automatic fire sprinkler design - draft

AUTOMATIC FIRE SPRINKLER SYSTEM DESIGN

Content

1) Classification of Occupancy

2) Water Supply/Storage Requirement

3) Sprinkler Spacing, Rating & Coverage

4) Piping Layout

5) Hydraulic Calculation

6) Pump Selection

Automatic Fire Sprinkler System

After the Architect has confirmed whether or not a building requires an automatic fire

protection system, the engineer must determine the appropriate Hazard Group

Classification.

The Hazard Group Classifications are, in order of risk from Low to High.

Light Hazard Occupancy

Ordinary Hazard Occupancy – Group I

Ordinary Hazard Occupancy – Group I

Ordinary Hazard Occupancy – Group II

Ordinary Hazard Occupancy – Group III

Ordinary Hazard Occupancy – Group III Special

High Hazard Occupancy

High Hazard Occupancy– Process Risks

High Hazard Occupancy – High Piled Storage Risks

Classification of Hazard Group


Determine Hazard GroupThe Hazard Group Classification is a measure of the likely relative severity of a fire based on

the occupancy of the space. Spaces with different occupancy types may have different hazard

group classifications.

Example – MazdaOccupancy of space includes,

- Office - (OH 1) , clause 3.2.3.1

- Motor garages, including public and private car park- (OH 2) , clause 3.2.3.2

- Showroom - (OH 3) , clause 3.2.3.3

- Painting (Spray booth) - (HH, Process risk / Cat 3) , clause 3.2.4.1


Determine Hazard Group

Example – Mazda Occupancy of space includes,




- Painting (Spray booth) - (HH, Process risk / Cat 3) , clause 3.2.4.1

Content



3) Sprinkler Spacing

4) Piping Layout


6) Pump Selection


Water Supply/Storage Requirement

Based on Hazard group to determine Minimum Capacity Water Storage

Storage requirement with Calculated design flow rate with Automatic inflow (900

L/min)

a) 30 mins for LH plus 1.3 time (clause 13.8.2.3)

b) 60 mins for OH and,

c) 90 mins for HH.

- Notes: Water supplies to sprinkler systems require a high level of reliability. Deem no

reliable source of Town water supply.

Minimum capacity of water supplies

a) Table 16 for Ordinary Hazard (Sprinkler & Hose reel)

b) Table 24 for High Hazard


Example – Mazda for Water Storage Tank

There having several occupancy groups. Occupancy of space includes,




- Painting (Spray booth) - (HH, Process risk / Cat 3) , clause 3.2.4.1.

The water supply must be capable of meeting the most hydraulically demanding area of the

systems. (NFPA 13 – Water Supply).


Example – Mazda for Water Storage Tank There may chose with many options for minimum storage capacity.

In Myanmar, automatic inflow form Town water supply is still yet to improve

The calculation of water storage capacity with design flow rate is only suitable for

Light Hazard Occupancies.

The Ordinary and High Hazard recommend to use as per CP 52, Table 16 for

Ordinary Hazard and Table 24 for High Hazard.


Water Storage Capacity for Ordinary Hazard


Water Storage Capacity for Ordinary Hazard

Maxi Height of spk is about 15 m @ 135 000 L ,or 135 m3


Water Storage Capacity for High Hazard


Water Storage Capacity for High Hazard

Density of Discharge is 7.5 mm/mm @ 237 000 L or 237

m3


Example – Mazda for Water Storage Tank Design Data for Spray booth (Mazda)

Occupancy - Paint and varnish works (solvent based)

Design Density – 7.5 mm/min (Table 20)

Calculate Minimum Water Storage) Option1, (From Table 23, 2nd column) )

2300 L/min x 90 min = 207 000 Liters or 207 m3 or,

237 000 Liters or 237 m3

Calculate Minimum Water Storage Option 2, with Area x Density of discharge

Spray booth area – 47 m2

Density of Discharge - 7.5 mm/min

Minimum flow for Sprinklers – 325.5 L/min

Minimum storage to be maintained – 90 min

Minimum storage capacity – 325.5 x 90 = 31725 Liters or 31.73 m3


Example – Mazda for Water Storage Tank

Determine the Minimum Water Storage Capacity From Pump Flow with OH3 (15 m), if ignore HH for spray boot

