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C.6.3.2.3 Polymeric fuel array

The polymeric fuel array consists of 4 sheets of polymer, which are cut to 405 mm ± 5 mm high by 200 mm ± 5 mm wide. The thickness of the sheets shall be as follows:

• polymethylmethacrylate (PMMA): (10 mm ± 1 mm);

• polypropylene (PP): (10 mm + 1 mm);

• acrylonitrile-butadiene-styrene polymer (ABS): (10 mm + 1 mm).

Sheets are spaced and located as shown in Figures C.8 and C.9. The bottom of the fuel array is located 43 mm from the floor. The fuel sheets shall be mechanically fixed at the required spacing. The sheets of plastic shall not significantly bend during the test.

The fuel array shall be located centrally within the enclosure.

C.6.3.2.4 Fuel shield

A fuel shield consisting of a metal frame with sheet metal on the top and two sides shall be provided around the fuel array as indicated in Figures C.8 and C.9. The fuel shield is 380 mm wide, 850 mm high and 610 mm deep. The 610 mm (wide) x 850 mm (high) sides and the 610 mm x 380 mm top are metal sheet. The two remaining sides and bottom are open.

The metal sheet shall have a wall thickness of 2 mm to 3 mm.

The fuel array is oriented in the fuel shield such that the 200 mm dimension of the fuel array is parallel to the 610 mm side of the fuel shield.

Dimensions in millimetres

Key

1. vertical metal angle frame

2. fuel guide bars (angle form)

3. fuel guide bar (U-form)

4. heptane pan

5. channel metal frame covered with metal sheeting on top and two sides

6. drip tray

Figure C.8 — Polymeric sheet fireDimensions in millimetres

a) Front, side and plan view

NOTE Material: 3 mm thick metal.

b) details of fuel guide bars

Key

I 1 vertical metal angle frame 2 fuel guide bars (angle form) 3 fuel guide bars (U-form)

Figure C.9 — Support rack for plastic sheet

s

C.6.3.2.5 External baffles

External baffles are constructed as shown in Figure C.10 and are located around the exterior of the fuel shield. The baffles are placed 90 mm above the floor. The top baffle is rotated 45° with respect to the bottom baffle.

Key

1. polycarbonate or metal baffles

2. cinder block

3. 10 — Polymeric fire baffle arrangement

C.6.3.3 Test procedure

C.6.3.3.1 Pretesting

Prior to commencing tests, the composition of the extinguishing gas shall be determined by analysis. Record the weight of the plastic sheets prior to the test.

C.6.3.3.2 Operation

The heptane shall be ignited and allowed to burn completely. 210 s after ignition of the heptane, all openings shall be closed and the extinguishing system shall be manually actuated.

At the time of actuation of the system, the amount of oxygen within the enclosure at the level of the fuel shall not be more than 0,5 % (volume fraction) lower than the normal atmospheric oxygen concentration. During the test, the oxygen concentration shall not change more than 1,5 % (volume fraction) due to fire products. This change shall be determined by comparing the oxygen concentration measured in the cold discharge test with the oxygen concentration measured in this fire test (averaged values).

The enclosure shall remain sealed for a total of 10 min from the end of discharge. After the soak period, ventilate the enclosure and observe to determine that sufficient fuel remains to sustain combustion and for signs of re-ignition. The following shall be recorded:

1. presence and location of burning fuel;

2. whether or not the fire re-ignites;

3. weight of the fire structure after the test.

If necessary, amend the extinguishant concentration and repeat the experimental programme until 3 successive, successful extinguishments are achieved.

C.6.3.3.3 Recording of results

After the required pre-burn period, record the following data for each test:

4. the effective discharge time, i.e. for liquefied extinguishants the time of the pre-liquid gas phase plus the time of the two-phase flow; for non-liquefied extinguishants the time from opening the container valve(s) to cutting off the discharge; the discharge time for liquefied extinguishants has to be determined by nozzle pressure, nozzle temperature or combination of both;

5. the time to achieve “knock-down” of the flames, that means the time when there are only flames at the top edges of the two inner plastic sheets, in seconds; this time shall be determined by visual observation or other suitable means;

6. the time required to achieve extinguishment, in seconds; this time shall be determined by visual observation or other suitable means;

7. the total mass of extinguishant discharged into the test enclosure;

8. The soaking time (time from the end of system discharge until the opening of the test enclosure).

NOTE End of discharge is the point when discharge has effectively ceased. For superpressurized liquefied extinguishants it is the instant when the discharge is predominantly gaseous. For non-superpressurized liquefied extinguishants and non-liquefied extinguishants where a cut-off mechanism is used to stop discharge, it is the instant when the pressure at the nozzle reduces to zero.

