From the transfer of highly corrosive and toxic chemical raw materials in the chemical industry to the transfer of sauces and beverages in the food industry where hygiene standards are stringent; from the treatment of sewage and sludge in the environmental protection industry to the precise metering of high-purity pharmaceuticals in the pharmaceutical process, diaphragm pumps have become the ideal choice for many industrial scenarios due to their unique working principle and excellent performance. Their leak-free, self-priming capability and ability to adapt to complex media ensure the continuity, stability and safety of the production process.
Mastering its correct selection method and effective daily maintenance techniques is key. Next, let us explore the diaphragm pump selection points and maintenance.
一.Diaphragm pump selection strategy
1.Among the different diaphragm pumps, based on the differences in power sources, they are mainly divided into three categories: pneumatic diaphragm pumps, electric diaphragm pumps and hydraulic diaphragm pumps.
Pneumatic diaphragm pump: it is powered by compressed air, in operation, the pump will not overheat, exhaust is the expansion of the heat absorption process, will not discharge harmful gases; without electricity, grounded to prevent static sparks, so especially suitable for work in flammable and explosive environments, such as petroleum, chemical industry and other hazardous areas of the industry. It can also pass through the particle-containing liquid, the shear force of the material is extremely low, can transport from low viscosity to high viscosity, from corrosive to viscous various fluids, the flow rate can be adjusted by installing a throttle valve in the material outlet, and has a self-absorption function, can be empty running, diving work, there is no complex control system, small size, light weight, easy to move, easy maintenance, will not be contaminated because of drips and leaks in the working environment . However, its pressure will be limited by the pressure of the gas source, the flow rate is usually not too large, mostly used in small systems.
Electric diaphragm pump: rely on the motor to provide power. It does not need to be irrigated to draw water, self-priming capacity of more than 7 metres, through the performance is good, the diameter of the following 10 mm particles, slurry, etc. can easily pass. As the diaphragm will transport media and drive mechanical parts separately, the media will not leak outward, and the pump itself without shaft seal, the service life is greatly extended. The part of the pump body through which the medium flows can be made of cast iron, stainless steel, rubber lining and other materials according to the requirements of the user, and the motor has a variety of choices such as ordinary, explosion-proof and speed-regulating type. Its small size, light weight, the use of planetary cycloid drive structure, compared with the same type of pump, the volume and weight are reduced by about half. However, when used in flammable and explosive environments, explosion-proof motors need to be selected, and energy consumption is relatively high.
Liquid-operated diaphragm pump: driven by the pressure of the liquid medium (such as oil). Its self-priming capacity can reach more than 5 metres, the outlet pressure can reach 20kgf/cm², through the performance is good, can be pumped viscosity in 1500 centipoise below, the particle diameter of 10 mm or less, temperature resistance of up to 150 ℃ of the medium. The upper part is equipped with oil cylinder, there are replenishment valve and safety valve, replenishment valve can automatically replenish oil to the front and rear ends of the plunger, the safety valve in the pump outlet part of the blockage or pressure exceeds the rated value, can make the hydraulic oil automatically discharged, to play the role of protecting the pump. However, its structure is relatively complex, need to be equipped with special hydraulic system, maintenance costs are high.
2.Selection according to working conditions
Flow and pressure: flow refers to the volume of the medium conveyed by the diaphragm pump per unit time, and pressure refers to the output pressure that the pump can provide. In determining the flow rate, according to the actual demand for production or conveying materials, consider the possible maximum flow rate and minimum flow rate, for example, in chemical production, the reaction process on the addition of raw materials have strict requirements, need to ensure that the diaphragm pump in different working conditions can meet the flow rate requirements. Pressure, to consider the length of the transport pipeline, height, resistance and the characteristics of the medium and other factors, such as transporting the medium to the high storage tanks, you need sufficient pressure to overcome gravity and pipeline resistance .
Media characteristics:
Corrosivity: If the transport medium is corrosive, such as strong acid, alkali, etc., the pump body and diaphragm material must have good corrosion resistance. For the transport of hydrochloric acid and other highly corrosive media, fluorine plastic lined pump body and PTFE diaphragm; for general corrosive media, stainless steel pump body and fluoroelastomer diaphragm may be sufficient.
