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dealing with all the pressure you need fans and blowers for extraction, cooling, ventilation, aeration, vacuum and drying • Backward curved bladed single inlet centrifugal blowers • Flow rates up to 850m 3 /hr (500CFM) • Pressures upto 150mBar (60in.SWG) • Exceptionally low noise levels • Reliable and maintenance free • ATEX versions • Many configurations and add-ons ACI’s Multi Stage Range of directly driven blowers offers exceptionally quiet running and maintenance free solutions for many higher pressure applications. Direct mounting of the impellers and low motor speeds minimise noise levels whilst providing high pressure performance. The Multi Stage’s modular system design gives a flexible choice in the number of stages combined. Power supply options available. Please contact us for further detailed specifications and to discuss suitability for your application. www.aircontrolindustries.com the solution providers for air movement problems Air Control Industries Ltd Silver Street, T: +44(0)845 5000 501 Chard, F: +44(0)845 5000 502 Somerset,TA20 2AE, UK E: sales@aircontrolindustries.com ELECTRICAL EQUIPMENT & DESIGN Time to check your cable glands? Terry Spriggs of Hylec Components helps to keep your knowledge up-to-date by giving an overview of what has changed and what is now available There are now more variations of cable gland available than ever, and with more choice comes the requirement for more knowledge in order to make the right selection. Considerations such as suitability for purpose, sealing, safety and installation time all need to be balanced against cost, which is always an issue. It is as easy to overlook a cable gland as it is to under-specify or to over-specify it. With a huge range of fast new push-fit designs, tighter regulations and new materials coming onto the market it is essential to look at what is fit-for-purpose. Essential criteria include the quality of the hole available for the cable entry, the thickness of the cable, the ingress protection required, the mechanical cable retention strength required, and the environment it is being exposed to. Exposure to heat, weathering and any fire requirements such as building regulations, halogen free requirements, Ex rating or ATEX zones have to be considered. One of the original and simplest types of cable gland is the ‘stuffing gland’ offering basic sealing and protection for cables passing through panels or bulkheads. A locking nut is used to apply pressure via a skid washer onto the sealing rings that spread to form a seal around the cable. This method of cable feedthrough achieves three basic functions. It protects the cable from possible damage due to any sharp edges on the bulkhead/wall/cabinet. It provides a barrier to moisture and debris entering the equipment housing (IP ratings are generally low as they will not withstand pressurised water or immersion). And it provides a measure of cable retention. The stuffing gland has been around for many years and is used in an enormous number of applications today. However, a major problem with these particular types of traditional gland is the limited mechanical performance and its protection rating of IP54. Many applications require better cable retention, in terms of factors like superior mechanical strength, a wider clamping range and a higher rating of IP65, or IP68 (which can be buried and/or kept under full emersion in water). These needs are catered for by a dome topped cable gland. These glands are also more aesthetically pleasing, looking more modern and smartening up an installation. A number of variations of this type are available in both Nylon and metal but the salient features that ensure superior performance to the traditional stuffing gland are in its construction. The cable is again fed through a sealing ring but in this case, the sealing ring is placed within an 'iris' that closes onto the sealing ring, clamping the cable and forming a high IP seal as the dome top is screwed down. Dome top variations Many different cable gland variations exist in dome top configurations covering a variety of general industrial applications. Specialist applications may require additional protection over and above the common plastic variations. There are, for example, products designed to meet the requirement of ATEX 100a for hazardous areas such as petrochemical. And there are glands designed for EMC compatibility and certified by VDE in compliance with VG 95373 part 40. Stainless steel versions should be considered in food and chemical process applications 28 More details: Write in 280 on the free information card INDUSTRIAL TECHNOLOGY • May 2008
Enclosures, Cabinets & Fans Warning safe in where wash down is essential for hygiene. Nylon and plated brass glands are suited for general industrial or marine applications. Most new developments are focused on speeding up the process of cable sealing and retention, offering push-fit glands and grommets in a range of designs. The main issue with these variations is that they provide limited mechanical grip and will only seal up to IP67. Because the retention material is soft, it is generally less resistant to extreme heat, but can be more resistant to corrosive atmospheres and liquids. They are not currently suitable for any Ex applications. Grommet options There are a number of membrane plug/grommet products available that offer good sealing up to IP67 that are very fast to use. As a grommet they are a push fit design both to install and to feed the cable through. Recent grommet designs will allow for a variety of cable and conductor widths. They are resistant to vibration and will provide for easy adjustment. They are not suitable for Ex applications or extreme heat and most don’t provide a great deal of cable retention force, unlike a clamped dome topped gland. There is a range of fast-fit grommet seals that clip into standard drilled and knockout holes that provide positive cable retention. The Klikseal from TST, for example, is moulded using two materials – a softer compound for the body/seal, and a stiffer inner material that applies positive clamping and cable retention. It will accommodate a few millimetres of wall thickness – self adjusting up to 5mm – and a range of cable diameters for each size. The added benefit of these designs is that they do not protrude far from the surface. Many contractors and OEMs are focused on reducing inventory and reducing overall line items, which is where these products really score. No tools are needed to fit them once there is a suitable aperture available, and the manufacturers claim they deliver a 90% time saving. Enclosure manufacturers have also developed junction boxes that are manufactured using dual materials, injection moulding a softer compound into the wall design so that it forms self sealing cable entries. These will generally take a range of cable sizes providing sealing up to IP65 for a cable that is simply pushed through the flexible membrane. More suited to indoor applications or instances where there is secondary protection available such as a control cabinet, these junction boxes can certainly speed-up installation and assembly, particularly when the enclosures arrive onsite pre-populated with terminals and breakers. One such product is a junction box capable of connecting two or three round profile cables via an integral connector block that features a similar sealing method to the dome top gland. It is moulded in one piece and hinged so that the threaded sections of the cable entries fold together. The cables are then inserted through a seal and locking cap and the cap screwed into position to complete the assembly. In conclusion, the humble cable gland can be a boon when it is specified correctly, speeding-up production and installation time, and a liability if it is wrongly specified. The consequences of a water leak into a junction box can be catastrophic, not just for the internal components, but more importantly for the process, building or machinery that relies upon that connection. MORE INFORMATION: Enter D285 or visit ‘latest issue stories’ at www.industrialtechnology.co.uk for further details from Hylec Components all areas fans and blowers for extraction, cooling, ventilation, aeration, vaccum and drying • Curved forward bladed centrifugal fans • Flow rates up to 4500m 3 /hr (2600CFM) • Pressures upto 15mBar (6in.SWG) • Reliable and robust • ATEX versions • Many configurations and add-ons ACI’s single inlet centrifugal blowers offer quiet, powerful air delivery for localised air movement. Ideal for high velocity where space to fit a fan is at a premium. Please contact us for further detailed specifications and to discuss suitability for your application. www.aircontrolindustries.com the solution providers for air movement problems Air Control Industries Ltd Silver Street, T: +44(0)845 5000 501 Chard, F: +44(0)845 5000 502 Somerset,TA20 2AE, UK E: sales@aircontrolindustries.com May 2008 • INDUSTRIAL TECHNOLOGY More details: Write in 290 on the free information card 29
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