Chemical Pump Sizing Calculator

Total dynamic head (TDH) is the sum of the static heads and friction: suction static head (positive for flooded suction, negative for lift), discharge static head, and friction losses in pipe, fittings and valves. The pump must be selected for this TDH at the required flow — not for the discharge pressure alone, which changes with liquid SG.

A tank at 38 m above the pump with 2 m of friction needs 40 m TDH. That 40 m is the number to read on a pump curve, because curves are drawn in head, which is liquid-independent.

Hydraulic power is flow × TDH × SG ÷ 367. Divide by pump efficiency for shaft power, then select the next IS 1231 motor frame. The SG makes chemical pumps heavier: the same 40 m duty needs 4.19 kW for water but 5.03 kW for 50 % caustic (SG 1.2) — and 6.4 kW for 98 % sulphuric acid (SG 1.84).

Motor efficiency and power factor are applied separately in the motor calculator; this tool gives the frame size directly.

Before sizing, confirm the wetted materials can survive the liquid at operating temperature. For HCl, PTFE and PFA rate excellent at all concentrations; PP swells above 30 %; SS316 pits. For caustic, PP and SS316 work well up to moderate temperature. The calculator shows the recommended families from the compatibility matrix for the liquid you choose, and the full compatibility selector covers temperature limits and elastomers.

Chemical pumps typically run 50–70 % efficiency at duty. If your existing pump computes below 40 %, it is worn or badly off its best efficiency point — plan an overhaul or re-rating. The repair-vs-replace decision comes down to the lifecycle cost, which the LCC calculator covers. Teflow sizes, builds, repairs and re-rates PTFE, PFA, PP and SS pumps — call +91 98251 62709 for a duty review.