The difference between explosion -proof and essential safety

Electric equipment must sometimes be installed in areas where combustible steam and gas may be used. These are usually called "dangerous places" and are defined by the US National Electrical Specification (NEC) or Canadian Canada Electrical Specification (CEC).

When the device must be installed in a dangerous place, there are strict requirements for the installation construction, including materials and design requirements.

In order to prevent electrical equipment from accidentally igniting flaw gas and steam, the two most common protection methods are "explosion -proof" and "essential safety". These methods are also related to gas detection equipment. Here we will discuss these methods based on fire and gas detection systems.

Explosion -proof
Generally speaking, "explosion -proof" is a more common method for detect/sensor components in a fixed gas detection system. It may encounter higher voltage and power requirements, and installation is permanent.

The essential safety method can also be used for detectors/sensors is a permanent installation of relatively low power equipment. Almost all portable instruments use the "essential security" method.

sensor/ transmitter means that the design and structure of the shell can prevent flash or explosion.

This shell is usually made of aluminum or stainless steel, and has sufficient quality and strength. It can safely control the explosion when igniting the flames or steam through the shell and internal electronic equipment or lines.

Design must prevent any surface temperature from exceeding the fire temperature of the gas or steam covered by its group level (see below). If the sensor element is high -temperature equipment (such as catalytic pearl or "catalytic ball"), it may be protected by the fireproofer to prevent high temperature gas from spreading to the environmental atmosphere.

Essential Security
The "essential security" classification and design refers to the electronic circuit and its wiring of no sparks or arcs, and cannot store sufficient energy to ignite the flammable gas or steam, nor can it produce sufficient surface temperature to cause ignition.
This design is not explosion -proof and does not require explosion -proof. For permanent installation, such installations may include "essential security barriers" located outside the dangerous position and restrict the energy available in equipment located in the dangerous area.

North American categories related to the dangerous places related to flammable gas and steam:

I Class: Gas and Vapor

Part 1: Gas or vapor usually exist and/or may exist at any time to cause the danger of explosion at any time.

Part 2: Gas or vapor usually does not exist. Only when a safety shell or pipeline leaks, it also has a concentration of potential danger.

A, B, C, D group: The atmosphere of volatile and/or fire temperature classification. For gas and steam, "A" is the most dangerous, and "D" is the most dangerous group.

Group A: The atmosphere of acetylene is contained.

Group B: An environment containing hydrogen or gas or steam with the same risk.

C group: The environment containing ether vapor, ethylene or cyclopenide.

D group: The atmosphere of gasoline, hexane, petroleum, benzene, cytane, alcohol, acetone, benzene, paint steam or natural gas (methane) atmosphere.