Safety Q&A 2: Requirements for installation of explosion-proof equipment in hazardous locations

Question 1 : What are the requirements when installing the instrument in explosion hazardous locations?

A: 1 Instruments, electrical equipment and installation materials used in explosion hazardous locations such as junction boxes, junction boxes, and terminal boxes must have an explosion-proof certificate issued by a domestic authorized agency. Before installation, check whether their specifications and models meet the design requirements. Requirements, its exterior should be no damage, cracks.

(2) Positive pressure explosion-proof meter boxes can also be installed in explosion hazardous locations. Non-explosion-proof meters and other electrical equipment are installed. The ventilation ducts of the meter box must be kept open. Before the power transmission, the volume of the box should be more than 5 times the gas volume . Replacement.

3 The instrument wiring of explosion hazardous area 1 must ensure that in the event of an accident such as grounding, short circuit, or disconnection, it will not form an ignition source. Therefore, the cables and wires must be laid through the pipe. The pressure-explosion-proof metal pipe, between the protection pipe and between the protection pipe and the junction box, the junction box, and the cable box should be connected by a threaded pipe, and the thread can effectively mesh with the thread. Should be more than 5-6 deductions. The flexible connection pipe should be used when flexible connection is required.

Instrument wiring in Zone 2 should generally be piped, but only to protect the insulation of cables and wires from injury.

(4) Sealing measures should be taken to prevent the explosive gas from entering a dangerous place and entering into another dangerous place when the line trunking, cable trenches, and protection pipes pass through the boundary lines of explosion hazardous locations of different grades.

5 When the protection pipe is connected with field instruments, detection components, electrical equipment, meter boxes, junction boxes, junction boxes, pull boxes, etc., explosion-proof sealed pipe fittings shall be installed within 0.45m of the joint, and the protection pipe of 2in or more shall be 15m should be set up with a sealed tube.

Question 2 : What are the requirements for installing intrinsically safe meters?

A: 1 Different series of intrinsically safe instruments and associated devices such as safety barriers should not be mixed. They must be appraised by the relevant departments to confirm that their technical performance is compatible before they can replace each other.

2 Intrinsically safe associated devices such as safety barriers, galvanic isolators, buffer amplifiers, etc. shall be installed on one side of a safe place and be reliably grounded.

3 In order to prevent dangers caused by intrinsically safe system wiring and intrinsically safe associated wiring, general circuit wiring wiring, electrostatic induction, and electromagnetic induction, it is necessary to use pipe laying. Intrinsically safe lines and non-intrinsically safe lines should not share a cable or protective tube. The intrinsically safe circuits of two or more different systems shall also not share a single cable (except where the core wires are separately shielded) or share the same protective tube (excluding those with shielded wires).

(4) When laying the intrinsically safe line and the non-intrinsically safe line in the same cable trough and cable channel, use grounded metal plates or insulation to isolate them. Otherwise, they shall be arranged separately with a spacing greater than 50 mm and fixed separately.

5 The terminal boards of the intrinsically safe and non-intrinsically safe lines in the instrument panel shall be separated from each other with a spacing of more than 50 mm . Otherwise, the insulation boards shall be used for isolation. The two types of wiring shall be laid separately and securely tied.

6 The length of the intrinsically safe line shall be such that its distributed capacitance and distributed inductance do not exceed the maximum allowable value specified by the instrument manufacturer.

7 The wiring of the IS system should generally be set with a blue mark.

8 Intrinsically safe circuits should not be grounded in general, but should be grounded when it is necessary to set the signal ground reference point. This grounding point should be a single grounding point for all intrinsically safe instrument system grounding conductors and be separated from the power grounding system.

Question 3 : 1 Explosion-proof grade CT4 high or CT6 high ?

Some people think that the explosion-proof rating of CT4 is higher . Can it withstand 450 degrees without deforming or what ?

Some people think that the explosion-proof grade of CT6 is high , and the surface of the component can only produce a temperature below 85 degrees . It will not ignite the surrounding gas.

Question 4 : What is the maximum allowable temperature on the surface of the component?

A: T6 and T4 refer to the surface temperature of the explosion-proof product when it is working, not the temperature tolerated. The surface temperature of the T6 product when working is lower than that of the T4 group. Of course, it is better for the T6 group. For example, you bought a TV. Of course, you don't want the surface temperature to be too high when it is on. Explosion-proof products are also a good idea. It is safer to work at low surface temperatures. The surface temperature of T4 is allowed to be 135 degrees, T6 surface temperature is 85 degrees, and the technical requirements for explosion-proof equipment are higher.

Question 5 : The meaning of IIC in the certificate only contains H2

A: Look at the picture Our products are suitable for hydrogen-containing gases in IIC gas applications. Except for acetylene and carbon disulfide, they can be used.