Application of CMP / Hawke Explosion Proof Gran in Field Instrument

Application of CMP / Hawke / CCG / Peppers Explosion-proof Gran in Field Instrument

Keywords: CMP / Hawke Explosion-Proof Gran, CCG / Peppers Explosion-Proof Gran, explosion-proof instrumentation, explosion-proof motor, explosion-proof electric control box, Shanghai Yipin Automation

Abstract: In the industrial production automation control system, the part in a very harsh environment is the field instrument. The on-site instrument has been subjected to various corrosive gases, temperatures, and humidity for a long time, reducing the service life of the internal components of the instrument, causing the performance of the instrument to decline, the error becoming larger, and the control quality of the system to decline The instrument is damaged. This article will introduce the application of explosion-proof gland in field instruments.

In the industrial production automation control system, the part in the very harsh environment is the field instrument. The on-site instrument has been subjected to various corrosive gases, temperatures, and humidity for a long time, reducing the service life of the internal components of the instrument, causing the performance of the instrument to decline, the error becoming larger, and the control quality of the system to decline The instrument is damaged.

A statistical analysis of the damaged on-site instrument found that 60% of the failures were caused by water in the instrument, which caused the circuit board to burn out. In the retrospective investigation of the cause of water inflow, it was found that more than 80% of the water inflow of the instrument was that rainwater entered the interior of the instrument along the cable through the cable connection of the instrument. Therefore, it is found that the waterproof measures of the on-site instruments are the effective measures to reduce the damage rate of the instruments. The first thing to be solved for the waterproof measures of the instruments is the sealing and waterproofing of the cable of the instrument connection port.

In the industrial production site, there may be dangerous sex gases on site, so the instruments selected on site must have explosion-proof performance. The flexible connecting tube as a cable connection must also have explosion-proof performance, and the metal connector of the flexible connecting tube and the inlet of the instrument must also have explosion-proof performance. The connection between the flexible connection tube and the instrument is hard-sealed to achieve explosion-proof performance. It is forbidden to add any non-conductive substances to the connection sealing surface to achieve the equipotential connection between the instrument shell and the metal flexible tube, so the waterproof ability of the field instrument cable interface is not allowed by winding the waterproof Teflon of.

The connection form of the flexible explosion-proof hose used in the factory and the instrument:

The previously used flexible explosion-proof hose is directly connected to the cable inlet of the instrument through a metal connector, and a special-shaped Y-type explosion-proof junction box is connected to the front side of the metal flexible explosion-proof hose. By injecting explosion-proof glue into the explosion-proof junction box to achieve the isolation of dangerous gases, in order to meet the explosion-proof requirements. This explosion-proof method can not achieve the leakage and sealing measures of the rainwater on the side of the explosion-proof hose, which causes the rainwater to flow into the instrument along the inner wall of the flexible explosion-proof hose, causing the circuit board to enter the short circuit and burn.

The explosion-proof glue injection point used when the bypass explosion-proof hose is directly connected to the instrument is shown in the figure:

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How to use one measure to achieve the explosion-proof requirements of the instrument cable and improve the waterproof performance of the instrument? Through years of trial use comparison and exchange of experience in the same industry, imported explosion-proof glands such as Hawke, CMP explosion-proof glands, etc. were used in the factory's new project installation.

Installation drawing of explosion-proof gland used in newly-built production equipment:

This explosion-proof gland tightens the outer sheath of the incoming cable through the squeeze deformation of the internal rubber sealing ring, and realizes the elastic rubber seal of the incoming cable. It not only fulfills the requirements of explosion-proof, but also blocks the way of rainwater entering the interior of the instrument along the cable sheath, which serves two purposes. The end of the explosion-proof gland uses a conical connection thread interface form, and the inlet connection port of the instrument is realized by a hard seal extruded by the conical thread, which not only meets the explosion-proof requirements but also achieves the waterproof purpose, and uses the waterproof effect on site Significantly.