Non-electrical disable devices shall be approved in accordance with EN 12094-6.
Time delay devices shall be approved in accordance with EN 12094-1 or EN 12094-2.
For normally occupied areas
The minimum safety precautions taken shall be in accordance with Table 2.
Table 2 — Minimum safety precautions
|
Maximum concentration |
Time delay device |
Automatic/manual switch |
Disable device |
|
Up to and including the NOAEL |
Required |
Not required |
Not required |
|
Above the NOAEL and up to the LOAEL |
Required |
Required |
Not required |
|
LOAEL and above |
Required |
Required |
Required |
|
NOTE The intent of this table is to avoid unnecessary exposure of occupants to the discharged extinguishant. Factors such as the time for egress and the risk to the occupants by the fire should be considered when determining the system discharge time delay. Where national standards require other precautions, these should be implemented. |
|||
5.2.2 For normally unoccupied areas
The maximum concentration shall not exceed the LOAEL for the extinguishant used unless a disable device is fitted.
It is recommended that systems where the NOAEL is expected to be exceeded be placed in non-automatic mode whilst the room is occupied.
WARNING: Any change to the enclosure volume, or addition or removal of fixed contents that was not covered in the original design will affect the concentration of extinguishant. In such instances the system shall be recalculated to ensure that the required design concentration is achieved and the maximum concentration is consistent with Table 2.
5.2.3 For unoccupiable areas
The maximum concentration may exceed the LOAEL for the extinguishant used, without the need for a disable device to be fitted.
5.3 Occupiable areas
In areas which are protected by total flooding systems and which are capable of being occupied, the following shall be provided.
time delay devices:
for applications where a discharge delay does not significantly increase the threat from fire to life or property, extinguishing systems shall incorporate a pre-discharge alarm with a time delay sufficient to allow personnel evacuation prior to discharge;
time delay devices shall be used only for personnel evacuation or to prepare the hazard area for discharge;
automatic/manual switch, and disable devices where required in accordance with 5.2;
NOTE Although disable devices are not always required, they are essential in some situations, particularly for some specific maintenance functions.
exit routes, which shall be kept clear at all times, and emergency lighting and adequate direction signs to minimize travel distances;
outward-swinging self-closing doors which can be opened from the inside, including when locked from the outside;
continuous visual and audible alarms at entrances and designated exits inside the protected area and continuous visual alarms outside the protected area which operate until the protected area has been made safe;
appropriate warning and instructions signs;
where required, pre-discharge alarms within such areas, which are distinctive from all other alarm signals, and which, upon detection of the fire, will operate immediately on commencement of time delay;
means for prompt natural or forced-draft ventilation of such areas after any discharge of extinguishant. Forced-draft ventilation will often be necessary.
Care shall be taken to completely dissipate hazardous atmospheres and not just move them to other locations, as most extinguishants are heavier than air;
instructions and drills of all personnel within or in the vicinity of protected areas, including maintenance or construction personnel who may be brought into the area, to ensure their correct actions when the system operates.
In addition to the above requirements, the following are recommended:
self-contained breathing apparatus should be supplied and personnel trained in its use;
personnel should not enter the enclosure until it has been verified as being safe to do so.
Electrical hazards
Where exposed electrical conductors are present, clearances no smaller than those given in Table 3 shall be provided, where practicable, between the electrical conductors and all parts of the system that may be approached during maintenance. Where these clearance distances cannot be achieved, warning notices shall be provided and a safe system of maintenance work shall be adopted.
The system should be so arranged that all normal operations can be carried out with safety to the operator.
Table 3 — Safety clearances to enable operation, inspection, cleaning, repairs, painting and normal maintenance work to be carried out
|
Maximum rated voltage kV |
Minimum clearance from any point on or about the permanent equipment where a person may be required to standa |
|
|
To the nearest unscreened live conductor in air (section clearance) m |
To the nearest part not at earth potential of an insulator15 supporting a live conductor (ground clearance) m |
|
|
15 |
2,6 |
|
|
33 |
2,75 |
|
|
44 |
2,90 |
|
|
66 |
3,10 |
|
|
88 |
3,20 |
2,5 |
|
110 |
3,35 |
|
|
132 |
3,50 |
|
|
165 |
3,80 |
|
|
220 |
4,30 |
|
|
275 |
4,60 |
|
Measured from position of the feet.
° The term insulator includes all forms of insulating supports, such as pedestal and suspension insulators, bushings, cable sealing ends and the insulating supports of certain types of circuit breaker.
Electrical earthing
Systems within electrical substations or switchrooms shall be efficiently bonded and earthed to prevent the metalwork becoming electrically charged.
Electrostatic discharge
The system shall be adequately bonded and earthed to minimize the risk of electrostatic discharge.
System design
General
This clause sets out the requirements for the design of the extinguishing system.
All ancillary systems and components shall comply with the relevant national or European or International Standards.
