Watermist for Risk Control

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Oct 28, 2013 (3 years and 7 months ago)

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice


Watermist for Risk Control

(Why it’s not as simple as all that!)

RISCAuthority Seminar 2012



Dr Jim Glockling

Technical Director,

Fire Protection Association

Director RISCAuthority

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

1

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Watermist


What is watermist?


Why is it ‘different’ to other forms of suppression?


Why will it always be complicated to specify and prove?


Where equivalency is asked for what comparisons need
making

o
What makes a system ‘perform’?

o
What makes a system ‘reliable’?


What’s RISCAuthority doing to help?



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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

What is watermist?

1.
Provision of finely divided water droplets, typically 200um

2.
Droplets created at higher pressures than traditional sprinkler
systems, through small orifices

3.
Sometimes driven by compressed gas or HP pumps

4.
Generally described as a 2
-

part action:


Thermodynamic cooling during evaporation


Oxygen reduction through steam displacement

5.
Operated as:


Deluge systems


Bulb Actuated *



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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Why is watermist ‘different’?

‘Guidance’ of the type given for sprinkler and gaseous
systems is too difficult to give


Sprinklers



mm/min water for each ‘Hazard Category’

Inert gaseous systems


%O2 for hazard (O2 index) + Safety Factor

Halcocarbon gas systems


%gas for hazard (cup burner test) + SF


Watermist


more problematic since there are many modes of operation
and the properties of the fire and the enclosure may
determine which one, if any, occurs.



There is no concept of ‘Safety Factor’

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Example modes of operation of 3 challenges

5


O2 depletion

Foam delivery

Surface cooling

Key parameters:

Fire size, Compartment size, Compartment height,
Compartment Ventilation, Amount of clutter, Nozzle
location, Use of foam, Temperature of equipment

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

So is it ‘gas


like’ or ‘sprinkler


like’?

The safest bet is to assume:



It is ‘gas


like’ in that it requires a well sealed enclosure



It is ‘sprinkler


like’ in that it must have direct access to
the fire

Unless someone can convince you through appropriate testing to think
otherwise.


Retailers will often vary the answer to suit the argument:


Use in warehousing


Use in cluttered environments


Where poor distribution has been established

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

How long the fire has been burning effects performance

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Fire size effects performance

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Ventilation effects performance

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Watermist density effects performance

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Summary


Fires that have been burning for
LONGER
, are hotter, and have
less oxygen available and may therefore be EASIER to
extinguish



Fires that are
BIGGER
, are hotter, and have less oxygen
available and may therefore be
EASIER

to extinguish



Fires with
LESS VENTILATION
cannot replace the oxygen
displaced by steam as quickly and may therefore be
EASIER

to
extinguish



Fires subjected to
MORE DROPLETS

can produce steam more
rapidly which may
BENEFIT

extinguishment

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

That’s all well and good but …

LONGER, BIGGER, LESS VENTILATION, MORE DROPLETS


may mean different things in different sized enclosures with
different size fires. The challenge of:



Physically SMALL fire in a physically BIG enclosure


Physically LARGE fire in a physically SMALL enclosure


Physically LARGE fire in a physically BIG enclosure


Physically SMALL fire in a physically SMALL enclosure


Will be different, and what’s more, as the fire becomes affected, will
change in size and alter dynamically ….. cycling of fires is not
uncommon.

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

A very special set of circumstances need to exist
for water mist to operate




effectively



robustly



reliably


as an extinguishing or control system

CONCLUSIONS

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Watermist

Strengths


High heat output fuels


Liquid fuels


Hot environments


Enclosed environments


Direct application


Environmental cooling


Hidden fires (if large)


Weaknesses


Ventilated spaces


High ceiling heights


Small fires


Hot surfaces (sustained
ignition sources)


Deep seated fires


Hidden fires (if small)


Little residual benefit one
water exhausted


Class A fuels


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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Building regulations and codes which specify or
reference active protection in England and Wales


The Building Regulations 2000: Approved Document B


Compensatory feature for variation from AD ‘B’


BS 9999:2008 Code of practice for fire safety in the design,
management and use of building


Fitting of sprinkler systems allows adjustment of the risk profile and
permits:


Reduction in the fire growth rate;


Allowing larger travel distances;


Larger compartments;


Reduced fire resistance periods;


Other provisions recommended in the standard


BS 7974 Application of fire safety engineering principles to the design
of buildings

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

What BS 9999 states about sprinkler protection

‘Other systems’ must be
equivalent

to Sprinklers:
Performance

&
Reliability

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

What makes sprinkler systems
Perform?


Historical record of over 100 years with continuous development
and improvement



Substantial number of fire tests in support of design and
development for


Ordinary Hazard; and


High Hazard risks



Proven equipment reliability;



Proven installation standards which create a level playing field in
a competitive marketplace.


RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

What makes sprinkler systems
Reliable (1)?

Reliability of sprinkler systems and equipment was problematic in the
early years of sprinkler protection. Most problems have been resolved
by:



Specifications for equipment;



Specified clearances between moving valve parts



Sprinkler orifice minimum size limits (8mm ND)



Continuous refinement of detailed installation design specification;



Robust definition of hazard vs. design requirements



Robust water supply design (Security)



Duplication



RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

What makes sprinkler systems
Reliable (2)?


