Fire Pumps in Firefighting

Fire pumps are the heart of any water-based fire protection system. They ensure
sufficient water pressure and flow rate to deliver water to firefighting equipment
such as sprinklers, fire hose cabinets, deluge systems, and more. Fire pumps activate
automatically upon detecting a pressure drop caused by the activation of any system
component.
Types of Fire Pumps
1. Main Fire Pump
The primary source for providing required pressure and flow during a fire.
Must operate continuously for at least 90 minutes.
Typically powered by electricity or diesel.

2. Standby Fire Pump

A backup pump, typically of a different type from the main one (e.g., diesel if the
main is electric).
Activates if the main pump fails.

3. Jockey Pump
Small-capacity pump used to compensate for minor pressure drops due to leakage.
Not intended for actual fire conditions.
Flow rate usually 1% to 1.5% of the main pump’s capacity.
🔥 Fire Pump Types

 Centrifugal Pumps
 Positive Displacement Pumps
Fire pumps are categorized based on their design and mechanism. The most
common types include:
Centrifugal Pumps (Ch.6):
 Widely used in fire systems.
 Must generate positive pressure at suction.
 Provide high pressure and flow rates.
 Common types of centrifugal pumps:
1. End Suction Pump:
2. Vertical Inline Pump:
3. Horizontal Split Case Pump:
4. Vertical Turbine Pump:

Determining Suction Pipe Diameter According to NFPA Standards

Source: Table 4.26(a) - Summary of Centrifugal Fire Pump Data

Pump Rating Minimum Suction Pipe Size Minimum Discharge Pipe Size
(GPM) (in) (in)
25 1 1½
50 1½ 2
100 2 2½
150 2 2½

📌 Important Notes for Suction Pipe Design:

 The diameter of the suction pipe is determined after identifying the pump's
suction inlet diameter using the table above.
 There are three cases depending on how the connection is made between the
pipe and the pump inlet, as shown in the pump’s specific catalog:
1. If the pipe and the suction inlet are the same size → direct connection
is allowed.
 2. If the pipe is smaller than the suction inlet diameter → use a reducer,
but it must be installed at a distance not less than 10 times the
diameter (10D) before the pump.
3. If the pipe is larger than the suction inlet → use an eccentric reducer
with the flat side on top, in order to:
 Avoid air pockets, which can cause cavitation and damage the
pump.
 This is the most common configuration.

Positive Displacement Pumps (Ch.8):

Used in applications requiring very high pressure but low flow . Commonly found
in foam systems and specialized industrial applications.
o These pumps work by trapping a fixed amount of fluid and forcing
(displacing) it into the discharge pipe.
o Typically used to compensate for pressure losses in the fire water
network, especially in systems where maintaining constant pressure is
critical.
o Not as common as centrifugal pumps in standard fire systems, but
important in specialized applications.
Components of a Fire Pump Room
 Fire pumps: Main + Diesel + Jockey.
 Control panels: One for each pump.
 Water tank: Supplies water to the system.
 Check Valve, Relief Valve, Pressure Switch: Ensures safe operation and
control.

Electric Fire Pumps

Powered by an electric motor, these pumps provide a reliable and energy-efficient
water supply for firefighting, making them a common choice for many fire
suppression systems. They are typically used in buildings with a reliable power
source.
Diesel Fire Pumps
Diesel-powered fire pumps offer a critical backup option in the event of power
outages. Their independent power source ensures continuous water flow during
emergencies, ensuring a constant water supply for fire suppression even during
power failures.

Jockey Pumps
Smaller pumps designed to maintain consistent pressure within a fire sprinkler
system. This constant pressure prevents water loss and ensures immediate water
availability when a fire is detected by the sprinkler system, allowing for rapid and
effective fire suppression.
Pump Operation Sequence
 The jockey pump starts automatically upon minor pressure drop.
 If pressure continues to drop, the main pump activates.
 If electrical power fails, the diesel pump kicks in.
 Visual and audible alarms are available on control panels for every status
(running, failure, test).

Fire Pump Requirement

✅ Rated Flow Rate – Performance Conditions for Fire Pumps

To differentiate a fire pump from other types of pumps, three essential performance
conditions must be met, according to NFPA standards:

1️-Rated Flow and Pressure Requirement:

 The pump must provide the required flow rate (Rated Flow) and required
pressure (Rated Head) according to the design.
2️-Overload Performance Limits:

 The pump must deliver up to 150% of its rated flow.

 At this flow rate, the pressure must not drop below 65% of the rated head.
 This ensures the pump maintains adequate performance even in high-
demand scenarios.

3️-Shutoff Pressure Limit (Churn or No-Flow Condition):

 The maximum pressure produced by the pump at zero flow (Shutoff

Pressure or Churn Pressure) must not exceed 140% of the rated head.
 This value is usually found in the pump catalog or performance curve.

⚠️If any of these three conditions is not met, then the pump does not qualify as a
certified fire pump.
Fire Pump Testing
 Per NFPA 25, regular testing includes:
 Weekly Test: No-load start-up test.
 Monthly Test: Loaded functional test.
 Annual Test: Full-capacity test measuring flow and pressure via test header.

Installation Considerations

The pump room should be:

 Safe and away from hazards.

 Properly ventilated.

 Equipped with drainage.

 Connections:

Suction line (from tank)

Discharge line (to system)

Test line (for flow testing)

Drain line (for maintenance)