Check list for preventive maintenance of centrifugal pumps

Carry out the checklist for preventive maintenance of centrifugal pumpsThe main reason for this is that well-maintained equipment requires fewer repairs and represents lower costs for the company.

Most of the pump maintenance activities focus on the verification of gaskets and mechanical seals for leakage, as well as the validation and correct functioning of the engineHowever, it is necessary to consider the performance, reliability and efficiency over the lifetime period, which is affected by the environment to which it is exposed.

In this article, we will focus on the idea of what activities to consider in a check list for preventive maintenance of centrifugal pumps. Establishing in the first instance the efficiency of the pump, as improving efficiency will reduce maintenance and operating costs.

The efficiency of a machine indicates its ability to convert one form of energy into another. If one unit of energy is input to a machine and its output is half a unit, the efficiency of the machine is 50%.

The total efficiency of a centrifugal pump is the product of mechanical, volumetric and hydraulic efficiencies:

• Mechanical efficiency accounts for losses in the bearing frame, stuffing box and mechanical seals.
• Volumetric efficiency includes losses due to leakage or wear of rings, bores and vane clearances (in case of semi-open impellers).
• Hydraulic efficiency includes liquid friction and other losses in the volute and impeller.

While the mechanical and volumetric losses contribute significantly to the overall efficiency, hydraulic efficiency is the most important factor. Therefore, some basic measures have to be taken into account when managing industrial Preventive Maintenance and checklist for preventive maintenance of centrifugal pumps to ensure optimum performance.

Check list for Preventive Maintenance of Centrifugal Pumps

• Monitor bearing temperaturesThe lubricant level and vibration. To check the verification the lubricant must be clear and without signs of foaming.
• Check any cooling water for effective operation. Manual test differential on coolers, jackets and exchangers, if necessary Disassemble and clean.
• The mechanical seals should not show signs of visible leakage. Some leakage at the gasket is normal, but this should not exceed a rate of approximately 40 to 60 drops per minute.
• Observe for vibration in the pump, as excessive vibration may be the result of a change in the pump's pump alignment or cavitation resonances between the pump, its base or valves located in the suction and/or discharge lines.
• Daily Check the operability of the heat tracing generated, due to the packaging.
• Monitor changes in the pressure level, as a gradual decrease in the developed head pressure of the pump may indicate that the impeller clearance has widened.

Up to this point, the check list for the preventive maintenance of centrifugal pumps must be carried out daily.

• Monthly check the oil in the bearing reservoirs, add if necessary and ensure that the oil level is at the correct distance from the shaft centre line.
• Check the condition of the bearing brackets monthly and clean dirt if necessary. The drain hole must be open.
• On a quarterly basis Check the integrity of the pump base and verify that the fastening bolts are not tightened.
• Quarterly for oil-lubricated pumps, change the oil after the first 200 hours of operation for a new pump, and then every three months or 2,000 hours of operation, whichever comes first.
• Grease the motor bearings according to the manufacturer's instructions, also on a quarterly basis.
• Semi-annually apply a light coat of rust inhibitor to expose machined surfaces to prevent rust and corrosion.
• Once a year, the pump performance should be checked and recorded in detail. Performance benchmarks should be established for a new pump during the early stages of a pump's operation, when the installation settings are correct.

The data to be verified in order to structure a comparative assessment are as follows:

1. Head pressure, measured by suction and discharge gauges.
2. Centrifugal pump flow rate.
3. Amplifier drainage.
4. Pump vibration shape.

Basic measures to be considered to improve efficiency before carrying out the check list for preventive maintenance of centrifugal pumps:

With these measures, you can control and improve the efficiency of the centrifugal pumps, thus enabling you to start the check list for preventive maintenance of centrifugal pumpsaccording to the established periods (daily, weekly, quarterly, half-yearly and annually).

1. Switch off unnecessary pumps.
2. Return to normal operation once you notice that the performance has changed.
3. Reposition the impellers if you notice that the head is higher than necessary. This activity is suggested because medium and large centrifugal pumps generally operate with efficiencies above 75%, and smaller pumps generally fall within the range of 50% to 70%.
4. Change the speed of a pump for the most efficient combination of power requirements with output. Or install a variable speed drive that will serve the same purpose.

The check list for preventive maintenance of centrifugal pumps is applicable to the inspection of any type of pump. Therefore, it is recommended to use online monitoring systems, so that possible failures during operation can be detected and predicted.

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