Gear pumps are the most common type of positive displacement pump, ideal for transferring high viscosity fluids such as automotive oils, plastics, paint, adhesives, and soaps. They operate by creating suction at the inlet with a rotating assembly of two gears –a drive gear and an idler. Pump flow is determined by the size of the cavity (volume) between gear teeth, the amount of slippage (reverse flow), and the speed of rotation (rpm) of the gears.
As with any pump, proper operation and regular maintenance are vital to reducing costly pump repairs and maximizing pump efficiency. Below are helpful tips for operating your gear pump and ensuring it achieves a long operating life through regular maintenance.
Gear Pump Operation
– Operate close to the maximum rated speeds. Because gear pumps have poor volumetric efficiency at low speeds and low flow rates, they should be operated as close as possible to their maximum rated speeds for higher production and efficiency.
– Use special materials when pumping liquids with abrasives. A gear pump’s toothed gear construction allows particles to become trapped in small spaces, accelerating wear and reducing efficiency. If you need to transfer fluid containing abrasives, consider contacting the pump manufacturer to discuss hardened material options.
– Ensure that total life does not exceed 7.5 PSI. A gear pump cannot create a perfect vacuum, necessitating total lift (including pipe friction losses) to be one-half of the atmospheric pressure (approximately 7.5 PSI).
– Avoid low viscosity fluids. Gear pumps (especially internal gear pumps) are designed to handle high viscosity fluids to minimize slip. Pumping low viscosity fluids results in reduced flow rate and efficiency because it ‘slips’ through the tight spaces from the higher-pressure discharge side of the pump to the lower-pressure suction side of the pump.
– Do not run dry. Unlubricated gear teeth will rub together, creating friction and heat as the cogs expand and begin rubbing against the housing. This can destroy the pump, requiring costly repair and downtime.
Gear Pump Maintenance
– Keep maintenance records. One of the most important things you can do to ensure your pump operates smoothly is to keep a detailed record of baseline pump performance, regular maintenance, and any repairs. This will aid you in determining how the pump will operate in the future and the best way to either repair or replace specific parts.
– Check bearings regularly. The bearings are the most important area of a gear pump to maintain because they can cause imbalance if misplaced or defective. Check bearings regularly and replace as necessary by removing the defective bearing with a puller. Excessive noise can be an indication of bearing wear.
– Check gear pump clearance. A new gear pump has .007 to .005 inches of clearance from both the teeth and chamber of the gears. Periodically check for wearing of the teeth by attempting to pass a piece of paper between the clearances. If it passes between the clearances easily, it indicates that the bearings have been worn down and should be replaced.
By following regular maintenance schedules and adhering to proper operation procedures, gear pumps can be an efficient and productive solution to high-viscosity pumping needs.