A pump is a machine for conveying fluid or pressurizing fluid. It is mainly used to convey water, oil, ore pulp, acid and alkali liquid, emulsion, suspension emulsion, gas mixture and liquid metal, etc. It is a common conveying equipment in mining, chemical and metallurgical industries. Here we have sorted out the dynamic working principles and characteristics of 19 kinds of pumps (gear pumps, centrifugal pumps, screw pumps, reciprocating pumps, piston pumps, hydraulic plunger pumps, mud pumps, pneumatic diaphragm pumps, axial flow pipeline pumps, self-priming pumps, vortex pumps, water ring vacuum pumps, Roots vacuum pumps, rotary vane vacuum pumps, air-to-air booster pumps, air-liquid booster pumps, steam jet pumps). We hope that this will be of some help to you in the selection and use of pumps.
01. Gear Pumps
How it works
The teeth of the two gears of the gear pump separate from each other, forming a low pressure, sucking the liquid in and sending it to the other side along the shell wall. The two gears on the other side close together, forming a high pressure to discharge the liquid.
Advantages: simple and compact structure, small size, light weight, good processability, low price, strong self-priming, insensitive to oil contamination, large speed range, able to withstand impact loads, easy maintenance and reliable operation.
Disadvantages: unbalanced radial force, large flow pulsation, loud noise, low efficiency, poor interchangeability of parts, difficult to repair after wear, and cannot be used as a variable pump.
02. Centrifugal Pumps
How it works
When the centrifugal pump is working, the liquid fills the pump casing, the impeller rotates at high speed, and the liquid generates high speed under the action of centrifugal force. The high-speed liquid passes through the gradually expanding pump casing channel, and the dynamic pressure head is converted into static pressure head.
Performance characteristics:
- High efficiency and energy saving: The pump has a high hydraulic profile and high working efficiency.
- Easy installation and maintenance: The vertical pipeline structure, the inlet and outlet of the pump can be installed at any position and direction of the pipeline like a valve, and the installation and maintenance are extremely convenient.
- Smooth operation, safe and reliable: The motor shaft and the water pump shaft are coaxially directly connected, with high concentricity, smooth operation, safe and reliable.
- Stainless steel sleeve: The mechanical seal position of the shaft is relatively easy to rust. Once the direct-connected pump shaft is rusted, it is easy to cause the mechanical seal to fail. The use of inlaid stainless steel sleeves can avoid rust, increase the life of the shaft, and reduce the operation and maintenance costs.
- Bearing: The bearings at the middle and lower shaft extension ends of the motor equipped with the pump adopt closed bearings. During normal use, the motor bearings are free of maintenance.
- Mechanical seal: The mechanical seal base generally uses a rubber bellows structure, and the seal on the shaft of the traditional mechanical seal is changed from the line seal of the O-ring to the two-face seal of the rubber part, which improves the sealing effect in the clear water medium.
03. Centrifugal Pumps
How it works
Compared with single-stage pumps, multistage centrifugal pumps have more than two impellers, which can absorb and pressurize water in stages, thereby lifting water to a very high position. The head can be increased or decreased according to the needs of the number of pump impellers.
Multistage centrifugal pumps are available in two types: vertical and horizontal. The pump shaft of a multistage centrifugal pump is equipped with two impellers connected in series. Compared with general single-stage centrifugal pumps, it can also achieve a higher head.
Performance characteristics:
- Multistage pumps are mainly used for mine drainage, urban and factory water supply. Compared with reciprocating pumps such as piston pumps and diaphragm pumps, they can also pump larger flows. Multistage centrifugal pumps are highly efficient and can meet the needs of high head and high flow conditions. They have been widely used in petrochemical, chemical, electric power, construction, fire protection and other industries.
- Due to its own particularity, compared with single-stage centrifugal pumps, multistage centrifugal pumps have different and higher technical requirements in design, use and maintenance.
04. Screw pump
How it works
The twin-screw pump is very similar to the gear pump. One screw rotates, driving the other screw. The liquid is intercepted in the meshing chamber, pushed along the rod axis, and then squeezed to the center for discharge.
