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In a pump string, and even adjust the way: When single station can not meet a pump delivery tasks can be used in parallel or in series in a pump operation. Centrifugal parallel two of the same model, although head changed little, but increased the total transportation flow, the same overall efficiency in parallel with a single pump efficiency of the pump; open pump series increases the total pressure head , little change in flow rate, the overall efficiency of the pump the same series with a single pump efficiency. After two pumps in parallel flow and pressure head are improved, but due to the constraints pipeline characteristic curve, the line resistance increases, the total throughput of two pumps in parallel is equal to twice the amount of the original single pumping. After two pumps in series, the pressure head and flow will improve, but the total head of two pumps in series is still less than twice the original single pump head.
In a pump casing
In a pump casing (2)
Cavitation in a pump: a pump inlet of pressure P1 which is equal to or less than the saturated vapor pressure at the same temperature PV of the liquid, the liquid vaporization occurs, air bubbles under high pressure, or rupture quickly gather produce great pressure, high frequency the impact of strong vibration and noise may pump the liquid flow rate, pressure head (outlet pressure) and decreased efficiency. This phenomenon is called centrifugal pumps cavitation.
In a pump operation (energy conversion): Before starting the pump, pump shell filled with liquid to be transported; after the start, the impeller shaft driven by the high-speed rotation, the liquid between the blades must also be with the rotation. Under the effect of centrifugal force, the liquid from the impeller center was thrown to the outer edge and gain energy at high speed away from the outer edge of the impeller into the volute casing. In the volute, the liquid due to the gradual expansion of the flow channel and the deceleration, in turn part of the kinetic energy into static pressure energy, and finally to a higher pressure flowing into the discharge pipe to the required place. When the flow of liquid from the center of the outer edge of the impeller, the impeller center to form a certain vacuum, the pressure tank above the liquid surface is greater than the pump inlet pressure, the liquid is then continuously pressed into the impeller. Visible, as long as the impeller constant rotation, the liquid will continue to be sucked and discharged.
The selection principles in a pump
In a pump is a large number of widely used general-purpose surface mechanical equipment, it is widely used in petroleum, chemical, power metallurgy, mining, choose ship, light industry, agriculture, civil and defense sectors, occupies in the national economy important status.
What is a reasonable choice in a pump, is to consider the investment and operating costs of the pump units and pumping stations and other comprehensive technical and economic indicators, to be in line with economic, security, the principle applies. Specifically, the following aspects:
1, must meet the flow and head requirements, which called for the pump operating time point (the intersection of device characteristic curve and pump performance curve) keep running in the high range, so not only save power and is not easy to damage the parts.
2, the selected pump should not only small size, light weight, low cost, but also has good characteristics and high efficiency.
3, has a good anti-cavitation performance, smooth operation and long life.
4, the selected pump works less investment, low operating costs.
In a pump selection step
1, the basic data are listed in a pump:
Comprising: characteristics of the medium, the medium contained by the particle diameter of the body, how much content, medium temperature, the desired flow pressure piping system data
Second, determine the flow head
OK 1, traffic
a, if the production process has been given the minimum, normal, maximum flow, maximum flow should be considered.
b, if the production process is given only normal traffic, you should consider leaving a certain margin.
For ns> 100 large flow of its unexpectedly low lift pump, flow margin to take 5% of ns <50 is lifted and the small flow pump, flow margin to take 10%, 50≤ns≤100 pump, flow margin also take 5% of the poor quality and poor operating conditions of the pump, flow margin should take 10%.
c, only if the basic data flow to the weight, should be converted into a volumetric flow rate.

S, SH-single-stage double suction pump inlet and outlet are at the bottom of the pump axis, horizontal axis and vertical position, the pump casing. In the open, without having to remove the water when the overhaul, the discharge line and the motor ( or other prime mover) from the coupling viewed in the direction of the pump, water pumps are reverse-inch needle direction. As according to the special order can be changed to cis-inch needle rotation.
S, SH-single-stage double suction pump main parts: pump, pump cover, impeller, shaft, double suction seal rings, bushings, bearings. In addition to the axis of materials for high-quality carbon steel, and its remaining multi-cast iron.
Pump and pump cover constitute studio impeller, flange out of the water in the system have to install a vacuum gauge and pressure gauge tube screw out of the water formed with the lower flange of the drain pipe holes.
Impeller static balance check, with the sleeve nuts on both sides of the sleeve and fixed, the axial position can be adjusted through the sleeve nut, the axial force of the impeller use its leaves are arranged symmetrically balanced, there may be some left the remaining axial force coaxial side of the bearing.
Shaft by two single row radial ball bearings, bearing mounted in bearings at both ends of the pump body with grease lubrication, double suction seal ring to reduce the water pump pressurized water chamber to drain back to the suction chamber.
Pumps by coupling direct drive from the motor.
Seal soft packing seal, in order to cool and lubricate the seal chamber prevent air leakage into the pump, seal ring between fillers, a small amount of high-pressure water pipe into the water seal when the pump is working by packing chamber from the water seal effect.