Sprinkler actuator

Details Sprinkler actuator Sprinkler actuator

1997-11-10

1999-04-06

Kashnikow, Andres

Fire extinguishers

Sprinkler heads

169 38, 169DIG3, A62C 3708

Patent

active

058905430

DESCRIPTION:

BRIEF SUMMARY
The invention relates to an actuating unit for a sprinkler.
Such actuating units are used in automatic fire extinguishing systems where water serves as a fire extinguishing agent and is led through a firmly installed network of pipes and distributed to the seat of a fire via automatically opening spray valves, the sprinkler heads. The type of releasing can be differentiated into solder link, melt crystal and glass bulb sprinkler.
In the latter case, the spray valve is sealed by a glass bulb filled with liquid. When hot conflagration gases reach the sprinkler, the glass bulb is bursted by the explosive liquid and the spray valve is released so that the extinguishing water can be discharged. Depending on conditions and requirements at the place of use, sprinklers with nominal values of the releasing temperature .differential..sub.A from 57.degree. . . . 260.degree. C. and the response time t.sub.A from 10 . . . 50 are used.
.differential..sub.A is the temperature at which the glass bulb heated in a tempering bath bursts. t.sub.A is measured as the duration from immersing the sprinkler in a defined hot air stream (e.g. 135.degree. C. /2.5 m/s at .differential..sub.A =68.degree. C.) until the bulb bursts. Tolerances and measurement conditions are laid down by the international approval authorities.
After success in the Eighties in developing fast responding sprinklers, in recent years in the field of fire protection it has been acknowledged that recognition and extinguishing as early as possible is a precondition for effective damage limitation. Since then, the demand, in particular for fast responding glass bulb sprinklers with response times of 14 s and under has sharply increased.
The figure shows typical dimensions of a glass bulb for this intended purpose. Diameter and wall thickness have already been extensively optimised with this construction with regard to the previously available explosive liquids, the stabilities and tolerances required for release temperature and response time.
In order to shorten the response time whilst maintaining the simple and thus low-cost construction, various suggestions have been made. Thus EP B1 0 301 052 lists a series of physical properties of liquids which favour their suitability as explosive liquid:


______________________________________ 1. Thermal capacity density .cedilla. .ltoreq. 1.5 MJ/m.sup.3.K 2. Dynamic viscosity .eta. .ltoreq. 0,8 mPa.s 3. Thermal conductivity .lambda. .gtoreq. 0,15 W/m.K 1) 4. Temperature-pressure coefficient .beta. .gtoreq. 1 MPa/K ______________________________________ compressibility .chi.. 052 are incorrect. Approximately correct values in W/m.multidot.K are obtained by multiplying by the factor 5.8.
Furthermore, EP B1 0 301 052 shows that poorer values for one or several properties could be balanced out to a certain degree by better values for other properties. Thus, for example, excessive .cedilla. values which lengthen the response time can be compensated for by higher .beta. values by using thinner glass bulbs with thicker walls which are used to retain the stability. The increased releasing temperature distribution due to the thicker cylinder walls can be balanced out by the more rapid rise in pressure due to the higher temperature-pressure coefficient.
Whether all of the liquid parameters determining the releasing speed are covered by .cedilla., .eta., .lambda. and .beta. and how the response time can be calculated from this for a given bulb under given circumstances is not currently known.
As besides the further properties mentioned, attention has to be paid to properties such as chemical and thermal endurance, simplicity of finishing, boiling point and melting point, toxicity, environmental compatibility, availability and price, the selection of a suitable liquid can be difficult. In order to fulfil these requirements, the extension from the EP B1 0 301 052 known range of substances therefore is urgently desired.
The object of this invention is to provide such a sprinkler actuator which guarantees a short releasing

REFERENCES:
patent: 1771826 (1930-07-01), Taylor
patent: 4938294 (1990-07-01), Mohler et al.

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