Corrosion-resistant self-priming pumps are pumps with self-priming function. Self-priming of corrosion-resistant self-priming pumps means that the suction pipe does not need to be filled with water (but there must be enough water in the pump body) to start the pump. The function of the gas in the human tube enters normal work after a short period of operation. The self-priming pump must be filled with enough water before starting for the first time, and it will be started again by the water left in the pump body to enter normal operation when starting later. Corrosion-resistant self-priming pump suction pipe because the liquid level is lower than that of the pump, the self-priming pump needs to pump the pipe to a negative pressure in the suction process before water can be pumped up, so it is better to compare the corrosion-resistant self-priming pump suction pipe The layout and installation of the road should be arranged and installed in accordance with the following self-priming pump installation specifications:
(1) In order to prevent air leakage in the suction pipe of the self-priming pump, the suction pipe must be completely sealed and no air can be sucked in. The suction pipe of the self-priming pump is usually made of steel pipe, and the joints are connected by welding or flange.
(2) When the water in the suction pipe contains dissolved gas, it will escape due to the decrease of pressure in the pipe. If gas accumulates somewhere in the suction pipe, an air bag will be formed, which will affect the water passing capacity of the pipe. In severe cases, it will destroy the water absorption of the real house. In order to enable the pump to discharge the gas in the suction pipe in time. The suction pipe should have a slope that continuously rises along the direction of the water flow. And i≥0.005. The gas in the pipe is discharged from the top of the pump casing at the inlet of the water pump.
(3) The installation and laying of the suction pipe of the self-priming pump should avoid the formation of air pockets in the pipe. Figure 6-13 introduces several correct and incorrect installation methods of the suction pipe.
(4) The suction pipe is installed in the suction well, and the effective volume of the suction well should not be less than the 5 minutes pumping capacity of a larger pump. In order to prevent swirling at the inlet of the suction pipe to suck air. Therefore, the entrance is required to have a certain submerged depth, overhang height and a certain distance. The position requirements of the suction pipe inlet in the suction well are shown in Figure 6-14. The specific size requirements are:
1) The submerged water depth of the suction pipe inlet of the self-priming pump is h≥0.5～1m, otherwise a horizontal partition should be installed. The side length of the horizontal partition is 2D or 3d, as shown in Figure 6-15.
2) The inlet of the suction pipe of the self-priming pump should be equipped with a bell mouth to make the water flow at the inlet of the suction pipe stable and reduce losses. The diameter of the big bell mouth is D—1.3～1.5d, (d is the diameter of the suction pipe); the height of the bell mouth is (3.5～7) (D--d).
3) The distance h1 (overhanging height) between the bottom edge of the bell mouth and the bottom of the well should be greater than 0.8D.
4) The distance Ll between the outer edge of the bell mouth and the outer wall should not be less than (0.75～1)D.
5) The distance L2 between the bell mouths is not less than (1.5--2)D.
(5) Each self-priming pump should be equipped with a separate suction pipe. The length and fittings of the suction pipe should be minimized to reduce the head loss of the suction pipe. When the number of self-priming pumps is 3 or more running together, multiple pumps can be used to suck water from the common suction main pipe, but the number is not less than two, and one fails. The remaining suction pipes can still pass the designed water volume. As shown in Figure 6-16, a gate valve should be installed on the suction main pipe to facilitate switching and maintenance. When setting up a common suction pipe, the suction main pipe should be in a positive pressure state.
(6) When the water level of the suction pool is higher than the axis of the pump, a gate valve should be installed on the suction pipe to facilitate the maintenance of the pump.
(7) When there are a lot of impurities in the water, a filter screen should be set under the bell mouth. When the water pump is manually filled with water or when the pump is started by using the water in the pressure pipe. A bottom valve should be provided on the suction pipe. The bottom valve is a non-return valve with a filter screen and high resistance. There are two types of bottom valve: underwater type and water type. The underwater bottom valve is installed at the end of the suction pipe. Because it is easy to be damaged, it needs frequent maintenance, which brings inconvenience to use. At present, water-type bottom valves are mostly used, as shown in Figure 6-17. It has the characteristics of good use effect and convenient installation and maintenance. When using an over-water bottom valve, make sure that the horizontal section of the suction pipe has sufficient length to ensure that sufficient vacuum can be generated in the pipe when the pump is filled with water.
(8) The design flow rate of the suction pipe of the self-priming pump is generally: when the diameter of the suction pipe is less than 250mm, the flow rate is 1.0~1.2m/s; when the diameter of the suction pipe is 250~1000mm, the flow rate is 1.2~1.6m/s; When the pipe diameter is greater than 1000mm, the flow rate is 1.5～2.0m/s. For self-filling pumps such as ISG pipeline centrifugal pumps, the design flow rate of the suction pipe can be appropriately increased.
For self-priming pumps with strong self-priming ability, it is recommended to use self-priming pumps with a self-priming height of 9 meters without water filling. This series of products can also be equipped with diesel-driven diesel self-priming pumps that are equipped with a vacuum assist system.
