Two types of Scotch Mist® pumped system are available;
- Deluge (fixed duty) systems, where open nozzles are connected to a water delivery system capable of supplying all nozzles simultaneously upon initiation, either by automatic detection or manually.
- Automatic Wet or Dry Pipe (variable duty) systems, where automatic nozzles are fitted to a pressurised pipe network that delivers water to any activated nozzles when the system is initiated by a drop in the monitoring pressure.
Scotch Mist® variable duty pumps are suitable for fluctuating loads where the operating pressure and water flow from the discharging nozzles may vary. They can therefore be used for monitored, wet or dry pipe systems where the load may vary from one to however many nozzles have been designed as the maximum to operate under a fire condition. They can also be used for shared systems, even though every system may not have the same quantity of nozzles operating at the same pressure and flow.
Scotch Mist® pump sets are designed and manufactured using the documented quality control procedures of BS EN ISO 9001 Parts 1, 2 and 3, assessed and monitored by BSI. The operating specification is based on our own high standards and the working specification associated with any particular project.
Pumps are manufactured almost entirely from AISI 316 stainless steel and are approved by the WRAS for use on potable and non-potable water applications. The pumps are of the vertical, multi-stage, in-line type with direct-coupled motors and ceramic faced tungsten carbide mechanical seals.
Each pump set is fitted with Return-to-Tank System-Isolate valves, which enable the pump set to be tested periodically, and check valves are fitted to the outlets.
The pump set package comprises a single or twin inverter driven pump, small volume hydraulic accumulator, pressure transducer, pressure gauge, interconnecting stainless steel pipework and a basic control panel, all mounted on a common painted steel baseplate.
Under quiescent conditions, the pump will run periodically to maintain the set pressure in the system up to the manifold or selector valve. When there is no demand and the system is up to pressure, the pump will be stationary and the accumulator membrane will also 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 forces water out of the accumulator and into the system, thereby satisfying such demands.
When topping up the system pressure, the pump will start once the pressure has dropped below the nominal set point of the system less the differential setting. The pump will run for a while under pressure transducer and inverter PID control until the required pressure has been reached and the minimum run timer expired, at which point the pump will stop.