The functions and comprehensive introduction of explosion-proof buttons

In hazardous environments such as petroleum, chemical, coal mining, and metallurgy where flammable and explosive gases or dust exist, explosion-proof buttons are core control components to ensure the safe operation of electrical control systems. Their design and manufacture strictly follow national and international explosion-proof standards, effectively preventing the ignition of surrounding explosive mixtures by electric sparks and high temperatures generated during button operation. Avoid the occurrence of explosion accidents from the root.

I. Core Functions of Explosion-proof Buttons

(1) Basic control functions

The core basic function of explosion-proof buttons is the same as that of ordinary industrial buttons. They are responsible for the on-off control of circuits and the transmission of signal instructions, and are the “command switch” in electrical control systems.

1. Start/Stop control: In the motor drive system of oil drilling platforms and the pump body equipment in chemical workshops, operators can connect the motor circuit of the equipment and drive it to operate by pressing the start button of the explosion-proof button. Pressing the stop button cuts off the circuit, causing the equipment to stop working and achieving precise start and stop control of production equipment.

2. Signal switching and indication function: Some explosion-proof buttons integrate signal switching modules, which can be switched between different circuit loops to meet the mode conversion requirements of the equipment, such as the switching of stirring speed gears in chemical reaction vessels. Meanwhile, the explosion-proof buttons with indicator lights can provide real-time feedback on the circuit’s on-off status or the equipment’s operating conditions. The colors of the indicator lights usually follow industry standards – red represents stop, fault or warning, green represents start or normal operation, and yellow represents standby or early warning, facilitating operators to quickly determine the equipment’s status in complex environments.

3. Emergency stop control function: The explosion-proof emergency stop button is a key component for ensuring safe production. It is usually designed in a red mushroom head style and has a prominent visual recognition. Some products also have a self-locking function. After being pressed, it needs to be rotated clockwise to reset. When emergency situations such as equipment failure or personnel danger occur at the production site, operators can quickly press the emergency stop button to forcibly cut off the power supply of the equipment and prevent the accident from further expanding.

(2) Explosion-proof safety functions

The explosion-proof safety function is the core feature that distinguishes explosion-proof buttons from ordinary buttons. Its design focuses on “suppressing the generation of ignition sources” and “limiting the explosion range”, which can be specifically divided into the following two types of functions corresponding to the explosion-proof principles:

1. Flameproof type (Ex d) safety function: The flameproof explosion-proof button adopts a high-strength metal casing (such as cast aluminum alloy or stainless steel), which has sufficient mechanical strength to withstand the pressure generated by the explosion of the explosive mixture inside. Meanwhile, the connection surfaces of each component of the casing are designed with flameproof joint surfaces. Through strict control of gap and length parameters, To ensure that the flame and high-temperature gas generated by the internal explosion are fully cooled when passing through the joint surface, reducing the temperature below the ignition temperature of the surrounding explosive mixture, thereby preventing the flame from escaping the casing and igniting the external hazardous medium.

2. Increased safety type (Ex e) Safety function: The increased safety type explosion-proof button reduces the operating temperature of electrical components and the possibility of electric spark generation by optimizing the internal structure design. Its casing usually adopts a sealed structure to prevent explosive gases or dust from entering the interior. At the same time, the insulation performance and mechanical stability of the components are strengthened to ensure that no ignition source sufficient to ignite hazardous media is generated under normal operation and specified fault conditions.

3. Intrinsically safe (Ex ia/ib) safety function: Intrinsically safe explosion-proof buttons are intrinsically safe electrical equipment. Their internal circuits are designed with current limiting and energy limiting. Even in fault conditions such as short circuits and open circuits, the energy and temperature of the electric sparks generated by the circuit are far lower than the minimum ignition energy of explosive mixtures, fundamentally eliminating the generation of ignition sources. Intrinsically safe explosion-proof buttons are usually used in conjunction with associated equipment (such as safety barriers) and are suitable for high-risk explosive environments like Zone 0 and Zone 1.

(3) Environmental adaptability function

Explosion-proof buttons need to work for a long time in harsh industrial environments with strong corrosiveness, high humidity and a lot of dust, so they have excellent environmental adaptability.

1. Corrosion resistance: The shell material is mostly cast aluminum alloy and stainless steel, and has undergone surface spraying and passivation treatment. It can resist the erosion of corrosive media such as acids, alkalis, and salt spray, and is suitable for environments such as chemical plants and offshore platforms.

2. Dust and water resistance: The protection grade of explosion-proof buttons is usually no less than IP65, and some products can reach IP67, which can effectively prevent dust from entering the interior. At the same time, it can withstand short-term immersion in water, meeting the usage requirements in outdoor and damp workshops.

3. Anti-shock and vibration function: The internal components adopt a shockproof fixed structure, and the shell has excellent anti-shock performance, capable of withstanding mechanical vibrations and collisions during the production process, ensuring stable operation in strong vibration environments such as mines and metallurgy.

Ii. Structural Composition of Explosion-proof Buttons

The structural design of explosion-proof buttons centers on “safety and reliability”, and mainly consists of the following parts:

1. Housing assembly: The housing is the core protective component of the explosion-proof button, consisting of two parts: the shell and the cover. Materials include cast aluminum alloy, stainless steel, engineering plastics, etc. Different materials are suitable for different environments and explosion-proof grades. The joint surface of the enclosure of flameproof products must strictly comply with the flameproof gap requirements, while the enclosures of increased safety and intrinsically safe products focus on sealing performance.

2. Operating components: These include button heads, operating rods, reset springs and other parts. The shapes of button heads are diverse, such as round, square, and mushroom-shaped. Their surfaces are usually made of anti-slip and wear-resistant materials, facilitating the operator’s pressing operation. The mushroom-shaped design of the emergency stop button increases the pressing area, facilitating quick operation in emergency situations.