1350 L/min x 60 min = 81 000 Liters or 81 m3

From Table 16 & 24

135 000 Liters or 135 m3 with OH3 (15 m) Hazard if ignore HH for spray boot

237 000 Liters or 237 m3 with High Hazard

Content




4) Piping Layout


6) Pump Selection


Sprinkler Spacing, Rating & Coverage

Light Hazard (LH)a) Criteria

Assumed area of operation – 84m²

Design density – 2.25mm/min

Max. coverage per sprinkler

- Sidewall – 17m2

- Other sprinklers – 21m²

b) Max distance between sprinkler

Sidewall – 4.6m

Other sprinklers – 4.6m

Size of sprinkler – 10mm

c. Max distance from wall or partition

Sidewall sprinklers from end walls – 2.3m

Other sprinklers – 2.3m


Ordinary Hazard (OH)a) Criteria

Assumed area of operation

- Group I – 72m², Group II – 144m², Group III – 216m² , Group III S – 360m²

Design density

- 5mm/min

Max. coverage per sprinkler

- Sidewall – 9m2

- Other sprinklers – 12m²

b) Max distance between Sprinklers

Sidewall – 3.7m

Other sprinklers

Spacing between rows – 4.2m

- Standard spacing– 4.2m

- Staggered spacing – 4.6 m

- Size of sprinkler – 15mm


High Hazard (OH)a) Criteria

Process Risks

- Assumed area of operation – 260m²

- Design density – 7.5mm/min to 12.5mm/min

High Piled Storage Risks

- Assumed area of operation – 260m² to 300m²

- Design density – 7.5mm/min to 12.5mm/min

Max. coverage per sprinkler – 9m² (except rack sprinklers)

b) Max. distance between sprinklers – 3.7m

Size of sprinklers

- 15mm

- 20mm

Content




4) Piping Layout


6) Pump Selection


Hydraulic Calculation

Design Points Sprinkler design points are the hydraulic most demanding point(s) in the sprinkler system immediately

prior to the group of heads that are required to discharge.

These are the points for which the system inlet pressure and distribution pipe sizing must be designed to

provide adequate water pressure at the sprinkler heads.

The design points are typically at the most remote ends of any sprinkler array.

The design numbers of heads to discharge are as follows:

a) LH – after 6 sprinklers

Flow rate – 48 L/min per spk

Minimum discharge pressure – 70 kPa

b) OH – after 16/18 sprinklers

Flow rate – 70 L/min per spk (or),


Full flow at 1800 L/min and fiction loss shall not exceed 150 kPa (including main distribution

pipe and all risers)

c) HH – depends on area of operation. Refer to CP 52 Table 20.



Hydraulic Calculations and Pipe Sizing• Full hydraulic calculations are required for LH & HH systems.

• Partial hydraulic calculations are permissible for OH systems.

• Hydraulic calculations are required for sprinkler systems to confirm:

• The pressure drop from Control Valve to the Design Point in order to size the Fire Pump and size the

distribution pipework.

• The pressure drop from Pump to Control valve to confirm pressure at CV is not less than that

specified in CP52.

• To determine the pressure that will occur in sprinkler pipework branches closer to the pump and

assess if excess sprinkler flow may be a difficulty.


Pre Hydraulic calculation

This friction loss from CV to DPs may not exceed 150 kPa based on design flow rate of

1800 L/m as specify by code.

Pressure drop from 90 ° bend is equivalent to 3m pipe length.

Sprinkler Pump Head

The pump head required is the sum of the pressure drop from the pump suction to

the sprinkler CV plus the minimum head specified in CP 52 Table 5.


Pump Head Requirement The pump head required is the sum of the pressure drop from the pump suction to the sprinkler CV

plus the minimum head specified in CP 52 Table 5.


Pump Head Requirement

automatic fire sprinkler design - draft

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