Boiler Feed Pump Calculation — Pump Power & Motor Sizing Tool

Calculate hydraulic power, shaft power, and recommended motor size for boiler feed pump systems. Free online calculator with metric and imperial unit support, step-by-step breakdowns, and industry-standard safety factors.

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Boiler Feed Pump Calculator

Enter your system parameters to calculate hydraulic power, shaft power, and recommended motor size with safety factor.

Enter parameters and click Calculate Pump Power to see results.

Boiler Feed Pump Power Formula Explained

The boiler feed pump power formula calculates the energy required to move feed water from the deaerator or feed tank into the boiler drum against system pressure and elevation.

Hydraulic Power (kW) = (Q × H × ρ × g) / 1000

Where Q = flow rate (m³/s), H = total head (m), ρ = density (kg/m³), g = 9.81 m/s²

Shaft Power (kW) = Hydraulic Power / ηpump
Motor Power (kW) = Shaft Power / ηmotor × Safety Factor

Imperial Formula

Water HP = (Qgpm × Hft × SG) / 3960
Brake HP = Water HP / ηpump

Variable Definitions

  • Q — Flow rate of boiler feed water (m³/hr or GPM)
  • H — Total Dynamic Head including static, pressure, and friction losses (meters or feet)
  • ρ / SG — Fluid density in kg/m³ (water = 1000) or Specific Gravity (water = 1.0)
  • ηpump — Pump efficiency, typically 65% to 85% for centrifugal boiler feed pumps
  • ηmotor — Motor efficiency, typically 90% to 96% for industrial motors
  • Safety Factor — Design margin, typically 1.10 to 1.15 for boiler feed applications

How to Calculate Boiler Feed Pump Power Requirements

Follow these engineering steps to accurately size a boiler feed pump for your steam system:

  1. Determine required flow rate — Calculate the total feed water demand based on boiler steaming rate plus blowdown and any deaerator vent losses.
  2. Calculate Total Dynamic Head (TDH) — Sum the static head (elevation from deaerator to boiler drum), pressure head (boiler operating pressure converted to head), and friction losses in piping, valves, and fittings.
  3. Compute hydraulic power — Use the formula Hydraulic kW = (Q × H × ρ × 9.81) / 1000 with Q in m³/s.
  4. Determine shaft power — Divide hydraulic power by pump efficiency to get the actual power required at the pump shaft.
  5. Size the motor — Divide shaft power by motor efficiency and multiply by the safety factor (1.10–1.15) to select the appropriate motor rating.

For a boiler requiring 50 m³/hr at 200 m TDH with water at 1000 kg/m³, 78% pump efficiency, and 95% motor efficiency: hydraulic power = 27.25 kW, shaft power = 34.94 kW, recommended motor = 42.3 kW (select 45 kW motor).

Boiler Feed Pump Calculation Examples

Example 1: Medium-Pressure Boiler (Metric)

A boiler requires 50 m³/hr feed water at 200 m TDH. Fluid density is 1000 kg/m³, pump efficiency 78%, motor efficiency 95%, safety factor 1.15.

Q = 50 / 3600 = 0.01389 m³/s
Hydraulic kW = (0.01389 × 200 × 1000 × 9.81) / 1000 = 27.25 kW
Shaft kW = 27.25 / 0.78 = 34.94 kW
Motor kW = (34.94 / 0.95) × 1.15 = 42.3 kW → Select 45 kW motor

Example 2: Industrial Boiler (Imperial)

A boiler requires 220 GPM at 656 ft TDH. Specific gravity 1.0, pump efficiency 80%, motor efficiency 94%, safety factor 1.15.

Water HP = (220 × 656 × 1.0) / 3960 = 36.44 HP
Brake HP = 36.44 / 0.80 = 45.56 HP
Motor HP = (45.56 / 0.94) × 1.15 = 55.7 HP → Select 60 HP motor

Example 3: High-Pressure Boiler (Metric)

A boiler requires 120 m³/hr at 450 m TDH. Fluid density 980 kg/m³ (hot water), pump efficiency 82%, motor efficiency 96%, safety factor 1.12.

Q = 120 / 3600 = 0.03333 m³/s
Hydraulic kW = (0.03333 × 450 × 980 × 9.81) / 1000 = 144.3 kW
Shaft kW = 144.3 / 0.82 = 176.0 kW
Motor kW = (176.0 / 0.96) × 1.12 = 205.3 kW → Select 210 kW motor

Real-World Boiler Feed Pump Applications

  • Power Generation: Sizing feed pumps for utility and industrial steam boilers in power plants with capacities from 10 MW to over 1000 MW.
  • Chemical Processing: Determining pump requirements for process steam boilers in refineries, petrochemical plants, and manufacturing facilities.
  • HVAC & District Heating: Calculating feed water pump sizing for centralized steam heating systems in campuses and commercial districts.
  • Food & Beverage: Sizing boiler feed systems for food processing plants requiring sanitary steam for cooking, sterilization, and cleaning.
  • Pulp & Paper: Engineering feed pump systems for recovery boilers and power boilers in paper mills with high feed water demands.
  • Marine Engineering: Designing boiler feed systems for shipboard auxiliary and propulsion boilers with space and weight constraints.
  • Cogeneration Plants: Optimizing feed pump sizing for combined heat and power systems to maximize overall plant efficiency.

