In the field of industrial coating, Coating Equipment Gear Metering Pumps have become core components for ensuring product coating quality, thanks to their precise metering and stable delivery performance. However, in practical applications, many users easily fall into common usage misunderstandings due to insufficient knowledge or improper operation. These misunderstandings not only affect the performance of the pumps, but may also lead to equipment damage, production interruptions and even product scrapping. Identifying these misunderstandings and mastering the correct solutions is crucial for maximizing equipment value.
Misconception 1: Ignoring the Matching Between Medium Viscosity and Pump
l Wrong Perception: Considering gear metering pumps as “universal” devices that can ignore medium viscosity changes, or simply assuming one pump can be used for all coating viscosities.
l Potential Hazards: When the viscosity of the transferred medium is much higher than the pump’s designed range, it will cause motor overload, gear shaft fracture or premature seal damage. Conversely, if the viscosity is far below the designed value, the pump cannot form an effective lubricating film internally, which will intensify dry friction between gears and the pump cavity. Meanwhile, internal leakage increases, leading to a serious decline in metering accuracy.
l Solutions: Take the working viscosity of the medium as a core parameter during the selection phase. Provide accurate viscosity data to suppliers and let them recommend suitable pump models, gear clearances and drive configurations. For working conditions with large viscosity variations, consider equipping frequency converters or variable-speed drive devices to adapt to different flow characteristics by adjusting rotational speed.
Misconception 2: Long-term Dry Running and Idling
l Wrong Perception: Brief idling has little impact on the pump, or frequent inching idling is acceptable for testing after cleaning.
l Potential Hazards: The precision mating surfaces inside gear metering pumps (such as gear end faces and side plates) rely on the transferred medium for lubrication and cooling. Dry running will cause severe friction and high temperature on these components in an instant, leading to scuffing, seizing and even complete jamming, resulting in catastrophic damage.
l Solutions: Establish the principle of “strictly prohibiting dry running” firmly. Before starting, ensure the pump cavity is fully filled with medium. For working conditions requiring emptying or cleaning, introduce cleaning fluid first or design a liquid injection port in the inlet pipeline. Clearly prohibit any form of pump idling in equipment commissioning and maintenance procedures.
Misconception 3: Reverse Rotation and Confusion Between Inlet and Outlet
l Wrong Perception: Gear pumps can work with both forward and reverse rotation, and reversing the inlet and outlet only affects the flow direction.
l Potential Hazards: Gear metering pumps have strictly specified rotation directions and inlet/outlet ports. If incorrect motor wiring causes reverse rotation, or the inlet and outlet pipelines are connected reversely, the pump will not only fail to build normal output pressure, but its internal force-bearing state will also be completely wrong. This will cause abnormal wear of side plates, rapid failure of shaft seals under reverse pressure and even gear damage.
l Solutions: There is usually an arrow indicating the rotation direction on the pump body or drive shaft, which must be strictly followed during installation and wiring. Carefully check the marks on the pump body (“IN” for inlet, “OUT” for outlet) before connecting the inlet and outlet pipelines. After installation, conduct an inching test first to confirm that the outlet pressure builds up quickly; otherwise, check the rotation direction immediately.
Misconception 4: Ignoring Necessary Filtration and Impurity Protection
l Wrong Perception: It is normal for coatings to contain particles, and gear pumps are robust enough to grind or pass small impurities.
l Potential Hazards: Gear metering pumps are precision components with minimal gear meshing clearances. Hard particles (such as welding slag, paint skin, agglomerated fillers) entering the pump cavity will grind precision surfaces like sandpaper, causing scratches and pitting corrosion. In severe cases, gears will be jammed directly, resulting in downtime.
l Solutions: Must install a filter with appropriate precision (80–120 mesh is recommended, adjusted according to the medium) at the front end of the pump inlet. Incorporate filter cleaning and maintenance into the daily inspection plan. Clean coating barrels and delivery pipelines regularly to ensure the cleanliness of the source and eliminate impurity sources fundamentally.
Misconception 5: Over-tightening or Incorrect Seal Maintenance
l Wrong Perception: Tighten the gland vigorously as soon as there is slight leakage at the seal, or use mismatched sealing materials.
l Potential Hazards: For packing seals, over-compression will cause severe friction between the packing and shaft sleeve, generating high temperature, accelerating wear and consuming motor power. For mechanical seals, rough installation will damage their precision flatness, leading to immediate failure. Using sealing materials not resistant to medium solvents will cause them to corrode, swell or dissolve quickly.
l Solutions: Follow the manufacturer’s installation guidelines. For packing seals, allow extremely slight leakage for lubrication and cooling. When replacing seals, confirm that their materials (such as Viton, PTFE, ceramics) are compatible with the transferred chemicals. Use special tools for mechanical seal installation to ensure uniform force application and strictly control installation dimensions.
Misconception 6: Neglecting System Venting Operations
l Wrong Perception: A small amount of air in the pipeline will be carried away naturally without special treatment.
l Potential Hazards: Residual air in the pump and pipeline will cause “cavitation”, leading to flow and pressure fluctuations, noise and vibration, as well as damage to gears and bearings. Long-term operation under cavitation will significantly shorten the service life of the pump.
l Solutions: Consider installing vent valves at the high points of the pipeline during system design. Before starting the pump, open the vent valves or slightly loosen the outlet connectors to exhaust all air from the pipeline and pump cavity until a continuous flow of medium comes out.
In conclusion, the correct use and maintenance of Coating Equipment Gear Metering Pumps is a technology that requires carefulness and professional knowledge. Avoiding these common misunderstandings can not only ensure the stable operation of the equipment, but also give full play to its advantage of precise metering, bringing lasting efficiency and quality improvement to your coating production.
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