Vacuum pump common problems analysis
1. Liquid ring vacuum pump of reason and treatment of low vacuum degree
Liquid ring vacuum pump of reason of low vacuum degree:
(1) The water supply of liquid ring vacuum pump is not enough.
(2) Part of the packing leaks.
(3) The bearing deflection causes the collision and friction between the impeller and the side cover to produce the scuffing and air leakage.
(4) The circulating water becomes hot and the temperature rises (generally lower than 25 ℃).
(5) The liquid ring vacuum pump or the flow part of the pipeline is blocked.
(6) The clearance between impeller and side cover is too large.
How to improve the vacuum degree of liquid ring vacuum pump?
(1) Open the valve to increase the water supply.
(2) Check and straighten the parts with leaky air seal. Tighten the connecting bolt and plug at the sealing position, replace the packing, increase the sealing water volume and replace the gasket.
(3) Repair the side cover of liquid ring vacuum pump, adjust the clearance to the specified value, and check and adjust the bearing.
(4) Increase cold water supply and reduce water temperature.
(5) Check and clean the impeller and pipeline of liquid ring vacuum pump to remove the obstruction.
2. Liquid ring vacuum pump of effect of scale on mechanical efficiency
Scale has a certain influence on the liquid ring vacuum pump, because the working fluid (water) usually contains calcium, magnesium and other carbonate substances. During the normal operation of the liquid ring vacuum pump, the solubility of the corresponding carbonate substances in the water will be reduced under the action of the heating temperature rise of the working fluid. After the vacuum pump runs for a long time, the substances will gradually crystallize and precipitate and attach to the disc, impeller, vacuum pump body and other parts.
After a long-term operation of the liquid ring vacuum pump, the internal scaling of the vacuum pump body will become very serious, which often leads to the reduction of the gap between the disc and the impeller. During the operation of the liquid ring vacuum pump, abnormal noise, excessive starting current, significant reduction of suction capacity, vacuum degree and other phenomena occur, resulting in the reduction of the efficiency of the real air vacuum pump.
At this time, the rotor can be pulled to use 10% oxalic acid to completely descale the vacuum pump, and then use clean water to wash. If it is found that the scale in the vacuum pump body is thick, it is necessary to disassemble the vacuum pump, remove the scale in detail locally, increase the internal volume of the vacuum pump, and improve its operation efficiency.
For liquid ring pump, there are many factors that affect its actual operation efficiency. Therefore, in the process of daily operation and maintenance, it is necessary to establish perfect system measures for vacuum pump design, transformation and type selection, and operation and maintenance from the aspects of suction medium (water) level and flow, as well as the quality of working water, etc., so as to ensure that the vacuum system always works under the optimal working conditions, save a lot of maintenance funds for the hospital, and effectively improve the actual operation of the vacuum system Mechanical efficiency in the process.
3. Liquid ring vacuum pump treatment of the abrasion of the parts
In the long-term use of liquid ring vacuum pump, the wear of parts will be caused, which will affect the vacuum degree and service life of the vacuum pump. In view of this kind of wear phenomenon, the technicians of vacuum pump factory provide you with several methods to deal with the wear of parts:
(1) In view of the corrosion of the pipe fittings of the liquid ring vacuum pump, we changed the ordinary pipe fittings to wear-resistant and corrosion-resistant stainless steel pipe fittings, and basically eliminated the damage of the pipe fittings.
(2) In the early stage, we carried out surfacing repair for the front and rear distributors, side covers and internal walls of vacuum pump casings. According to the deep and long wear area (along the circumference), the deep wear area (between the suction port and the air pressure port) of the distributors, the corrosion degree of the shallow wear area (at the end face) of the side covers is not the same, and the method of welding repair is not the same for different situations. Finally, the height of welding repair is 1-2mm higher than the actual height. It shall be planed and ground smooth with angle grinder.
After the repair and reassembly, the vacuum degree of the liquid ring pump increased when it was running again, and the effect was obvious. After 3 months of operation, after opening the distributor, it was found that there was only slight wear at the overlay.
