NFPA Fire Pumps Standard

There are many answers to this question, but most experts agree that a fire pump should be large enough to provide enough water (flow and pressure) for the maximum flow expected from any individual sprinkler or deluge system, plus an additional amount (fire hose) for firefighting needs. For example, if the maximum sprinkler demand is 1000 gpm at 60 psi and the required demand (fire hose) is 500 gpm, then a minimum flow rate of 1500 gpm at 60 psi is expected from the combination of the fire pump and the public water or dedicated reservoir. There is no one-size-fits-all answer to the question of how to size a fire pump. Some insurers and regulatory authorities prefer that the maximum flow demand not exceed the pump’s rated operating point (100 percent flow and pressure), but others will accept anything between the rated point and the maximum flow point, although the maximum flow point is rarely accepted.
It is also common practice to install a redundant pump in very large units because even if one of the pumps fails or is out of service for repairs, there will be no problem in providing sufficient water. Although an electric fire pump is reliable, it is highly dependent on the availability of a reliable electrical power supply. Diesel fire pumps are also reliable, but they also require their own power source (diesel fuel). A common and reliable method for large units is to use an electric pump and a diesel fire pump simultaneously.
b) Types of fire pumps
There are four types of fire pumps approved by the NFPA 20 standard:
1- Horizontal Single-Stage Centrifugal Pumps Horizontal End Suction Centrifugal Pump
2- Vertical In-Line Pumps
3- Horizontal Split-Case or Double Suction Centrifugal Pump
4- Vertical Turbine Pumps
Each of the above pumps is divided into different types. For example, vertical in-line pumps are divided into rigid coupling and flexible coupling types, as well as other cases that can be referred to the NFPA 20 standard.
C) Fire pump material
Pump shell Depending on the working pressure of the pump, the pump shell may be gray cast iron GG 25, GGG 40, ductile iron, bronze or cast stainless steel
Impeller According to the NFPA 20 standard and UL 448-FM 1311, the impeller of fire pumps must be either bronze or stainless steel. Cast iron impellers should never be used in fire pumps.
The pump shaft shall be stainless steel. In addition, FM 1311 and UL 448 standards provide clear rules for the design of the shaft of fire pumps.
Graphite tape sealing (asbestos-free type)
Bearings Grease lubricated bearings. The bearings shall be strong enough to last at least 5000 hours at maximum load.
D) Fire Pump Performance Curve
According to NFPA 20, the fire pump characteristic curve is defined as follows:
a) Shot head F. For all types of pumps, the shot head F shall not exceed 140% of the working head.
b) Flow rate and working point pressure. The pump characteristic curve must pass through the intersection of flow rate and working point pressure or above this point. In other words, in fire pumps, negative tolerance is not allowed for the pump.
c) Overload. The pump performance curve should be such that at flow rates exceeding 150% of the operating point, the pump head does not drop more than 65%.
e) The effect of impeller design on the performance curve of fire pumps.
Pump impellers are designed for low, medium and high heads based on their application. The figures below show the effect of impeller design on pressure and flow characteristics.
c) Other characteristics of fire pumps
– All measurements and calculations must be made for clean water at a temperature of 20°C.
– For the case where the flow rate reaches 150% of the operating point, the required motor power must be determined and, if requested by the employer, the rated driving power must be selected based on this case.
– To ensure the performance of the pumps under the required conditions, the manufacturer must test each pump separately with water and provide test certificates. The test certificate must show the performance curve, motor absorption power and efficiency curve.
– Centrifugal pumps should not be used when the pump must perform negative suction.
– Each pump must have a separate nameplate. The nameplate of the pump must state the working pressure, the duty point flow rate, the rotation speed and the motor performance factors.
– Each pump must have a pressure gauge on the discharge and suction sides.
– The shell of each pump must have a pressure relief valve.
– The pump motor coupling and other rotating pump components must be equipped with a guard.
g) Electric Motors
– Electric motors must be in accordance with NEMA MG-1 standard.
– All electric motors must be suitable for continuous operation.
– Engines should not have a service factor less than 1.15.
– In cases where there is a possibility of water splashing, electric motors must be TEFC type.
– In times when there is uncertainty in the supply of electricity, a backup power source must be provided.
– When a generator is used to power an electric pump, the power source must meet the requirements of the NFPA 110 standard.
h) Diesel Engines
– Diesel engines used in fire pumps must be reliable, high quality and designed for firefighting systems.
– If a diesel engine is selected, the ambient temperature and altitude must be taken into account.
– The pump and diesel engine must be coupled by flexible couplings.
– Diesel engines must be equipped with a governor and have the ability to adjust diesel speed between 10% of shut-off and maximum pump load.
– The diesel engine must have an over speed shut-down device that shuts down the diesel when the speed increases by 20 percent.