Extinguishant supply
Quantity
The amount of extinguishant in the system shall be at least sufficient for the largest single hazard or group of hazards that are to be protected against simultaneously.
Where required, the reserve quantity shall be as many multiples of the main supply as the authority considers necessary.
Where uninterrupted protection is required, both the main and reserve supply shall be permanently connected to the distribution piping and arranged for easy changeover.
Quality
The extinguishant shall comply with the relevant part of EN 15004.
Container arrangement
Arrangements shall be made for container and valve assemblies and accessories to be
accessible for inspection, testing and other maintenance when required.
Containers shall be adequately mounted and suitably supported according to the systems installation manual so as to provide for convenient individual servicing of the container and its contents.
Containers shall be located as near as is practical to the enclosure they protect, preferably outside the enclosure. Containers can be located within the enclosure only if sited so as to minimize the risk of exposure to fire and explosion.
Containers shall not be located where they will be subjected to severe weather conditions or to potential damage due to mechanical, chemical or other causes. Where potentially damaging exposure or unauthorized interference are likely, suitable enclosures or guards shall be provided.
NOTE Direct sunlight has the potential to increase the container temperature above that of the surrounding atmospheric temperature.
Storage containers
General
Containers shall be designed to hold the specific extinguishant. Containers shall not be charged to a fill density greater than specified in this document relating to the specific extinguishant.
The containers used in these systems shall be designed to meet the requirements of relevant national standards.
Where required, the container and valve assembly should be fitted with a pressure relief device complying with the appropriate national standard.
Container valves shall be approved in accordance with EN 12094-4.
Contents indication
Means shall be provided to indicate that each container is correctly charged.
If pressure gauges/switches or mechanical weighing devices are used these shall be approved in accordance with EN 12094-10 or EN 12094-11.
Marking
Each halocarbon container shall have a permanent name-plate or other permanent marking specifying the extinguishant, tare and gross mass, and the superpressurization level (where applicable) of the container. Each inert gas container shall have a permanent marking specifying the extinguishant, pressurization level of the container and nominal volume.
Manifolded containers
When two or more containers are connected into the same manifold, automatic means (such as check valves) shall be provided to prevent extinguishant loss from the manifold if the system is operated when any containers are removed, e.g. for maintenance.
Check valves shall be approved in accordance with EN 12094-13.
Containers connected to a common manifold in a system shall be:
of the same nominal form and capacity,
filled with the same nominal mass of extinguishant,
pressurized to the same nominal working pressure.
Different sized storage containers connected to a common manifold may be used for non-liquefied gas containers, provided they are all pressurized to the same nominal working pressure.
Operating temperatures
Unless otherwise approved, in-service container operating temperatures for total flooding systems shall not exceed 50 °С nor be less than - 20 °С (see also 7.3.1.).
External heating or cooling should be used to keep the temperature of the storage container within the specified range unless the system is designed for proper operation with operating temperatures outside this range.
Distribution
General
Pipework and fittings shall comply with the appropriate national standards, shall be noncombustible and able to withstand the expected pressures and temperatures without damage.
Before final assembly, pipe and fittings shall be inspected visually to ensure they are clean and free of burrs and rust, and that no foreign matter is inside and the full bore is clear. After assembly, the system shall be thoroughly blown through with dry air or other compressed gas.
A dirt trap consisting of a tee with a capped nipple, at least 50 mm long, shall be installed at the end of each pipe run. Drain traps protected against interference by unauthorized personnel should be fitted at the lowest points in the pipework system if there is any possibility of a build up of water.
In systems where valve arrangements introduce sections of closed piping, such sections shall be equipped with the following:
indication of extinguishant trapped in piping;
means for safe manual venting (see 6.3.1.5);
automatic relief of over pressures, where required.
Over-pressure relief devices shall be designed to operate at a pressure not greater than the test pressure of the pipework, or as required by the appropriate national standard.
Pressure relief devices, which can include the selector valve, should be fitted so that the discharge, in the event of operation, will not injure or endanger personnel and, if necessary, so that the discharge is piped to an area where it will not become a hazard to personnel.
In systems using pressure-operated container valves, automatic means shall be provided to vent
any container leakage that could build up pressure in the pilot system and cause unwanted opening of the container valve. The means of pressure venting shall not prevent operation of the container valve.
The manifolds to the container and valve assembly shall be hydraulically tested by the manufacturer to a minimum pressure of 1,5 x maximum working pressure (see 3.19), or as required by the appropriate national standards.
Adequate protection shall be given to pipes, fittings or support brackets and steelwork that are
likely to be affected by corrosion. Special corrosion-resistant materials or coatings shall be used in highly corrosive atmospheres.
Piping
Piping shall be of non-combustible material having physical and chemical characteristics such that its integrity under stress can be predicted with reliability. The thickness of the pipe wall shall be calculated in accordance with the relevant national standard. The pressure for this calculation shall be the developed pressure at a maximum storage temperature of not less than 50 °С. If higher operating temperatures are approved for a given system, the design pressure shall be adjusted to the developed pressure at maximum temperature. In performing this calculation, all joint factors and threading, grooving or welding allowances shall be taken into account.
