Boiler duty
1.1–1.25 typical
Awaiting Valid Duty Parameters
Adjust the parameters on the left to compute live hydraulic values, ranges, and sizing verdicts.
Feed pump losing pressure?
Worn multistage feed pumps cost boiler efficiency. We repair and re-rate boiler feed pumps with genuine stages and balanced rotors.
Boiler feed pump sizing explained
Flow: evaporation plus margin
The feed flow must cover the boiler evaporation plus blowdown and margin — typically 10–25 % above evaporation. A 3000 kg/h boiler at 1.2× needs 3600 kg/h, or 3.6 m³/h. The calculator applies your margin factor to the evaporation you enter.
Feed pumps run continuously, so efficiency and reliability dominate the choice; multistage centrifugal pumps are the standard for feed duties above a few bar.
Head: pressure is the hard part
Feed head is the drum pressure converted to metres (10.2 m per bar) plus feed-line friction plus a margin. A 10.5 bar boiler needs about 107 m from pressure alone; with 5 m friction and 5 m margin the duty is roughly 117 m — far beyond a single-stage pump, which is why feed pumps are multistage.
Hot water and NPSH matter on the suction side: feed water near boiling has high vapour pressure, so the deaerator or feed tank must sit high enough. Check the NPSH calculator at the feed temperature.
Motor and running costs
Feed pump power follows the standard formula — 3.6 m³/h at 117 m needs about 1.9 kW shaft and a 2.2 kW motor — but boiler feed pumps run 24×7, so energy cost dominates the lifecycle. An oversized or worn feed pump is a permanent electricity leak; the energy-cost calculator quantifies it. Teflow repairs and re-rates multistage feed pumps across Gujarat — call +91 98251 62709.
Technical & Operational FAQs
Q1.How do I size a boiler feed pump?
Feed flow = boiler evaporation × 1.1–1.25. Required head = drum pressure (bar) × 10.2 + feed-line friction + 5 m margin. Then power = flow × head ÷ (367 × efficiency). For a 3000 kg/h boiler at 10.5 bar: 3.6 m³/h at ~117 m, about 2.2 kW motor.
Q2.Why are boiler feed pumps multistage?
Feed duties need 100 m or more of head — far beyond a single centrifugal stage (typically 15–30 m per stage). Multistage pumps stack stages to reach the required head at reasonable efficiency and compact size.
Q3.What is the feed flow margin?
The feed pump must cover evaporation plus blowdown and allow control margin — 10–25 % above evaporation is common practice. The calculator applies your margin factor to the evaporation rate.
Q4.How much head does 10.5 bar need?
Pressure converts to head at 10.2 m/bar, so 10.5 bar is about 107 m. Add feed-line friction and a margin: a typical 10.5 bar boiler needs a feed pump rated around 115–120 m.
Q5.Why does my feed pump lose pressure?
Worn or corroded stages, a trimmed impeller, recirculation valve leaking, or suction problems (air, low NPSH, clogged strainer) all drop feed pressure. Check the discharge against the multistage curve at the feed flow, then inspect the stages and seals.
Related Engineering Tools
NPSH Available Calculator
Chemical Pump Sizing
Pump Energy Cost
Multistage Pump Repair
Pump Repair Service
Pump Consultancy
Need a custom hydraulic audit or specific duty curve verification? Call +91 98251 62709 or Request a Detailed Engineering Quote.