3. Electrical components: They are the core functional parts of explosion-proof buttons, including contact systems, indicator light modules, terminal blocks, etc. The contact system is made of silver alloy material, which has good electrical conductivity and arc resistance, and can withstand frequent on-off operations. The indicator light module adopts LED light source, featuring low power consumption, long service life and high brightness. The terminal block is designed with an anti-loosening structure to ensure a firm connection of the circuit and prevent poor contact caused by vibration.

4. Explosion-proof sealing components: including sealing rings, sealing gaskets and other parts, the materials are mostly oil-resistant and aging-resistant rubber. They are used to fill the gaps between the casing and the operating rod and wiring ports to prevent explosive gases and dust from entering the interior, and at the same time, they play a role in waterproofing and dustproofing.

Iii. Classification of Explosion-proof Buttons

(1) Classification by explosion-proof principle

1. Flameproof type (Ex d) : The most widely used explosion-proof type, suitable for Zone 1 and Zone 2 explosive hazardous environments. It has high enclosure strength and strong anti-explosion ability, and can be used in most hazardous places such as petroleum and chemical industries.

2. Increased safety type (Ex e) : Explosion-proof is achieved by reducing the temperature of components and enhancing insulation performance. It is suitable for explosive hazardous environments in Zone 2 and is mostly used in control circuits, signal circuits and other occasions where there are no drastic on-off operations.

3. Intrinsically safe type (Ex ia/ib) : Intrinsically safe type, suitable for explosive hazardous environments in Zone 0, Zone 1 and Zone 2, with the highest safety. It needs to be used in conjunction with safety barriers and is often used in high-risk places with high concentrations of flammable and explosive gases, such as the gas environment in underground mines.

4. Encapsulated type (Ex m) : Electrical components are encapsulated in insulating materials such as epoxy resin to isolate contact with external hazardous media. It is suitable for explosive hazardous environments in Zone 1 and Zone 2 and has strong corrosion resistance.

(2) Classification by function

Explosion-proof start and stop buttons: The most basic type, divided into normally open contacts and normally closed contacts, are used for the routine start and stop control of equipment.

2. Explosion-proof emergency stop button: Red mushroom head design, with self-locking function, used to cut off power supply in emergency situations to ensure the safety of personnel and equipment.

3. Explosion-proof button with light: Integrated indicator light, it has both control and status indication functions, allowing operators to keep track of the circuit status in real time.

4. Explosion-proof selection button: Also known as explosion-proof conversion button, it has multiple positions and can achieve circuit switching control, suitable for mode conversion of equipment.

(3) Classification by installation method

1. Wall-mounted explosion-proof button: Fixed on the wall or equipment casing through a bracket, it is easy to install and suitable for on-site operation.

2. Panel-type explosion-proof buttons: Embedded and installed on the panels of control cabinets and operation consoles, they are aesthetically pleasing and neat, and are suitable for centralized control scenarios.

Iv. Selection and Usage Precautions of Explosion-proof Buttons

(1) Selection principles

1. Select the type based on the explosion hazard area: For Zone 0, intrinsically safe explosion-proof buttons should be given priority. For Zone 1, flameproof type and intrinsically safe type can be selected. For Zone 2, either increased safety type or flameproof type can be selected.

2. Select based on the hazardous medium: For different explosive gases or dusts, products that meet their ignition temperatures and explosion-proof grades should be chosen. For example, in a hydrogen environment, explosion-proof buttons of grade ⅡC should be selected, which is higher than the grade ⅡB requirement in an acetylene environment.

3. Select the type based on the usage function: For regular start and stop, choose a common explosion-proof button; for emergency situations, select an emergency stop button; and for status indication, choose a button with a light.

4. Select the type based on environmental conditions: For corrosive environments, choose stainless steel enclosures; for humid environments, select products with a protection grade of IP67; and for strong vibration environments, choose flameproof products with good impact resistance.

(II) Precautions for Use

1. Installation specifications: During installation, it is necessary to ensure that the mating surfaces of the casing are clean and undamaged, the sealing components are intact, the connection terminals are firm, and the grounding is reliable. The enclosure bolts of flameproof products must be tightened to the specified torque and must not be disassembled at will.

2. Daily maintenance: Regularly inspect the appearance of the buttons, the status of the contacts, and the brightness of the indicator lights, and promptly clean the dust and oil stains on the surface. If any damage to the casing, failure of the seal, or erosion of the contacts is found, stop using it immediately and replace it.

3. Strictly prohibit violation of operating procedures: Do not disassemble explosion-proof buttons at will in explosive environments. Do not replace components that do not meet the explosion-proof grade. Before resetting the emergency stop button, check for faults and confirm safety before operation.

V. Application Fields of Explosion-proof Buttons

Explosion-proof buttons, with their excellent safety performance and environmental adaptability, are widely used in various industrial sites with explosion hazards

1. Petrochemical industry: In places such as oil refineries, chemical plants, gas stations, and oil depots, it is used to control the start and stop of pump bodies, compressors, conveyors and other equipment, and is an indispensable control component in the production process.

2. Mining industry: In underground coal mines, metal mines and other places, intrinsically safe explosion-proof buttons are used to control roadheaders, coal shearer, hoisting equipment, etc., which can effectively prevent gas explosions.

3. Metallurgical industry: In steel mills, non-ferrous metal smelters and other places, it is used to control furnaces, fans, conveying equipment, etc., to resist harsh environments such as high temperatures, dust and vibration.

4. Pharmaceutical and food industry: It is used in flammable and explosive solvent production workshops of pharmaceutical factories, dust workshops of food factories and other places to control production equipment and ensure the safety of the production process.