Hawke and the ATEX Directive
What Is Atex?
ATEX is the term used for the European Union's Directive 94/9/EC which concerns equipment and protective systems intended for use in potentially explosive atmospheres. The purpose of the directive is to facilitate trade within the EU by aligning the laws of the Member States regarding the safety requirements for hazardous area products.
It comes into force in July 2003 and has implications on plant owners, engineering design companies, contractors and manufacturers of equipment for use in hazardous areas.
ATEX brings with it new test requirements for Cable Glands which include pull out and heat cycling.
Pull out involves two tests: one for unarmoured and braided cables, the other for armoured cables.
Unarmoured and Braided Cables
In the case of unarmoured and braided cables, the cable gland is fitted to a minimum and maximum acceptance mandrel and a pull applied to the mandrel. The cable gland has to withstand a designed pull force without movement of the mandrel within the cable gland. In this case the entire force is applied to the cable gland seals.
In the case of armoured cables, the cable gland is fitted to minimum and maximum size cables and the armour is terminated in the armour clamping device. The same pull force is applied to the cable as for unarmoured cables and there must be no movement of the cable in the cable gland. In this case the force is applied to both the seal and armour clamping device.
It is, obviously, easier to meet the pull out requirements when the armour clamping device is operable and most cable gland manufacturers have been able to meet this. However, meeting the requirement for unarmoured and braided cables is much harder. Hawke has developed a new back seal that exceeds the required pull out tests for both armoured and unarmoured/braided cables. There is also an additional advantage for the user as this new seal has a much larger cable diameter acceptance and does away with the need for special outer seals.
Barrier Cable Glands
Heat cycling has caused particular problems to cable gland manufacturers with barrier Cable Glands.
The test requires the cable gland to be terminated to copper conductors, which simulates the cable. The cable gland is then heat cycled. After heat cycling a pressure is applied through the cable gland entry to simulate an explosion. The compound seal has to withstand this pressure without any leakage.
Barrier Cable Glands employ a brass or plastic pot in which the sealing compound is formed around the cable conductors. During the heat cycling test the pot expands at a different rate to the compound, causing the surface between pot and compound to separate. When the pressure is applied to the cable gland, leakage occurs.
Hawke has overcome this by using an elastomeric compound pot which, when the cable gland is assembled, compresses onto the compound creating a perfect seal.
A further advantage to the user is that the elastomeric pot is designed to be removed from the compound for inspection and if any voids are detected, these can be repaired and the cable gland reassembled.
The incorporation of these new features has necessitated the need for some dimensional and style changes, but Hawke has retained the same cable gland designations to avoid confusion and the need to change purchase records and customer drawings.
These new ATEX requirements have given us the opportunity to include new benefits for the user across its entire range.
Published: 27/09/2001
