Explosion Proof Solenoid Valves
Explosion Proof Solenoid Valves
ASCO are world leading manufacturers of solenoid valves designed to control the flow of air, gas, water, oil or steam – this section provides an overview of the explosion proof solenoid valve ranges with ATEX and IECEx certification including the following explosion proof concepts:
- Exd Flameproof
- Ex m Encapsulated
- Ex e mb Increased Safety & Encapsulated
- Ex ia Intrinsically Safe
- Ex nA Non-Sparking Explosion Proof
This type of explosion protection involves enclosing the solenoid coils in a robust enclosure which will contain an internal explosion should it occur and prevent its transmission to the surrounding explosive atmosphere.
N-Type Protection (Non-incendive) – generally applied to non-sparking electrical equipment such as a solenoid valve or coil which will not get abnormally hot even if the armature is locked out.
Encapsulation – this involves enclosing the solenoid valve or coil and any associated electrical components in a compound so as to prevent
the ignition of a surrounding explosive atmosphere.
Intrinsically Safe – intrinsic safety is a concept of explosion protection that achieves safety by limiting the electrical-spark energy (and surface temperature) that can arise in hazardous area circuits to levels that are insufficient to ignite an explosive atmospheres.
An intrinsically safe system consists of a certified intrinsically safe interface which passes a signal to and from the process (hazardous area zone) but limits the energy (that is voltage and current) that can reach the hazardous area under fault conditions. The interface is usually mounted in the safe area and can be either a shunt diode safety barrier or a galvanic isolator. In the hazardous area “simple” or “non-energy storing devices” (switches, thermostats and LEDs) can be used without certification but “energy-storing equipment” such as solenoid valves must be designed so as to prevent this energy escaping and of necessity need to be of sufficiently lower power to operate within the constraints of the IS signals.
Special protection offers combination of one or more methods of explosion protection and in the case of solenoids these are usually ‘e’ and ‘m’, where the coil is encapsulated, has over temperature protection and the terminals are approved under the increased safety requirement.
Explosion proof solenoid valves are designed and manufactured with a coil or enclosure that is specified to contain any explosion originating from within the coil or housing and prevent any internal spark from igniting any combustible gas, vapours or particulates in the surrounding environment that could cause a much larger explosion.
There are a number of standards for classifying equipment for hazardous environments. The most common are; NEMA (National Electrical Equipment Manufacturers Association (USA)), IEC Ex (International Electrotechnical Commission Explosive (global)) and ATEX (ATmosphères EXplosibles (EU)). If you are purchasing an explosion-proof solenoid valve be sure you see one of these marks on the valve, which may vary depending on which standard was followed.
NEMA has four hazardous location enclosure ratings (7-10) which correspond to specific environments (indoor/outdoor) and materials (explosive gases and particulates).
NEMA follows the NEC (National Electric Code) Divisions System for Gas & Dust Groups. The IEC Ex & ATEX have a Hazardous Area Zone System for Gas & Dust Groups. They cover many of the same materials but are laid out differently.
➡ Thorne & Derrick International distribute the most extensive range of ASCO valves including general service and hazardous area solenoid valves (2-way, 3-way and 4-way) to handle flow control of liquids, gases and oil in both onshore and offshore installations.
Valves are available with ATEX and IECEx certification and classification for safe installation into hazardous areas in a range of materials including brass, aluminium and stainless steel and various pipe connection configurations.
What Are Solenoid Valves?
ASCO solenoid valves are electronic devices used to provide precise flow control and are operated by opening and closing an orifice in the valve body that permits or prevents flow through the valve.
The orifice is operated through the use of a plunger that is raised or lowered within a sleeve tube by energizing the solenoid coil. The solenoid comprises a coil, core, core tube and enclosure. Key valve selection factors include voltage, valve type, flow capacity, pressure rating, wattage and connection type.
ASCO offers the worlds largest selection of 2-way, 3-way and 4-way solenoid valves, designed to handle the most demanding fluid control applications. ASCO 327 solenoid valves are ATEX and IECEx certified for hazardous areas in the oil, gas and petrochemical industries.
ASCO valve product range also includes cylinders, angle body piston valves, regulators, valve manifolds, filters, lubricators and valve accessories.
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