Knowledge of pipeline accessories selection of the

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Knowledge of the selection of metering pump pipeline accessories

(1). Air chamber

1) because the liquid delivery of the reciprocating positive displacement pump has two strokes of suction and discharge, its lead screw and moving beam are composed) and the working oil cylinder, piston, workbench, light rod and upper beam are composed) the instantaneous flow is pulsating. With the increase of the flow value, the pulsating pressure on the metering pump pipeline also increases, This will cause the vibration of the pipeline. In order to reduce the vibration of the pipeline and make the output flow more stable, it is recommended that the user equip the discharge pipeline with an air chamber for the metering pump with a flow rate of Q ≥ 1000L/h; Due to the impact of inertia head at the inlet end, water hammer phenomenon occurs, causing pipeline vibration. It is recommended that the user equip the suction pipeline with an air chamber for the metering pump with flow ≥ 3000l/h

2) working principle of air chamber:

air chamber is a very effective device to eliminate the flow pulsation in the pipeline. It uses the compression and expansion of air in the air chamber to store or release some liquid, so as to reduce the flow pulsation in the pipeline. Take the exhaust air chamber as an example: when the instantaneous flow of the reciprocating pump is greater than the average flow, the resistance in the exhaust pipeline increases due to the increase of the flow, the pressure in the hydraulic cylinder rises, and the gas in the air chamber is compressed, so a part of the liquid is stored in the air chamber, which reduces the flow of the exhaust pipeline; Similarly, when the instantaneous flow is less than the average flow, the gas in the air chamber expands, discharging part of the liquid stored in the air chamber into the discharge pipeline, increasing the flow in the pipeline, thereby reducing the pulsation of flow and pressure in the pipeline

3) selection of air chamber:

attachment 1. Air chamber volume simplified computer tensile testing machine is mainly used for the mechanical property experimental calculation of stretching, tightening, bending, shearing, tearing, peeling, cycling and other methods in wire and cable, waterproof materials and other industries with the highest molding efficiency of metal wire, metal foil, plastic film, wire and cable, adhesive, wood-based panel, plastic parts

1. Symbolic significance

s: plunger stroke (DM); d: Plunger diameter (DM); A: Plunger or piston area, a= π × d2÷4;

ar: extension rod area; α: Area ratio, α= (A-Ar)/A; VK: volume of air chamber

2. Value of flow pulsation rate Q of pump

single cylinder single acting pump (general metering pump):q=1; Double cylinder single acting pump (two tandem single acting pumps): q=0.6

triplex single acting pump (general 3D pump):q=0.15; Single cylinder double acting pump (zj4, whichever is the smaller of the piston):q ≈ 0.6

three cylinder double acting (3d3, 3d3b, take α ≈0.8):q=0.3;

3. calculation of effective primary stroke volume V1 V1 = q × A × S;

4. volume calculation of atmospheric air chamber:

4.1 when the pressure fluctuation rate is 5% and the pipeline pressure is ≤ 0.2MPa, vk= (50 ~ 100) × V1 (take the larger value when the pump flow is small or the pressure is high)

4.2 when the pressure fluctuation rate is n%, vk= (250 ~ 500) ÷ n × V1。

4.3 when 0.2MPa < pipeline pressure < 1.6Mpa, for each increase of 0.1MPa, he said, "there is still a big gap with developed countries in product quality, quality and packaging technology. The volume of air chamber increases by 10%.

5. Calculation of volume of pre compressed air chamber:

5.1 when the pressure pulsation rate is 5%, VK = (25 ~ 50) × V1 (take the larger value when the pump flow is small or the pressure is high)

5.2 when the pressure fluctuation rate is n%, vk= (125 ~ 250) ÷ n × V1。

the volume of the air chamber is recommended to be selected according to the following table:

f) inflatable air chamber capsule material:

4) precautions for the installation and use of the air chamber:

a) the air chamber should be installed as close to the pump inlet pipeline or the hydraulic end as possible

b) when resonance occurs in the air chamber and pipeline system, the inflation pressure should be changed, and the diameter or length of the pipeline should be changed to eliminate it. The resonance can also be eliminated by adding pipeline support

c) when the inlet and outlet of the air chamber are arranged horizontally, the inlet and outlet should have a height difference and cannot be on the same axis. (end)

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