We found that when the DFP type corrosion-resistant multi-stage centrifugal pump is started, if there is air in the pump, the centrifugal force generated due to the low density of the air is also small. At this time, the center of the impeller can only cause a small negative pressure, which is not enough to suck in. Liquid will cause idling of the impeller, which will damage the DFP corrosion-resistant multistage centrifugal pump. In order to avoid this air-binding phenomenon, except for centrifugal pumps and self-priming pumps whose impeller is immersed in water, the pump must be filled with water before starting the pump, commonly known as water diversion. There are two methods for filling and exhausting DFP corrosion-resistant multistage centrifugal pump:
One is to directly inject water into the pump (the vent hole should be opened to remove the air in the pump); the other is to pump out the gas in the pump, establish a certain degree of vacuum (close the outlet pipe gate valve at this time), and introduce the water source.
(1) Install valves at the inlet and outlet to fill water. This method is to install a valve in the water inlet pipe, connect the water pipe to fill the pump with water.
(2) Fill water with hand pump. Some water pumps have their own hand pumps, or they can be purchased or self-made small hand pumps. Install a gate valve at the water inlet. After closing the valve, first fill the water press with a small amount of water to divert water. After the hand pump is out of water, it means that the pump is full of water and can be turned on.
(3) Use vacuum equipment to exhaust and fill water. The self-exhausting of the centrifugal pump is the same as the vacuum pumping negative pressure exhaust, so the water ring vacuum pump is used to exhaust the water to fill and divert water.
The so-called centrifugal pump uses the rotation of the impeller to make the water produce centrifugal movement to work. Before the water pump is started, the pump casing and suction pipe must be filled with water, and then the motor is started, so that the pump shaft drives the impeller and water to make high-speed rotation. The water undergoes centrifugal movement and is thrown to the outer edge of the impeller and flows through the volute pump casing. The channel flows into the pressurized water pipeline of the water pump. However, the centrifugal pump also needs to be filled with water before use. The editor shares several filling methods for water users to choose:
1. Manual water filling method: For small pumping stations with a water inlet pipe diameter of less than 300mm, there is usually a bottom valve at the inlet of the water inlet pipe. The manual water filling method is generally used, that is, from the dedicated water filling vent on the upper part of the shell. A water-filled funnel (or an inverted ordinary bottle with the bottom of the bottle removed) is filled with water. For small pumping stations with an inlet pipe diameter of less than 300mm, there is usually a bottom valve at the inlet of the inlet pipe, and the pump can also be filled with water from the outlet of the pump (pumping stations with short outlet pipes). Since there is no need to purchase other water filling equipment, this kind of water filling method is more common in small rural pumping stations. For small pumping stations that do not have bottom valves or check valves and have short pipelines, it is also possible to start up while filling the water pump from the outlet of the water outlet to gradually take out the air in the pump and pipeline , Generally, after a few minutes of continuous water filling, the water pump can work normally.
2. Vacuum water tank filling method: For small pumping stations without bottom valve, vacuum water tank filling method can be used. The vacuum water tank is a closed water tank made of iron sheet welding. Its volume is at least 3 times the volume of the inlet pipe. The location of the water tank should be as close as possible to the pump, and the bottom height of the water tank should also be slightly lower than the axis of the pump. The height of the vacuum water tank is generally twice the diameter of the water tank. Before starting, fill the water tank with water to seal it. After the water pump is started, the water pump enters the water from the vacuum tank. As the water level of the water tank drops, a certain vacuum is formed in the water tank. The water in the water tank will enter the water tank through the water inlet pipe under the action of atmospheric pressure, thereby forming a water circulation, so that The pump started to operate normally. This water filling method has the following advantages: low hydraulic loss, high pumping station efficiency, low labor intensity of technicians, easy start-up, and is conducive to automatic control of the water pump unit.
3. Jet pump water filling method: When the diesel engine is used to drive the water pump to pump water, the exhaust gas discharged from the diesel engine can be used to pass into the jet that is connected to the top of the water pump to pump air and fill water, thereby removing the bottom valve of the water pump. When the water 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 valve cover and close the control valve. The advantage of this water filling method is that it makes full use of the power machine, and the other is that it improves the efficiency of the pumping station.
4. Manual pump water filling method: As a kind of reciprocating positive displacement pump, manual pumps are widely used in rural my country. Farmers can use their own manual pumps as vacuum pumps to fill centrifugal pumps with water, which is convenient and economical.
5. Self-diversion and water-filling method: For a semi-submerged pump house (that is, a pumping station whose inlet pipe and pump top are all below the water surface of the inlet pool), water can be introduced into the pump by itself without manual irrigation. The disadvantage of this kind of pumping station is that it does not make full use of the pump's water absorption capacity. At the same time, the installation height of the pump is reduced, which not only increases the amount of foundation excavation, but also has less convenient operation and management; but the advantages are also obvious, that is, it is easy to realize the pumping station. Automation and timeliness is strong.
6. Self-suspension water diversion and water filling method: It uses the difference in bulk density of water and air and realizes it through the principle of "water-air replacement". This method can remove the bottom valve of the water pump. First of all, design a ventilation tank with an appropriate amount of containers. The ventilation tank is generally made of plastic products, but can also be thin metal parts, and the cost is only half of the bottom valve. Then, the ventilating tank is placed at the water inlet of the water pump to form a communicating body with the water pump and the pipeline. At the same time, install an air exchange control valve on the air exchange channel between the air exchange tank and the water pump. When filling water, fill the gas exchange tank with water in advance, then cover and seal, and then open the gas exchange valve. After the air exchange is completed, close the air exchange valve, and a part of the water will be suspended in the inlet pipe. Repeat this method several times, the air will be exhausted, and the water inlet pipe will be filled with water. At this point, the water pump can be started for lifting operations. Before shutting down, as long as the gate valve is closed and then shut down, the water diversion will not sit back. There is no need to irrigate and divert water next time you start it.