C.6.3.4 Determination of design extinguishant concentration

The extinguishing concentration for each fuel is that concentration which achieves satisfactory extinguishment of the fire over three successive tests (only flames at the top edges of the 2 inner plastic sheets at 60 s after end of discharge, no flaming 180 s after end of discharge and no re-ignition after 10 min from end of discharge). Alternatively, three successful, non-successive tests may be used providing the highest concentration is taken (that is, the test with the greatest mass of agent discharged and the longest discharge time).

The minimum design concentration is the highest of the laboratory concentrations for the three fuels (see C 6.3.2.2) multiplied by an appropriate 'safety factor’.

Annex D
(normative)

Method of evaluating inerting concentration of a fire extinguishant

D.1 General

This Annex specifies a method for determining the inerting or inhibiting concentration of the extinguishant based on flammability diagram data on ternary systems (fuel, extinguishant, air).

D.2 Principle

Fuel/extinguishant/air mixture at a pressure of 1 atm (1 bar or 14,7 psia) is ignited using a gap spark and the rise in pressure is measured.

D.3 Apparatus

D.3.1 Test vessel, spherical, with a capacity of 7,9 I ± 0,25 I, with inlet and vent ports, thermocouple and pressure transducer, as shown in Figure D.1.

D.3.2 Igniter, for nominal resistance of 1 Q comprising four graphite rods ("H" pencil leads) held together by two wire ties at either end, leaving a gap between the ties of approximately 3 mm.

D.3.3 Capacitors, two 525 mF, 450 V, wired in series with the igniter.

D.3.4 Internal mixing fan, suitable to withstand the temperature and overpressure of an explosion.

D.4 Procedure

D.4.1 The sphere (D.3.1) and components should be at nominal room temperature (22 °С ± 3 °С). Note any temperature difference outside of this range.

D.4.2 Connect the pressure transducer to a suitable recording device to measure the pressure rise in the test vessel to the nearest 70 Pa.

D.4.3 Evacuate the test vessel (D.3.1).

D.4.4 Admit the extinguishant up to the concentration required by the partial pressure method and, if a liquid, allow time for evaporation to occur.

D.4.5 Admit fuel vapour and air [(50 ± 5) % relative humidity] up to the concentration required by the partial pressure method until the pressure in the vessel is 1 atm (1 bar or 14,7 psia).

D.4.6 Turn on the fan (D.3.4) and allow to mix for 1 min. Turn off the fan and wait for 1 min for the mixture to reach quiescent conditions.

D.4.7 Charge the capacitors (D.3.3) to a potential of 720 V to 740 V (DC), producing a stored energy of 68 J to 70 J.

D.4.8 Close the switch and discharge the capacitors.

NOTE The capacitor discharge current results in ionization of the graphite rod surface causing a corona spark to jump across the connector gap.

D.4.9 Measure and record the pressure rise, if any.

D.4.10 Clean the inside of the test vessel with distilled water and cloths to avoid any build up of decomposition residues.

D.4.11 Retain the fuel/air ratio and repeat the test using varying amounts of extinguishant until conditions are found that bracket a pressure rise of 0,07 times the initial pressure.

NOTE The definition of the flammable boundary is taken as that composition that just produces a pressure rise of 0,07 times the initial pressure or 1 psi when the initial pressure is 1 atm (1 bar or 14,7 psia).

D.4.12 Repeat, varying the fuel/air ratio and the extinguishant concentration to establish the highest extinguishant concentration needed to inert the mixture.

D.5 Inerting concentration

The inerting concentration is the concentration established in step D.4.12.

Key

1 septum port 6 vacuum

2 gas inlet 7 pressure gauge

3

8 thermocouple

7,9 I test vessel

4 igniter 9 test chamber 5 vent

3. 1 — Inerting apparatus

Annex E
(normative)

Door fan test for determination of minimum hold time

E.1 General

This Annex contains information to establish the integrity of rooms and enclosures with respect to maintaining the extinguishant concentration for the relevant period (hold time). It includes details of testing and assumes that air-handling plant will not be operating during the hold time.

This procedure cannot be used to predict what extinguishant concentrations may develop in adjoining spaces.

This procedure is only suitable providing:

1. an adequate return air path exists (see E.2.4.2 and E.2.7.1.3);

2. the fan unit(s) can develop an enclosure pressure of 25 Pa (this is a function of the size of the enclosure, its integrity, and the number and capacities of the fans (see E.2.2.1 and E.2.7.4.3).

The calculation procedures used are suitable for both heavier than air extinguishants and extinguishants that are lighter than air. The hold time calculation models, for enclosures without continuous mixing, assume that the enclosure is either a standard enclosure or a non standard enclosure. A standard enclosure is one that has a uniform horizontal cross sectional area with horizontal upper and lower boundaries. A non-standard enclosure is one with a non uniform horizontal cross sectional area and/or sloping upper and/or lower boundaries.

