Normal Pump StartUp

with controlled valve opening At some pumping plants, the pump is brought up to speed against a closed valve on the discharge side of the pump. The valve is then opened slowly, and there is very little waterhammer in the discharge line. However, it will be found that nearly all of the pump flow in the discharge line is established with only a relatively small valve opening because the head losses across the valve decreases very rapidly during the opening stroke. For long discharge lines, the head loss and flow characteristics of the valve during the opening stroke must be considered in determining the optimum rate of opening.

with check valves At pumping plants where the pipeline is held full with pump check valves, waterhammer in the discharge line due to a pump start-up can be objectionable in some cases. If the motor comes up to speed very rapidly, the pump will develop a pressure rise in the discharge line as the sudden increase in flow moves into the line. As noted previously and in Reference 1, this pressure rise is lower for radial-flow (low-specific-speed) pumps than for axial-flow (high-specific-speed) pumps (see Section 8.1).

with casing unwatered At pumping plants equipped with large pumps, normal starting of a pump is often performed with the pump casing unwatered. This is accomplished by depressing the water level below the pump impeller by means of compressed air, which is admitted into the pump casing with the pump discharge valve closed and the discharge line full. After the motor has been synchronized on the line, the compressed air in the pump casing is released, allowing water to re-enter the pump from the suction elbow, after which the discharge valve is slowly opened. This type of operation has been satisfactory with most large pumping units, and there are normally no significant waterhammer effects on the discharge line. However, there have been some difficulties with this type of operation at a few large pump units. In the latter case, when the rising water level in the suction elbow first reaches the pump impeller, a very fast pumping action occurs within a few seconds and a severe uplift of the pump and motor from the thrust bearing could occur at this moment. If the discharge valve is still closed when this fast pumping action occurs, there is no waterhammer effect in the discharge line.

with surge OR air chambers With a surge tank or air chamber at the pumping plant, it makes very little difference whether the increased pump flow is sudden or gradual, inasmuch as the major portion of the sudden increased flow will enter the surge tank or air chamber. With these devices, the steep front of the pressure rise at the pump is transformed into a smaller pressure rise in the discharge line and a subsequent slow oscillating movement in the surge tank or air chamber.

normal pump shutdown The pumping installation that produces the least waterhammer effect in a pump discharge line during a normal pump shutdown is one in which the control valve on the discharge side of the pump is first closed and the power to the pump motor then is shut off. if only check valves are in operation on the discharge side of the pumps and the power to one of several pumps motors connected to the same discharge line is cut off, the flow at the pump that has been shut down will reverse rapidly and the check valve will close rapidly. The use of antislam or slow-closing features at the check valves will reduce the waterhammer effect in the discharge line.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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