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Role of the Consulting Engineer in the Application of Water Mist Systems

Role of the Consulting Engineer in the Application of Water Mist Systems

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Role of the Consulting Engineer in the Application of Water Mist Systems

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  1. Role of the Consulting Engineerin the Application of Water Mist Systems P. J. DiNenno, P.E. For Jack Mawhinney,PEng

  2. Presented at NFPA/IMWA Conferenceon Water Mist Fire Suppression Systems Dallas, TX May 2003

  3. Role of the Consulting Engineer … • Research and development, first principles science • Water Mist Design = Performance Based Design • 3rd Party Review of Designs by Vendors • Acceptance testing • Conclusion

  4. Chronology of Water Mist • NFPA 750, Standard for Water Mist Fire Protection Systems • Committee formed in 1993 – New Technology, New Standard • Many interested parties: casual to vital • Provided fire protection engineering basis for development • Research Era 1990 to 1998 … • Market Emergence (1995 to present …)

  5. Chronology … • NFPA 750, Standard for Water Mist Fire Protection Systems • Committee formed in 1993 – New Technology, New Standard • Research Era • 1990 to 1998 (?) intense research – 1 st principles • Water based fire suppression, efficiency, limits, opportunities • Manufacturers’ R & D efforts still on-going • Military special applications still on-going • Market Emergence (1995 to present …) • Commercial development of technology, invention,

  6. Chronology … • NFPA 750, Standard for Water Mist Fire Protection Systems • Committee formed in 1993 – New Technology, New Standard • Research Era • 1990 to 1998 (?) intense research – 1 st principles • Market Emergence (1995 to present …) • Commercial development of technology, invention, • Marine sector = sprinkler equivalence – rapid growthOther sectors = halon replacement – very slow growth,except in niches Standards development (IMO, NFPA 750; CEN TC 191) • Formalized Test Protocols

  7. Chronology … • Acceptance Era (2000 to Present) • By End User - Growing • By AHJ - Approvals getting easier • Growth is uneven - • Oil fields, Marine, Co-Generation well advanced • Land-based, heritage, commercial, computer rooms • Slow in the US – depends on AHJ • Rapid in Europe – Every End User decides for themselves • Engineering and Construction Era (2000 + …) • Design & approval methods established • Specifications, Design Drawings, Construction Supervision

  8. Chronology … • Acceptance Era (1997 to Present) • Engineering and Construction Era (2000 + …) • Specifications, Design Drawings, Construction Supervision • Hydraulics; mixtures of gas and water; achieving duration; piston pumps; materials; techniques; trained installers • Acceptance Testing • Maintenance and Reliability • Costs

  9. Performance Based Design • NFPA 750 Chapter 5: Design • Design of a water mist system must be based on results of comprehensive fire tests, conducted by an internationally recognized laboratory. • Comprehensive Test Protocols: Marine machinery spaces; turbine enclosures; wet benches; marine accommodation and public spaces; light and ordinary hazard occupancies. • The test protocol seldom exactly matches the application • Interpretation is required

  10. Performance Based Design • NFPA 750 Chapter 5: Design • Application of a water mist system to a real space • Confirm performance objectives of the protocol are appropriate…. • E.g. full extinguishment, control for 10-minutes …? • Confirm compartment size, ventilation, obstructions, fuel quantities, and other features of the application match the assumptions in the test protocol • It requires fire protection engineering knowledge to evaluate whether the design meets the End User’s objectives. • Major Source of Misapplications • Uncertainty transfers risk

  11. End User’s Objectives Extinguish or control fire in combustible ceiling and prevent fire spread to adjacent galleries Control a “normal” fire at floor level (light hazard) Have no water “over the collection” (preaction system) Design to provide capacity for future expansion (pumped system) Address issues of incomplete listings for equipment Specification recognizing “pending approval” Ultimately, provide a system that meets NGA performance expectations, complies with intent of NFPA 750, and is a listed, approved system National Gallery of Art Water Mist System

  12. National Gallery of Art • Listing of nozzles essentially appropriate • Application not exactly conforming to listing • Nozzles listed, but pump unit not listed (pending) • Specifications drafted to suit installation by fire protection contractor new to high pressure piping and water mist systems equipment • Professional responsibility of consultant vs. “acceptance” by informed End User acting as own AHJ

  13. Engineering Challenges • Decision-points arise all the time • Water mist technology is still under development. • Special invention, adaptation is often encountered • How do you advise the AHJ or End User about the engineering suitability of situations encountered for the first time? • Example: • Deluge control valves for high pressure systems • Capacity of largest listed valve is less than required for the system demand • Solution: manifold a series of small capacity sectional valves • Issue: what is the effect on reliability?

  14. Consultant’s Role in Peer Review • End User or AHJ does not have resources to provide a review to the desired level of thoroughness. • Engage a qualified consultant who has the knowledge to judge whether a proposed system meets the End User’s needs

  15. Low pressure, twin fluid, gas driven (Securiplex) Intermediate pressure, single fluid, gas driven (Chemetron, Fike) High pressure, single fluid, gas driven (Marioff, Fogtec, others ...) High or Low pressure, single fluid, pumped (Marioff, Fogtec, UniFog, Aquamist, … ) Decaying pressure, hybrid gas-water (Marioff) Cycled discharge versus continuous discharge (Securiplex, Fike, Chemetron, others … ) Consulting engineer must be able to compare technologies

  16. Twin Fluid, Low Pressure, Gas driven Regulator Detectors Low Pressure High Pressure Air 11 Control Panel 9 8 7 Duration of discharge typically 10 minutes Cycled discharge (on-off) Stored water Water Reservoir 1 Slave Master 18 Compressed Gas Cylinders (atomizing medium)

  17. Single fluid, intermediate pressure, gas driven Detectors Duration of discharge typically 10 minutes Cycled discharge (on-off) Stored water Control Panel 11 7 8

  18. Pumped system, high or intermediate pressure Detectors Sectional Control Valves Releasing Panel Test Line Unloader Q P Gas-driven “jockey” pump 8 M M Controller Water Supply (potable) 6 Filters 7

  19. Consultant’s Required knowledge • Compare pros and cons of different types of systems • Compare costs of different systems • Understand differences in long term maintenance needs • Compare reliability … to the extent known • Equipment is often too new to be able to quantify its reliability • Understand Construction and ITM infrastructure

  20. M M 27 kW 27 kW M M 27 kW 27 kW Acceptance Testing • The Vendor should not be the only party in the room who knows how the system works … To sump To sump Water Supply

  21. Evaluating High Pressure Pump Performance Test Result for 4 motors, 8 pumps. 160 For System: k = 31.749 328 l/min @ 107 bar 140 Flow Test Result 316 l/min @ 107 bar 120 100 Calculated demand, K = 31.749 80 Flow Test Objective 400 l/min @ 105 bar 60 1 2 3 4 40 Discharge, L/min 150 200 100 250 300 350 400 450 500

  22. Role of the Consulting Engineer …Conclusion • The increasing acceptance of water mist systems creates increased demand for independent expertise • Water mist systems represent a “performance based design” paradigm • The consulting engineer (3rd party reviewer) must appreciate the pros and cons of all water mist technologies • Required knowledge for entry is difficult to acquire, but is still based on fundamental engineering principles of hydraulics and systems reliability