Maintenance Guide for Cooling Tower Water Pumps

The cooling tower water pump is constantly exposed to high temperature, high humidity, corrosive media and frequent start-stop conditions. If maintenance is lacking, it is very likely to cause mechanical seal leakage, bearing burnout, impeller cavitation and motor overload. To transform "post-event pump rush" into "predictive management", it is necessary to adhere to the ten-point policy of "cleaning, lubrication, tightening, cooling and monitoring", and establish a five-level closed loop of "daily inspection, weekly maintenance, monthly repair, quarterly maintenance and annual repair", so as to achieve the longest trouble-free period at the lowest cost. The following guidelines have been verified on-site by hundreds of people and can be directly implemented.

Before taking over each shift, complete the "look, listen, touch and smell" rapid physical examination within five minutes: check whether the outlet pressure gauge is stable within ±3% of the rated value, and check if there is any dripping water in the mechanical seal return water hole. Listen to whether the noise of the bearing is uniform. If there is a high-frequency whistling sound, it is mostly due to insufficient lubrication; if there is a low-frequency rumbling sound, it indicates that the bearing track is peeling off. Touch the pump casing and the motor bearing housing. If the temperature rise is 35℃ higher than the ambient temperature, immediately switch to the standby pump and conduct an investigation. Smelling for a burnt odor can help detect overcurrent in the windings or cables in advance. Simultaneously record the original values of current, pressure and vibration to establish a baseline for trend analysis.

Once a week, flush the Y-shaped filter screen at the pump inlet to prevent packing debris or algae in the tower from being sucked into the impeller. Use an infrared thermometer to scan the machine seal cover. If the hot spot exceeds 65℃, it indicates that the friction pair is dry grinding and the pump must be stopped and re-leveled. Check the torque of the anchor bolts, couplings and outlet flange bolts. The cooling tower vibrates greatly. Loosening the bolts can cause the rubber gasket of the coupling to tear and the shaft extension to bend. For bearings with oiling nozzles, add lithium-based molybdenum disulfide grease until the old grease is just squeezed out. It is strictly forbidden to add too much to avoid the increase in internal pressure pushing the grease into the mechanical seal and causing contamination.

Every month, remove the front cover of the pump to check the depth of the cavitation pitting on the impeller. If it exceeds 1mm, it must be welded and then reshaped on a lathe; otherwise, the efficiency will drop by more than 5%. Use a feeler gauge to measure the alignment of the coupling. The radial deviation should be no more than 0.05mm, and the angular deviation should be no more than 0.05mm/100mm. If the deviation exceeds the limit, level it with a stainless steel gasket. It is strictly forbidden to strike the motor feet. Clean the scale and sand particles in the mechanical seal cavity. When reassembling, apply silicone grease to the new O-ring to prevent dry grinding. For long-term standby pumps, turn the bearings by hand at 180° and jog them for 5 seconds every week to ensure uniform force distribution on the bearings and prevent false Brinell indentations.

Every 2,500 hours of operation or one cooling season, entrust a professional section to carry out a core-pumping major overhaul: Use a 5% sulfamic acid circulation to clean the scale inside and outside the pump body, then spray the bearing chamber with an electronic cleaner, dry it and fill it with new grease. When replacing the mechanical seal, use a special fixture to compress the spring to the working length to ensure uniform specific pressure on the sealing surface. After reassembly, conduct a performance curve test. If the flow rate drops by 7% or the current increases by 5%, disassembly, inspection and repair are required. The maintenance data is entered into the CMMS system. By using the three trend charts of vibration velocity, bearing temperature and mechanical seal leakage, the remaining life is predicted three months in advance, achieving zero inventory of spare parts.

During the annual shutdown season, the water pump motor is sent to a test station with CNAS qualification to complete tests such as 1500V power frequency withstand voltage, B-level temperature rise loading, and bearing vibration ≤2.8mm/s. Meanwhile, update the lubrication ledger. Send the old grease for inspection in accordance with ISO 4406. If the iron powder grade is greater than 18/16/13, it indicates that the bearing has entered the fatigue spalling period and spare parts should be prepared in advance. Finally, spray epoxy coal tar asphalt on the pump body shell to prevent corrosion by damp chloride ions. By adhering to the above closed loop, the average mean time between failures of the water pump can be extended to five years, the failure rate can be reduced by 60%, and the comprehensive energy consumption can be further decreased by 3%, truly achieving the long-term, low-cost and high-efficiency operation of the "heart" of the cooling tower.