hello everyone! Today let's talk about pneumatic diaphragm pumps, which are very common in industrial production. They can be used to transport corrosive liquids, high viscosity materials, and media with particles. However, in order to make this device obediently and stably operate, we need to first understand its "temperament". Next, I will talk to you about the principle of pneumatic diaphragm pumps, precautions during operation, and how to deal with common faults.
1、 The principle of pneumatic diaphragm pump: how does air "push" liquid?
The working principle of a pneumatic diaphragm pump is actually not difficult to understand. We can imagine it as two small rooms that can "breathe", separated by a diaphragm in the middle. Each room has a feeding port and a discharging port. These two diaphragms are like two 'small pistons', driven by compressed air.
Specifically, pneumatic diaphragm pumps are mainly composed of pump body, diaphragm, intake valve, exhaust valve, and inlet/outlet check valves. When compressed air enters the air chamber on one side of the pump body through the air inlet, it will push the diaphragm to move to one side. At this time, the volume of the chamber on the other side of the diaphragm will increase, the pressure will decrease, and negative pressure will be formed. Under the action of atmospheric pressure, the material will push open the inlet one-way valve and enter this chamber, which is the process of "suction".
The diaphragm pushed by compressed air will squeeze the material inside its chamber, pushing the material out of the one-way valve at the outlet, which is called "discharge". When the diaphragm reaches its end, a clever design - the reversing mechanism - comes into play, changing the flow of compressed air and allowing it to enter the other side of the chamber, pushing the diaphragm on that side to move in the opposite direction. In this way, the original suction chamber begins to discharge materials, and the original discharge chamber begins to suck materials. The two diaphragms alternate and reciprocate in this way, continuously conveying materials.
Simply put, a pneumatic diaphragm pump relies on compressed air to "push" the diaphragm, which in turn "pushes" the liquid. By constantly switching the air flow direction, it achieves continuous material transportation. It has no complex rotating parts and does not require electricity, making it particularly suitable for working environments that are flammable, explosive, and highly corrosive.
2、 Operation precautions: tips for making diaphragm pumps work "healthily"
1. Pre startup inspection
-Air source inspection: Pneumatic diaphragm pumps rely on compressed air to "extend their life", so it is necessary to check whether the air source pressure is within the specified range before starting up. Generally speaking, a gas source pressure of 0.4-0.7MPa is more suitable. The pressure is too low, the flow rate and head of the pump are not enough, and the work is boring; Excessive pressure can increase the wear of diaphragms and other components, shortening their service life. At the same time, it is also necessary to check whether the compressed air is dry, whether there is moisture and impurities. If there are, air filters and dryers need to be installed, otherwise these dirty things will enter the pump body, block the air path, and corrode internal parts.
-Material inspection: Confirm whether the material to be transported meets the requirements for pump use. The corrosion resistance and applicable materials of diaphragms and pump bodies made of different materials vary. For example, nitrile rubber diaphragms are oil resistant but not resistant to strong acids and bases; Fluororubber diaphragms have strong corrosion resistance and can withstand various strong acids and alkalis. If there are particles in the conveyed material, it is also necessary to check if the particle size is within the allowable range of the pump. Particles that are too large can easily get stuck in the one-way valve and affect the normal operation of the pump.
-Pipeline inspection: Carefully check whether the feeding and discharging pipes are blocked or damaged, and whether the connecting parts are tightened. If there is a leak in the feeding pipe, it will cause the material to not be sucked in; If the discharge pipe is blocked, the pressure inside the pump will increase, which may damage the diaphragm. In addition, there are also requirements for the length and height of the feeding pipe. If it is too long or too high, it will increase the difficulty of suction. Generally speaking, the vertical height of the feeding pipe should not exceed 2 meters.
2. Observations during operation
-Listen to the sound: During normal operation, the sound of the pneumatic diaphragm pump is smooth and regular. If you suddenly hear a strange "click click click" sound, or if the sound becomes dull, you need to pay attention. It may be due to loose or worn internal parts, or foreign objects entering the pump body. At this point, it is important to quickly shut down the machine for inspection to prevent minor issues from turning into major malfunctions.
-Check flow rate and pressure: Regularly observe whether the flow rate and outlet pressure of the pump are stable. If the flow suddenly decreases, it may be due to insufficient feed, blocked one-way valve, or damaged diaphragm; If the export pressure fluctuates greatly, in addition to checking whether the pipeline is blocked, it is also necessary to check whether the gas source pressure is stable.
-Touch temperature: After running for a period of time, touch the surface of the pump body with your hand (be careful not to get burned!). If the temperature is too high and exceeds the normal range, it may be caused by insufficient lubrication, excessive diaphragm friction, or poor air flow. The cause should be investigated in a timely manner.
