Heavy Oil Pump Selection Guide

Why Heavy Oil Selection Differs from Light Oil Selection

Heavy fuel oil, residual oil and bunker grades are chosen for heating value, but that makes them hard to pump: viscosity can reach thousands of centistokes at ambient temperature and changes steeply with it. A pump that runs perfectly on diesel will starve, cavitate or overload on cold heavy oil, so the whole heavy oil pump selection exercise starts with the oil's viscosity behaviour, not a catalogue of sizes.

Heavy oil is normally handled hot, and the oil itself is often the only lubricant in the pump. Water, abrasive sediment and asphaltene deposits erode close clearances, ruin seals and block strainers, so the medium must be described honestly before any machine is compared. For difficult-media technology in general, see the best pump for high-viscosity liquids guide.

Step 1: Collect the Fluid and Duty Data First

Every serious selection starts with a written duty specification; without it, a supplier can only guess. The minimum dataset for heavy oil:

• Viscosity at pumping temperature — and at the coldest start-up temperature.
• Pumping temperature and heating method — tank heater, trace heating or jacket.
• Flow rate and discharge pressure — normal, maximum and any low-flow circulation requirement.
• Contaminants — water, solids, wax or asphaltenes.
• Suction conditions — flooded or lift, pipe length, available NPSH at the inlet.
• Duty pattern — continuous, batch, or intermittent with long standstill periods.

Step 2: Match the Pump Family to the Viscosity Band

The first filter is the pump family. Centrifugal pumps are efficient on thin liquids, but performance collapses as viscosity rises: friction losses inside the impeller grow quickly and head and flow fall away. As a general engineering rule, once viscosity exceeds roughly 150 cSt, a positive displacement pump is the more reliable choice.

Step 3: Choose Between Gear and Screw Machines

Within positive displacement, the two workhorses for heavy oil are external gear pumps and screw pumps. Gear pumps trap oil between meshing teeth and the casing; they are compact and proven on heated fuel-oil supply, but need clean, fluid oil because the pumped liquid seals their clearances.

Where the oil is heavier or hotter, screw pumps take over. Qingdao Green Power's G-type single screw pump moves high-viscosity oils, resins and slurries at 0.1–150 m³/h with pressures of 0.6–2.4 MPa, while the 3GB triple screw pump covers 2.4–241.7 m³/h for lower-viscosity oils at high temperature up to 350°C, with smooth, nearly pulsation-free flow.

Step 4: Check Heating, Cold Start, Sealing and Materials

Most heavy-oil pump failures trace back to start-up, not running: at ambient temperature the oil may be too thick for the motor to reach rated speed, or so solid that the suction line starves. Bring the whole suction path — tank outlet, strainer and pipework — up to temperature before starting, and fit a relief valve, which is mandatory on positive displacement pumps: a closed discharge will otherwise push pressure until a casing, seal or pipe fails.

Heavy oil that cools inside a mechanical seal face can solidify and tear the faces at the next start, so steam-quenched or flushed seal plans are common on hot-oil service, and materials must tolerate the oil's sulphur content at operating temperature. Practical tricks for near-solid media appear in our article on how to pump extremely viscous fluids.

Step 5: Confirm the Model and Drive with the Manufacturer

The final step is confirmation, not guesswork. Frame size, speed, motor power, relief setting, seal plan and heating arrangement must be checked against the real duty — including the cold-start case — because the pump, heating and pipework must be specified as one system. KCB-style gear pumps are treated on this site as a technical-reference topic, so confirm current model availability and specifications with Qingdao Green Power before procurement, and use the contact form to send your duty data for a formal recommendation.

Frequently Asked Questions