water pump and the questions

- Oct 18, 2017 -

Water pump:

A pump is a machine that transports liquids or pumps liquids. It transfers the mechanical energy or other external energy of the prime mover to the liquid and increases the energy of the liquid. It is mainly used to transport liquid, including water, oil, acid base liquid, emulsion, suspension emulsion and so on.

Liquid metals, etc., can also transport liquids, gas mixtures, and liquids containing suspended solids. The technical parameters of pump performance include flow, suction, head, shaft power, water power, efficiency, etc.

Volumetric pumps, vane pumps and so on. The volume pump uses the change of its chamber volume to transfer energy; the vane pump uses the interaction between the rotary vane and water to transfer energy, such as centrifugal pump, axial pump and mixed flow pump.

Flow rate refers to the amount of water flowing through a section of a pipe in unit time. Symbol is Q, commonly used units are: M3/S, M3/MIN, M3/H and so on. The basic task of the water supply system is to meet the user's demand for traffic.

Lift: the energy gained by a unit mass of water when it is pumped up is called a lift. Symbol H, commonly used unit is M.

Method of regulating flow rate

In the water supply system, the most basic control object is the flow. Therefore, in order to discuss energy saving, we must start with investigating the method of regulating flow. The common methods include valve control method and speed control method of two kinds.

1. valve control method

The valve control method is to adjust the flow by closing or opening the valve, while the speed remains the same (usually the rated speed)

The essence of the valve control law is: the water supply capacity of the pump itself is constant, but by changing the resistance in the waterway to change the ability of water supply. (reflecting the flow of water supply) to meet the user's demand for traffic. At this point, the pipeline characteristics

It will change with the opening of valve, but the characteristics of head will not change.

2. speed control method

The speed control method is to adjust the flow rate by changing the speed of the pump, while the valve opening remains constant (usually the maximum opening).

The essence of speed control method is to meet the user's demand for flow by changing the full head of the pump. When the pump speed changes, the head characteristics will change, while the pipe resistance characteristics remain unchanged.

Problems existing in the operation of the existing water pump system:

(1) the actual use of water pumps are mostly using valve control method for water level regulation. That is to say, the water level is changed by changing the opening degree of the water supply regulating door, and the throttling loss is large because of the high outlet pressure and the large amount of the head.

(2) the pressure loss before and after the adjustment of the water gate is large, which makes the valve leak seriously and causes frequent replacement.

(3) when the unit load changes, it can only be adjusted by adjusting valve, so it is difficult to control.

(4) the valve has poor linearity and poor regulating quality. At the same time, the reliability of the valve is decreased due to the frequent operation of the water regulating door.

(5) the unit load is low, the pump motor appears big horse pull trolley phenomenon, wasting a lot of electric energy.

At present, energy saving water pump in the high and low pressure areas are involved, 380V, 3KV, 6KV and 10KV are used, the industry covers petrochemical, mining, cement, electricity, chemical industry, papermaking, petroleum, food, medicine, construction, municipal, water conservancy and other relationship beneficial to the people's livelihood areas.

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