Fire extinguishers – Special applications – Condition responsive control
Patent
1996-04-03
1998-04-21
Pike, Andrew C.
Fire extinguishers
Special applications
Condition responsive control
169 54, 169 61, A62C 300
Patent
active
057408670
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a preventive safety system and then particularly, but not exclusively, to a system which can be applied in a process, normally an industrial process, in which loosely formed material is produced in a first unit and transported from said unit to a receiving, second unit.
By loosely formed material, it is meant any type of material that can be transported by a vehicle gas or in a gas or gaseous mixture, normally air, in which the particles of material are mutually discrete.
Material of the kind meant here may consist in extremely fine, dust-like particles. It may also consist in powdery material or granular particles, and also wood chips, pellets, straw, and like transportable materials.
The concept on which the present invention is based requires the treatment of the material within the first unit to be liable to generate individual particles or several discrete particles that have been heated to a temperature which is sufficiently high to cause a fire and/or an explosion within the selected transportation path and/or at least within the second unit.
The path along which the loosely formed material is transported between the first unit and the second unit will typically include a stabilizing zone (or disturbance zone), an indicating zone which is operative in indicating the presence of hazardous high-temperature particles, an effectuating zone, an extinguishing zone, and a risk zone.
The stabilizing zone is intended to enable those particles of low energy content and which do not constitute a fire or an explosion risk within the downstream zones, and particularly the risk zone, to reduce their energy content so that these particles will not be indicated by the indicating zone located immediately downstream.
Located within the indicating zone are one or more sensors or detectors which are intended to indicate the presence of particles whose energy contents are sufficiently high to incite burning, i.e., fire, when the particles arrive in the downstream zones and then particularly in the risk zone. The sensors are arranged to coact with an indicating and activating unit such that when one of the sensors detects the presence of such high-temperature particles, there is activated a device or an arrangement which delivers an extinguishing agent and/or removes said particles from the system and which coacts with the extinguishing zone.
The indicating zone is followed by an effectuating zone whose length is so adapted that, upon activation of a device within the extinguishing zone, the device will have time to form an extinguishing barrier before or when the particle or particles reach said zone.
The extinguishing zone may also have the form of a valve which functions to deflect particle collections that include said high temperature particles from the transportation path leading to the risk zone.
DESCRIPTION OF THE PRIOR ART
A preventive safety system of the aforedescribed kind is known and marketed by Firefly AB, Huddinge, Sweden. The purpose of the preventive safety system is to indicate the presence of sparks and glowing particles and to apply an extinguishing agent or a smothering agent which will prevent glowing particles from reaching a downstream process unit, such as a filter, a silo, or like device in which combustion and/or an explosion could otherwise occur.
Also pertinent to the present standpoint of techniques is the fact that the risk of fire and explosion in modern industrial processes increases with increasing and higher production rates and within larger production plants.
As volumes of material that are transported have successively become greater, practical experience has shown that most fires and explosions that occur in modern process plants are caused by sparks, glowing particles, and airborne burning flakes or the like. Although these sparks, glowing particles, etc., have a very small energy content, the energy content is, nevertheless; sufficiently high to initiate a fire and/or an explosion.
It is thus known to take certain measures or p
REFERENCES:
patent: 3909954 (1975-10-01), Zoukourian
patent: 5154237 (1992-10-01), Cooper
patent: 5193622 (1993-03-01), Tibbling
"Unit for Smouldering Particles Detection in Pneumo Transport Ducts--Using Light Conductors Whose Receiving Ends Are Situated in Fan, and Are In Plane Perpendicular to Material Flow Direction", Derwent's Abstract, No. 93-115518/14, week 9314, Abstract of SU 1729528 (Optical Inst Vavilov), 30 Apr. 1992.
Firefly AB
Pike Andrew C.
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