1, pressure
Generally we only consider the difference between the import and export pressure, but separately understand the import pressure and export pressure, for the correct selection is critical. Because sometimes the pump inlet may be negative pressure, sometimes may be positive pressure. If it is the case of negative pressure, you need to know the specific negative pressure value, when the pump's inlet pressure is less than atmospheric pressure, gear pumps at the same speed and differential pressure, the flow rate will be lower than the normal value in the performance curve. When the inlet vacuum reaches an extreme value, the gear pump will not work properly. In addition, each gear pump has a maximum allowable working pressure, that is, the gear pump's maximum pressure, when the gear pump's inlet pressure & gt; atmospheric pressure, we must ensure that the export pressure & lt; gear pump's maximum pressure, that is, "the inlet pressure + differential pressure & lt; gear pump's maximum pressure", so as to ensure that the gear pump's This will ensure that the gear pump can work safely for a long time.
2, viscosity
The viscosity of the liquid has an impact on the performance and power of the pump, viscosity and at the same time by the temperature and even the effect of shear. Because of the existence of internal leakage of the gear pump, the pump in the transmission of viscosity the greater the liquid, the smaller the internal leakage, the actual output flow will be large. So compared with the low viscosity of water, conveying high viscosity liquid, the same type of gear pump at the same speed and differential pressure, the actual output flow rate of the gear pump will be larger. But as the viscosity of the liquid rises, the fluidity of the liquid itself declines, while the gears rotating in high viscosity liquids need to consume power will also rise sharply, so with the viscosity of the conveyed liquid rises, the working speed of the pump should be appropriately lowered, so that not only can reduce unnecessary energy consumption, but also prevent the occurrence of cavitation.
3, the corrosiveness of the liquid
The corrosiveness of the liquid will seriously affect the service life of the gear pump, so we must ensure that all the parts of the gear pump in contact with the liquid, are able to withstand the corrosion of the liquid conveyed.
4, particles
Because of the tiny gap inside the miniature gear pump, any particles close to the gap range may jam the pump, in addition, even if it is a very small hard particles, may be in the case of high-speed gear operation, the gear or bearing permanently damaged. Some particles are present in the liquid, and in many cases the liquid may be clean, but there may be particles in the system piping and containers, joints, welds, especially in new installations or remodeling of the system is very common. Therefore, it is recommended that users install a 300-400mm filter at the pump inlet to protect the pump.
5, temperature
When it comes to temperature, we need to consider the temperature of the liquid as well as the ambient temperature of the pump:
(1) Liquid temperature
Gear pump components to ensure that the temperature range of the liquid can be a stable long-term work, including the pump body, bearings, gears, shafts, magnetic drive and sealing ring materials. At the same time, we also have to consider the maximum allowable working pressure of the gear pump in the extreme temperature change. In particular, the pressure-bearing capacity of the thinnest part of the pump body, the magnetic cover.
(2) ambient temperature
The ambient temperature will have a great impact on the motor selection. May have to configure low or high temperature motor, if the configuration of brushless DC motor, then the ambient temperature on the performance of the drive is also quite large. In addition, some liquids at room temperature or low temperature in winter will solidify, then you need to consider the use of pump head heating to ensure that the pump is normally on, the more common way is to wrap the heat tape on the pump head.
6, the liquid is sensitive to shear
Gear pumps in the work of the active and driven wheel meshing between the wheel will produce shear. Some liquids are very sensitive to shear, and the properties of the liquid will change until it can not be used under large shear. For these liquids, must be used to reduce the working speed of the pump, increase the pump clearance to minimize the shear.
7, inlet and outlet piping
Generally speaking, the inlet and outlet pipe diameter should be not less than the diameter of the interface of the pump body. In order to ensure the normal suction of the pump, the inlet pipe diameter is hoped to be as short as possible, and to reduce the number of elbows.
8, the type of motor and power selection
Generally speaking, the motor can be divided into AC motors (ordinary AC motors, inverter motors, explosion-proof motors, inverter explosion-proof motors, single-phase motors, etc.), brush DC motors, brushless DC motors (BLDC), stepper motors and servo motors. In the industrial field all kinds of AC motors are used more, first of all, look at whether 1x220V or 3X220V or 3X380V, the voltage is determined and then look at whether it is to be explosion-proof (explosion-proof level) or frequency.
9, flow and pressure control
Gear pump flow control is generally achieved by controlling the pump speed. AC frequency conversion motor or DC brushless motor to control the speed of the gear pump to achieve the flow rate adjustment is a very good way, in the higher precision requirements of the occasion or recommend the use of servo motors.