Disadvantages of screw pumps:
High processing and assembly requirements for the screw; the performance of the pump is sensitive to changes in the viscosity of the liquid.
Advantages of screw pumps:
- Wide pressure and flow range. The pressure is about 3.4-340 kgf/cm2, and the flow rate can reach 100cm3/min;
- The types and viscosity of the transported liquids are wide, and the mineral processing plant can use it to transport collectors, flocculants, etc.;
- Because the inertia force of the rotating parts in the pump is low, a very high speed can be used;
- Good suction performance and self-priming ability;
- Uniform and continuous flow, small vibration, low noise;
- Compared with other rotary pumps, it is less sensitive to incoming gas and dirt;
- Solid structure, easy installation and maintenance.
05. Reciprocating pump
How it works
When the reciprocating pump is working, the piston moves to the right, the pressure in the cavity decreases, the upper valve is pressed down, the lower valve is lifted, and the liquid is sucked in; the piston moves to the left, the pressure in the cavity increases, the upper valve is lifted, the lower valve is pressed down, and the liquid is discharged.
Advantages of reciprocating pumps:
- High discharge pressure can be obtained, and the flow rate is independent of pressure, with good suction performance and high efficiency, of which steam reciprocating pumps can reach 80%~95%;
- In principle, any medium can be transported, almost without being restricted by the physical or chemical properties of the medium;
- The performance of the pump does not change with changes in pressure and viscosity of the transported medium.
Disadvantages of reciprocating pumps:
The flow rate is not very stable. It is larger than a centrifugal pump at the same flow rate; the mechanism is complex; the capital consumption is large; it is not easy to maintain, etc.
06. Double-acting reciprocating pump
How it works
When the double-acting reciprocating pump is working, the piston moves to the right, the lower left sucks liquid, and the upper right discharges liquid. The piston moves to the left, sucks liquid at the lower right, and discharges liquid at the upper left. The piston reciprocates once, sucking and discharging liquid twice, and the flow rate is more uniform.
07. Piston pump
How it works
The high-pressure plunger of the gas-liquid booster pump controls the one-way valve to continuously discharge the liquid. The outlet pressure of the booster pump is related to the air drive pressure. When the pressure between the drive part and the output liquid part reaches a balance, the booster pump will stop running and no longer consume air. When the output pressure drops or the air drive pressure increases, the booster pump will automatically start running until the pressure reaches a balance again and then stop automatically.
How it works
The piston pump is also called an electric reciprocating pump. It is divided into single-cylinder and multi-cylinder types in terms of structure. When the piston pump is working, the reciprocating action of the piston in the cylinder causes the volume in the cylinder to change repeatedly to inhale and discharge the fluid.
Performance characteristics of piston pumps:
- Piston pumps are suitable for high pressure and small flow occasions, especially when the flow is less than 100m3/h and the discharge pressure is greater than 9.8 MPa, it shows its higher efficiency and good operating performance.
- It has good suction performance and can pump various media and liquids of different viscosities. It can be used for water injection, oil injection and oil production in oil fields and coal seams. If the flow-through parts are made of stainless steel, corrosive liquids can be transported. In addition, according to different structural materials, high-temperature tar, mineral mud, high-concentration slurry, high-viscosity liquids, etc. can also be transported.
Piston pumps are widely used in petrochemical industry, machinery manufacturing industry, papermaking, food processing, and pharmaceutical production.
08.Hydraulic piston pump
How it works
The hydraulic piston pump or solid pump is driven by a hydraulic power pack to drive the hydraulic cylinder, which pushes the conveying cylinder to output the material in the conveying cylinder to the pipeline.
Generally divided into single-plunger and double-plunger, the basic principle of the plunger pump is very simple. This pump uses the momentum of a relatively large moving water body to pump a relatively small volume of water to a high place.
Hydraulic piston pumps are widely used in sewage treatment, solid waste treatment, mining and metallurgy, silt removal, dredging, petrochemical industry, power plants, cement industry and other fields.
