Power Cables - Cable glands: slipping through the safety net


Largely regarded as an everyday consumable for electrical contractors, you could be forgiven for choosing price over quality when it comes to cable glands. How different could one gland possibly be from another? The answer is dangerously different. With cheap, substandard imports flooding the market and no industry body regulating them, there is a growing need to raise safety standards in this area. Here, Clive Haley, category manager for Newlec cable management at Newey & Eyre explains the real cost of buying inferior cable glands

With safety still very much a top priority on the public agenda, the electrical industry has been hit by a raft of legislation in recent years to raise standards within the sector. Part P of the Building Regulations was introduced in January 2005 to reduce the risk of death and injury caused by electricity or fires started by faults in electrical installations, which account for 30 per cent of all electrical accidents. More recently, the 17th edition of the IEE Wiring Regulations (BS 7671:2008) has been introduced, comprising of an even stricter regulations book that extends to over 400 pages.

Despite an array of rules and regulations permeating the industry, there is still one product area which can significantly impact the quality of electrical installations and yet continues to slip through the safety net - cable glands.

Although the British Approvals Service for Cables (BASEC) has been set up to approve and monitor cable standards, there is still no such industry body for glands, leaving them vulnerable to poor quality products. Following the recent surge of cheap, foreign and potentially highly-dangerous imported cable glands into the UK market, this should in itself present a massive cause for concern. Surprisingly then, there is still a commonly held belief in the industry that cable glands aren't really that important.

Unaware or unconcerned these products are covered by European legislation, meaning supplying any that do not comply with the relevant standards is punishable by large fines or even imprisonment, some wholesalers are supplying these cheap imports to be more price competitive.

Worse still, some contractors are often too busy concentrating on high value items such as cable, to focus on the quality of the cable glands. Many assume when it comes to cable glands, ‘brass is brass' and all products are seemingly the same. In reality however, the difference can be quite astonishing.

To understand why the price of this low cost item can vary so immensely, we need to look at the wider picture. Being a globally traded commodity, the cost of quality extruded brass; the predominant component of cable glands, around the world is similar. Therefore, to get around this level playing field the very low cost products are generally manufactured from what is known as ‘honey' brass - melted down scrap, mixed with other materials and re-cast into lengths to be worked on by manual machines. While good quality brass is a strictly controlled alloy of mainly copper and zinc, in proportions detailed in EN12168, this ‘honey' brass typically has a poorly controlled amount of other metals and impurities. This means that although the resulting metal has a deceivingly ‘brass-like' appearance, its properties and performance will be very different to true brass.

With the primary factors affecting the safe performance of cable glands being the integrity of their mechanical design and the quality of materials used in their production, the inferior and impure way in which these recycled brass versions are produced undermines the design strength of the product, which in turn carries massive implications for the integrity of an electrical installation.

Concerns surround the quality of brass being used to manufacture the glands. Brass can be affected by exposure to salt water and certain chemicals and the result is that some of the zinc leeches out of the alloy, a process also known as de-zincification, which can reduce the strength of the gland. While glands made from a true brass alloy are strong enough to withstand any reduction in strength (and can be nickel plated if the lifetime exposure is expected to be extreme), those made using low grade brass are much less able to withstand the de-zincification process. They can become brittle and break, or can become detached affecting the earth continuity, both of which can cause an installation to completely fail. Furthermore, because they are typically manufactured with the minimum amount of metal in them, the range of armour sizes that they can grip is usually less than a good quality gland and there is a high risk of shearing threads when tightening them.
Other problems with these cheap imports include the degradation of seals over time. Sealing materials can vary greatly in their ability to withstand attack from airborne pollutants and environmental elements, and an effect known as ‘compression set'. This is where the seal material is compressed for long periods. If it suffers from compression set then it will eventually take up its compressed shape, which means that it is no longer exerts a sealing force against the cable. While reputable manufacturers will have tested their seals to prolonged exposure, inferior products made using low grade materials are more prone to compression set and can become weak, especially when installed outdoors, making them liable to fail.

In addition to the various safety implications of failed electrical installations, there are also return visits for maintenance for the contractors -  due to the difficult nature of locating them, replacing failed glands can take anywhere up to half a day's work to repair. In addition, there is the inconvenience inflicted upon the end-users.

Another consideration is liability. In a society which is ever more driven by a ‘blame culture', traceability is increasingly important. Should poor quality products be to blame for an accident or fatality, the consequences will be serious, as ultimate responsibility lies with the contractor, rather than a product which was ill-chosen for the application - not a good recipe for business success in an industry where reputation is everything.

Unfortunately, a visual comparison of cable gland products will reveal very little difference in quality, which is why control is difficult. This is why specifiers should verify the quality of a cable gland by confirming it (or its packaging) is CE marked, stamped with the manufacturer's name or logo and sourced from a reputable manufacturer. It is illegal to supply product without the CE mark and if the manufacturer is not identified any traceability ends with the installer or supplier.

Based on the European standards, principally BS6121 and BS: EN 50262, most premium manufacturers use the latest techniques to ensure that cable gland products reach installers in peak condition and offer superior performance. In meeting the tests contained within the standards, these glands ensure a sufficiently robust design; able to withstand continuous shearing forces at the point of entry into the product, and that the cable is adequately retained by the gland's seals and/or armour clamp.

Going forward, a more serious approach to cable gland specification needs to be adopted. It is no use paying careful attention when selecting the high value products for installation and then undermining the safety of the entire project by overlooking cable glands quality. Cable glands form part of a system and the wrong choice of product can result in the whole system failing, not to mention the incalculable damage to an installer's reputation and the cost of repairing the actual job. Only by assessing the quality of their cable glands can contractors fully and confidently guarantee the quality of their work and protect themselves and their business.

Newlec offers a wide range of quality, fully tested, CE marked cable gland kits produced by a British manufacturer. All Newlec cable glands are made from brass manufactured to comply with EN12168. With over 20,000 product lines in stock at any one time, Newey & Eyre holds more major brands than any other electrical wholesaler. The company is also well known for its specialist expertise and ability to quickly source rare or unusual electrical items from around the world.