Fire water pumps requirement for hazardous Industries
The provision of fire water pumps is exclusively for firefighting
purposes. These pumps may be horizontal centrifugal type or vertical turbine
submersible pumps. It includes Main pumps, Standby pumps and jockey pumps.
While selecting the numbers of fire pumps, there should be combination of
electrically driven and diesel operated pumps to manage the black out or
failure of electrical power supply. Only centrifugal type pumps are suitable
for firefighting purpose.
![]() |
Fire water pumps requirement for hazardous Industries |
Fire water pumps requirement for hazardous Industries
According to standards, the fire water system must be designed
for a minimum residual pressure of 7.0 kg/cm2 at the hydraulically remotest
point of application at the designed flow rate at that point. To meet this
requirement, fire water network must be kept pressurized by jockey pumps higher
than 7 Kg/cm2. Actual network pressure to maintain all time, depends on total
fire water demand, piping design and length of piping network.
Requirement for main and standby Fire pumps
While deciding the numbers of main and standby fire pumps,
combination of electric motor driven centrifugal pumps and Diesel engine driven
centrifugal pumps should be considered.
Including standby pumps, the number of diesel driven pumps must
be minimum 50% of the total calculated number of pumps requirement based on
total fire water demand. Minimum 50% of total flow requirement should be
available through diesel driven pumps all the time. All such pumps should be
identical in capacity.
With reference to total water demand calculation and capacity
selection of fire pumps, if the total number of working pumps derived as one or
two then 100% standby pumps must be considered. If the total numbers of working
pumps derived more than two, then 50% standby pumps must be provided. In major
industries where two fire water pump houses or two sets of firewater storage
and pumps are provided, then the number of fire pumps at each location will be decided
according to hydraulic analysis of piping network.
For Example:
As per total fire water demand calculation and capacity
selection of pumps, if the required fire main pumps are four numbers then there
should two more pumps as standby pumps.
So, the total fire pumps will be 6 numbers (04 Nos Main + 02
Nos Standby).
Out of above six pumps, there should three diesel driven and
three electrical driven. All these six pumps must be identical in capacity.
While selecting the sequence of operation, out of four main
pumps, there should be two electrical and two diesel driven. Similarly, for two
standby pumps, there should be one electrical and one diesel driven.
Requirement for Jockey pumps
The jockey pump maintains the designed pressure in the fire
water network to compensate the minor leakages and to avoid non-emergency
starting of the main fire pump.
There should be two jockey pumps (main + standby) and must be
maintained in auto mode. Both the pumps should be electrically driven.
The capacity of the jockey pumps must be enough to compensate the
desired fire water system pressure in the event of any minor leakages from
valves, piping or operation of single hydrant etc. to avoid non-emergency starting
of the main fire pump.
The capacity of jockey pumps should not be less than 5% and should
not be more than 10% of the design fire water rate. As these pumps maintains
the header pressure in non-emergency situation and therefore it’s head shall be
higher than the main fire water pumps.
Know more about requirement of jockey pumps
Capacity of Fire water main and standby pumps
To deal with fire and explosion hazards in hazardous
industries such as chemicals, fertilisers and oil & gas including
refineries and petrochemicals, robust firefighting system must be designed.
Fire water system is very crucial and therefore selection of adequate numbers
of fire pumps with suitable capacity must be decided according to national and
international standards.
While deciding the capacity of fire water pumps, each selected pumps must be designed in such a
way that it should capable to discharge 150% of its rated capacity at a minimum
of 65% of the rated head. The shut-off head should not exceed 120% of rated
head, for horizontal fire pumps and 140% in case of vertical turbine type fire pumps.
Based on the total fire water demand calculation and designed
fire water rate, the capacity and number of main fire water pumps should be
considered. While deciding the capacity of each pump, it should not be less
than 400 m3/hr or more than 1000 m3/hr. Whatever the capacity calculated for
fire pumps, all pumps should be identical with respect to capacity and head
characteristics.
For Example:
Suppose the total fire water demand is calculated as 2400
m3/hr then the numbers of main pumps may be four numbers of capacity 610 m3/hr
each.
Standby pumps will be two numbers of identical capacity and in
head characteristic. So, total pumps will be six numbers. Out of these six
numbers, there will three electrically driven and three diesel driven.
Other than above six pumps, there will two jockey pumps (one
main and one standby) of capacity 120 m3/hrs each (5% of total water demand).
Sequence of operation of fire main pumps
All the fire water pumps should be maintained in auto mode and
operation philosophy should be as per designed pressure. Pumps must start
automatically and sequentially with PT/ PLC on fire water mains. The system
shall ensure auto start of the standby pump in case a pump in sequence failed
to take start.
Main pump will be started automatically but stop will be
manual.
For example:
Suppose, the designed header pressure is calculated as 10.5
kg/cm2 to be maintained in the fire water network at all time then the jockey
pump operational sequence may be set as; auto start at 10 kg/cm2 and auto stop
at 10.5kg /cm2.
Whereas for Main fire pumps, below auto start sequence may be
considered;
1st pump – start at 9.5 kg/cm2
2nd pump – start at 9 kg/cm2
3rd pump – start at 8.5 kg/cm2
4th pump – start at 8 kg/cm2
5th pump – start at 7.5 kg/cm2
6th pump – start at 7 kg/cm2
All above main pumps shall be stopped manually.
Power Supply to Fire water pumps
Power supply to the electric driven pumps should be from two
separate feeders and dedicated only to fire pumps from the sub-station to ensure
reliable power supply. Emergency power supply must be provided for jockey pumps
to deal with black out event. The direct feeder line from electrical substation
should not run along with other HT cables.
All the pump should be provided with local manual ON/OFF
switches and remote selection switch on controller. Push button should be
provided near the diesel pumps and all the diesel engines must be quick
starting type with the help of these push buttons or can be operated from remote
location
Fuel tank
for each diesel engine should be provided independently and must be adequate
for 6 hours continuous running of the pump.
No comments
Please don't add links in the comments, they will be treated as spam comments