NOTE For gas/air mixtures heavier than air, the calculation procedures have been verified by comparison of calculation results from door fan testing with hold times from real flooding tests. This has not yet been done for gas mixtures lighter than air.

E.2 Test for determination of predicted hold time

E.2.1 Principle

A fan is temporarily located within an access opening to pressurize and depressurize the enclosure. A series of pressure and airflow measurements is made from which the leakage characteristics of the enclosure are established.

The predicted hold time is calculated using these leakage characteristics on the following assumptions:

3. that leakage occurs under the worst conditions, i.e. when one half of the effective leakage area is at the maximum enclosure height, and the other half (the lower leakage area) is at the lowest point in the enclosure;

4. the direction of flow through the enclosure, during the hold time, is downwards for extinguishants heavier than air, and upwards for extinguishants lighter than air;

5. that all leak flow is one-dimensional, i.e. ignoring stream functions;

6. that flow through any particular leak area is either into or out of the enclosure and respectively either from or into an infinitely large space;

7. that the enclosure and surroundings are at a temperature of 20 °С, and atmospheric pressure is 1,013 bar absolute.

E.2.2 Apparatus

E.2.2.1 Fan unit, consisting of a frame which will fit into and seal an access opening in the enclosure, and one or more variable speed fans, with low flow facilities, capable of giving a differential pressure of not less than 25 Pa across the enclosure boundary.

E.2.2.2 Pressure measuring devices, two in number, one to measure enclosure differential pressure and one to measure fan flow pressure.

E.2.2.3 Flexible tubing, for connecting the pressure measuring devices.

E.2.2.4 Chemical smoke pencils and/or smoke generator.

E.2.2.5 Thermometers, two in number, for measuring ambient temperatures.

E.2.2.6 Signs, reading ”DO NOT OPEN - PRESSURE TEST IN PROGRESS” and "DO NOT CLOSE - PRESSURE TEST IN PROGRESS”, displayed during the test operation.

NOTE Additional apparatus, such as measuring tapes, barometer for measuring atmospheric pressure, torches, ladders, tools to remove floor and ceiling tiles, computer or other calculating device, camera, may be necessary or convenient.

E.2.3 Calibration and accuracy of apparatus

E.2.3.1 Fan unit

The fan unit (E.2.2.1) shall be calibrated at the intervals and by the method recommended by the manufacturer. Records shall be kept and also copies of the appropriate calibration certificates. The flow rate shall be accurate to ± 5 % of the measured value.

E.2.3.2 Pressure measuring devices

The pressure measuring devices (E.2.2.2) shall be accurate to ± 1 Pa and shall be calibrated at regular intervals. Records shall be maintained and where appropriate calibration certificates. The pressure measuring device to measure the fan flow pressure may have a different accuracy as long as the requirements for the accuracy of the flow rate (see E.2.3.1) is fulfilled. The atmospheric pressure measurement shall be accurate to ± 100 Pa.

If inclined manometers are used, change the fluid at the intervals recommended by the manufacturer. Level and zero inclined manometers before each test.

E.2.3.3 Temperature measuring devices

Temperature measuring devices shall be accurate to ± 1 °С.

E.2.4 Preliminary preparation

E.2.4.1 Obtain a description of air-handling equipment and extinguishant extraction systems, serving the enclosure and its surroundings, from the user.

E.2.4.2 Check for the following:

1. raised platform floors and false ceiling spaces;

2. visually obvious leaks in the enclosure;

3. adequate return paths outside the enclosure between all leaks and the fan unit;

4. conflicting activities in and around the enclosure;

5. leakage areas in the hold time condition by visually checking the door closure, or other opening selected for mounting the fan unit.

E.2.4.3 Provide the following information to the user:

1. description of the test;

2. time required to complete the test;

3. what assistance will be needed from the user's staff;

4. information on any necessary disturbance to the building or its services during the test; e.g. removal of floor or ceiling tiles, shutdown of air handling systems, holding doors open and/or shut.

E.2.5 Evaluation of enclosure

E.2.5.1 General

Obtain or prepare a sketch plan showing the enclosure and its surroundings, the location of door and other openings through which air will flow during the test, and the location of any ducts penetrating the enclosure, and any dampers in the ducts. Show the status (i.e. whether open, closed, on, off during the hold time) of each door, hatch, damper and other significant items (e.g. fans), and which access opening(s) is (are) to be used for the fan unit.

Show the location of floor and sink drains.

