Pros and cons of the Gear Pump – Part 4 of the best metering pump

A magnetic drive gear pump is a type of rotary, positive displacement pump made from alloy or non-metallic materials. This makes the gear pump a good option for the fuel and chemical industries, where static seals can ensure leak-proof operation.

How does a gear pump work?

A gear pump generates flow by using two meshed gears that are inside the pump’s body cavity. Liquid is trapped in the gear teeth and carried in the valleys between these, positively displacing each unit of fluid. The mesh point of the gears prevents the fluid from returning to the inlet, forcing it out as the gear teeth mesh on the discharge side.

Magnetic-drive gear pumps are used because they offer very precise metering. The metered flow is proportional to the volume of the gear tooth gaps times the number of revolutions per minute.

However, a small caveat to note is volumetric efficiency. The amount of fluid that actually makes it to the outlet, in relation to the amount that theoretically should, is known as volumetric efficiency. A small percentage of the carried fluid continually ‘slips’ back, creating a slight difference between the amount in theory and in practice.

Difference between conventional and non-metallic gear pumps

The conventional cavity style pump seals the gear tips by placing the gears inside a cavity. The sides are sealed by placing the cavity plate between the pump body and the pump bearing plate

Gaskets or O-rings are used to seal between the three metallic components: bearing plate, cavity plate and pump body.

Meanwhile, TEF-MAG, non-metallic gear pumps utilize a cavity gear liner that absorbs wear to the gear, instead of this affecting the pump body.

Magnetically coupled pumps are often paired with a static seal that is not subject to wear from moving parts. Using a static seal reduces maintenance costs and virtually eliminates the possibility of contamination or leakage.

Main uses for gear pumps:

Magnetic-drive gear pumps are commonly used in the fuel industry as well as food, construction, paint, and chemical industries.

Let’s review the pros and cons of magnetic-drive gear pumps to evaluate where they should be on our list of the best metering pumps.

Pros of gear pumps

• Wide range of materials of construction
• Compatible with most chemical applications (full range of plastics and alloys)
• Good metering range/turndown (100:1 is most practical)
• Very smooth flow with no pulsation
• Low maintenance complexity, with few moving parts
• Frequency of maintenance depends on application, but gear life is typically 3-5 years
• 100% leak-free design offers excellent chemical containment
• Some off-gassing if gas pockets large enough, but this will not interrupt pumping
• Viscosity / shear sensitivity is good at lower speeds

Cons of gear pumps

• Cannot pump solids
• Wet suction lift is moderate, but provides extremely poor dry suction lift
• Medium cost of operation – becomes cost competitive above 400 LPH

Clearly, the type of pump you need depends on the exact application and speed of your operation. To find out if a magnetic-drive gear pump is the best choice for your operation, or if a vane or peristaltic pump would be a better bet, keep reading the series as we weigh up the pros and cons of each.

If you need help deciding, give us a call on 1-800-367-4180 (toll-free). As your metering pumps supplier, we’re here to help you choose, install, maintain, and monitor a variety of equipment. And to answer questions about things you’ve previously tried gone wrong.