Commonly used mud pumps are piston or plunger type. The power machine drives the crankshaft of the pump to rotate, and the crankshaft drives the piston or plunger to reciprocate in the pump cylinder through the crosshead. Under the alternating action of the suction and discharge valves, the purpose of pressurizing and circulating the flushing liquid is achieved.
A mud pump is a machine that delivers mud or water or other flushing fluids into the borehole during the drilling process. It is an important component of drilling equipment.
In the commonly used positive circulation drilling, the surface flushing medium – clean water, mud or polymer flushing fluid – is sent directly to the bottom of the drill bit through a high-pressure hose, a faucet and the center hole of the drill string under a certain pressure to achieve the purpose of cooling the drill bit, removing the cut rock chips and transporting them to the surface.
How it works
In order to prevent the piston from directly contacting the corrosive liquid when the pneumatic diaphragm pump is working, the cylinder cavity and the liquid are separated by a diaphragm, which is actually the principle of the reciprocating pump. There are four types of materials for pneumatic diaphragm pumps: engineering plastics, aluminum alloy, cast iron, and stainless steel.
- The flow rate is adjustable, and a throttle valve can be installed at the material outlet to adjust the flow rate.
- It has the function of self-priming.
- It can run empty without danger.
- It can work while diving.
- The fluids that can be transported are extremely wide, from low viscosity to high viscosity, from corrosive to viscous.
- There is no complex control system, no cables, fuses, etc.
- Small size, light weight, easy to move.
- No lubrication required, so maintenance is simple, and the working environment will not be polluted by dripping.
- The pump can always maintain high efficiency and will not be reduced due to wear.
- 100% energy utilization, when the outlet is closed, the pump automatically stops, the equipment moves, wears, overloads, and heats up.
- There is no dynamic seal, so maintenance is simple and leakage is avoided. There is no dead point when working.
Performance characteristics of pneumatic diaphragm pumps
Using compressed air as the power source, it can be used for various corrosive liquids. Different materials can be used according to different liquid media to meet the needs of different users.
- The pump will not overheat: compressed air is used as the power source, and it is an expansion and heat absorption process when exhausting. The temperature of the pneumatic pump is reduced when it is working, and no harmful gas is discharged.
- No electric sparks will be generated: the pneumatic diaphragm pump does not use electricity as the power source, and static sparks are prevented after grounding
- Can pass through liquids containing particles: because it works in a volumetric manner and the inlet is a ball valve, it is not easy to be blocked.
- The shear force on the material is extremely low: it is sucked in and spit out when working, so the agitation of the material is minimal, which is suitable for the transportation of unstable materials
11. Axial flow pipeline pump
How it works
The impeller of the axial flow pipeline pump is designed as axial flow, with a very high speed. If the motor power, impeller diameter and pipeline diameter are large enough, the flow rate can be very large.
Performance characteristics of axial flow pipeline pump:
- The pipeline pump has a compact structure, integrated machine and pump, and is small in size. Its vertical structure has a small installation area, smooth operation, and no adjustment is required during installation.
- The pump inlet and outlet are designed to have flanges with the same specifications and are located on the same center line. They can be installed directly on the pipeline like a valve, and the center is low, which facilitates pipeline layout and installation.
- The pump and motor are coaxial and have short axial dimensions, making the pump run more smoothly and with low noise.
- The traditional shaft seal method is cancelled, which avoids the leakage of the conveyed medium, so it has the remarkable feature of being completely leak-free.
12. Self-priming pump
Before starting the water pump, fill the pump casing with water (or there is water in the pump casing itself). After starting, the impeller rotates at high speed to make the water in the impeller groove flow to the volute. At this time, a vacuum is formed at the inlet, causing the water inlet check valve to open, and the air in the suction pipe enters the pump and reaches the outer edge through the impeller groove.
Performance characteristics of self-priming pumps:
Self-priming pumps are self-priming centrifugal pumps with the advantages of compact structure, convenient operation, stable operation, easy maintenance, high efficiency, long life, and strong self-priming ability.
The pipeline does not need to be installed with a bottom valve. Before working, it is only necessary to ensure that a certain amount of lead liquid is stored in the pump body. Self-priming pumps of different materials can be used for different liquids.
