Trigger element for a sprinkler

Details Trigger element for a sprinkler Trigger element for a sprinkler

1988-10-13

1990-07-03

Peters, Jr., Joseph F.

Fire extinguishers

Sprinkler heads

Collapsible strut

169 37, A62C 3714, A62C 3732

Patent

active

049382942

DESCRIPTION:

BRIEF SUMMARY
In the field of permanently installed fire-fighting equipment, thermally triggered sprinkler installations screwed to the water mains represent the most widely used extinguishing system. In the case of glass barrel sprinklers, the water outlet nozzle is closed by a small glass barrel filled with a suitable liquid. In the event of fire, the hot smoke gases effect heating of the expanding liquid; the latter expands and, when the triggering temperature pre-determined by the quantity of liquid filled in a barrel is reached, bursts the small glass barrel. As a result, the nozzle is automatically freed and sprays the seat of the fire with an extinguishing jet dispersed into droplets.
Even though the first automatic sprinkler extinguishing systems have been installed as early as in the last century, their development is not yet complete even now. In order to be able to fight a fire immediately after it has broken out, it is above all necessary still to shorten the response time of glass barrel sprinklers--that is to say the time required for heating the expanding liquid to the triggering temperature. Fast-response sprinkler installations provide improved protection of material property and, above all, also persons present in the room at risk. At the same time, the resulting decrease in effective area allows a reduction in the fire-fighting water required.
The nominal opening temperatures of the glass barrel sprinklers can easily be recognised by the color of the expanding liquid, which is obtained by the addition of suitable dyes. The color markings are given in Table I which follows:


TABLE I ______________________________________ Nominal opening temperature (.degree.C.) Color ______________________________________ 57 orange 68 red 79 yellow 93 green 141 blue 182 light violet 204/260 black ______________________________________
Not only the heat capacity of the expanding liquid but also its thermal conductivity and viscosity play an important role in the response time of the glass barrel sprinklers. To ensure that the scatter of the triggering temperature is within the span of the narrowest possible tolerances of about 5%, the expanding liquid should in addition cause the steepest possible pressure rise on heating, that is to say it should have a high value of the ratio, which determines the pressure rise with temperature (dP/dT), of the co-efficient of thermal expansion to the compressibility (>10 bar/K). The response time can be influenced on the one hand by the important physical properties and on the other hand by constructional measures. A shortening of the response time results, for example, from reduction in the wall thickness of the small glass barrel, from an increase in the thermal conductivity of the glass material and/or the expanding liquid, in the same way as form a reduction in the capacity of the small glass barrel. For this purpose, German Offenlegungsschrift DE 3,220,124 A1 published on 1st Dec. 1983 describes a reduction in the filling volume of liquid by means of an inserted displacement body. At present, the expanding liquids used for glass barrel sprinklers are predominantly alcohols, namely n-butanol, isopropanol and glycerol, and less frequently also paraffin oil or most recently ethyl acetate.
The present invention shortens the response time by the use of special expanding liquids, with which the heat absorption takes place particularly rapidly, as the internal filling of the small sprinkler glass barrels. It has been found experimentally that the response time of the small glass barrels used as trigger elements depends, on the one hand, on the product of the mean heat capacity of the expanding liquid with its density and the volume of the glass barrel (heat capacity of the internal filling), but on the other hand also on the thermal conductivity of the expanding liquid and its viscosity. The co-efficient of thermal expansion, the toxicity and the chemical stability of a liquid in the course of time also play a role in its use as an expanding liquid.
The exper

REFERENCES:
patent: 1771826 (1930-07-01), Taylor
patent: 1905676 (1933-04-01), Barclay
patent: 2125510 (1938-08-01), Lewis

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