ATEX Explosion Suppression Systems
The technique of explosion suppression involves the detection of a developing explosion at an early stage and extinguishing it before a destructive pressure is reached. Typically, it takes 30-100ms before a destructive pressure is reached.
Product list
- Hot Water Advanced Inerting System
- The Atex HWAIS is an innovative solution to the complex problem of non-contaminating explosion suppression in large volumes. Superheated water is released under pressure to quickly disperse microscopic droplets over a large area creating an inert atmosphere which immediately extinguishes flame.
- Dry Chemical Explosion Suppression System
- The Atex Dry Chemical-based Advanced Inerting System is a multi-purpose, high efficiency suppressor discharging non-toxic flame-extinguishing powder.
For a closed vessel without suppression the pressure rises in a manner illustrated in by the red curve. [#TODO curve graph - float:right] The blue curve shows the path of a suppressed explosion.
An explosion suppression system consists of an explosion detector, control system and suppressor unit. The suppressor unit contains the suppressant material which is stored under pressure and released at high speed.
The choice of suppressant material depends on a number of factors, however, a good suppressant should have most of the following properties:
- Quenching Ability
- This involves rapid heat absorption from the combustion zone by energy transfer.
- Dilution
- The suppressant concentration in the inburned mixture should have the effect of diluting it to a point where it is non-flammable.
- Wetting (if liquid suppressant)
- The unburnt dust particles are rendered non-flammable by the absorption of liquid suppressant.
- Chemical Action
- The chemical composition of the suppressant directly interferes with the combustion process.
The most common types of suppressants:
- ATEX Suppression System (ASS) use powders such as sodium bicarbonate in suppressors pressurised to 60 bar, however product contamination needs to be considered once a system operates. Dry powders also settle out relatively quickly after they have been discharged so plant shutdown is essential to protect against re-ignition.
- HALONS (normally at 20 bar) were widely used up to a few years ago. Now all CFC related halons are being phased out of production with the advent of the Montreal Protocol, because of their effect on the ozone layer.
However, Halon 1011, related to chlorobromomethane, is still in use but cannot be refilled and will be phased out soon. - WATER based suppressants (normaly at 20 bar) have also been shown to be very effective against a wide variety of explosion. However, applications have been limited because of difficulties distributing the water in a form suitable to maximise it's quenching ability.
One system that overcomes this problem is the Advance Inerting System (AIS). It is a Pressure (10 bar) Hot (180 C) Water Explosion Suppression (PHWES) system which uses water under conditions of temperature and pressure to suppress an explosion.
This system is particulary suitable to large volume sterile applications. - The Control and Indicating Equipment (CIE), electrical supply and monitoring unit provides system firing current, continuous circuit monitoring, plant shutdown, remote functions, and battery back up in the event of mains failure.
- An explosion detector unit,(static) can either be a single unit or a combined explosion detector with an auxiliary over pressure sensor as an optional extra. Recent developments have introduced the explosion sensor with transducer functions like rate of rise activation and event data capture. This minimise false activations.