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Sprinklers - The Most Effective Way Of Preventig The Spread Of Fire.
Industrial/manufacturing

Sprinkler systems are widely recognised as the single most effective method of fighting the spread of fires in their early stages in industrial and manufacturing occupancies. In addition to protecting the property, they may also serve for the protection of life.

The financial burden of buildings and contents insurance can be greatly relieved by the provision of sprinkler systems and companies often recoup the cost of the system within twelve months with their reduced insurance premium.

Hazard identification and classification provides the basis for the design of the sprinkler system and is a skilled operation, which is usually carried out by the Insurer or Fire Authority. The hazard classification affects the choice of installation, operational method, water supply arrangements and pipe work design.
Industrial occupancies typically have abnormal fire loads within them and are classified as high hazard and sub-classified as:
Process high hazards
High piled storage high hazards
Potable spirit storage hazards
Oil and flammable liquid hazards
Process high hazard is applicable where the occupants use materials mainly of a hazardous nature and which are likely to develop into rapidly and intensely burning fires. Typical examples of process high hazard types are shown in table below, which are from BS 5306. Type 1 is the least severe, while Type 4 is the most severe.
Table 4: Process high-hazards showing typical examples of types
Type 1 Type 2 Type 3 Type 4
floor cloth and linoleum manufacture fire lighter manufacture cellulose nitrate manufacture firework manufacture
paint, colour and varnish manufacture manufacture of category III (see table 2) foam plastics, foam rubber, foam plastics goods manufacture and foam rubber goods manufacture excluding category IV (see table 2)    
rubber substitute manufacture tar distilling    
wood wool manufacture      

The density of discharge for the sprinkler system can be established using this table.High piled storage is applicable where the occupants are storing goods of low to moderate risk, usually within beam pallet racking, shelving and post or box pallets. Freestanding goods stored to a certain height also fall within this classification. In order to determine a density of discharge for the sprinkler system, the goods stored must first be categorised. This is done using the table below from BS 5306.

The lists included in the table are not exhaustive but provide a basis for interpretation of goods.
Table 2: High-piled storage hazards showing typical examples in goods categories
Category I Category II Category III Category IV
carpets baled cork bitumen-coated or wax-coated paper off cuts and random pieces of foamed plastics or foamed rubber
clothing baled waste paper cellulose nitrate rolls of sheet foamed plastics or foamed rubber
electrical appliances cartons containing alcohols in cans or bottles esparto (loose)  
fibreboard cartons of canned lacquers which dry by solvent evaporation foam plastics and foam rubber products, with or without cartons, other than those specified in category IV  
glassware and crockery, in cartons chipboard flammable liquids in combustible containers*  
groceries flammable liquids in non-combustible containers* rolled asphalt paper (vertical storage)  
metal goods, in cartons linoleum products rolled pulp and paper (vertical storage)  
textiles palletised whisky stocks rubber goods  
all forms of paper storage not listed under categories II or III plastics (non-foamed) other than cellulose nitrate ventilated wood stacks  
ordinary combustible materials, and non -combustible materials in combustible wrappings rolled pulp and paper, horizontal storage waxed or asphalt-coated paper and containers in cartons  
  rolled asphalt paper, horizontal storage wood wool  
  veneer sheets wooden pallets and wooden flats (idle)  
  wood patterns all materials having wrappings or preformed containers or foamed plastics  
  wooden furniture    

Note: The lists are not exhaustive, Category I does not automatically include goods or materials not sited here as categories II, III or IV.

*Excluding aerosol dispensers which are a special case.
Once the category of goods has been established, consideration needs to be given as to how the goods are stored. Table 1 from BS 5306, (see copy below) illustrates the various types of storage solutions by coding them S1 to S8. It also shows the maximum allowable storage heights for certain storage categories and hazard classes.
Table 1: Classification of stacked goods and limitations on storage methods
Type (and storage method) Goods category reference (see 5.1 and table 2) Maximum storage height for protection by roof or ceiling sprinklers only Limitations (ordinary and high hazard) Design density and stock height given in
Ordinary hazard Group III (m) High Hazard (m)
S1
Free standing or block stacking

