Explosion-proof electromagnetic flow meter
is installed in the inflammable and explosive occasions, a more than ordinary electromagnetic flowmeter
explosion-proof function, and the shell material is better than normal.
Commonly used form of anti-explosion flame-proof (
And this (
, because the electromagnetic flow meter used in the power energy is larger, if you are using a two wire system of power supply, is unable to provide enough power, so the transmitter part generally use explosion-proof, explosion-proof instrument shell than the ordinary instrument, heavy chamber sealing good,
Instrument cover screw close)
, generally for the double chamber design, that is, the power of by XianQiang and signal XianQiang isolation.
The cable and split type explosion-proof type flowmeter, as a general rule, be explosion-proof armored cable.
But in some special measurement occasions there are two wire system of electromagnetic flowmeter may also use this explosion-proof, no difference in appearance of the structure with the ordinary flowmeter, but because of the power supply is different, so the instrument internal circuit board with ordinary flameproof electromagnetic flowmeter is different.
This safety type industrial instrument power supply in accordance with the different on the second table output signal can be divided into two types of output current and voltage output, current output of the secondary output table 4 -
20 ma current signal, the output voltage of the secondary output 1 - table
5 v voltage signal, the user can choose according to need.
According to the national standard GB 3836 & ndash;
83, our country of explosion-proof electrical equipment the explosion-proof structure have 8 kinds, listed as follows.
Structure symbol structure type flameproof oil charge d o e increased safety type sand mold filling q intrinsically safe type I no spark n positive pressure p is special type s * first kind is flameproof instrument, specific characteristics are as follows: a flame-proof also called pressure explosion-proof, it can ignite explosive mixture of instrument parts enclosed in a shell, the shell is particularly strong, can withstand the internal pressure, the explosion of explosive mixture and stop to the shell of booster explosive mixture.
Such as above what we call this type flameproof electromagnetic flowmeter is this, that is to say, flameproof instrument shell exploded inside is possible, but not to the shell to outside, so the appearance of the various components of the joint surface, such as the meter cover thread laps, screw thread accuracy, zero, range adjustment screw and watchcase, transmitter detection of clearance between components and conversion components, as well as wire mouth and so on, all have strict requirements of explosion-proof.
Flameproof instrument besides relatively heavy, the other is simpler, don't need such as safety grid connection equipment.
But before open the table cover, must turn off the power supply first, otherwise produce sparks, one thousand will be exposed to the atmosphere, resulting in dangerous.
Two for intrinsically safe instrument, specific characteristics are as follows: a intrinsically safe instrument and i. s. instrumentation.
It is the feature of the instrument under normal and fault condition, sparks and reach the temperature of the circuit, system will not ignite an explosive mixture.
Its explosion is mainly composed of the following measures: (1) USES a new type of integrated circuit components such as instrument circuit, work in low voltage and small electric work flow;
(2) the dangerous sites with safety barrier for the dangerous sites and the circuit of separating, restricted by the dangerous sites to a dangerous place to energy;
(3) the instrument of the wire connection shall form excessive stray inductance and capacitance, to reduce the storage in the circuit.
This system secure instrument explosion-proof performance, not the ventilation, gas, oil filled, flame-proof external measures, such as itself, but by the circuit is intrinsically safe.
It can be applied to all the dangerous places and all the mixture of explosive gas, steam, and can be conducted under the condition of the electricity maintenance and adjustment.
However, it cannot be used alone must and the associated equipment (Ann
, external wiring together the Ann circuit, can play a explosion-proof function.
The Ann type instrument of ia and ib of the difference between a level of ia & ndash;
Under normal working state, and there is a fault or two faults in the circuit, all cannot ignite explosive gas mixture.
In type 1 circuit, working current is limited under 100 ma.
The ib level & ndash;
Under normal working state, as well as the circuit there is a failure, not lighted explosive gas mixture.
In the ib circuit, the working current is limited silks under 150 ma.
Type ia instrument applies to 0 and 1 area, ib type instrument applies only to 1 section.
Or, from the essence safety point of view, the ib type instrument applies to the coal mine, type ia instrument applies to the factory.
The third is positive pressure type (
Explosion-proof instrument to instrument a shell filling the positive pressure of the clean air, inert gas, or continuous access to clean air, non-combustible gases, keep the shell internal protective gas pressure is higher than the pressure of the surrounding environment risk, to prevent external explosive gas mixture into the shell, and make the electrical components of the hazards and the isolation of instrument and equipment.
A fourth type for increased safety (
Instrument answer under the condition of normal operation does not produce ignite sparks or dangerous explosive mixture temperature, and take measures on structure (
Such as seals, etc. )
, to improve the safety degree, in order to avoid lit up under the normal and overload conditions prescribed by the phenomenon of instrumentation equipment.
Other special type (
Instrument answer is in addition to d, e, I, p, n the special form, besides, or a combination of the above several kinds of form, adopt the structure form of explosion-proof instrument called a special type of instrument.
Explosion-proof electrical equipment is divided into two broad categories: type I: the coal mine electrical equipment;
Class II: using electrical equipment factory.
According to the national standard GB 3836 & ndash;
83, divided into 3 class II explosion-proof electrical equipment, signs of A, B, C respectively.
In this paper by embellish instrument technology co. , LTD. Arrange release.
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