1995-08-11_REVISION - M1977493 (12)

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Page 4 In the mill control room lights are activated for the pump sets running. The "Pump Station Alarm" signal mEans that there is a problem at the pumping station which must be investigated. III Pump Pressures There are three gauges at each set of pumps . The first gauge on the left measures line pressure and should be 180 psi with one system operating and 210 psi while two systems are operating. The second and third gauges are gland water pressures. The second gauge should read the same as the line pressure. The third gauge should be one-half of that shown on the second gauge. Static pressure (nothing pumping) is 110 psi . IV Surge Suppressors Each discharge line has a surge suppressor. The two surge suppressors are located in the basement and are connected to the discharge lines, Fig. 2. Surge suppressors are needed because water hammer in pipelines can cause piping damage and flooding . of the pumping station. Water hammer is shock wave created when the water's velocity is abruptly changed. if the pumps go down the water in the pipeline under oes a change in its velocity and this energy is converted to pressure. A 9 surge suppressor prevents water hammer by allowing the water's velocity to decelerate gradually and thereby preventing excessive surge pressures. Water hammer is illust- rated in Fig. When the pumps go down, the pressure at thesurge suppressor connection to the line decreases and a pressure imbalance results. The surge suppressor automatically reacts to this in.balance by pumping water rapidly into the line Fig. 5a. This outflow action continues until the fluid column in the pipeline comes to rest and starts its return flow back towards the pump. As the water returns Fig. 5b, the surge suppressor acts as a brake by absorbing the return energy. The air compressor serves to maintain. proper water level in the surge suppressor. This level is determined by electrodes and is monitored by observing sight gauges attached to the sides of the surge suppressors. The air compressor will start up automatically to replace air lost to the water, it is important that the valves between the surge suppressors and the discharge lines are left open during normal operations. If they are closed the surge suppressors are useless and flooding of the building could occur if the pumps went down during a power surge. V Washdown Pump In the basement at the east end, there is a washdown pump that will supply water to . the various washdown stations. The stop-start switches are located at the washdown stations. Before starting this pump be certain that the suction supply valve is open. Use caution around the pump because full line pressure is available.when the main pumps are running.