by the pumps at the outputs should be at least equal to the system demand pressure plus the minimum pressure drop in the Elastomeric valve. As long as the pressure generated by the pump is higher than this threshold pressure the deluge system can be expected to work satisfactorily.
The schematic would therefore be as shown below –
5.6.3. Assignment of Specifications:
In this system there are two input/output nodes both of which are inputs. As before, they operate at 0 barg because they are the input to the pumps.
Design Phase Specifications – As we know we must assign flowrates to all but one input/output nodes. In this case, as there are five input/output nodes, we need to give four design phase flowrates. In this case the actual value is not important as long as it is reasonable. The total required output flowrate from the system is 40,000 lit/min. So we can assign 20,000 lit/min to one input because there are two inputs. The three outputs can simply be given their required flowrates.
As before, the dialog boxes for the two input nodes are shown below –
Note that as before, node 17 only has an analysis specification and node 18 has both design and analysis specifications.
For the three output nodes the specifications are given as shown below.
5.6.4. The Simulations:
Scenario 1 – All the 3 deluge systems, the 2 monitors and the 2 pumps are working.
The specifications as given above are sufficient for running the calculation.
Scenario 2 – All the 3 deluge systems working and the 2 pumps are working.
The two monitors can be turned off simply by switching of the nozzles. This can be done either in the data window or in the properties window.
Scenario 3 – All the 3 deluge systems working with only one pump running.
The data will be the same as that for scenario 2 except that the pump inlet pressure specification for one pump is changed to 0 flowrate specification rather than 0 pressure.
In particular the analysis specification on node 18 is changed from 0 barg to 0 lit/min.
Scenario 4 – All the 3 deluge systems working with only one pump running with pipe label 8 blocked.
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