Fire extinguishers – Special applications – Condition responsive control
Reexamination Certificate
2001-09-05
2004-05-11
Ganey, Steven J. (Department: 3752)
Fire extinguishers
Special applications
Condition responsive control
C169S016000, C169S054000, C169S060000, C340S578000, C340S584000
Reexamination Certificate
active
06732810
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to a detector arrangement and more specifically to a detector arrangement which is designed to detect in a stream of loose material the presence of one or more individual particles that has/have a temperature and/or an energy content such as to be able to incite fire or cause an explosion to take place in a downstream particle or material collecting risk zone.
By loose material is meant any type of material that can be transported by or in a gas mixture, normally air, wherewith the individual particles of the loose material are normally spaced from one another.
Loose material of this kind may consist of very fine particles in the nature of dust, or may consist of powder particles or granular particles. Wood chips, pellets, straw and like materials can also be transported in this way.
The inventive detector arrangement is adapted to be included in a preventative, protective system that includes one or more sensor units, an evaluation unit evaluating the output signals of said sensor units, and an activation unit connected to said evaluation unit, wherein at least one individual particle that can be sensed by the sensor units and having an energy content determined in the evaluation unit as exceeding a predetermined value will cause the activation unit to switch from a first state (a rest state) to a second state (an activating state).
More particularly, the detector arrangement can be adapted for use in a process in which loose, process material is produced in a first unit and transported therefrom to a receiving, second unit, wherein treatment of said material in said first unit may result in one or more particles being heated to a temperature that is sufficiently high to initiate fire and/or an explosion in at least the second unit, and in which arrangement the transport system required to transport the loose material between said first unit and said second unit includes a stabilising zone or disturbance zone, a zone that indicates the presence of high temperature particles, an effectuating zone, an extinguishing zone, and a downstream risk zone adjacent to or within said second unit.
The stabilisation zone is intended to allow particles that have a low energy content and do not constitute a fire risk or explosion risk within the downstream located zones, and particularly within the risk zone, to reduce their energy content and therewith prevent said particles being indicated as a hazard within the immediate downstream indication zone.
The indication zone includes one or more sensor units which function to indicate the presence of one or more individual particles whose energy content is liable to incite fire or some other damage should said particle or particles appear in the downstream zones and then particularly in the risk zone.
Each of the aforesaid sensor units can co-act with a unit which evaluates the output signals of a sensor unit, and with an activation unit such that when the sensor units indicate the presence of such a hazardous particle, the activation unit will activate an extinguishing means associated with said extinguishing zone and/or a particle removal means.
The indication zone is followed by an effectuating zone whose length is adapted so that upon activation of means in said extinguishing zone said means will have time to generate an extinguishing barrier before or as the particle reaches said zone.
The extinguishing zone may also include a valve, which deflects a collection of material containing said particle from the transportation path to the risk zone.
DESCRIPTION OF THE BACKGROUND ART
A preventative, protective system that includes one or more sensor units and associated detector arrangements of the aforedescribed kind is previously known and marketed by Firefly AB, Stockholm, Sweden. The preventative, protective system functions to indicate sparks and individual, glowing particles in a stream of loose material, such as granular material or dust, and to apply extinguishing means or smothering means so as to prevent such glowing particles from reaching the downstream process unit, such as a filter, a silo or the like, or from reaching the risk zone, which would otherwise be set on fire and/or caused to explode.
The preventative, protective system utilises in operation various detector systems and detector arrangements for sensing and detecting individual particles.
With regard to sensor units included in detector arrangements of the aforesaid kind and similar preventative applications, it has been found that they have a delayed reaction in industrial processes or are not sufficiently sensitive to be considered as an effective damage limiting means, which also applies to the output signal evaluating unit and the activation unit.
Sensor units of this kind tend to react to individual particles that are not harmful in certain circumstances, while in other circumstances they fail to react to individual particles that can cause damage by fire or explosion.
In this regard, it has been found necessary to maintain a safety range that is so large as to cause the equipment to react to particles that can cause no damage rather than not react to particles that are liable to cause damage, this being a preferred safety measure.
It is known to use temperature detectors in the present context, although experiences have shown in practice that these detectors often fail to react until a fire has already developed.
Although flame detectors used in the present context are sensitive to small (low) flames, their use in a preventative, protective system is excluded because they react much too late.
It is also known to use pressure detectors that operate with high sensitivity and with small time constants, but also such detectors normally require an initial explosion or combustion in order to react.
It is also known to use wavelength-related detector arrangements.
Practical experiences, however, indicate that even discrete particles that radiate solely within one wavelength range, solely for thermal radiation in a transport path, having a temperature in the range of 400° C. are a fire and explosion risk in various process plants where combustible, finely divided and loose material is transported with the aid of a vehicle gas or vehicle gas mixture, preferably an air stream.
The contents of Patent Publication U.S. Pat. No. 5,193,622, which describes a detector arrangement that includes a sensor unit, also belongs to the known prior art. Patent Publication SU-A1-1,729,528 teaches a detector arrangement that includes several sensor units.
With respect to the features associated with the present invention, it can be mentioned that Patent Publication U.S. Pat. No. 5,749,420 describes a detector arrangement in which an indicating and activating unit
12
is adapted to evaluate and sense the radiation intensity from each of a number of sensor units
105
,
107
.
With respect to the aforementioned publications, the sensor units used are adapted to receive summated each wavelength-related radiation intensity from a large wavelength range or from the whole of the wavelength spectrum of the particle.
DISCLOSURE OF THE INVENTION
Technical Problems
When taking into consideration the technical deliberations that a person skilled in this particular art must make in order to provide a solution to one or more technical problems that he/she encounters, it will be seen that on the one hand it is necessary initially to realise the measures and/or the sequence of measures that must be undertaken to this end, and on the other hand to realise which means is/are required to solve one or more of these problems, and on this basis, it will be evident that the technical problems listed below are highly relevant to the development of the present invention.
With respect to the singularities associated with the present invention, it is necessary to realise that each individual, discrete particle of loose particulate material carried in a transport system that has an elevated energy content will generate radiation that can spread within a wide wa
Dykema Gossett PLLC
Firefly AB
Ganey Steven J.
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