Our caustic pump seals fail every few months. Why?

Almost always crystallisation: caustic dries and crystallises at the seal faces during idle periods, then the crystals shred the faces at restart. Face material selection and a proper flush or quench arrangement fix this — tell us the concentration and duty cycle.

What SG should I use for 50% caustic?

Approximately 1.52 — roughly 50% more power than water for the same duty point. We size motors on the actual liquid, always.

Application Guide

Caustic Soda (NaOH) Transfer Pumps

Alkaline duty that crystallises, freezes and burns.

Caustic soda is everywhere — pulp and paper, textiles, soaps, water treatment, alumina. It is chemically gentle on many materials but physically treacherous: it crystallises in seal faces, approaches its freezing point in winter lines at 50% concentration, and causes severe burns on any leak.

The pumping challenges

Crystallisation at seal faces causes premature seal failure
50% caustic freezes around 12 °C — cold-weather line blockages
High SG (1.5+ at 50%) increases power demand
Severe chemical burns from even small leaks

Material options

PP handles caustic across most concentrations and temperatures

SS 316 metallic construction for higher temperatures and duties

EPDM elastomers — caustic degrades incompatible rubbers

Technical considerations

Seal selection must anticipate crystallisation — discuss flush options for concentrated duty
Motor sized on actual SG, not water
Trace-heating or drainage planning for outdoor winter lines at 50%
PP is often the economical, corrosion-proof answer below 70 °C

Honest limits: no pump material is universally compatible with every concentration and temperature of a chemical. Final selection is confirmed against your exact duty — that's why we ask before we quote.

Suitable PT Pumps

Pumps for this duty

PP & PVDF Centrifugal Pump

Up to 100 m³/hr · 45 m head · 90 °C

View specifications

PP & PVDF Monoblock Centrifugal Pump

Up to 70 m³/hr · 60 m head · 90 °C

View specifications

Centrifugal Chemical Process Pump

Up to 400 m³/hr · 150 m head · 200 °C

View specifications

FAQs

Common questions on this duty

Both work — PP up to 70 °C is the corrosion-proof, economical choice; SS 316 suits higher temperatures. The deciding factors are usually temperature, duty size and whether crystallisation at seals needs special arrangements.

Enquire

Get a pump selected for this duty

Fill in the duty point — the form is pre-tagged for this application. An applications engineer responds with a confirmed selection and budgetary quotation.