E.2.5.2 Mixing during hold time

Enclosures with continuous mixing are enclosures in which there will be continuous good mixing e.g. due to strong heat sources or recirculating air handling equipment, so that an interface does not form and a uniform extinguishant concentration is maintained throughout the enclosure during the hold time.

Enclosures without continuous mixing are enclosures in which there is partial or no mixing during the hold time, so that an interface forms between the extinguishant/air mixture and the incoming air.

If it is uncertain whether the enclosure is one with or without continuous mixing, then perform the hold time calculations for both cases. Use the lower of the two hold time values.

E.2.6 Measurement of enclosure

E.2.6.1 Standard enclosures without continuous mixing

Standard enclosures are those with a uniform horizontal cross sectional area and horizontal upper and lower boundaries. Measure the protected enclosure as necessary and record the following:

1. the overall height of the protected enclosure, H_o;

2. the required protected height, H;

3. the net volume of the protected enclosure, V.

E.2.6.2 Non-standard enclosures without continuous mixing

Non-standard enclosures are those with non-uniform horizontal cross sectional area, such as enclosures with non-horizontal upper and/or lower boundaries. Measure the protected enclosure as necessary and record the following:

1. the overall height of the protected enclosure from its lowest to its highest point, H_o

2. the required protected height from the lowest point in the enclosure, H

3. the net volume of the protected enclosure, V

4. the horizontal cross-sectional area, A, at various heights, sufficient to determine its variation with height so that r_e and dl’_e can be evaluated using equations (E.24) and (E.25). See E.2.8.9.3.

E.2.6.3 Enclosures of any shape with continuous mixing

Measure the protected enclosure as necessary and record the following:

1. the overall height of the protected enclosure from its lowest to its highest point, H_o,

2. the net volume of the protected enclosure, Г.

E.2.6.4 Opening for mounting the fan unit

If the door or other closure, replaced by the fan unit for the purpose of test, has significant measurable leakage openings in the hold time condition then these should be measured and recorded.

E.2.7 Test procedure

E.2.7.1 Preparation ,

E.2.7.1.1 Advise supervisory personnel in the area of the test.

E.2.7.1.2 Remove papers and objects likely to be disturbed by the air stream from the fan.

E.2.7.1.3 Block open sufficient doors outside the enclosure envelope to provide an adequate return path for air between the fan unit and the enclosure boundaries while correcting any breach of any requirements of the facility, including requirements for security, fire protection and environmental boundaries.

E.2.7.1.4 Using the sketch plan (see E.2.5) set the enclosure air-handling equipment and extinguishant extraction systems to the state they would be in during the hold time, except that:

1. recirculating air-handling equipment without fresh air make up or exhaust which does not give a bias pressure across the enclosure boundary or otherwise preclude accurate testing, and which would be shut down on extinguishant discharge, may be left operating during the test if this is needed to avoid temperature build-up in equipment such as computers;

2. air-handling equipment, with fresh air make up or exhaust, which would continue to operate on extinguishant discharge should be shut down as it may create excessive bias pressure during the integrity test.

E.2.7.1.5 Post the appropriate signs on doors (see E.2.2.6).

E.2.7.1.6 Open doors and remove floor or ceiling tiles within the extinguishant protected portions of the enclosure envelope so that the extinguishant protected volume is treated as one space. Do not remove false ceiling tiles if the volume above the false ceiling is not protected with extinguishant.

CAUTION — The removal of raised floor tiles creates a serious safety hazard. Appropriate precautions should be taken.

E.2.7.1.7 Set all doors and windows and other openings in the enclosure envelope to the state they would be during the hold time.

E.2.7.1.8 Check that liquid traps in the floor and sink drains are sealed with liquid.

E.2.7.1.9 Record the conditions (enclosure, surroundings and services) during the fan test.

E.2.7.2 Setting up the door fan unit

E.2.7.2.1 Set up the fan unit in an access opening leading from the enclosure into the largest volume of building space which will complete the air flow path from the fan, via the enclosure, leaks, and building space back to the fan.

E.2.7.2.2 Gently blow into, or suck from, the flexible tubing so that the readings of the pressure measuring

devices traverse the full scale. Hold the maximum reading for not less than 10 s.

Release the pressure and zero the devices.

E.2.7.2.3 Connect the enclosure differential pressure measuring device and the fan pressure measuring device. Ensure that the open ends of the flexible tubing near the fan unit are away from its air stream path and any other air flows which might affect the readings.

E.2.7.2.4 Use the fan(s) to raise or lower the pressure of the enclosure to the maximum safe pressure obtainable. Check all dampers with smoke and ensure that they are closed properly. Check doors and hatches and ensure correct closure. Inspect the wall perimeter (above and below any false floqr) and the floor slab for any major leaks and note their size and location.