Pump Selection Based on Fluid Properties

The Fluid Data Sheet Every Quote Needs

Suppliers can match a pump to the duty only when the liquid is fully described — the same data set Qingdao Green Power uses for a quotation:

• Flow rate — average and maximum duty in m³/h, plus future margin.
• Head or pressure — total dynamic head in metres, or discharge pressure, at the worst case.
• Liquid identity — name, temperature, specific gravity and viscosity, with solids content.
• Available NPSH — suction head at the pump flange, worst case.
• Site conditions — motor voltage and IP class, plus installation orientation.

Viscosity: The First Filter

Viscosity usually decides between centrifugal and positive displacement technology. A centrifugal impeller accelerates thin liquid efficiently, but viscous drag multiplies friction losses inside the casing, so efficiency, flow and head fall steeply as the fluid thickens. As a practical rule, above about 150 cSt a gear or screw pump is the better technology. Qingdao Green Power publishes its IS/ISW centrifugal pump range at 1.5–1600 m³/h, 2–125 m head and up to 80 °C for water and low-viscosity liquids, while its G-type single-screw pump in the screw pump range handles viscous oils, resins, sludge and slurries at 0.1–150 m³/h and 0.6–2.4 MPa. See our high-viscosity pump application guide for more on thick media.

Temperature Sets the Pump Class

Temperature acts on the liquid and the machine together: hot liquid has higher vapour pressure, which reduces available NPSH, and it changes seal, gasket and material limits. For thin process liquids up to 80 °C the standard IS/ISW range applies; for inline circulation from -20 °C to 120 °C the ISG/GDL pipeline series fits. Heat transfer fluid is different: thermal oil must not contact a standard water pump, and the RY thermal oil circulation pump serves -20 °C to 350 °C with air-cooled bearings and no external cooling-water circuit. Always confirm the cold-start condition: an oil that pumps easily at operating temperature can be far too viscous at ambient start-up.

Corrosivity Selects the Wetted Materials

Chemical compatibility is decided by the liquid, its concentration and its temperature. Qingdao Green Power's chemical pump range splits the duty cleanly: the IH series in SS304 or SS316L handles mild chemicals, dilute acids and weak alkalis up to 80 °C, while the IHF fluoroplastic-lined series (PTFE, FEP or PFA) handles strong mineral acids such as sulfuric, hydrochloric and hydrofluoric acid, strong alkalis and oxidising agents up to 100 °C. Both series are published at 3.5–400 m³/h and 4.5–125 m head, with single or double mechanical seals depending on the duty. Always verify the specific concentration and temperature against the compatibility chart.

Solids, Abrasives and Shear-Sensitive Products

Entrained solids, abrasiveness and shear sensitivity change the pump type and its internal design. A single-screw pump moves slurries, sludge and pastes gently, provided solids stay below the minimum flow passage dimension; the stator elastomer (NBR, EPDM or FKM) must match the chemical and temperature. Never run such a pump dry — the rubber stator is destroyed within seconds. For corrosive liquid stored in a tank or pit below ground level, a ZJL/LZ submerged pump mounted on the tank top avoids long suction lines and keeps mechanical seals out of the liquid.

Vapour Pressure and the NPSH Check

Fluid vapour pressure is the hidden partner of every suction calculation. If available NPSH falls below the pump's required NPSH, the liquid flashes at the impeller eye and cavitation begins — noise, vibration, lost capacity and rapid impeller pitting. High temperature, high suction lift, long suction lines, strainers and low tank level all reduce available NPSH, so check the worst case. When the tank sits below the pump and gravity feed is impossible, choose a submerged or self-priming configuration rather than a pump that cavitates all day.

Where two technologies could both work, compare them over the real operating range using the logic of our pump efficiency improvement guide, then confirm current model availability with Qingdao Green Power before procurement.

Frequently Asked Questions