Granularity: when the medium contains particles, the diaphragm pump overflow parts need to be wear-resistant, and the flow channel design should be reasonable to prevent particles from clogging. For example, conveying sewage containing sand and gravel, you can choose the inlet for the ball valve, flow channel larger diaphragm pump, its volumetric principle of operation so that it is not easy to be clogged.
Viscosity: For high viscosity media, such as paint, ink, etc., it is necessary to choose a diaphragm pump that can provide sufficient power and suitable flow rate. Some diaphragm pumps are specially designed to accommodate high viscosity media to ensure smooth operation.
Temperature and pressure: different diaphragm pumps have different tolerance ranges for the temperature and pressure of the medium. In the high temperature environment, the diaphragm and pump body materials need to have good high temperature resistance, such as oil refining in the transport of high-temperature oil, need to use high temperature diaphragm and pump body materials; in the high-pressure conditions, the pump structure and sealing performance to be able to withstand the corresponding pressure, to ensure safe operation.
二．Diaphragm pump routine maintenance
1.Before starting
Before starting the diaphragm pump, the diaphragm pump needs to be inspected carefully. First of all, to carefully check the pump and piping at the combination of whether there is loose phenomenon, any one of the loose may trigger leakage during operation and other problems, affecting the normal operation of the equipment. Next, manually rotate the pump, feel whether its rotation is flexible, if the rotation of the jam or abnormal resistance, it may mean that the internal components are faulty, need to be promptly investigated.
The steering of the motor should not be ignored, the correct steering is the premise of the normal work of the pump. If the steering is wrong, not only can’t realise the medium delivery, but also may damage the pump body. Adding an appropriate amount of bearing lubricating oil to the suspension is like injecting vitality into the joints of the machine to ensure that the bearings are well lubricated during operation and reduce wear and tear. At the same time, perform the filling and priming operation, this step is crucial for diaphragm pumps with self-priming capability, which helps the pump to quickly build up its pumping capacity. Finally, close the relevant gate valve and instrumentation, fully prepared for start-up.
2.In operation
After the diaphragm pump began to run, it is necessary to pay attention to its operating status . To strictly control the flow and head of the pump, so that it runs within a reasonable range. This is like driving a car to control the speed, to avoid damage to the vehicle caused by speeding or low-speed driving. If the flow is too large or head is too high, may lead to excessive load on the pump, shorten its service life; Conversely, the flow is too small or head is too low may affect the productivity .
In the process of operation, but also regularly remove the air compressor and pipeline rust water. If this rust water is not discharged in time, it may enter the pump body and cause corrosion to the internal parts, affecting the performance and life of the pump. At the same time, the periphery of the diaphragm pressure plate and the outside of the guide valve sleeve should be closely inspected for leakage, wear and other abnormalities. Once the problem is found, it should be shut down in time to avoid the problem from expanding .
3.After shutdown
When the diaphragm pump is shut down after completing the work, first of all, the pump should be emptied of the medium to prevent the medium from remaining in the pump, resulting in corrosion or clogging. Then, the pump chamber and the inlet and outlet conduits are cleaned to remove residual impurities and dirt and keep the interior clean. If the diaphragm is found to be ruptured during operation, it is also necessary to thoroughly clean the air valve and pump chamber to prevent impurities from entering the valve and affecting its normal operation .
Cleaning the surface of the pump body is also an essential step, removing surface dust, oil, etc., not only to maintain the beauty of the equipment, but also to prevent these pollutants from causing corrosion of the pump body. In addition, to regularly replace the diaphragm, the diaphragm as a diaphragm pump key wearing parts, with the increase in the use of time, will gradually wear aging, regular replacement to ensure stable pump performance .
Diaphragm pumps as a key equipment in industrial production, its selection and routine maintenance work is critical. Correct selection is to ensure the efficient operation of diaphragm pumps based on a comprehensive understanding of the characteristics of different types of diaphragm pumps, accurately grasp the needs of the working conditions, strictly identify the quality of the product, and take into account after-sales protection. Negligence in any part of the selection process may result in the equipment failing to meet the production requirements, or even lead to potential safety hazards.
Effective routine maintenance is the guarantee of long-term stable operation of diaphragm pumps. Meticulous inspection before startup, close attention during operation and careful care after shutdown are all indispensable steps. At the same time, we also need to master the special circumstances of the coping strategy, in order to be able to quickly take measures to reduce losses in the event of equipment failure.
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