13. Vortex pump
How it works
The liquid in the groove of the blade of the vortex pump is thrown to the flow channel by centrifugal force, which increases the pressure once; the liquid in the flow channel forms a low pressure due to the liquid in the groove being thrown out, and enters the groove again and increases the pressure again; multiple vortex motions of groove-flow channel-groove can achieve a higher pressure head.
Advantages of vortex pumps:
- W-type single-stage direct-connected vortex pumps are used to pump clean water or liquids with physical and chemical properties similar to water. The liquid temperature does not exceed 60°C. They are often used as boiler feed water. They are widely used in shipbuilding, textile, chemical industry, metallurgy, machinery manufacturing, aquaculture, fixed fire protection pressure stabilization, heat exchange units, agricultural remote sprinkler irrigation and other departments.
- The small size and light weight of vortex pumps have great advantages in ship installations. They have self-priming ability or can achieve self-priming with the help of simple devices.
- They have a steep drop in head characteristic curve, so they are insensitive to pressure fluctuations in the system. Some vortex pumps can achieve gas-liquid mixed transmission. This is of great significance for pumping volatile liquids containing gas and high-temperature liquids with high vaporization pressure.
- The vortex pump has a simple structure, and the casting and processing processes are easy to implement. Some vortex pump parts can also use non-metallic materials, such as plastic and nylon molded impellers.
Disadvantages of vortex pumps:
- The efficiency is low, not exceeding 55% at most. The efficiency of most vortex pumps is 20-40%, which hinders its development towards high power.
- The cavitation performance of vortex pumps is poor.
- Vortex pumps cannot be used to pump viscous media. As the viscosity of the liquid increases, the pump head and efficiency will drop sharply, and the viscosity of the medium is limited to 114 centistokes (15°E).
- The strict requirements for the radial clearance and axial clearance between the vortex pump impeller and the pump body bring certain difficulties to the processing and assembly process.
- The pumped medium is limited to pure liquid. When the liquid contains solid particles, the axial and radial clearances will increase due to wear, which will reduce the performance of the pump or cause the vortex pump to fail to work.
14. Water ring vacuum pump
How it works
The liquid in the groove of the blade of the vortex pump is thrown to the flow channel by centrifugal force, which increases the pressure once; the liquid in the flow channel forms a low pressure due to the liquid in the groove being thrown out, and enters the groove again and increases the pressure again; multiple vortex motions of groove-flow channel-groove can achieve a higher pressure head.
The impeller of the water ring vacuum pump blade is eccentrically installed in the cylindrical pump housing. A certain amount of water is injected into the pump. When the impeller rotates, the water is thrown to the pump housing to form a water ring, and the inner surface of the ring is tangent to the impeller hub. Since the pump housing and the impeller are not concentric, the intake space 4 between the right half of the hub and the water ring gradually expands, thereby forming a vacuum, allowing the gas to enter the intake space in the pump through the intake pipe. Then the gas enters the left half, and the pressure increases due to the gradual compression of the volume between the hub ring, so the gas is discharged to the outside of the pump through the exhaust space and the exhaust pipe.
Advantages of water ring vacuum pump:
- Simple structure, low manufacturing precision requirements, easy processing.
- Compact structure, high pump speed, generally can be directly connected to the motor, no reduction device is required. Therefore, with a small structural size, a large exhaust volume can be obtained, and the footprint is also small.
- The compressed gas is basically isothermal, that is, the temperature change of the compressed gas process is very small.
- Since there is no metal friction surface in the pump chamber, there is no need to lubricate the pump, and the wear is very small. The seal between the rotating parts and the fixed parts can be completed directly by the water seal.
- Uniform suction, stable and reliable operation, simple operation, and convenient maintenance.
Disadvantages of water ring vacuum pump:
- Low efficiency, generally around 30%, and the better ones can reach 50%.
- Low vacuum degree, this is not only due to structural limitations, but more importantly, it is limited by the saturated vapor pressure of the working fluid. Using water as the working fluid, the ultimate pressure can only reach 2000~4000Pa. Using oil as the working fluid, it can reach 130Pa.
