Category: Blogs March 21, 2022
By , contributing editor
Pumping systems have many moving parts and subsystems that could go wrong. Yet many continue to run efficiently after 20 years or more. One important reason why: regular inspection and maintenance.
Periodic monitoring and maintenance finds and fixes problems before they erode performance or damage equipment. With that in mind, what should a regular pump maintenance program include? Here are some thoughts:
Documentation. All commercial and industrial pumps come with installation, operation and maintenance manuals that spell out inspection and maintenance routines and schedules. They may also reference well-known codes and standards. Build this information into your inspection practices and schedule, though you may want to tailor monitoring to meet the criticality of the equipment.
Duty condition. Check and verify that the duty condition is within the pump’s allowable operating region. Anything outside that range can result in poor reliably. Commissioning a pump properly includes determining its operation point to check it against its design. These measurements are most often based on measuring pressure, electrical power, flow rate, or estimated based on some combination of the three. Be sure to use this approach consistently when taking measurements.
Clean up. Remove any dirt, dust, or sludge from bearing housings, motors, and areas around parts with close clearances to reduce corrosion. Also, keeping these areas clean enables you to spot leaks and other problems with your system.
Bearings. Failed bearings can cause pumps to break down in many ways. In facilities where a catastrophic pump failure would shut down operations, maintenance personnel often opt for predictive maintenance using a vibration analyzer to trend vibration and look at specific fault conditions. In facilities with backup capacity and more readily replaceable smaller pumps, predictive maintenance is less common based on cost benefit analysis. Maintenance personnel should listen for unusual vibrations and noise and check for elevated temperatures as they make their rounds.
Lubricants. Some smaller pumps have sealed bearings that last as long as the grease sealed inside them. Other bearings may require a regressing or an oil lubrication system. That means changing oil when it is degraded, usually after a specified number of operating hours. In between those changes, check the lubricant level. Also, monitor for temperature and contaminants to make sure the oil—and your bearing—are not beginning to degrade prematurely.
Leaks. As long as there have been gaskets, packing and mechanical seals, there have been leaks. They require regular checking when doing rounds. Depending on the liquid (i.e. water), a small leak may not require immediate attention but should be monitored closely. If leakage begins to increase or the base plate starts showing signs of corrosion, it is a concern to address. Also, make sure to look at flanges and preassembled pump joints, which should not be leaking.
Alignment. Initial precision alignment is important, and coupling alignment should be checked periodically and realign if necessary. While you can do this with a simple straight edge or dial indicator, facilities that want to improve reliability use laser alignment tools to achieve precise coupling alignment. Maintaining good alignment reduces vibration and improves performance while reducing wear.
Gland packings. Gland packings usually consist of woven fabric often impregnated with a slippery PTFE-type material. Compress the packing just enough to maintain the concentric alignment of the gland follower, but not so tightly that it wears out quickly. Gland packings allow a small amount of leakage to bleed off heat and prevent the packing and follower from overheating, so keep track of any changes in fluids coming off the packings.
Auxiliaries. Many pumping systems include heat exchangers, clean flush, lubricating oil, and other auxiliary systems. Include them in the maintenance plan so ensure they continue to function properly.
Inventory. Make sure to stock the right spare parts so you can address problems and return pumps to service quickly. Start with enough inventory to meet the manufacturer’s recommended consumable replacement schedules. Then consider normal supplier lead time when ordering parts and whether you have enough backup capacity to take a pump offline. For pumps used for severe duty and subject to erosion, consider stocking parts that are not ordinarily considered consumables, like impellers, shafts, and casing liners.
Records. Record the results of your inspection and maintenance procedures. When problems arise, note when a component failed or needed repair, the cost in labor-hours and parts, and, if possible, the cause. This is your baseline data for all future reliability improvement programs.
This outlines a basic pumping system maintenance program. For more information about how to maintain your system, refer to Hydraulic Institute standard ANSI/HI 14.4.
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June 20, 2022