Theoretical and Experimental Studies on Piezoelectric Thermal Fire Annunciator

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International Journal of Engineering Research & Science (IJOER) ISSN: [2395-6992] [Vol-3, Issue-12, December- 2017]
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Theoretical and Experimental Studies on Piezoelectric Thermal
Fire Annunciator
Mammadov R.G.1, Rahimova E.G.2
Azerbaijan State Oil and Industry University, the department of Instrumentation Engineering, AZ 1010, Azadliq avenue, 20,
Baku, Az1010, Azerbaijan
Abstract The paper presents theoretical and experimental studies on testing the possibility of using piezoelectric
converters as a signaling device in fire protection systems. The advantage of this process is the absence of the necessity to
connect electrical lines, which in most cases they themselves cause fire.
Keywords Piezoelectric converter, transformer mode, depolarization, signaling device, fire security.
I. INTRODUCTION
The systems, designed for remote registration of occurrence moment of fire situation at oil and gas industry facilities, contain
a primary converter (located directly at the facility), a communication channel and a signaling device installed in the control
room.
Practice shows that, the reliability of such systems is mainly determined by the primary converter, so that their design is
presented by very stringent require ments. Therefore, currently, several types of devices have been developed reacting either
to an increase in the a mbient temperature caused by it [1,2,3]. The converters used in practice are mainly fusible and
ferromagnetic fuses and photoelectric signaling devices.
II. STATEMENT OF THE PROBLEM
The disadvantage of the first two types of converters is that their work is connected with the need of using sufficiently
powerful electrical circuits, which in case of fault , they themselves can be sources of an explosion or a fire. Photoelectric
converters operation is connected with the need of using special power supplies and amplifiers complicating the signaling
scheme, thus, reducing its reliability. These shortcomings can be eliminated if a piezoelectric ceramic, having the ability t o
be depolarized under the effect of temperature is used as a sensitive element [4,5].
III. SOLUTION
Fig 1. presents the diagram of the device, which can b e recommended as a signaling device on the occurrence of a fire
situation. The device contains a piezoelectric transfor mer, the first section 1being connected to the 220 V network, however,
the secondary one-2 is loaded onto gas-discharge indicator 4through the communication channel 3.
FIG.1: SIGNALING DEVICE ON THE OCCURRENCE OF A FIRE SITUATION
The transformer is installed at the facility; however, the gas-discharge indicator is installed in the control room. Under
normal co nditions, the transformable voltage in the network maintains luminescence indicator. When the temperature
increases on the object, the piezo-ceramics becomes depolarized, the voltage transformation stops to the indicator and it goes
down, signaling the occurrence of a fire situation.
International Journal of Engineering Research & Science (IJOER) ISSN: [2395-6992] [Vol-3, Issue-12, December- 2017]
Page | 2
Since the problems, related to the design of piezoelectric transformers, have been sufficiently fully illuminated in [6], the
results of the studies on thermal depolarizatio n and piezo-ceramics inertia are of practical interest in constructing signaling
schemes. This is d ue to the fact that depolarization rate and heating time of piezo-cera mics to the po int of phase tra nsition
determine such an important parameter of the system as its speed.
In accordance with the known thermodynamics dependence, the thermal time constant of the converter can be determined by
the following formula [7]:
21
3
ll
Cml
(1)
where C- is the heat capacity, cal/g·deg.; λ- is thermal conductivity, cal/s·m deg.; m- is the transformer mass, g; l1, l2, l3- are
length, width and thickness of the transformer, m.
a)
b)
FIG. 2: RESULT OF EXPERIMENTAL STUDIES
As a result of experimental studies (Fig. 2, a, b), it was discovered that the average heat capacity for piezoceramics ZTL-19
(zirconate-titanate-lead) is (0.2-0.4) cal./g·deg.;, while temperature is close to the point of the base transition, its value
increases to (0.8-1) cal./g·deg;.
The study of the heat capacity enabled to determine the temperature at which the piezo-ceramics was completely depolarized.
This temperature for ceramics, ZTL-19 is (305 ÷ 308)0С.
FIG.3: THERMAL CONDUCTIVITY MEASUREMENT OF PIEZO-CERAMICS
The thermal conductivity measurement of piezo-ceramics ZT L-19 (Fig. 3) allows us to conclude that its value, depending on
the ambient temperature, varies from 0.7 W/m·deg;. at normal temperature to 1.1 W/m·deg.; at phase transition temperature.
The signaling s ystem speed is determined not only b y thermal ti me constant. T his is due to the process of depolarization
having certain inertia. Currently, there are no sufficiently simple analytical dependencies allowing deter mining the
depolarization inertia, in connection with the fact that this parameter has been determined experimentally.
International Journal of Engineering Research & Science (IJOER) ISSN: [2395-6992] [Vol-3, Issue-12, December- 2017]
Page | 3
Fig. 4 defines a curve allowing determining the depolarization degree of ceramics ZTL-19 depending on the exposure time to
it of the phase transition temperature.
FIG.4: DETERMINE THE DEPOLARIZATION DEGREE OF CERAMICS ZTL-19
In this case it is advisable to use a number of relative values to characterize the depolarization degree [8].
0
E
E
KE
(2)
where Eτ- is the current value of permanent polarization in piezoceramics; E0- is the initial value of permanent polarization.
For piezoceramics, ZTL-19 E0 = 2ˑ106 V/m.
IV. CONCLUSION
The analysis of the available experimental data allows us to conclude that the duration of depolarization does not exceed 10
c. Thus, taking into account the thermal inertia, the total time required for triggering the signaling system from the
occurrence moment of a fire situation does not exceed (10 ÷ 15) s.
REFERENCES
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[2] Fomenko A.A.Dotty maximum thermal fire annunciator: construction and applicationfeatures. // Security Systems. 2007. - N. 5. P. 85.
[3] EN 54-5: 2000 Fire alarm systems -Part 5: Heat detectors - Point detectors.
[4] Sharovar F.I. Comparative evaluation of the application effectiveness of thermal maximum, differential and smoke fire
annunciators//Groteck security systems. 2003. №1. P. 62.
[5] Bakanov V., Neplokhov I. Thermal fire annunciators. Part 2. Application problems. Security Algorithm, 2011, № 6.
[6] A.N. Members. Modern thermal fire signaling: the main characteristics and features of the application. “Security S ystems”, N. 1 (55),
2004.
[7] R.G. Jagupov, A.A. Erofeev - Piezoelectric elements in instrumentation and automation, L., “Mechanical Engineering”, 1988.
[8] V. Sharapov, M. Musienko, E. Sharapova- Piezoelectric sensors, M: “TECHNOSPHERE”, 2006.