Calculate Main Fire Pump Capacity with Head and other Characteristic as per NBC 2016 / IS 12469 / IS 15301.

January 31, 2025 1 Comment

EXAMPLE:

Calculate Main Fire Pump Capacity with Head and other characteristic as per NBC 2016 / IS 12469 / IS 15301 for following Details.

  • Type of Hazard:
  • Fire Type is Light hazard
  • Fire Protection Area (Building) Detail:
  • There are 4 Nos of Residency Building having 12 Nos floor and each floor have of 3.2 Meter height. (Building Height 38.40 Meter).
  • Fire Fighting Pipe Network Detail:
  • The maximum horizontal length of fire System header is 50 Meter.
  • Up to Furthest Location in Fire Network System, the maximum bend in Horizontal Line are 6 Nos and Vertical Line /Header are 2 No. The Losses on each bend is 1.5 to 2 Meter.
  • The Water Friction losses are approximately 3%

CALCULATION:

  • We will derive calculation as per following sequence.
  1. Calculate Size of Main Fire Pump.
  2. Calculate Head of Fire Pump.
  3. Calculate RPM of Pump.
  4. Calculate Pump Pressure.
  5. Check Pump Characteristic as per Clauses.

(1) Calculate Size of Main Fire Pump:

  •  Type of Building occupancy is Residency and type of hazard is Light. The Building Height is 38.40 Meter.
  • AS PER NBC-2016:
  • As per NBC 2016, Table-7, Note No 10 , The Main Fire Pump Capacity will be 2850 Liter/Min.

  •  AS PER IS: 12469:
  • Total No of Hydrant for Building = 1 No for Each Floor, hence approximate 1×12 (Floor) x4 (Tower) =48 No’s,
  • As per IS 12469 , Fire Pump Capacity Shall be 137 M3/Hour = 2282 Liter / Min

  • From Above consideration Capacity Main Fire Pump Shall be 2850 Liter /Min.

(2) Calculate Head of Main Fire Pump:

  • Vertical Head
  • Vertical Head =No floor x Floor Height
  • Vertical Head =12 x 3.2 = 38.40 Meter.
  • Head Losses due to Bend= 2 x Head Losses of Each Bend
  • Head Losses due to Bend= 2 x 1.5 = 2.06 Meter.
  • Equivalent Vertical Head=Vertical Head+ Head Loss due to bend
  • Equivalent Vertical Head=38.40+2.06 =40.46 Meter.
  • Total Vertical head= Equivalent Vertical Head x Friction Losses.
  • Total Vertical head= =40.46 x 1.03= 41.67 Meter——-(A)
  • Horizontal Head
  • Horizontal Head=Maximum Horizontal Length
  • Horizontal Head=50 Meter
  • Head Losses due to Bend= 6x Head Losses of Each Bend
  • Head Losses due to Bend= 6 x 1.5 = 9 Meter.
  • Equivalent Horizontal Head= Horizontal Head+ Head Loss due to bend
  • Equivalent Horizontal Head=50+9 =59 Meter.
  • Total Horizontal head= Equivalent Horizontal Head x Friction Losses.
  • Total Horizontal head= =59 x 1.03= 60.77 Meter——-(B)
  • Total Head:
  • Total Head =Horizontal Head + Vertical Head
  • Total Head =41.67+60.77= 102 Meter.
  • As per above Calculation Head for Fire Pump shall be 110 Meter.

(3) Calculate Speed of Main Fire Pump:

  • As per IS 15301:
  • As per IS 15301 (Clause 6.2) , Electric motors required to feed the pump up to 2280 Liter/Min are usually running at 2900 RPM and the pumps required to match the motors must also run at the same revolutions per minute.
  • As per above Consideration Fire Pump speed shall be 2900 RPM.

(4) Calculate Main Fire Pump Pressure:

  • As per IS 12469:
  • As per IS 15301 (Clause 6.2) , Fire Pump Delivery Pressure shall be 7.0 Kg/cm2
  • As per above Consideration Fire Pump speed shall be 7.0 Kg/cm2.

 

 (5) Check Pump Characteristic as per Clauses.

  • For Calculation consider Pump Flow rate 171 M3/Hour and head is 110 Meter.
  • As per IS 12469:
  • As per IS 12469 ,Following Two Condition shall be satisfied for Fire Main Pump.
  • Pump shall be capable of not less than 150% of rated Capacity at Head of not Less than 65% of Rated Head.
  • The Shut off Head Shall not exceed 140% of Rated Head.
  • Pump Graph for 171 m3/hour is as per following.

  • Condition-1:
  • Pump shall be capable of not less than 150% of rated Capacity at Head of not Less than 65% of Rated Head.
  • Pump Shall be capable to supply =150% of rated Capacity
  • Pump Shall be capable to supply =150% x 171 = 256.5 M3/Hour.
  • Pump shall capable of Head not less than=65% of Rated Head
  • Pump shall capable of Head not less than=65% x 110 = 72 Meter
  • As per Graph for flow rate of 256.5 M3/Hour Pump head is 95 Meter ( Which is less than 72 Meter)
  • Condition-1 is satisfied.
  • Condition-2:
  • The Shut off Head Shall not exceed 140% of Rated Head.
  • The Shut off Head Shall not higher =110×1.40 =154 Meter.
  • As per Graph for flow rate of 256.5 M3/Hour, shut off Pump head is 120 Meter (Which is less than 154 Meter)
  • Condition-2 is satisfied.

CONCLUSION:

  • Size of Main Fire Pump: 2850 Liter/Min
  • Head of Fire Pump: 110 Meter.
  • RPM of Pump & Motor: 2900 RPM
  • Calculate Pump Pressure: 7.0 Kg/cm2
  • Check Pump Characteristic as per Clauses: Satisfied.

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