What are the troubleshooting methods for gear pump noise?

In the vacuum oil filter, the gear pump is used as an oil discharge pump to overcome the vacuum suction force when the oil that has been purified in the vacuum separation tank is discharged out of the vacuum tank. The noise generated by the gear pump is the main noise source of the vacuum oil filter noise. Analyzing the cause of the noise generated by the gear pump and controlling its noise will help improve the quality of the vacuum oil filter.

What are the troubleshooting methods for gear pump noise?

Causes of Noise Caused by Gear Pumps The main reasons for the noise generated by the gear pump are the following four aspects: (1) pressure shock or cavitation caused by trapped oil phenomenon, thereby generating noise; (2) due to errors in gear manufacturing, when it is engaged in operation , Gear teeth may be subject to sudden loading shock caused by vibration and noise; (3) The pulsation of the flow caused by pressure pulsation and issued noise; (4) The bearing is not accurate or the noise caused by poor installation, and between the side plate and the gear side Friction and excitation noise.

The most important of these are the reasons (1) and (2). In particular, the phenomenon of trapped oil has the greatest impact on noise. In order to ensure the smooth running of the gears, the overlap coefficient must be greater than 1, then there are two pairs of gear teeth meshing at a time, so that neither oil nor oil can be formed between the two pairs of gears. The trapped oil volume. The law of the change in trapped oil volume. When the trapped oil volume changes from large to small (change amount is Ah), its internal pressure rises, causing shock and vibration; When trapped oil volume increases from small to large (change amount is AF2), its internal pressure decreases to form a vacuum Causes cavitation. This is the so-called trapped oil phenomenon.

In order to solve the noise caused by the trapped oil phenomenon, an effective measure is to process the relief groove on the side plate. The principle is: when the trapped oil volume is greatly changed, it is connected to the pressure chamber through the relief groove to discharge the oil. Liquid; When the trapped oil volume increases from small to large, with the aid of unloading tank to make it communicate with the suction chamber, thereby sucking people to break the oil, which can avoid the phenomenon of trapped oil.

If the relief groove is opened accurately, noise can be reduced by about 7dB(A).

Gear pump noise failure analysis and countermeasures For a shaped gear pump, its unloading groove has been processed, its tooth accuracy, bearing accuracy and installation accuracy have been determined. Gear pumps sometimes still generate large noise, especially in gear pumps used as drain pumps in vacuum oil filters. Since the suction force of the vacuum needs to be overcome when the oil in the vacuum tank is to be discharged, this makes it more difficult for the gear pump to drain the oil. If the treatment is not proper, it may generate a large amount of noise.

When the gear pump in the vacuum oil filter generates a large amount of noise, you can find the cause and take measures from the following aspects:

(1) Part of the suction line or filter in front of the gear pump is blocked. At this point, it can be seen from the tubing that there is very little oil sucked in. Insufficient oil absorption will cause dry grinding and cavitation, and it will give off loud noise. At the moment, the plugging point should be found, the dirt should be removed, and the oil sucking should be smooth.

(2) Suction line in front of gear pump Suction air. At this point, bubbles can be seen from the suction pipe, and bubbles can be seen from the discharged oil. The cavitation noise is generated when the gear pump sucks air. The key row of parts is the inlet flange seals of the various valves and pumps of the pump, and the self-tightening oil seal of the pump, which should be quickly eliminated after finding it.

(3) The flow area of ​​the inlet filter is too small. If you rule out the modern tool on the HSS tool body. The use of physical vapor deposition (PVD) to coat thin layers of wear-resistant material can greatly improve the performance of high-speed steel tools, in general. TiN, TiC, etc. are used for the coating material. However, with the TiN coating, the surface of the tool is golden yellow. Thick coated high-speed steel cutters appeared in the international market in about 1980.

The development has been extremely rapid. For more than ten years, it has been used in high-speed steel tools for cutting tools, endmills, drills, etc. to improve cutting efficiency. Obtained significant economic benefits. The study of coated idle steel cutters in China began in the 1980s. In the past ten years, the tool manufacturing industry has been from the United States. Japan has introduced nearly 10 sets of PVD coating equipment and has sold various coated high-speed steel cutting tools. In various regions and departments, there are a large number of domestically produced coating equipment, and different physical vapor deposition methods are used, such as arc plasma vapor deposition, plasma gun electron beam ion plating, and hollow cathode gun electron beam emission. The ion plating method, e-beam gun electron beam ion plating method, etc. have their own characteristics, advantages and disadvantages, and the quality of coating products also varies. Arc plasma vapor deposition method is used most.

The coated high-speed steel cutter has a thermal conductivity of 29.31 W/(mC) and a linear expansion coefficient of (9.319.39)xl (T6/C.) whereas the high-speed steel substrate has a hardness of only HV800850. Therefore, the coated high-speed steel The tool has a hard layer on the surface, good wear resistance, and a low coefficient of friction with the material being processed, and the toughness of the base material does not decrease. Practical applications show that the coated high-speed steel is compared with uncoated HSS tools. The cutting force of the tool can be reduced by 5~10%. Due to the thermal barrier effect of the layer material, the cutting radius of the cutting part of the tool body is also reduced; the surface roughness of the workpiece has been reduced; the tool should be considered into the oil filter Choosing whether to adapt to the problem, such as too small a flow area of ​​the inlet filter, can also make the suction oil insufficient, causing dry grinding and cavitation, and making a loud noise.The solution is to replace the filter with a comparable flow area.

(4) The pump speed is too high. Each type of gear pump has the recommended optimal operating speed. If one wants to increase the flow rate by increasing the rotational speed, the gear meshing vibration will be accelerated, and the suction of the pump will be insufficient, resulting in a drastic increase in the noise of the pump. In this case, the speed should be reduced in time. (5) The pump shaft is not concentric with the motor shaft. Gear pumps require the use of shaft sleeves or elastic shaft joint transmission methods. For example, if two shafts are not concentric, vibration in the transmission will be enhanced, and the gear pump will be subjected to alternating load and the noise will be large. Therefore, the gear pump should be reassembled. Stay concentric.

Summary: This article only makes some simple analysis of the reason why the gear pump generates squeaks in the vacuum oil filter. In other areas, noise is generated by using a pinwheel pump. It is also possible to find the cause and eliminate it from the above five aspects.