[Q&A] 2017.4.16

Lubricating oil, cooling water, mechanical seal flushing, pressure, flow rate, vibration, temperature

1) Ensure that the bearing temperature does not exceed 75°C. For rolling bearings without oil rings, the oil level should be above the center of the balls; for bearings with oil rings, the oil level should cover one-fifth of the diameter of the oil ring. Water and impurities must not enter, and the oil must not become emulsified or turn black； 2. Listen to the sounds; abnormal noises usually occur when rolling bearings are damaged ； 3. Are the readings of the pressure gauge, ammeter, etc. normal? ； 4. Is there vibration in the pump body? ； 5. Is the sealing function working properly?

1 Ensure the oil level is normal. 2 Keep the cooling water flowing smoothly. 3 Conduct proper temperature and vibration monitoring. 4 Do not operate the machine beyond its capacity. 5 Maintain cleanliness of the pump

When a pump in use fails, it should be possible to switch over promptly to ensure normal operation and prevent disruptions in chemical production. This requires necessary maintenance of the standby pump to keep it in good condition while it is not in use. Especially for the standby pump involved in automatic switching, its inlet and outlet valves are open, the pump is filled with the medium to be transported, and it can start operating immediately once the drive mechanism rotates. For the standby pump during shutdown, the quality and quantity of the lubricant should be checked regularly. The pump body and the medium inside the pump, which require heating and insulation, must be heated and insulated. To prevent the rotor from bending under its own weight, and to avoid adhesion between the shaft and bearings that could cause difficulties in starting, the standby pump must be rotated regularly. For pumps that have not been in use for a long time, the plugs on the pump body should be removed to drain all the liquid inside, so as to prevent the pump body from being damaged by freezing in cold weather. If necessary, open the pump body, clean the internal parts thoroughly, and apply rust preventive oil. For pumps that have been out of use for a long time, whether they are on-site or in storage, they should be rotated regularly.

a) Check the bearings of the pump and motor; ensure that the lubricating oil is of proper quality and that the oil level is within the specified range.  b) Inspect and adjust the stuffing box to ensure that its leakage is within acceptable limits.  c) Check all screws to ensure there is no looseness or absence.   d) Keep the unit and its accessories clean; there should be no abnormal noises during operation.  e) The pressure gauge is sensitive and accurate, and the connection points are clean, tight, and leak-free.

Clean the surface of the water pump regularly; for those lubricated with oil, replace the oil every month of use； Lubricated with butter; the butter should be replaced every six months. Avoid pumping in turbid water with excessive sediment, as this can easily cause wear on the impeller, mouth ring, packing, and other components. Before storing the water pump in winter, a thorough inspection should be carried out, covering the power unit, transmission equipment, and electrical equipment

Check the sealing condition； The bearing temperature must not exceed 75℃

Maintenance during operation (1) Be careful that the bearing temperature should not exceed 75°C. (2) Check whether the packing seal is leaking; adjust the tightness of the packing gland so that liquid drips out drop by drop. (3) Replace the lubricating oil regularly. The light oil should be replaced every 500 hours, while the butter should be replaced every 2000 hours of operation. (4) The centrifugal pump should undergo periodic inspection after 200 hours of operation, with worn parts replaced.

To prevent vacuum conditions and excessive vibration, be careful not to overload it

I. Is the bearing operating properly? 1. Oil temperature: It should not exceed 60°C. 2. Oil level: For rolling bearings without oil rings, the oil level should be no lower than the center of the balls ； In bearings with oil rings, the oil level should be at a depth equal to one-fifth of the diameter of the oil ring. To monitor the oil level, a dipstick or oil gauge is installed on the bearing. 3. Oil quality: It must not allow water or impurities to enter, and it must not emulsify or turn black. 4. Are there any abnormal noises? In particular, abnormal sounds usually occur when rolling bearings are damaged. II. Are the readings of the vacuum gauge, pressure gauge, and ammeter normal? 1. The pointer of the vacuum gauge should not swing excessively; excessive swinging may indicate vaporization at the inlet. Additionally, the vacuum gauge reading should not be too high; a high reading may indicate that the inlet valve is blocked or stuck, or that the inlet valve flap has fallen off, or that the water level in the suction tank has dropped. 2. If the pressure gauge reading is too low, it may be due to faulty operation of the pump’s internal components or severe wear of the sealing rings. Additionally, when the system’s water demand is high, the pump outlet pressure also decreases. 3. An excessively high ammeter reading may be due to a large water supply volume or friction inside the pump. If the ammeter reading is too low, it indicates that the pump has sunk underwater or that the outside environment does not require such a large amount of water. III. Whether the pump body vibrates: The vibration amplitude of a water pump generally should not exceed 0.08 millimeters. (Special requirements for pumps are to be specified separately.) Reasons for vibration include: 1. The centers of the water pump and the motor are not aligned. 2. The anchor bolts of the pump body or motor are loose, or the foundation is not solid. 3. The bearing cover is not tightened sufficiently. This caused the bearing shells to vibrate inside the body. 4. Unbalanced rotor mass. 5. Volute pumps, especially those with high head, can also experience vibration to varying degrees at low flow rates, as radial forces act on the rotor at such times. When the outlet valve is opened to a certain extent, the vibration disappears. IV. Is the sealing working properly? 1. The packing should allow a slight amount of water to drip; it should not be too tight, otherwise it will heat up and emit smoke. But if it's too loose, it will cause significant leakage, and oil can easily get into the bearings, leading to oil emulsification. The packing should be replaced regularly, as it loses its ability to provide shaft sealing when it hardens. Prolonged soaking can cause damage to the filler tank. 2. The end-face seal must be filled with liquid before operation to prevent dry friction; for equipment that has not been in use for a long time, it is best to manually rotate the shaft. For media that tend to crystallize or are in granular form, and when the medium temperature is ≥100 degrees, the most effective approach is to implement appropriate flushing, filtering, cooling measures, as well as auxiliary sealing devices.