Thermal oil pumps

Why thermal oil circuits use a gear pump

Thermal oil is the heat transfer fluid of choice where steam is not available or not wanted: it circulates in a closed loop between a heater and the users, such as the heating jacket of a bitumen pump, a storage tank, a reactor or a press. The fluid is thin when hot and viscous when cold, and the circuit must restart reliably after every shutdown, drawing the oil from the expansion tank without priming problems.

A self-priming external gear pump gives the loop what it needs: a constant flow proportional to speed, regardless of the pressure drop across heaters and users, and a pump that primes on its own at every start. The ZV series, flanged to the motor, and the NAV series both suit thermal oil circulation.

ZV or NAV: choosing the diathermic oil pump

• ZV series — compact gear pumps flanged directly to the motor, with threaded ports and no baseplate: no alignment, fewer vibrations, minimal footprint. Ten models from 0.47 to 102 l/min, the right size for the circulation loop of a jacketed pump, a small tank or a laboratory heater. The 8 ZV with a 6-pole motor is the auxiliary pump of our self-contained hot-spot heating circuit.
• NAV series — flanged pumps DN 40 to DN 125 PN 16 on a cast iron base, nine models from 54 to 2,770 l/min, for plant-wide thermal oil loops serving several users, with high volumetric efficiency and continuous duty.

Both series are also used for fuel oils, lubricants and other industrial oils, so one pump family can cover the whole oil side of a plant.

Thermal oil as a heating medium for pumps

Thermal oil is not only a fluid we pump; it is the medium we use most often to heat our own pumps. On the CR series and on the SB series the heating jacket wraps the whole pumping chamber and is connected to the thermal oil loop of the plant, keeping bitumen, pitch, resins, adhesives and waxes fluid inside the pump body.

Where no central heater exists, the hot-spot circuit makes the pump self-sufficient: the CR jacket is filled with thermal oil heated locally by up to three 300 W electric elements, a maximum of 900 W, circulated by an 8 ZV auxiliary pump with a precision thermostat and an expansion tank. No boiler, no permits, no boiler maintenance; the pump must be insulated and allowed a few hours of preheating before the first start.

Applications of heat transfer fluid pumps

• Circulation loops of thermal oil heaters serving jacketed pumps, tanks and reactors in bitumen, chemical and food plants.
• Heating circuits of bitumen distributors and emulsion sprayers, where the SB pump jacket is connected to the vehicle oil loop.
• Heated storage tanks for heavy fuel oil, molasses, glycerine and other viscous fluids.
• Presses, calenders, dryers and moulds in the wood, rubber and plastics industries.
• Laboratory and pilot plant heaters, where the compact ZV flanged to the motor saves space and alignment work.
• Filling and draining of thermal oil circuits during commissioning and maintenance.

Stainless steel versions are available for synthetic heat transfer fluids that attack cast iron, and ATEX documentation for classified areas.

How we size your thermal oil pump

To select the right thermal oil pump we need the type of fluid (mineral or synthetic heat transfer oil), the working temperature of the loop, the flow required in l/min or m³/h, the pressure drop across the circuit, the position of the expansion tank relative to the pump and the preferred drive. For a jacketed pump tell us also the model to be heated, so that we can match the circulation flow.

Write on WhatsApp or use the quote form. Our Bologna factory, building self-priming external gear pumps since 1955 under ISO 9001:2015, answers with a technical proposal and the options that fit your heating circuit.