single point of failure of fire protection systems …...single point of failure of fire protection...

Single Point of Failure of Fire Protection Systems and What Can We Do About It?

M.C. HuiCPEng, CEng, NER, FIEAust, FIFireE, MSFPE, MSFS, RBP, C10, RPEQ

Technical DirectorRED Fire Engineers

Offices in Adelaide, Brisbane, Melbourne, Perth, Sydney Projects throughout Australia

Contents

• What is a single point of failure?

• Examples of single point of failure in active and passive fire protection systems

• How to deal with the single point of failure in egress provisions?

• Performance-based design

• Conclusions

19 August, 2019RED Fire Engineers Pty Ltd

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What is a Single Point of Failure

https://www.yourdictionary.com/single-point-of-failure

Single-point-of-failure

Noun

(plural single points of failure)

• A component in a device, or a point in a network, that, if it

were to fail would cause the entire device or network to fail;

normally eliminated by adding redundancy.


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https://www.yourdictionary.com/single-point-of-failure


https://www.computerhope.com/jargon/s/spof.htm

A single point of failure, also known as SPOF, is any component

of a system that causes the whole system to stop working if it

fails.

When designing reliable systems, SPOFs can be avoided by

implementing redundant components and replicating critical

parts of the system.


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• A single point of failure is a unique tapering extremity of non-performance.


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What does Mr Spock think?


Definition of Single Point of Failure

Fire Protection Systems

• SPOF is a point or part of a system where there is no backup in case of failure, and as a result the whole system will become disabled.


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Examples of Single Point of Failure


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The sprinkler control valve and the isolation valve can be duplicated to eliminate the SPOF.



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Duplication of the fire detection control and indicating equipment or a distributed network can eliminate the SPOF.



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Duplication of the fan (stair pressurisation or smoke exhaust) provides redundancy.



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Duplication of the fire rated doorset to the fire-isolated stair can also provide redundancy but could be impractical (fire rated lobby).



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A single stair in an existing 24 storeys unsprinklered building



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Provision of multiple exits

• Provide redundancy – if one exit becomes unavailable, then there is an alternative exit.

• Reduce queuing time when there is a large population on the floor.



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How to deal with single point of failure in egress provisions


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The common corridor is a single point of failure. The BCA is silent on its protection. The following fire safety measures may be considered:

• Sprinklers in the corridor

• Smoke extraction for the corridor

• Smoke seals for the SOU entry doors

• Pressurise the corridor



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Sprinklers in the corridor

• Fire not in the corridor

• Sprinkler spray is to drag the smoke layer towards the floor



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Smoke extraction for the corridor

• System tries to pull smoke from SOU of fire origin into the corridor

• Ceiling height of corridors could be 2.1 m (BCA F3.1), thus very shallow smoke layer

• Potential plugholing problems

• Ductwork within ceiling void



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Smoke seals for the SOU entry doors

1. Daniel Joyeux, “Experimental investigation of fire door behavior during a natural fire,” Fire Safety Journal, Vol. 37, pp. 605-614, 2002.

• Typical fire safety measure to support Performance Solutions on extended travel distances etc.

• Rely on the integrity [1] of the SOU entry door (chocked open; incapacitated occupant across doorway)

• Rely on the entry door having sufficient clearance to accommodate the seals; ongoing maintenance

Performance-based design


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Pressurise the corridor

• If the SOU entry doors and the bounding construction are intact, then

❖ corridor pressurisation system zone pressurisationsystem.

• If the SOU entry door loses its integrity or is left open, then

❖ potential energy (pressure) is converted to kinematic energy (air flow through opening).



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• SOU entry door open situation - Opposed air flow method.

• Demonstrated by Philip Thomas [2] to be successful in preventing smoke from flowing in a tunnel upstream of fire.

❖ cannot be directly applied in a building fire scenario, because, occupants downstream of RFO may be exposed to an enhanced flow of smoke when the RFO is not at the end of the corridor.

2. Thomas, P.H., “Movement of Smoke in Horizontal Corridors Against an Air Flow”, Fire Research Note No. 723, Fire Research Station, September 1968.



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• If SOU entry door is treated as an aperture in a wall, then the work of Heskestad and Spaulding [3] for wall apertures can be applied.

3. Heskestad, G. and Spaulding, R.D., “Inflow of Air Required at Wall and Ceiling Apertures to Prevent Escape of Fire Smoke,” Fire Safety Science – Proceedings of the Third International Symposium, pp. 919-928, 1991.



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For a 2m high door with a smoke temperature of 1200 K, 2.5m/s air velocity is required.

Experimentation


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The corridor pressurisation concept was tested against small flaming fires (012A, 012B), large flaming fire (012H) and fully developed fire (012D) in the CESARE test building in Fiskville, VIC (part of my Master thesis).

Experimentation


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Floor plan of the experimental facility on the fire floor

Experimentation


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Limiting conditions for tenability in the corridor

• Maximum of 100 °C at 2.0 m from floor level for convective heat.

• Maximum of 60 °C at 1.5 m for prolonged exposure to convective heat from saturated air.

• Maximum of 1 % (10,000 ppm) of carbon monoxide and 6 % of carbon dioxide based on incapacitation during five minutes exposure.

• Minimum visibility of 10 m (0.25 OD/m for back illuminated exit signs).

Key results [4] follows.4. M.C. Hui, “A performance-based design to protect the unprotected,” Proceedings of the International Conference on Engineered Fire Protection Design, Society of Fire Protection Engineers, San Francisco, June 2001.

Experimentation


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Temperature distribution at the centerline of the corridor in experiments(a) 012A, (b) 012B, (c) 012H and (d) 012D

Fan Fan

Fan Fan

Window Window

Window

Experimentation


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CO concentration at the centerline of the corridor 1.7 m above floor level in experiments(a) 012A, (b) 012B, (c) 012H and (d) 012D

Experimentation


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CO2 concentration at the centerline of the corridor 1.7 m above floor level in experiments(a) 012A, (b) 012B, (c) 012H and (d) 012D

Experimentation


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Smoke obscuration at the centerline of the corridor 1.7 m above floor level in experiments(a) 012A, (b) 012B, (c) 012H and (d) 012D

Experimentation


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Summary of the experiments

• The corridor pressurisation system used in the experiment could maintain the defined conditions for tenability in the corridor with respect to smoke temperature, CO and CO2 concentrations.

• However, visibility in the corridor was not significantly improved. This might be due to a lack of relief path for the pressurisation system. Further work to follow.

Conclusions


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• Single points of failure exist in both active and passive fire protection systems.

• Provision of redundancy generally eliminates the single points of failure in active fire protection systems, but such approach may be impractical for some passive fire protection systems, such as egress provisions.

• A performance-based approach employing fundamental fire engineering principles can be a viable method to improve the reliability of single points of failure of egress provisions.

Thank you for not looking at your mobile phone during the presentation

M.C. Hui

M: +61 402 639 794

E: [email protected]

W: www.redfireengineers.com.au

mailto:[email protected]

http://www.redfireengineers.com.au/

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