– The engine must be equipped with a tachometer.
– The engine must have an oil pressure gauge.
– The engine must have a temperature indicator.
– All engine control indicators must be properly connected to the control panel.
– Each diesel engine must be equipped with two backup batteries.
– Each battery should have twice the capacity to maintain the crank speed recommended by the manufacturer.
– Both batteries must have manual control contactors to enter the circuit.
X) Accessories
– Suction and discharge valves should be of the OS&Y gate type.
– In cases where there is a size difference between the diameter of the suction flange and the suction pipe, an eccentric adapter must be used.
– In cases where there is a size difference between the diameter of the thrust flange and the thrust tube, a center adapter must be used.
Fire pumps must have a casing relief valve, an air release valve at the outlet (for split-case double-suction pumps), and a pressure gauge.
d) Jockey Pumps
– Jockey pumps are used to maintain constant pressure in a fire system at all times.
– The jockey pump must have sufficient output pressure to provide the desired pressure of the fire protection system.
– Jockey pumps also prevent water hammer when the main pump enters the circuit.
Control system for electrically driven fire pumps
a) Specifications
– The panel shall be specially constructed for the operation of electrically driven fire pumps.
– All control systems must be assembled, wired, and tested by the manufacturer before being shipped from the factory.
– The control system design must be highly reliable.
– The meaning of each lamp or button, etc. on the panel, must be written in a way that cannot be erased or destroyed.
b) Enclosure
– The panel must be adequately protected against dripping water (at least according to NEMA and IEC recommendations). When the equipment is installed outdoors or in special environments, the degree of protection of the panel must be appropriate.
– The panel must be completely positioned on the ground.
– On-stood or wall-mounted panels must be equipped with all necessary equipment for installation.
– The panel must be securely locked.
C) Start-up and control
– Start-up and control should be manual or automatic.
– The automatic controller must be self-acting to start and protect the electric motor.
– When a pressure switch is used, a switch must be used that is independent of the high and low caliber settings in the control circuit.
– For all pumps, as well as the jockey pump, each controller must have its own separate pressure switch.
– For non-automatic mode, the manual operation switch on the control panel shall be such that the motor is started manually and the operation of the manual switch shall not affect the pressure switch. The system shall be such that when manually switched off, the system remains in the operating mode.
d) Signal and alarm equipment
– A visible indicator shall indicate the availability of power in all phases.
– Phase failure or phase reversal at the motor contactor terminals shall be monitored. All phases shall be monitored.
– The controller must be equipped with the following function circuits:
a) Motor and pump operation
b) Two-phase current
c) Phase reversal
d) The controller is connected to an alternative source.
Diesel Fire Pump Control System
a) Specifications
– Controllers shall be specifically designed for operation of diesel fire pumps.
– All control systems must be assembled, wired, and tested by the manufacturer before being shipped from the factory.
– All controllers must have the Diesel Engine Fire Pump Controller mark and the name of the device manufacturer must be included in an appropriate place.
b) Enclosure
– The controller should be installed as close to the diesel engine as practically possible and next to it.
– The controller must be installed in a location or protected in a way that prevents damage from water splashing from pumps or connections.
– The coating must comply with NFPA 70 standard.
C) Start-up and control
– Start-up and control should be automatic or non-automatic.
– The controller’s primary power source must not be AC power.
– When a water pressure control system is used, the control circuit must have a pressure switch that is independent of the high and low calibration settings.
D) Signal and alarm equipment
– There should be separate indicators and alarms for the following situations:
1) Automatic engine starter failure
2) Engine shutdown due to over speed
3) Battery failure
4) Battery charger failure
5) Very low oil pressure in the lubrication system
6) Cooling system temperature
E) Connections and wiring
– The controller wiring components must be suitable for continuous operation.

Fire Pump Construction Details According to NFPA 20
a) Fire Pump Specifications
Due to the special importance of fire pumps, NFPA has set standards for both the material and the performance curves of these pumps. A fire pump must comply with NFPA 20. It seems that the characteristics and performance curves of fire pumps are different from other examples. In other words, pumps in other industries are selected with maximum efficiency and economic considerations in mind, but in fire pumps this is not of primary importance. Fire pumps are designed for reliable operation throughout their life. Maximum safety and total outlet pressure criteria are of great importance in these pumps.

FM is an independent technical division of Factory Mutual Insurance Company that issues performance certifications for high-risk systems and equipment.
In fire pumps, FM certification is a requirement of the NFPA. FM certification usually indicates that the product is of a much higher quality than similar products.