The Scotch Mist® wet pipe monitoring system is again for use with installations to which automatic nozzles are connected.
The system will maintain a constant monitoring pressure throughout the discharge pipe network and, should this pressure fall away completely, discharge of the Scotch Mist® system will be automatically initiated.
A monitored wet pipe system therefore operates in an automatic mode whereby, under no-fire conditions, the system is quiescent and the pipework system wet but charged only at a pressure suitable for monitoring. Should a conflagration cause the frangible bulb of one or more nozzles to break, the monitoring pressure will fall away, the pump set will start and the pressure of the water in the pipework system will be increased to the working pressure, enabling those nozzles that have opened to discharge Scotchmist.
The Scotchmist Jockey Pump is a compact, self-contained pump set and has a small reservoir that will automatically control the water supply into the system piping at the required volume and pressure.
The pump will maintain system pressure constant at the setting of the regulator by monitoring the pressure via a 4-20mA pressure transmitter.
When there is no demand within the system, the pump will not run and the system will be at rest. The hydraulic accumulator membrane will be at its maximum pressure, pressurised by air between it and the steel shell of the vessel. When there is a small demand on the system, due to minor usage or non-return valves letting by slightly, air pressure between the membrane and the shell will force water out of the accumulator and into the system, thereby satisfying such demands.
When there is a larger demand that exceeds the stored capacity of the accumulator, the pressure in the system will continue to drop. At a predetermined point, the pump will start and continue to run, varying its speed as the demand increases and decreases until the system demand has been satisfied and the stored volume of the accumulator replenished. At this point the pump will accelerate for a few seconds and switch off.
Should the water supply fail, the pump will stop immediately. Once the water supply has been reinstated, the pump can be manually reset by switching off the mains electrical supply for 30 seconds. On switching back on the pump will restart.