A new flameproof cable gland range from Pratley allows for soft-bedding cables like PVC and the like, which are prone to creep, to be fitted to flameproof equipment without any concern regarding cable damage or poor long-term sealing.
The Pratley Taper-Tech flameproof range consists of glands in two unique categories. First is the Pratley Taper-Tech gland for armoured and braided cable. This is a ‘double compression’ gland, meaning it has both an inner and an outer seal. The second is the Pratley Taper-Tech single-seal flameproof gland, also for armoured and braided cable, but with a durable rubber shroud.
The unique feature of this flameproof cable gland range is that all versions are fitted with Pratley Taper-Tech flame seal technology, consisting of tapered seals made from superior, Pratley-developed, high-temperature and low compression-set elastomers. The seals all have a taper on the leading edge that abuts against the gland nipple taper on the inside. The taper on the bush and the one on the cable gland’s nipple are angled differently, which means that, under pressure from the front when it is tightened, this differential taper allows the bush to slide down the taper easily, reducing the force needed to achieve radial compression.
A major benefit of this technology is low initial radial pressure or a small amount of contact pressure on the cable. This is important because most cables in the field are made from PVC, which exhibits ‘cold flow’, meaning the relaxation of the cable bedding over time. Flameproof cable glands fitted to flameproof equipment are intended to seal against extremely high explosion pressures, which in many cases may be as high as 30 bar. For the seal to function properly, there must be adequate pressure between the seal and the gland bedding.
As the leading edge of the seal forms a taper in the direction of the applied explosive pressure, when this applied pressure increases so too does the contact radial seal pressure on the cable bedding. Once the pressure is relieved, the bush returns to its initial low-pressure state, so the high seal pressure is only on the cable when it is needed.
Taper-Tech completely negates cable damage usually experienced with subpar back seals, while complying to the stringent IECEx flameproof cable gland requirements.
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