Most industries have several pumps performing a variety of functions that are integral to the successful operation of the plant. If a pump malfunctions, it can be the cause of an entire plant shut down. As a leading manufacturer and supplier of progressive cavity type screw pumps and zero leak Rota pumps, Risansi emphasizes on doing proper pump maintenance at site to ensure long-life of pumps. Pumps maintenance is done in order to improve system reliability. Proper maintenance of a pump is important to ensure its trouble free and long service life. To keep pumps running properly, a regular maintenance schedule should be implemented and followed.
Maintenance can be of following types
- Preventive or predictive- Predictive maintenance (PdM) techniques are invaluable for keeping pump reliability high and life-cycle costs low. Diagnostic monitoring during pump operation such as vibration analysis, electrical monitoring, and lubricant analysis often reveal early signs of trouble
- Conditional Monitoring- Condition monitoring is a process used to monitor the condition of the pump which ultimately reduces the time required to identify and rectify the fault and increases the efficiency of the pump. It monitors parameters like temperature, vibration etc
- Periodic -Periodic maintenance is a strategy that requires maintenance tasks such as external cleaning of pump, leakage checks tightening of nuts & screw etc. to be performed at set time intervals while the pump is operational
- Breakdown- Breakdown maintenance is required when the pump completely breaks down and needs repair to resume operation. It can be planned and unplanned both
Important Check Points
One must ensure to check and follow below points for smooth maintenance of pumps
- DETERMINE MAINTENANCE FREQUENCY-A correct maintenance strategy is often based on manufacturers'/ OEM's recommendations. Select a time when the system is down. Pump to be overhauled at regular intervals. It is advisable to overhaul the motor also along with the pump.
- OBSERVATION IS KEY- A close observation of pump is important while it is running.
- Indication of pump parts wear can be identified from abnormal noise, vibration, loss of capacity, reduction in discharge pressure, leaks etc. Inspect internal parts carefully while overhauling
- Internal clearances in the pump, which are vital for its proper function. Acceptable wear can be determined only by experience of the actual application.
- Pump Vibration-Vibration imparts forces on each part of the seal components. Vibrations may be due to worn bearings, improper grouting and poor foundation of pump
- SAFETY FIRST- It is important to make sure that pumps are shut-down before performing the maintenance activities. Mechanical, electrical, as well as hydraulic isolation is important.
- MECHANICAL INSPECTION- • Check that foundation points are fixed properly. It is important to periodically inspect foundation bolts, couplings and performance of the pump as conditional monitoring to avoid breakdown maintenance.
MAINTENANCE STRATEGIES AT SITE
- Check mechanical seal, gland packing, flanges or other joints of pump for leakage
- Check the condition of small parts that are prone to wear and tear
- Replace small parts on time to ensure the complete life of large parts is availed.
- Wear of spare parts greatly depends on the pumping medium. Pump screw is lubricated by the pumping liquid itself. Please refer to our previously published article in June 2021 issue. So it is important to choose the correct RPM and model of the pump. The pump strainer must be cleaned regularly, by monitoring suction pressure of the pump to ensure that the solids are removed as far as possible.
- A gradual reduction in the suction pressure of the pump indicates that the suction filter is getting choked
- Gaskets and O-rings of the pump to be renewed while overhauling.
- Check shaft bearing for damages and renew if necessary
- Check the condition of the mechanical seal especially the faces and O-rings. Discard the seal if face is damaged or O-rings hardened. Excessively leaking shaft seals should be changed without delay, as the leakage normally will grow worse and cause additional damage.
- Relief valve, valve seat, springs to be checked.
- Inspect for any scratches inside.
- LUBRICATION CHECKLubricate the motor and pump bearing as per manufacturer's guidelines. It must not be over lubricated. Bearings damage occur due to over lubrication. The bearings must be lubricated in 6 months with high quality lubricant. Refer to the lubrication manual shared by the supplier
- ELECTRICAL ITEMS CHECKCheck motor amperage and relay settings.
- MECHANICAL SEAL- Mechanical seal may fail due to lack of lubrication and not following the quenching procedure. The temperature rises at the sealing faces that will damage the elastomer part of the mechanical seal.
- STATOR- If the pump is not to be used for 3 months or more, the stator (rubber elastomer) should be removed and kept separately in a clean, cool and dry environment It is important to note that most of the rubber products may change their physical properties under unfavourable conditions or if treated improperly, which will result in a shorter lifetime. They may also become useless through excessive hardening, aging, permanent deformation, cracking or other damages appearing to the surfaces.
- INTERNALS- Pump internals may rust if material of construction is not SS (Stainless steel). Anti-rust oil may be used on such parts.
- DRY RUN PROTECTION - Never run the pump dry as a few rotations in dry condition will damage the internal parts
- Storage of Screw Pump - If any pump is not to be installed immediately or the pump is not under operating condition for some time after being installed, the following points should be taken care of
- The pump should be kept in clean and moisture free area preferably with protective covering. If this cannot be ascertained, additional care should be taken to prevent rust formation.
- Pump should be kept after draining out the pumping fluid and preferably after flushing it from compatible fluid media. Anti-rusting oil or suitable agent must be applied on metallic parts and on those exterior, unpainted surfaces subject to corrosion.
- Ensure that the openings through suction and discharge ports are covered.
How to make Pumps More Efficient
Major factors affecting pump efficiency are throttled valves, pump over-sizing, seal leakage and operational breakdowncausing highest downtime and cost. Therefore, it is important to consider following points to make pumps more efficient
- Usage of Variable Frequency Drives (VFD) - As the name suggests, VFD is used to achieve capacity at a given range of RPM rather than what the rated capacity of pump is. VFDs are used to limit unnecessary energy consumption and maintenance spares' cost.
- Please connect a water flushing line.
- Connect a bypass.
- Since PCP is for viscous and abrasive fluids, do not switch the pumps frequently. Run the main pump (pump1) till maintenance is required and then switch to standby pump (pump2). Switch back to pump1 post maintenance. Periodic switching only to test standby pump can be done.
- Please refer to our previous article published in June 2021 issue for selection of pump as the model, curves, efficiency etc. depend upon capacity and pressure required.
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