Fire suppression systems

Margaret Holben Ellis <mhellis [at] morganlibrary__org> writes

>I'm having difficulty in obtaining comparative risk rates for fire
>suppression systems.  Setting aside the extent and kind of damage
>caused by various systems, which one(s) have the the highest risk of
>discharging accidentally, assuming regular maintenance.

If you have not done so, your question should be posed to your
insurance carrier.  The large insurance companies have available
consulting engineers who will have direct experience with the
various systems and an interest in getting you the best possible
advice

A good overview of fire suppression technologies is available in
Chapter 4 of the recently published second edition of, An Ounce of
Prevention:Integrated Disaster Recovery Planning for Archives,
Libraries and Records Centres by Wellheiser and Scott. Scarecrow
Press, Inc., ISBN 0-8108-4176-2 . In all systems the issue of
quality of installation and maintenance is critical.

In the planning for Canada's first purpose built archives facility I
lost more sleep over fire detection and suppression than any other
aspect of the building.

Wet pipe systems should be discharged monthly (to the outside
through an external valve), pumps, valves and pressure gauges
verified at that time.  A well designed system will include flow
monitors and pressure gauges to monitor the pressure on both sides
of the valves when closed. Once the pipe flange seals set after
installation and the system is monitored and maintained it is highly
reliable. There are probably more wet pipe systems than any others
and they have an excellent track record and of course fast response.
As long as it is not a deluge system, heads release as needed at a
pre-determined temperature as the fire progresses.

Dry pipe and pre-actioned dry pipe and combinations thereof are
considered to require more maintenance than wet pipe.  Corrosion is
a problem in systems with air or nitrogen in the pipes. However,
they do have a place in freezing environments.  There is a slight
delay before water gets to the head at the rated volume and
pressure.  As with wet pipe, flow and pressure monitoring will alert
you to problems.  The pre-actioned systems are activated by sensors
and water release can be total or zonal with the heads releasing
from heat of the fire.  Pre-action systems rely on smoke detection
so if the detection monitoring fails the system is not activated.

Both dry and wet pipe require that water be shut off manually.

Water mist systems are highly efficient but the technology is
expensive. Small diameter piping is a plus and the use of a mist
reduces damage to materials stored.

Fast response systems respond at an early stage of a fire.  There
are numerous types (release controls and heads) in this class of
system.

Gas flooding systems are activated by temperature and smoke detection
sensors. The gas is released under tremendous pressure. Statistics
Canada is reported to have damaged records (shredded them) stored
adjacent to the discharge nozzle.  In computer rooms gas pressure is
reported to have sent heavy floor tiles flying. These systems
require that the room be extremely well sealed (doors, windows,
ducts, piping etc) to achieve and hold the required concentration of
suppressant.  Should there be an equipment failure and the tank is
discharged, there is no back-up. This is also a problem if the fire
re-starts itself. The length of time to get a tank re-charged is a
period of complete vulnerability.

Clearly the most important aspect of fire suppression is the sensing
technology and monitoring (both technology and human, in-house and
external).  The next most important aspect after design is
installation and maintenance. Every aspect of installation must be
carefully monitored and inspected.  In one project, water pressure
to sprinklers in a large records storage room was supplied by two
750 gal/minute pumps.  The seals on the pumps were not evenly
tightened during routine maintenance which damaged the seals and the
shaft alignment after about 2 years.  Parts and repairs took almost
one month for each pump.  When a pump was out of service, we would
have had an inadequate water supply to fight a major fire but
sufficient for a small blaze.

The pump and valve room should be well secured to avoid sabotage.
Main supply valves should be locked open to avoid sabotage.  Pumps
require back-up power supply--another vulnerability.

At the end of the day there are no perfect solutions.  You wrestle
with options, choose one and accept the vulnerabilities. Establish
good monitoring, good maintenance and a disaster recovery plan.  You
will endure many sleepless nights.  Good luck,

Mark Hopkins
7 Croton Drive
Diego Martin, Trinidad, W.I.
868-632-6875
Fax: 868-633-6113


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                  Conservation DistList Instance 16:4
                  Distributed: Wednesday, July 3, 2002
                        Message Id: cdl-16-4-006
                                  ***