The centrifugal pump (except the self-priming pump) must fill the water pump and the inlet pipe with water before starting, otherwise the pump can't lift the water. After the centrifugal pump is started, there is no water, which is often caused by the air in the pump not being drained and the water not being filled. So, what are the water filling methods for various centrifugal pumps? Please see the detailed introduction:
There are two main types of water filling methods before the start of the centrifugal pump: one is to fill the water with the assembly bottom valve, and the bottom valve is a one-way valve, which is installed at the inlet of the inlet pipe. The disadvantage of this method is that the head valve head has a large loss. It affects the efficiency of the pump device; the other is the bottomless valve is filled with water. The biggest advantage of this method is energy saving, which can save 10%~15% compared with the pumping station with bottom valve. The following describes the water filling methods of several centrifugal pumps, which are selected by the user when running the water pump.
Manual water filling method For small pumping stations with inlet pipe diameter less than 300mm, the inlet valve is usually provided with a bottom valve at the inlet of the inlet pipe. Generally, the artificial water filling method is adopted, that is, the water is filled from the special water-filling vent hole in the upper part of the water pump casing. The funnel (or an inverted common bottle with the bottom of the bottle removed) is filled with water. For small pumping stations with a inlet pipe diameter of less than 300 mm, a bottom valve is usually provided at the inlet of the inlet pipe, and the pump can also be filled with water from the outlet pipe of the water pump (the pumping station with a short outlet pipe). Since there is no need to purchase other water-filling equipment, this method of water filling is more common in small-scale pumping stations in rural areas. For a small pumping station that does not have a bottom valve, a check valve, and a short pipeline, it is also possible to use a method of starting water while filling the water pump from the outlet pipe to gradually bring out the air in the water pump and the pipeline. After a few minutes of continuous water filling, the pump can pump normally. Vacuum water tank filling method For small pumping stations without a bottom valve, vacuum water tank filling method can be used. The vacuum water tank is a closed type water tank welded by iron. Its volume is at least three times the volume of the inlet pipe. The position of the water tank should be as close as possible to the water pump. The bottom height of the water tank should also be slightly lower than the axis of the water pump. The height of the vacuum tank is generally twice the diameter of the tank. Before the pump starts, fill the water tank with water to seal it. After the pump is started, the water pump enters the water from the vacuum box. As the water level of the water tank drops, a certain vacuum is formed in the water tank. The water in the water pool will enter the water tank through the water inlet pipe under the action of atmospheric pressure, thereby forming a water circulation. The pump starts to run normally.
The water filling method has the following advantages: small hydraulic loss, high pumping station efficiency, low labor intensity of the technician, simple starting, and favorable automation control of the pump unit. Jet pump water filling method When the diesel engine is used to drive the water pump to pump water, the exhaust gas exhausted by the diesel engine can be used to open the jet connected to the top of the water pump to pump the air to remove the bottom valve of the water pump. When the pump is started, the valve cover connected to the handle is closed, the exhaust gas is ejected from the jet, and the air in the pump is sucked out through the connecting pipe. After filling the water, open the bonnet and close the control valve. The advantage of this water filling method is that the power machine is fully utilized and the efficiency of the pumping station is improved. Manual pump water filling method As a kind of reciprocating volumetric pump, manual pump is widely used in rural areas of China. Farmers can use their own manual pump as a vacuum pump to fill the centrifugal pump, which is convenient and economical. The most common usage is to install the hand pump on the suction hole of the centrifugal pump or close to the water inlet pipe of the pump to pump the water to make it a tool for filling the water when the centrifugal pump is turned on, thus eliminating the water pump inlet pipe. The bottom valve reduces energy loss and improves the efficiency of the pump unit. Self-priming water filling method For the semi-submerged pumping station (that is, the pumping station with the elevation of the inlet pipe and the pump pump top below the water level of the inlet pool), the water can be introduced into the pump without the need to manually inject water. The disadvantage of this kind of pumping station is that the water pumping capacity of the pump is not fully utilized, and the installation height of the pump is reduced, which not only increases the amount of excavation of the foundation, but also is inconvenient in operation management; but the advantages are also obvious, that is, it is easy to realize the pumping station. Automated, time-sensitive. Self-suspending water-filling method The self-suspending water-filling method is realized by utilizing the principle of "water-gas displacement" by utilizing the difference in the weight of water and gas. This method removes the bottom valve of the pump.
First of all, design a gas container for a proper amount of containers. The gas exchange tank is generally a plastic product or a thin iron piece, and the cost is only one-half of the cost of the bottom valve. Then, the gas exchange tank is placed at the water inlet of the water pump to form a communication body with the water pump and the pipeline. At the same time, a ventilation control valve is installed on the air exchange passage between the ventilation tank and the water pump. When filling the water, fill the gas tank with water beforehand, then seal the valve and open the gas exchange valve. After the ventilation is completed, close the ventilation valve and a part of the water will be suspended in the inlet pipe. Repeat this method several times, the air will be completely drained, and the water inlet pipe will be filled with water. At this point, the pump can be started to lift the water. Before stopping the machine, as long as the gate valve is closed and then stopped, the water will not sit back. You don't need to pour water again the next time you start. The advantage of this water filling method is that the price of the gas tank is low, the manufacturing is easy, the labor intensity is low, and energy is saved. Vacuum pump water filling method For large and medium-sized pumping stations with inlet pipes larger than 300mm, or pumping stations with higher automation requirements, vacuum pumping devices are commonly used as water filling devices. It is assembled by a vacuum pump and other equipment. Most of the vacuum pumps used in irrigation and drainage stations are water ring vacuum pumps. An eccentric toothed impeller is mounted in the cylindrical pump casing of the water ring vacuum pump. The pump casing is filled with circulating water. When the vacuum is applied, the impeller rotates. Under the action of centrifugal force, the circulating water in the pump casing is smashed around the impeller, forming a rotating water ring on the inner wall of the pump casing. Since the impeller is eccentrically mounted in the pump casing, the space formed between the water ring and the toothed blade is different. When the impeller rotates clockwise, the space between the two blades in the right half gradually increases. Under the closed condition, as the volume of the air increases, the pressure decreases, forming a vacuum, and the air in the pump and the pipeline passes. The suction pipe, the crescent-shaped suction port that enters the right side of the pump casing of the vacuum pump is sucked into the vacuum pump, and the space between the two blades of the left half of the vacuum pump impeller is gradually reduced, so the air is compressed, the pressure is increased, and finally the vacuum pump is passed. The crescent-shaped exhaust port on the left side of the pump casing is discharged from the vacuum pump, enters the water-gas separation tank, and the recycled circulating water is separated and reused. As the impeller rotates continuously, the vacuum pump continuously inhales and vents, and finally fills the pump with water. Regarding the number of vacuum pumps, for small pumping stations, when there are less than 3 units, one is generally selected. When there are more than 4 units, 2 units are generally selected. For medium and large pumping stations, 2 units are preferred. When there are more, consider one spare. The advantages of vacuum pump water filling are short water filling time, high efficiency of pumping station, low labor intensity, and easy automation of pumping stations. The downside is that the investment is large.
Centrifugal pump water filling is an important part of pump operation management. It is believed that with the continuous exploration of water pumping methods by water conservancy researchers, there will be more and more water pump filling methods with the aim of “convenient, practical and efficient”. The effect of water filling will be better and better, thus making a positive contribution to the development of electromechanical irrigation and drainage.
