Best Pump for High-Viscosity Chemicals

Why Viscosity Changes the Pump Choice

Viscosity is a liquid's internal resistance to flow, reported in centistokes (cSt) or centipoise (cP). Water sits near 1 cSt, while concentrated resins, polymer melts, adhesives, pigment pastes and slurries reach hundreds of thousands or millions of centipoise.

A centrifugal pump converts impeller velocity into pressure, so thick-liquid friction makes head, flow and efficiency fall together. That is why viscosity, specific gravity and vapour pressure come first in any chemical pump fluid properties review.

G-Type Single Screw: The Positive Displacement Answer

For chemicals too thick for centrifugal action, the G-type single screw pump is a proven answer. A helical metal rotor turns inside an elastomeric stator, forming sealed cavities that travel steadily from suction to discharge, so flow is smooth, nearly pulseless and low in shear — qualities that protect shear-sensitive polymers and pastes.

Qingdao Green Power publishes the G-type at 0.1–150 m³/h and 0.6–2.4 MPa, covering high-viscosity oils and resins above about 1500 cSt, sludge, slurry, shear-sensitive polymers and abrasive liquids, provided solids stay below the minimum flow passage. Three rules protect the machine:

• Never run dry — the rubber stator is destroyed within seconds without liquid.
• Match the stator elastomer — NBR, EPDM or FKM for the chemical and temperature.
• Fit pressure protection — a relief valve guards pump and line at cold startup.

When the IH or IHF Chemical Pump Still Fits

Many chemical duties are thin — dilute acids and alkalis, salt solutions, solvents — and for these, centrifugal chemical pumps deliver large flows cheaply. The IH series (SS304 or SS316L) serves mild chemicals, dilute acids and alkalis up to 80°C; the IHF fluoroplastic-lined series (PTFE, FEP or PFA) handles strong acids such as sulfuric, hydrochloric and hydrofluoric acid, strong alkalis and oxidising agents up to 100°C. The published envelope is 3.5–400 m³/h at 4.5–125 m head, with single or double mechanical seals.

The family is described on the IH and IHF chemical pump product page. Keep the viscosity rule in mind: once a chemical behaves like a heavy syrup, its corrosion-resistant construction belongs on a positive displacement pump, not a centrifugal impeller.

Corrosion, Seals and Temperature Checks

With viscous chemicals, corrosion and viscosity act together. Wetted materials must resist the chemical at operating temperature — stainless for mild service, fluoroplastic lining where the acid attacks the metal; see our chemical pump materials and corrosion article.

• Sealing: single or double mechanical seals with a flush plan; double seals or quench arrangements protect against polymerising media.
• Temperature control: resins and adhesives that set when cool need jacketed pump heads and heat-traced lines; confirm the cold start.
• Elastomers: stators, O-rings and diaphragms must suit the chemical at its worst temperature — see our adhesive transfer pump notes for sticky media.

Selection Checklist for a High-Viscosity Chemical Duty

• Chemical identity, concentration and temperature — decide corrosion severity and wetted materials first.
• Viscosity at the worst case — a cold, thick start raises torque and suction losses; size for the peak.
• Flow and discharge pressure — PD flow rises with speed; confirm the maximum pressure and relief setting.
• Solids and shear sensitivity — abrasive or fragile products point to a progressive cavity design.
• Seal, elastomer and heating — match wetted polymers and seals to the chemistry.

The method in our chemical transfer pump selection guide applies unchanged when the chemical is viscous.

Frequently Asked Questions