- In short, since the gas compression in the water ring pump is isothermal, it can pump out flammable and explosive gases. Since there is no exhaust valve and friction surface, it can pump out dusty gases, condensable gases and gas-water mixtures. With these outstanding features, it is still widely used despite its low efficiency.
15. Roots vacuum pump
How it works
The working principle of Roots pump is similar to that of Roots blower. Due to the continuous rotation of the rotor, the pumped gas is sucked from the air inlet into the space v0 between the rotor and the pump housing, and then discharged through the exhaust port. Since the space v0 is fully closed after the air is sucked in, there is no compression and expansion of the gas in the pump chamber. However, when the top of the rotor turns over the edge of the exhaust port and the space v0 is connected to the exhaust side, due to the higher gas pressure on the exhaust side, part of the gas will rush back into the space v0, causing the gas pressure to suddenly increase. When the rotor continues to rotate, the gas is discharged out of the pump.
Roots pumps have the following characteristics:
- High pumping speed in a wide pressure range;
- Quick start-up, can work immediately;
- Not sensitive to dust and water vapor contained in the pumped gas;
- The rotor does not need to be lubricated, and there is no oil in the pump chamber;
- Small vibration, good rotor dynamic balance conditions, no exhaust valve;
- Low driving power, small mechanical friction loss;
- Compact structure, small footprint;
- Low operation and maintenance costs.
Therefore, Roots pumps are widely used in metallurgy, petrochemical, papermaking, food, and electronics industries.
16. Rotary vane vacuum pump
How it works
The working principle of Roots pump is similar to that of Roots blower. Due to the continuous rotation of the rotor, the pumped gas is sucked from the air inlet into the space v0 between the rotor and the pump housing, and then discharged through the exhaust port. Since the space v0 is fully closed after the air is sucked in, there is no compression and expansion of the gas in the pump chamber. However, when the top of the rotor turns over the edge of the exhaust port and the space v0 is connected to the exhaust side, due to the higher gas pressure on the exhaust side, part of the gas will rush back into the space v0, causing the gas pressure to suddenly increase. When the rotor continues to rotate, the gas is discharged out of the pump.
Since the volume of space A is gradually increasing (i.e. expanding), the gas pressure is reduced, and the external gas pressure at the pump inlet is greater than the pressure in space A, so the gas is sucked in. When space A is isolated from the air inlet, that is, it is transferred to the position of space B, the gas begins to be compressed, the volume gradually decreases, and finally communicates with the exhaust port. When the compressed gas exceeds the exhaust pressure, the exhaust valve is pushed open by the compressed gas, and the gas passes through the oil layer in the oil tank and is discharged into the atmosphere. The purpose of continuous air extraction is achieved by the continuous operation of the pump. If the exhausted gas is transferred to another stage (low vacuum stage) through the airway, it is extracted by the low vacuum stage, and then compressed by the low vacuum stage and discharged into the atmosphere, a two-stage pump is formed. At this time, the total compression ratio is borne by the two stages, thereby increasing the ultimate vacuum degree.
Performance characteristics of rotary vane vacuum pump:
Rotary vane vacuum pump is an oil-sealed mechanical vacuum pump, which belongs to low vacuum pump. It can be used alone or as a pre-stage pump for other high vacuum pumps or ultra-high vacuum pumps. It is widely used in production and scientific research departments such as metallurgy, machinery, military industry, electronics, chemical industry, light industry, petroleum and medicine.
- Small size, light weight and low noise;
- Equipped with gas ballast valve, which can extract a small amount of water vapor;
- Equipped with automatic anti-return oil check valve, easy to start;
- The air inlet is continuously unblocked and the atmospheric operation shall not exceed one minute;
- It is not suitable for extracting gases that are corrosive to metals, chemically react to pump oil, contain particulate dust, and contain excessively high oxygen, explosive, and toxic gases.
17. Air booster pump
How it works
The gas booster pump uses compressed air as power to increase the pressure of low-pressure gas and output it continuously. The final output pressure can be increased to twice or even dozens of times the pressure of the power source. It is a pollution-free gas booster device.