Where a static pressure-reducing device is used in a non-liquefied gas system, the maximum working pressure in the distribution pipework downstream of the device shall be used in the calculation of the downstream pipe wall thickness. If selector valves are used, this lower maximum working pressure shall not be used upstream of the selector valves.
Cast iron and non-metallic pipes shall not be used.
Flexible tubing or hoses (including connections) shall be of approved materials and shall be suitable for service at the anticipated extinguishant pressure and maximum and minimum temperatures.
Hoses and flexible connectors shall be approved in accordance with EN 12094-8.
Fittings
Fittings shall have a minimum rated working pressure equal to or greater than the maximum pressure in the container at 50 °С, or the temperature specified in the national standard, when filled to the maximum allowable fill density for the extinguishant being used. For systems that use a pressure-reducing device in the distribution piping, the fittings downstream of the device shall have a minimum rated working pressure equal to or greater than the maximum anticipated pressure in the downstream piping. If selector valves are used, this lower maximum working pressure shall not be used upstream of the selector valves.
Cast iron fittings shall not be used.
Welding and brazing alloys shall have a melting point above 500 °С.
Welding shall be performed in accordance with relevant national standards.
Where copper, stainless steel, or other suitable tubing is joined with compression fittings, the manufacturer's pressure/temperature ratings of the fitting shall not be exceeded and care shall be taken to ensure the integrity of the assembly.
Pipe and valve supports
Pipe and valve supports shall be of non-combustible material, shall be suitable for the expected temperature and shall be able to withstand the dynamic and static forces involved. Due allowance shall be made for the stresses induced in the pipe work by temperature variations. Adequate environmental protection shall be given to supports and associated steelwork. The distance between pipe supports shall be as specified in Table 4.
Adequate support shall be provided for nozzles and their reactive forces such that in no case shall the distance from the last support be greater than as follows:
<25 mm pipe <100 mm;
> 25 mm pipe < 250 mm.
Movement of pipework caused by temperature fluctuations arising from environment or the discharge of extinguishant may be considerable, particularly over long lengths, and should be considered in the support fixing methods.
Table 4 — Maximum pipework spans
|
Nominal diameter of pipe DN |
Maximum pipework span m |
|
6 |
0,5 |
|
10 |
1,0 |
|
15 |
1,5 |
|
20 |
1,8 |
|
25 |
2,1 |
|
32 |
2,4 |
|
40 |
2,7 |
|
50 |
3,4 |
|
65 |
3,5 |
|
80 |
3,7 |
|
100 |
4,3 |
|
125 |
4,8 |
|
150 |
5,2 |
|
200 |
5,8 |
Valves
All valves, gaskets, О-rings, sealants and other valve components shall be constructed of materials that are compatible with the extinguishant and shall be suitable for the envisaged pressures and temperatures.
Valves shall be protected against mechanical, chemical or other damage.
Special corrosion-resistant materials or coatings shall be used in severely corrosive atmospheres.
Selector valves shall be approved in accordance with EN 12094-5.
Nozzles
Nozzle choice and location
Nozzles, including nozzles directly attached to containers, shall be approved and shall be located with the geometry of the enclosure taken into consideration.
The type number and placement of nozzles shall be such that:
the design concentration is achieved in all parts of the enclosure (see EN 12094-7);
the discharge does not unduly splash flammable liquids or create dust clouds that might extend the fire, create an explosion or otherwise adversely affect the occupants;
the velocity of discharge does not adversely affect the enclosure or its contents.
Where clogging by foreign materials is possible, the discharge nozzles shall be provided with frangible discs or blow-out caps. These devices shall provide an unobstructed opening upon system operation and shall be designed and arranged so they will not injure personnel.
Nozzles shall be suitable for the intended use and shall be approved for discharge characteristics in accordance with EN 12094-7, or shall be approved under the procedure described in national, European or International nozzle standards.
Nozzles shall be of adequate strength for use with the expected working pressures, they shall be able to resist nominal mechanical abuse and shall be constructed to withstand expected temperatures without deformation.
Nozzle discharge orifice inserts shall be of corrosion-resistant material.
Nozzles in ceiling tiles
In order to minimize the possibility of lifting or displacement of lightweight ceiling tiles, precautions shall be taken to securely anchor tiles for a minimum distance of 1,5 m from each discharge nozzle.
NOTE The discharge velocities created by the design of nozzles can be a factor in the displacement of ceiling tiles.
Marking
Discharge nozzles shall be permanently marked to identify the manufacturer and size of the orifice.
Filters
The inlet of any nozzle assembly or pressure-reducing assembly which contains an orifice of area less than 7 mm2 shall be provided with an internal filter capable of preventing obstruction of the orifice.