(3) In addition to hardfacing repair of worn parts, the manufacturer is required to add wear-resistant coating (epoxy wear-resistant ceramic) on all flow passing surfaces of the vacuum pump body, with a spraying thickness of 1mm. Because the acid resistance, alkali resistance and wear resistance of epoxy wear-resistant ceramics are better than that of cast iron, the service life of epoxy wear-resistant ceramics is long. After nearly half a year’s operation, we found that there was only slight wear on the overflow surface of the vacuum pump body after opening the distributor and the effect was obvious.
4. Liquid ring vacuum pump importance of clearance to the vacuum degree
It should be noted that the vacuum degree of the high vacuum cylinder of the two-stage liquid ring vacuum pump is generally considered to be high, so the clearance should be smaller. In fact, this is not the case. It is precisely because of the high vacuum degree of the high vacuum cylinder and the large free path of the gas molecules. In the same gap, the gas molecules are not easy to penetrate the gap. In the low vacuum cylinder, because the free path of the gas molecules is small, the gap of the low vacuum cylinder must be strictly controlled, but the gap of the high vacuum cylinder can be appropriately relaxed. We have done a comparative test on a 15L / s double stage liquid ring vacuum pump, which proves that this viewpoint is correct and beneficial to improving the pumping rate. We have tested that the side clearance of high vacuum cylinder of E2M40 vacuum pump (nominal pumping speed 11.8l / s) is 0.095mm and that of low vacuum cylinder is 0.06mm; the side clearance of high vacuum cylinder of d-650k vacuum pump (nominal pumping speed 10.67l / s) is 0.07 ~ 0.08mm and that of low vacuum cylinder is 0.05mm.
5. Liquid ring vacuum pump reason of strong vibration
When the vibration of liquid ring vacuum pump body is too large, the vibration of the air inlet and exhaust pipelines connected with it is also large. If the vibration of the foundation and base is not large, the vibration caused by the loose foundation fixation can be eliminated, and the main reason is the vacuum pump body itself.
1) The valve plate is broken.
When the valve plate breaks. The vacuum pump body vibrates strongly and makes a lot of noise, which is generally manifested as large axial vibration.
2) Scaling of rotor blades.
After the blade scaling, the rotor mass is unbalanced and vibration occurs during rotation. Such factors generally have little influence.
3) The rubber pad of coupling is damaged.
The rubber cushion is easy to wear and even thrown out by grinding powder, which causes the two pairs of wheel pairs of the coupling to directly rub and aggravate the rotor vibration. The cushion with good quality must be used in work and its wear condition must be checked frequently.
4) liquid ring changes.
If the inner diameter of the liquid ring becomes larger (caused by insufficient water supply), the top of the blade will collide with the inner wall of the liquid ring, resulting in vibration. If the inner diameter of the liquid ring becomes smaller (caused by excessive water supply), the impeller’s turbulence and resistance loss will increase, which will cause vibration and increase the power consumption of the vacuum pump.
6. The reason and treatment for the obvious decrease of suction and vacuum degree of vacuum pump:
Reason:
(1) The flexible valve plate is damaged.
(2) After repair, the axial clearance does not meet the requirements.
(3) Corrosion of parts.
(4) Internal scaling is serious.
(5) Leakage of packing seal.
(6) The material with liquid medium is abraded to increase the clearance between internal parts.
(7) There is a leak in the system.
(8) The water supply is insufficient or the water temperature is too high.
Treatment method:
(1) Replace the valve plate.
(2) Readjust the end play.
(3) Replace parts.
(4) Remove scale.
(5) Tighten the packing gland slightly.
(6) Strengthen the regulation of tower top load, purify the medium, prevent the liquid from sucking into the vacuum pump, and replace the worn parts.
(7) Check the leakage point of the pipeline and try to stop it.
(8) Adjust the water supply and check whether the water pressure is too low or the water temperature is lowered.