According to the output pressure and structural form, it is divided into low-pressure pumps and high-pressure pumps.
Low-pressure pumps are mainly used to maintain the normal operation of pneumatic devices and meet the local high-pressure gas requirements of equipment when the on-site gas source pressure is insufficient or unstable and the minimum operating pressure of the pneumatic device cannot be guaranteed.
High-pressure pumps are mainly used to pressurize non-ordinary compressed air, such as nitrogen, helium, argon, etc. to tens of MPa and load them into high-pressure gas tanks.
Performance characteristics of gas booster pumps:
- The working pressure range is large. Different pressure areas can be obtained by selecting different types of pumps. The output pressure can be adjusted accordingly by adjusting the input air pressure. It can reach extremely high pressure, gas 90MPa.
- Wide flow range. For all types of pumps, only 0.1kg air pressure can work smoothly. At this time, the minimum flow rate is obtained. Different flow rates can be obtained after adjusting the air intake.
- Easy to control, from simple manual control to fully automatic control, it can meet the requirements.
- Automatic restart, no matter what the reason for the pressure drop in the pressure-maintaining circuit, it will automatically restart, replenish the leakage pressure, and keep the circuit pressure constant.
- Safe operation, gas drive, no arc and spark, can be used in dangerous places.
- The maximum energy saving can reach 70%, because maintaining the pressure does not consume any energy.
18. Gas-liquid booster pump
How it works
The high-pressure plunger of the gas-liquid booster pump controls the one-way valve to continuously discharge the liquid. The outlet pressure of the booster pump is related to the air drive pressure. When the pressure between the drive part and the output liquid part reaches a balance, the booster pump will stop running and no longer consume air. When the output pressure drops or the air drive pressure increases, the booster pump will automatically start running until the pressure reaches a balance again and then stop automatically.
Performance characteristics of gas-liquid booster pump:
- High output pressure: the maximum output pressure of liquid pump can reach 640MPa, and the maximum output pressure of gas pump can reach 200MPa
- Wide application range: the working medium can be hydraulic oil, water and most chemically corrosive liquids, and it has high reliability, maintenance-free and long service life.
- Wide output flow range: for all types of pumps, only a small driving air pressure is required to work smoothly, and a small flow rate is obtained at this time. Different flow rates can be obtained by adjusting the driving air intake volume.
- Flexible application: different pressure areas can be obtained by selecting different types of pumps.
- Easy to adjust: within the pressure range of the pump, adjust the regulating valve to adjust the air intake pressure, and the output hydraulic pressure can be adjusted accordingly.
- Automatic pressure maintenance: no matter what the reason for the pressure drop in the pressure maintenance circuit, it will automatically start to supplement the leakage pressure and keep the circuit pressure constant.
- Safe operation: gas-driven, no arc and spark, can be used in dangerous places.
A single air-controlled non-balanced gas distribution valve is used to achieve the automatic reciprocating motion of the pump. The air drive part of the pump body is made of aluminum alloy. The liquid contact part is made of carbon steel or stainless steel according to the different media. The full set of seals of the pump are imported high-quality products, thus ensuring the performance of the gas-liquid booster pump.
19. Steam jet pump
How it works
When the steam jet pump is working, steam enters the nozzle and is ejected at high speed, generating low pressure, sucking in the gas and mixing it in the mixing chamber. After passing through the expansion tube, the kinetic energy is converted into pressure energy. If the sucked gas comes from a container and the container is decompressed, it can be called a jet vacuum pump.
Performance characteristics of steam jet pump:
- This pump has no mechanical moving parts and is not restricted by friction, lubrication, vibration and other conditions, so it can be made into a pump with large suction capacity. As long as the structural material of the pump is properly selected, it is extremely beneficial for removing corrosive gases, gases containing mechanical impurities and water vapor.
- Simple structure, light weight, small footprint.
- The working steam pressure is 4~9×105Pa, and such water vapor sources are available in general metallurgical, chemical, pharmaceutical and other enterprises.
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