3. Maintenance after shutdown
-Cleaning the pump body: After shutdown, it is necessary to promptly clean the residual materials in the pump body and pipelines. Especially after transporting corrosive and easily crystallized materials, it is necessary to thoroughly clean them, otherwise residual materials will corrode the pump body and may clog the pipeline the next time it is turned on. You can rinse with clean water or a suitable cleaning solution. When rinsing, be sure to close the feed valve and open the discharge valve to allow the cleaning solution to flow out smoothly.
-Inspect components: While the machine is stopped, check for wear, aging, or damage to vulnerable parts such as diaphragms, check valves, and sealing rings. Replace the problem in a timely manner, don't wait until the next time it malfunctions during startup to regret it. In addition, it is necessary to check whether the bolts and nuts are loose and tighten them in a timely manner.
3、 Common troubleshooting: Hand in hand teaching you how to "prescribe the right medicine"
1. The pump is not working
-Reason 1: No air source or insufficient air source pressure: First, check if the air compressor is running normally and if there is any air leakage in the air source pipeline. If the compressor is fine, then check if the set pressure of the pressure reducing valve meets the requirements. If the pressure is too low, simply increase it to the appropriate value.
-Reason 2: Fault in reversing mechanism: The reversing mechanism is a key component that controls the flow of compressed air. If it gets stuck or damaged, the pump cannot reverse direction normally. At this point, the reversing mechanism can be disassembled to check for wear and blockage of internal components such as springs and valve cores, and to clean impurities or replace damaged parts.
-Reason 3: Blockage of intake or exhaust valve: Check the intake and exhaust valves to see if the valve ports are blocked by impurities. If it is blocked, you can carefully unclog it with a fine wire, or remove it and soak it in cleaning solution for cleaning.
2. Insufficient traffic
-Reason 1: Insufficient feeding: Check whether the feeding pipe is leaking or blocked, and whether the material in the tank is sufficient. If it is self-priming feeding, it is also necessary to check if the feeding height is too high, exceeding the self-priming capacity of the pump. You can lower the feed height or install a suction device on the feed pipe.
-Reason 2: One way valve failure: If the one-way valve is not tightly sealed or stuck by particles, it will cause material reflux and decrease flow rate. Disassemble the one-way valve and check if the sealing surfaces of the valve ball and seat are worn. If there is wear, it can be repaired by grinding or replaced with a new one-way valve. If it is stuck by particles, just clean up the impurities.
-Reason 3: Damaged diaphragm: Damaged diaphragm can cause compressed air to enter the material chamber, affecting the suction and flow of the pump. To determine if the diaphragm is damaged, you can observe whether there is any material spraying out from the exhaust port. If it is confirmed that the diaphragm is damaged, it is necessary to shut down and replace it with a new diaphragm. When replacing, pay attention to the installation direction and sealing of the diaphragm to ensure proper installation.
3. Unstable export pressure
-Reason 1: Fluctuations in air source pressure: Check if the pressure in the air compressor's storage tank is stable and if the regulating function of the pressure reducing valve is normal. If the pressure fluctuation of the gas source is large, the capacity of the gas storage tank can be increased, or a stabilizing device can be installed to keep the gas source pressure stable.
-Reason 2: Pipeline problem: Check if the discharge pipeline is blocked, bent, or if the outlet valve is abnormally closed. Clean up the blocked pipeline, adjust the pipeline direction, and ensure smooth discharge. In addition, it is necessary to check whether the support and fixation of the pipeline are firm to avoid pressure stability being affected by pipeline vibration.
-Reason 3: There is air inside the pump: If air is mixed into the pump, it will cause pressure fluctuations. You can open the exhaust valve on the pump body to let the air out until a stable material flows out. Before starting up, you can also fill the feed pipe with materials and exhaust the air to prevent air from entering the pump body.
4. Abnormal noise
-Reason 1: Loose parts: Check if the bolts, nuts, diaphragm fasteners, etc. on the pump body are loose. If it's loose, just tighten it with a wrench. However, it should be noted that the tightening force should be moderate and not too tight, which may damage the parts.
-Reason 2: Component wear: When components such as bearings, connecting rods, and diaphragms are severely worn, they can also produce noise. At this point, it is necessary to disassemble the pump body and check for wear and tear. If the wear is not severe, it can be alleviated by replacing lubricating oil, adjusting clearances, and other methods; If the wear is severe, new components can only be replaced.
-Reason 3: Foreign objects entering: Foreign objects, such as small stones, metal fragments, etc., entering the pump body can collide with internal parts and produce a harsh noise. In this situation, the machine should be stopped immediately, the pump body should be disassembled, foreign objects should be cleaned up, and any damaged parts should be checked for timely repair or replacement.
Alright, that's all for the principle, operating precautions, and common troubleshooting of pneumatic diaphragm pumps. I hope these contents can be helpful to everyone. If you encounter any problems with pneumatic diaphragm pumps in the future, you will have a clear understanding! If you have any other questions, please feel free to communicate and discuss at any time!