Testing and certification of hardware;



Certification of installing companies



Auditing of installing companies and their work



Rigorous inspection & testing of installed system;


Acceptance tests and inspections including flow tests


Weekly and periodic testing and inspections;


Checking installation control valve function;



Pump testing (if pumps are used);

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

And even then we still find problems albeit
rarely….

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Comparison of systems specifications

Sprinkler systems


LPC Rules incorporating BS
EN12845



Proven system design criteria



Published equipment
specifications
(EN12259)



Certificated equipment

Water mist system


No UK or European standard
(BS DD/CEN TS)



Few proven system design
criteria mostly for specialised
applications



No published UK or European
equipment specifications



Few certificated products



NFPA 750

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Comparison of systems

Installation control valves

Sprinkler installation control
valves


opens on demand

Secured against tampering

Water alarm gong



Water mist control valves take a
number of different forms but
often solenoids with electronic
activation

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Comparison of systems

Sprinkler systems


Sprinkler orifice size
(8mm minimum)

Water mist systems


No minimum orifice size

( orifice sizes can be <1mm)

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Comparison of systems

Testing of water supplies

Sprinkler system


All water supplies tested


At commissioning;


During service.


Water mist systems


Not all water supplies can
be tested;

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Comparison of systems

Duration of water supplies

Sprinkler systems


Ordinary Hazard


60
minutes



Wetting of fire load,
providing a controlling
influence even after water
supply duration

Water mist systems


Varies with design but
often 20 minutes or les



Protection provided for
duration of water supply


RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Comparison of systems

Water application rate

Sprinkler systems


Specified against hazard

Water mist systems


Varies depending on
system supplier



May be based on a single
fire test designed or
selected by the supplier

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Comparative fire tests conducted in the UK by
BRE on an Office fire load concluded
-

1



“Tests were conducted with industry providing low and high
pressure water mist systems against the BRE developed office
scenario. The results, with one exception, were of some concern
as effective fire suppression was not demonstrated.


Results indicate that the water mist systems, as installed for
testing, were not able to provide the intended level of fire
protection. Or, in terms of the design of the tested systems,
the
spacing between nozzles was too great and the quantity of
water discharged too low, to provide effective fire suppression
.”




RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Comparative fire tests conducted in the UK by
BRE on an Office fire load concluded
-

2

“One test with an industry provided low pressure water mist
system effectively suppressed the BRE developed office fire
scenario. This test was conducted at approximately 5mm/min,
an equivalent water coverage to that required by a sprinkler
system in accordance with the specifications of BS EN 12845.”


Reference: http://www.brebookshop.com/details.jsp?id=326685

RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Watermist equivalency with Sprinklers?


Reliability?


Performance?


There is little by way of codes or standards to dictate that watermist
systems will have many of the features that we know make
Sprinkler Systems effective for the long term protection of property
and business:


It will need to be specified separately!

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Why do we need questionnaires for
watermist
?


Repeated calls from insurers for guidance, especially when
proposed in place of sprinkler systems



A need for RISCAuthority to promote new technologies to where
they can provide most benefit for business and property
protection
-

in the right places watermist is the BEST option.



To allow the designer/
specifier

to demonstrate to the
purchasers/insurer that a full and appropriate job has been/will
be done in the design and implementation of the system

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

www.RISCAuthority.co.uk

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Why questionnaires and not guides?


Watermist function is complex



There are no appropriate standards or certification schemes to rely
on



To describe for every eventuality is impossible



Checking that all design elements:


have been considered


usual risk control logic has been followed


properly recorded


and are ‘owned’

is the only practical approach

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Common flaws and mistakes (General)


Design intention is not properly understood (i.e. property protection vs. LS)


Risk never properly investigated and/or understood


System design never validated against appropriate risk (marine)


System design does not consider all ‘modes’ of operation of the equipment it is
protecting


Very short water supply durations in comparison with shut down & control of
ignition sources


Activation not interlocked with:


Power / fuel / ignition sources


Ventilation /
Conveyancing

equipment


Inappropriate detection in the context of suppression system’s / risk’s needs


Insufficient control of ventilation


Insufficient guidance, training, and manuals


Inappropriate referencing of sprinkler equivalency


No overall ownership

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

Closing


Questionnaires ONLY ask details of the steps that MUST be
taken in the provision of an effective
watermist

response



Difficultly to complete may indicate that all the bases have not
been covered and should serve as a warning



The intention is to develop further questionnaires for gaseous
extinguishing systems


More information at the poster exhibition outside.


END

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RISK INSIGHT, STRATEGY AND CONTROL AUTHORITY

Reducing insurable risk through research, advice and best practice

NFPA 750


Scope. This standard contains the minimum requirements for
the design, installation, maintenance, and testing of water mist
fire protection systems. This standard does not provide definitive
fire performance criteria, nor does it offer specific guidance on
how to design a system to control, suppress, or extinguish a fire.
Reliance is placed on the procurement and installation of listed
water mist equipment or systems that have demonstrated
performance in fire tests as part of a listing process.

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