Expanding knowledge
Knowledge point one,Hydraulic Gear Pumps Which kinds
1, external gear pumps
external Gear pump by the shell, the active gear, driven gear, end cover and other components. In the process of the active gear drives the driven gear to rotate together, in the suction area, the wheel teeth are separated from each other, the volume between them increases, the pressure decreases, so that the hydraulic oil can enter. After rotation, the hydraulic oil is transported to the discharge zone, in the discharge zone, the wheel teeth are embedded in each other, hard to squeeze the hydraulic oil out.
2, internal gear pump
Internal gear pump also has two gears, just one inside and one outside, the rotary axis is offset. The main gear is a smaller diameter of the outer gear, driving the outside of the inner gear circle together with the same direction of rotation. In the suction area, the space between the teeth becomes larger and hydraulic oil can enter. Turning to the oil discharge area, the space between the teeth decreases, pushing the oil out.
3, screw gear pump
By the casing, the active screw and the slave screw **** with the composition of the sealing chamber. With the rotation, the sealing chamber from one end to the other, so that the hydraulic oil flow in the axial direction. The discharged hydraulic oil flow is fixed, independent of the screw position, without drastic pressure changes and low noise.
Knowledge point two,Screw pumps are mainly used in what occasions
1, screw pumps because of its variable delivery, self-priming ability, can be reversed, and can transport solid particles of liquid, etc., in the wastewater treatment plant, the screw pumps are widely used in the transfer of water, wet sludge and flocculant liquid.
2, screw pumps due to the structure and working characteristics, can transport high solid content of the media, flow uniformity, pressure stability, low speed is more obvious, due to good variable adjustability, and thus can be a pump for multiple purposes, transporting different viscosity of the media.
3, the installation position of the screw pump can be tilted arbitrarily, suitable for conveying sensitive goods and goods susceptible to damage by centrifugal force and so on.
Knowledge point three,Screw pump working characteristics
Screw pumps mainly have the following characteristics: simple structure, the use of safe and reliable, easy to use and maintain, the liquid continues to be an average, stable pressure, murmur and vibration of the small, with the ability of self-absorption, but the processing of the screw is more troublesome.
Knowledge point four,What is the three screw pump
Screw pump is a rotary displacement pump, according to the number of screws, can be divided into single-screw, twin-screw, triple-screw and multi-screw pumps, the three-screw pumps, that is, the three screw pump. Three screw pump, is a three screw screw pump, including an inserted in the pump cylinder in the active screw and its engagement of the two slave screw, the three mutually meshing screw, in the pump cylinder according to each lead to form a sealing cavity, resulting in the suction and discharge between the mouth of the seal.
Knowledge point five,peristaltic pump uses what
Peristaltic pumps of any of the use of the scene is to deal with fluid (can be any liquid with fluidity, can also be a mixture of solid-liquid), peristaltic pumps is the main role of the transfer. Peristaltic pump conveying accuracy can reach up to ± 0.5%, so it can meet the needs of quantitative conveying, but also can meet the needs of quantitative distribution.
From the level of product function, the use of peristaltic pumps is mainly: quantitative or metered delivery, quantitative or metered distribution. So where there is quantitative conveying and distribution needs of the application scenarios, can choose peristaltic pump to meet the application requirements.
Peristaltic pumps have excellent performance and reliability, so the application is very broad, to meet the application of various processes, including from experimental scientific research, analytical instruments to industrial production in many fields, so the peristaltic pump is very useful, the use of a very wide range of areas:
1, analytical instruments: chromatography, atomic fluorescence photometer.
2, the medical industry: medical equipment and diagnostic reagents instruments.
3, biopharmaceutical: coating machine, granulation and pill-making machine, fermentation tanks, for purification, fluid transportation, distribution filling, high-precision liquid dispensing.
4, experimental research: laboratory and research equipment.
5, food and beverage: ready-to-mix beverage machine, yogurt machine, self-service vending machine, intelligent milk tea machine, seasoning distribution adding, beer industry.
6, the environmental industry: water quality analysis instruments, quality control instruments, water quality sampling instruments, smoke analyzer.
7, printing and packaging: delivery of ink and coating solvents, coatings and adhesives.
8, airbrush ink: airbrush, printer.
9, washing and cleaning: washing machine, dishwasher.
10, ceramic industry: elimination of porosity, defoamer dosing, ceramic slurry.
11, mining: transmission of abrasive ore and tailings slurry, filter feed, flocculant dosing and chemical dosing, ore sampling, pumping thickener underflow.
12, industrial applications: sand-based colloid metering, metering abrasive-containing coating solutions, metering high-viscosity resins, chemical recycling, coatings and paints.
13, pulp and paper industry: fillers, processes in pulp pre-treatment, ideal pumps for pulp coatings, water and wastewater treatment in the pulp and paper industry, precise dosing of chemicals and additives, delivery of dyeing additives.
14, household appliances: intelligent toilet, soap dispenser, disinfectant dispenser, sweeper, mopping machine.
15, industrial machinery: mills, glass fiber spinning machine, photovoltaic production.