What is the difference between Intrinsically safe and flameproof equipment?
If a fault develops in a piece of electrical or electronic equipment situated in an area where flammable gases are present, the fault might trigger heat or sparks adequate to spark the gas and cause a catastrophe. There are 2 systems in general use to prevent such happenings.
(a) Flameproof/ Explosion-proof equipment
The equipment is merely contained in a heavy protective enclosure, usually made of die-cast steel, periodically plastic. If heat or stimulates from malfunctioning equipment within the enclosure fire up a combustible gas present with it the resulting explosion is consisted of within the enclosure. In The United States and Canada, metal avenue must be utilized for field electrical wiring. In Europe and elsewhere suitably ranked cable television is linked straight to the equipment using qualified flameproof cable glands.
Advantage -- basic to develop the system, appropriate for high power equipment
Disadvantage-- equipment ends up being extremely heavy & costly; opening the enclosure while powered is not allowed
(b) Intrinsically Safe
This approach restricts the energy available to the intrinsically safe (I.S.) equipment, normally less than 2 watts, by methods of a galvanic or Zener barrier in such a way that under no situation will the equipment be able to create adequate heat or sparks to ignite flammable gases. Both the I.S. equipment and the Zener barrier should be certified 'Intrinsically Safe' by BASEEFA, SIRA or a similar authority.
Advantage-- significantly cheaper than equivalent flameproof/ explosion-proof equipment, no special cabling required. Live maintenance allowed, no need to shut down the plant
Disadvantage -- only ideal for low power equipment e.g. sounders, beacons and smoke detectors (which need to be accredited Intrinsically Safe).