People Also Ask

Boiler feed pump power is calculated using Hydraulic Power (kW) = (Q × H × ρ × g) / 1000, where Q is flow rate in m³/s, H is total dynamic head in meters, ρ is fluid density, and g is 9.81 m/s². Shaft power equals hydraulic power divided by pump efficiency. Motor power equals shaft power divided by motor efficiency, multiplied by a safety factor of 1.10 to 1.15.
In imperial units, Water HP = (Q_gpm × H_ft × SG) / 3960. Brake HP = Water HP / pump efficiency. For a boiler feed pump moving 220 GPM at 656 ft with SG of 1.0 and 80% efficiency, Water HP = 36.44 HP and Brake HP = 45.56 HP.
Typical boiler feed pump efficiencies range from 65% to 85% depending on pump type, size, and operating conditions. Multistage centrifugal pumps commonly achieve 75-82% efficiency. Smaller pumps may operate at 60-70% while large industrial units can exceed 85%. Always consult manufacturer pump curves for accurate values at your specific operating point.
A safety factor of 1.10 to 1.15 (10-15%) is standard for boiler feed pump motor sizing per ASME and API guidelines. For critical uninterrupted service, 1.15 to 1.20 may be applied. This accounts for system degradation, fouling, and ensures the motor operates within its service factor.
Total Dynamic Head (TDH) is the total equivalent height a pump must overcome. For boiler feed pumps, TDH includes static head (deaerator to boiler drum elevation), pressure head (boiler operating pressure converted to head: 1 bar ≈ 10.2 m), friction losses in piping and fittings, and velocity head. A medium-pressure boiler at 20 bar typically requires 250-350 meters TDH.

Frequently Asked Questions

Yes. Toggle between Metric (m³/hr, meters, kg/m³, kW) and Imperial (GPM, feet, SG, HP) modes using the buttons above the input fields. Results are displayed in both kW and HP in either mode for convenience.
Hydraulic power (water power) is the theoretical energy transferred to the fluid. Shaft power (brake power) is the actual mechanical power required at the pump shaft, accounting for pump efficiency losses. Shaft power is always higher than hydraulic power because no pump is 100% efficient.
A safety factor accounts for uncertainties in system head calculations, future fouling or scaling, pump wear over time, transient operating conditions, and ensures the motor operates below its maximum rating during normal service. Standard practice per ASME and HI guidelines is 1.10 to 1.15.
Fluid temperature affects density. Hotter water is less dense: at 20°C water density is 998 kg/m³, at 100°C it drops to 958 kg/m³, and at 180°C it is approximately 887 kg/m³. Since pump power is directly proportional to density, using the correct density for your operating temperature is essential for accurate sizing.
Yes, the underlying pump power formulas apply to any centrifugal pump application handling Newtonian fluids. Adjust the fluid density (or specific gravity) and efficiency values to match your specific pump and fluid, and the calculations remain valid for water transfer, condensate return, cooling water, and other industrial pumping services.
Boiler feed pumps handle hot water near its boiling point, making NPSH (Net Positive Suction Head) critical. The deaerator must be elevated sufficiently above the pump suction to provide adequate NPSH Available (NPSHa). A common rule is 3-5 meters elevation plus a margin above NPSH Required (NPSHr) from the pump curve. Insufficient NPSH leads to cavitation and pump damage.

Boiler Feed Pump Glossary

Total Dynamic Head (TDH)

The total equivalent height a pump must overcome, combining static head, pressure head, friction losses, and velocity head. Measured in meters or feet.

Hydraulic Power

The theoretical power transferred to the fluid, calculated from flow rate, head, and fluid density. Also called water power or fluid power.

Shaft Power

The mechanical power required at the pump shaft, equal to hydraulic power divided by pump efficiency. Also called brake horsepower (BHP).

NPSH (Net Positive Suction Head)

The minimum suction pressure required to prevent cavitation. NPSHa (available) must exceed NPSHr (required) with an adequate margin.

Deaerator

A vessel that removes dissolved gases from boiler feed water using steam. Typically mounted at elevation to provide NPSH to the feed pump.

Specific Gravity (SG)

The ratio of fluid density to water density at standard conditions. Water has SG = 1.0. Used in imperial pump power calculations.

Multistage Pump

A centrifugal pump with multiple impellers in series, commonly used for boiler feed applications to generate high discharge pressures efficiently.

Safety Factor

A design margin applied to motor sizing (typically 1.10-1.15) to account for system uncertainties and ensure reliable operation under all conditions.

Editorial Review & Methodology

This boiler feed pump calculator was built and reviewed by the NumbrWiz Editorial Team in consultation with practicing mechanical engineers. The pump power formulas are based on fundamental fluid mechanics principles and align with Hydraulic Institute (HI) standards, ASME boiler feed pump guidelines, and standard engineering references including Perry's Chemical Engineers' Handbook and Cameron Hydraulic Data.

  • Formula verification: Cross-checked against Hydraulic Institute standards (HI 14.3) and ASME PTC 8.2 centrifugal pump test codes.
  • Edge case testing: Validated with zero-flow scenarios, extreme pressure conditions, low-efficiency limits, and variable fluid densities.
  • Industry alignment: Safety factor recommendations follow ASME BPV Code Section I and API 610 guidelines for boiler feed pump service.

Transparency note: All calculations run client-side in your browser. No data is collected, stored, or transmitted. Results are for educational and preliminary design purposes. Always verify final pump selections with manufacturer performance curves and a qualified engineer for critical boiler applications.

Page last reviewed: May 2026 · NumbrWiz Editorial Team