I
II
III
IV

4.0
3.0
2.1
1.2

7.6
7.5
7.2
4.4

None Table 8 for high-hazard, or table 7 for ordinary hazard
S2
Post or box pallets in single rows
 I
II
III (except rubber types)
IV 		3.5
2.6
1.7
1.2		 6.8
6.0
6.0
4.4		 Aisles shall be not less than 2.5m wide Table 9 for high-hazard, or table 7 for ordinary hazard
S3
Post or box pallets in multiple rows
 III (except rubber types) 3.5
2.6
1.7
1.2		 5.7
5.0
3.2
3.0		 No storage block shall exceed 150m square in plan area. Each storage block shall have aisles all round not less than 2.5m wide. Table 10 for high-hazard, or table 7 for ordinary hazard
S4
Open-bottom post pallets		 III (except rubber types) 1.7 7.2 None Table 8 for high-hazard, or table 7 for ordinary hazard
S5
Palletised rack (beam pallet racking)		 I
II
III
IV 		3.5 (see note 1)
2.6 (see note 1)
1.7 (see note 1)
1.2 (see note 1)		 6.8 (see note 1)
6.0 (see note 1)
6.0 (see note 1)
4.4 (see note 1)		 Intermediate sprinklers shall be fitted where the aisles are less than 1.2m wide (see 26.1.4) Table 9 for high-hazard, or table 7 for ordinary hazard
S6
Solid or slatted shelves 1m or less wide		 I
II
III
IV 		3.5 (see note 1)
2.6 (see note 1)
1.7 (see note 1)
1.2 (see note 1)		 5.7 (see note 1)
5.0 (see note 1)
3.2 (see note 1)
3.0 (see note 1)		 Gangways shall be not less than 1.2m wide, or storage blocks shall be not more than 150m square with aisles all round not less than 2.5m wide Table 10 for high-hazard, or table 7 for ordinary hazard
S7
Solid or slatted shelves over 1m and not more than 6m wide		 I
II
III
IV 		Not applicable Not applicable As S6 above. Intermediate sprinklers should be fitted under each shelf and shall be installed where storage blocks exceed 150m square in plan area or do not have aisles all round not less than 2.5m wide Table 10
S8
Solid or slatted shelves over 1m wide where intermediate sprinklers cannot be installed		 I
II
III
IV 		Not applicable 5.7 (see note 1)
5.0 (see note 1)
3.2 (see note 1)
3.0 (see note 1)

Continuous non-combustible full height vertical bulkheads shall be fitted longitudinally and transversely within each shelf (see 26.1.4)

No storage block shall exceed 150m square in plan area. Each storage block shall have aisles all round not less than 2.5m wide.

 Table 10
Note 1: Intermediate sprinklers shall be fitted under shelves where the maximum heights specified are exceeded.

Note 2: See clause 14 for design density and AMA/O according to storage heights and goods category.

This table illustrates that, as storage heights increase, so in turn does the hazard classification and discharge density.

Potable spirit storage hazard is applicable where the occupant is storing spirits, not in racked barrels, to heights exceeding those given in column 3 of the table . This is classified as high piled storage and is given storage Category 2 or 3.

Oil and flammable liquid hazard is applicable where the occupant is storing oil and flammable liquid in such quantities and in such a manner that standard sprinkler protection may not be effective. In these cases, a deluge installation using high velocity sprayers may be effective. Normal sprinkler installations may incorporate deluge systems to cover small areas of flammable liquid hazards.

Beam pallet racking
The storage within the rack is clothed in cardboard boxes. The cardboard element of the storage means that it is classed as Category 2 goods. The racks are type S5 and are 1 metre high, which means that in-rack sprinkler heads would need to be fitted, as roof protection would be inadequate.

A flammable liquid hazard
In this case, the liquid petroleum gas tanks are protected by a deluge system, which is an effective way of stopping a fire in one tank spreading to the others. Deluge systems also serve to damp down shockwaves produced by explosions and the cooling effect the mist-like spray gives has been put to good use, particularly on oil rigs and tanker unloading bays.

Typical type S1 or freestanding storage
Whey storage - to a height of 3 metres. Whey is classed as Category 2 goods and if only stored to 3 metres, ordinary hazard protection is adequate.

Category 2 goods, stored in S5 type racking

In this case, due to the way the racking itself has been constructed, it is impossible to install sprinkler heads within the rack structure. As a result, the sprinkler pipe work has been designed and positioned to provide a higher discharge density over the stored goods, to compensate for the lack of protection within the racks.

As you can see, the type, size and design of the sprinkler system is flexible so that the protection is appropriate to the hazard.

In all industrial applications, wet pipe installations are preferable. However, if the temperature of the premises cannot be guaranteed to remain above freezing at all times, an alternate system should be fitted; where only part of the premises may fall below 5°C during the winter, a tail end dry extension should be installed in that part as an extension to the wet installation.

Although local water authorities have a duty to supply water for domestic services, water supplies for sprinkler systems are provided only on request and are rarely adequate for high hazard industrial applications. Therefore, a dedicated, dependable supply usually has to be provided by means of a duplication pump set and storage tank.
If you would like any further information regarding sprinkler systems for industrial premises, please call 01769 574070 or email fds@fire-defence.com