Pump, jockey

Firewater Systems. These systems are best laid out by contractors or other specialists. National Fire Protection Association (NFPA) rules will spell out required coverage, typical pump size, and other standard items. A small jockey pump will maintain system pressure at all times. 

Small capacity pumps commonly referred to as "jockey" pumps are provided on a firewater system to compensate for small leakages and incidental usage without the main pump(s) startup. They are set to start 0.70 to 1.05 kg/sq. cm. (10 to 15 psi) above the start up pressure of main firewater pumps. In some cases a cross-over from the utility water system can be used in place of a jockey pump, however a check valve is installed to prevent drain down of the firewater by the utility water system. Jockey pumps do not require the... 

Pressure maintenance (jockey) pumps should be provided to maintain a predetermined pressure on the system and make-up normal leakage in the distribution system. Normally, the pressure maintenance pump will maintain 10-15 psi (69-103 kPa) above the starting pressure for the automatic starting of the main fire water pump. (See 7.4.4.3.9.)... 

The fire water distribution system is kept pressurized by means of a jockey pump. In the event of a sprinkler trip, three large diesel driven pumps come on line as needed to supply the tremendous quantity of water which may be required. In order to prevent the water pressure from dropping, which would result in low water flow to the sprinkler nozzles immediately after they are opened, an electric switch panel allows the diesels to be started directly from an electric notifier system. This permits the diesels to get the start signal about the same time water begins to flow which reduces the unwanted initial pressure drop. 

Figure 12.4 shows the use of fire zones. A ring main goes around the entire facility. It is filled with water whose pressure is maintained with a jockey pump. Connected to the ring main are multiple zones. The fire water headers in each zone are normally dry. In this example, there are two fire water pumps, each of which has sufficient capacity on its own to handle the design fire case. These pumps are placed in different locations at the facility so that, if one is destroyed, the other will provide a full flow of fire water. It is common for them to have different power supplies—in particular, one of them will be driven by a stand-alone diesel motor that operates independently of the facility s utility systems. 

A jockey pump maintains pressure on the firewater system at all times. The set pressure will typically be in the range 8—lObarg. Generally, the jockey pump will mm itself on and off depending on the header pressure. If the pump mns continuously its discharge should recirculate through a minimum flow bypass. 

Systems without jockey pumps need to have surge protection to avoid damaging the piping when the main pumps start. 

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