Summary of knowledge of fire pumps

Fire pump is through the rotation of the impeller energy transfer to the water, thereby increasing the kinetic energy of water, pressure energy, and will be transported to the fire-fighting equipment, in order to meet the various fire-fighting equipment, water volume, water pressure requirements.

Fire water supply system in the use of water pumps are mostly centrifugal pumps, because it has a wide range of adaptability, more models, continuous water supply, can be adjusted at will flow and other advantages. Including fire hydrant pumps, spray pumps, fire transfer pumps and so on.

Fire pump

1、Working principle

Before starting the fire pump, the impeller needs to be flooded with water, the prime mover drives the impeller to rotate through the pump shaft, and the blades are forced to rotate together with the impeller, and under the action of centrifugal force, the water is thrown to the outer ring by the centre and flows out from the impeller at high speed, and then is thrown into the outlet pipe. At this time, due to the impeller inside the thin space, so that the suction pipe caused a negative vacuum, the external water under the action of atmospheric pressure through the suction pipe into the thin space, was thrown into the outlet pipe. In this way, the water will continuously enter the pump to form a continuous water flow, to achieve the purpose of conveying water.

2、Basic performance parameters

(1) Flow (Q)

The volume of liquid conveyed by the pump in a unit of time, expressed in Q, commonly used units of m3 / h or L / s. (1m3 = 1000L)

(2) head (H)

Unit weight of liquid through the pump after the energy value-added (MPa), expressed in H, the unit is m. (1MPa = 100m head)

3, fire pump nameplate

In order to facilitate users to understand the performance of the pump, usually the pump model and flow, head, shaft power, speed, efficiency and allow suction on the vacuum height of the six main performance parameters marked on the pump pump casing on the label, that is, the nameplate of the pump. These performance parameters listed on the pump is designed to operate at speed, the efficiency of the highest when the value.

4, fire pumps and standby pumps set up conditions

(1) fire pumps should be set up standby pump, its performance should be consistent with the performance of the pump.

(2) automatic sprinkler system can be ‘one with a backup’ or ‘two with a backup’ ratio to set up a standby pump.

(3) The case of equipment pumps:

(1) Residential buildings with building height <54m and buildings with outdoor fire-fighting water supply design flow rate ≤25L/s.

(2) Buildings with indoor fire-fighting water supply design flow rate ≤ 10L/s.

Note: The fire hydrant system and automatic sprinkler system should be set up separately for fire pumps. When the automatic sprinkler system and the fire hydrant system are combined with fire pumps, the system pipelines should be separated in front of the alarm valve.

5、The main material of fire pump

(1) pump shell should be ductile cast iron.

(2) impeller should be bronze or stainless steel.

6, diesel fire pump setup requirements

(1) diesel fire pumps should be compressed ignition type diesel engine.

(2) The rated power of the diesel engine should be calibrated altitude and ambient temperature on the impact of diesel engine power.

(3) diesel fire pumps should have continuous performance, test run time should not be less than 24h.

(4) diesel fire pump battery should ensure that the fire pump at any time automatically start the pump requirements.

(5) diesel fire pump fuel tank should be determined according to the duration of the fire, and the minimum effective volume of the fuel tank should be configured according to 1.5L / kW, diesel fire pump fuel tank storage fuel should not be less than 50% of the storage capacity.

7, axial flow deep well pump setup requirements

(1) axial flow deep well pump installed in the well, the depth of submergence should meet the requirements of its reliable operation, in the pump flow rate of 150% of the design flow rate, the minimum depth of submergence should be the first pump impeller bottom water level above the line of not less than 3.2m, and the elevation of every increase of 300m, the minimum depth of submergence of deep well pumps should be increased by at least 0.3m.

(2) When the lowest water level of the fire fighting pool is lower than the centre line of the outlet pipe of the centrifugal pump or the water level of the water source can not guarantee the suction of the centrifugal pump, the axial deep well pump can be used, and should be installed on the fire fighting pool and other fire fighting water sources using the installation of wet deep pit

8, fire pump flow and head

(1) The performance of fire pumps should meet the requirements of fire water supply system flow and pressure.

(2) The power of the drive of the fire pump should meet the requirements of the selected pump flow and head performance curve at any point in the operation of the power requirements.

(3) When using motor-driven fire pumps, the motor should be selected dry installation of fire pumps.

(4) flow head performance curve should be no hump, no inflection point of the smooth curve, zero flow pressure should not be greater than 140% of the design working pressure, and should be greater than 120% of the design working pressure.