"Oil pump" is an umbrella term for very different pumps. It can mean the oil pump in an engine, the pump of a hydraulic power unit, or a transfer pump used to move oil out of drums, tanks and drip trays. This guide gives an overview of the types of oil pumps and shows when an air-operated diaphragm pump is the right choice.
Types of oil pumps
| Pump type |
Working principle |
Typical use |
| Gear pump |
Two meshing gears carry oil in the tooth gaps from suction to discharge side |
Engine lubrication, hydraulics, oil circulation |
| Internal gear pump |
Inner and outer rotor with different numbers of teeth form travelling chambers |
Engine oil pumps in vehicles, gearboxes |
| Vane pump |
Eccentrically mounted rotor with sliding vanes; the cells expand and contract |
Hydraulics, vehicles (variable oil pumps), vacuum pumps |
| Screw pump |
Intermeshing spindles move the oil axially with very low pulsation |
Lube oil systems, heating oil, large plants |
| Piston pump |
Piston displaces oil in the cylinder, very high pressures possible |
Hydraulics, grease and central lubrication |
| Air-operated diaphragm pump |
Two air-driven diaphragms displace the oil, ball valves control the direction |
Transfer, waste oil, drum and tank emptying, workshops |
| Hand pump |
Manually operated piston or lever |
Small quantities, canisters and drums |
How does an oil pump work?
Gear pump for oil
The gear pump is the most common oil pump. Two gears rotate in opposite directions. On the suction side the tooth gaps open and fill with oil; the oil is carried around the outside of the housing to the discharge side, where it is displaced as the teeth mesh. Gear pumps generate high pressures at constant flow but are sensitive to dirt and dry running.
Vane pump – how it works
An eccentrically mounted rotor turns inside a round housing. Vanes slide in its slots and are pressed against the housing wall by centrifugal force or springs. Cells form between the vanes, which expand on the suction side and contract on the discharge side. The flow rate can be adjusted by changing the eccentricity.
Mechanical oil pump in the engine
In a combustion engine, the oil pump is driven mechanically via crankshaft, chain or gear. It draws oil from the sump and pushes it through the filter and oil galleries to the bearings and camshaft. These engine oil pumps are vehicle parts and are not part of the aodd-pumpen.de range.
Pumping oil with an air-operated diaphragm pump
For transferring, emptying and moving oils in workshops, maintenance and production, the air-operated diaphragm pump is particularly practical:
-
Self-priming – draws from drum, IBC or drip tray
-
Can run dry – no damage when the container is empty
-
Tolerant of dirt – ideal for waste oil with particles
-
Stalls safely – can be used with a dispensing nozzle, the pump stops when the valve is closed
-
No electrics – also for flammable liquids in hazardous areas (ATEX version)
Suitable materials for oils
| Fluid |
Recommended diaphragm |
Housing |
| Mineral oils, hydraulic oil, gear oil, waste oil |
Nitrile (NBR) or FKM
|
Aluminium, cast iron |
| Synthetic oils, oils with additives, higher temperatures |
FKM or PTFE
|
Aluminium, stainless steel |
| Cutting fluids (emulsions) |
Santoprene®, NBR |
Aluminium, polypropylene |
| Edible oils |
FDA-compliant materials |
Stainless steel (FDA diaphragm pumps) |
This table is a guide. Exact compatibility depends on oil type, additives and temperature – check your fluid with our chemical compatibility check.
Viscous gear oils or cold hydraulic oils are best pumped with a slightly larger pump at a reduced stroke rate. More in Pumps for high-viscosity fluids.
Lubricant pumps and lubrication systems
There are dedicated systems for lubricating machinery:
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Manual lubrication: grease gun, hand lubrication pump, oiler
-
Single-line and progressive systems: central lubrication systems automatically distribute oil or grease to many lubrication points
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Circulating oil and oil mist lubrication: for gearboxes, spindles and bearings
Important: Air-operated diaphragm pumps are not suitable for pumping grease – pneumatic piston pumps with a high pressure ratio are used for that. Flowable lubricating oils, on the other hand, can easily be transferred and distributed with an AODD pump.
Frequently asked questions
Which pump is suitable for pumping out waste oil?
An air-operated diaphragm pump with aluminium housing and nitrile or FKM diaphragm. It can run dry, is self-priming and tolerates dirt particles.
Can I transfer hydraulic oil with a diaphragm pump?
Yes. Make sure you use oil-resistant diaphragms and a sufficiently large pump at low temperatures, when the oil becomes thicker.
What is the difference between a gear pump and a diaphragm pump for oil?
The gear pump delivers an even flow at high pressure but needs clean oil and must not run dry. The diaphragm pump is more tolerant of dirt and dry running and ideal for transfer.
