Flexible conduit systems can provide a proven safe and cost effective protection solution for cabling installed in explosive atmospheres. Better safe than sorry is a sensible approach, but make sure that you are not fooled into unnecessarily expensive options warns Tim Creedon, Sales and Marketing Director for Flexicon.

Explosive areas exist where a flammable mixture of gas and air or dust and air exist in large enough quantities and for long enough. If an ignition source exists then there is a real danger of an explosion.

Naturally we all think of the oil and gas industry in such situations, but there are a surprising number of other industries where explosive atmospheres could exist such as in building and construction, transport, marine and defence, food processing, water treatment and power generation to name but a few.

Wherever possible it is important to minimise the risk of explosive mixtures forming and/or prevent the risk of ignition. Where this is impossible or impractical then you need to consider providing protection.

Any electrical installation in such an environment is a potential source of ignition. The degree of protection any equipment requires depends to a large extent on the risk of an explosion occurring in a given area.

To understand the level or protection required, you must understand the nature of flammable mixtures and ignition sources and also how different zones are classified depending on the level of risk.

Gases are classified into 3 groups with group A being the least explosive and group C being the most. Equipment classification is from T1 to T6 according to the maximum allowed temperature resulting from the ignition temperatures of the gas/air mix. It is important to remember that certain fine dusts dispersed in the air can also be explosive.

Hazardous Zones

The above table shows the zone designations, which are divided first into the hazardous areas for gases, vapours and mists and secondly into the hazardous areas for dusts. It also shows their risk categories, i.e according to the probability of a risk being present.

Assuming that the electrical equipment is correctly specified, it is important not to overlook any cabling that connects into it.

Until recently those specifying cables for such areas had to select from the products offered by various cable manufacturers. In addition each individual cable needed a flameproof gland, which added to both the cost and the time needed for installation.

Such cables could also be difficult to terminate and, if a number need terminating in an enclosure, could necessitate the specification of a larger enclosure.

The development of flameproof ATEX and IECEx approved barrier glands for flexible conduit means that you can use liquid tight conduit systems in hazardous areas without compromising safety.

There are a number of ways of classifying protection techniques used to address hazardous zones. Most glands are classified as Ex d or Ex e.

An Ex d classified gland forms a flameproof or explosion proof barrier – they are strong enough to contain any explosion or fire that may occur. An Ex e classification is defined as ‘increased safety’.

If something is classified as Ex d then it can also be used for Ex e applications in Zone 1 and Zone 2 areas for gases and Zones 21 and 22 where explosive dust may be present. In most cases such glands do not add to the temperature of the enclosure into which it terminates, so it can be used with all temperature classes.

By using Ex d glands with liquid tight conduit, you can group several cables together into one system. The conduit provides protection for all of these cables and, if correctly selected, offers all the necessary mechanical protection for a given application.

So, for example, by using steel cored armoured metallic conduit you might be able to use standard cables instead of more expensive SWA specialist cables. In this example one braided conduit effectively takes the place of several more expensive braided cables. It also means that only one flameproof barrier gland is needed, rather than several.

This single termination, instead of the multiple terminations that would be needed with individual cables, limits the risk of the enclosure integrity being compromised since there is only one point of entry. Using a flexible conduit system also provides additional mechanical protection for the cables.

It is worth pointing out at this stage that it is the flameproof gland that is rated at Ex d so that if there were an explosion within the electrical equipment enclosure it would be contained. Some conduit manufacturers have in the past muddied the waters and inferred that the conduit is also classified as Ex d and been able to charge a premium.

The role of flexible conduit in any application is to protect cabling so you should take care in its specification. This is even more important in hazardous areas since you want the installation to remain safe throughout its lifetime, not just once the system is installed.

Fortunately when you specify the correct barrier gland, you can effectively use a liquid tight flexible conduit for the vast majority of applications.

There are a number of different types of liquid tight flexible conduit that are suitable for both indoor and outdoor applications.

With this in mind the specifier needs to conduct a thorough risk assessment of all of the hazards potentially faced by the conduit in addition to the explosive atmosphere.

From this risk assessment they can then accurately specify the most appropriate liquid tight conduit for the project. As an illustration Flexicon has eight different grades of liquid tight conduit which, between them, would suit most applications.

Other environmental factors

If conduit is left in an exposed situation, it could be crushed or there is a chance that something could be dropped onto it. For such applications you should specify conduit with an adequate compression and/or impact strength.

Other factors that you may need to consider when selecting the correct conduit might include: extremes of temperature, EMC screening requirements, moving equipment, abrasion, resistance to chemicals or corrosion and UV resistance for external installations.

Note this list is not comprehensive, hence the need for a full risk assessment. If you have any concerns then most manufacturers should be able to advise.

A great deal of attention has been paid to hazardous area equipment. Do not forget cable protection and electrical lugs.

For more information on our range of Flexicon flexible conduits, please contact our Sales Team.

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In our last blog post, we looked at the requirements of the BS7609 code of practice which covers the installation and inspection of uninsulated compression connectors for power cables with aluminium or copper conductors.

However, there is more to simply following these engineering guidelines to achieve the ‘perfect crimp’.

There is more to crimping a cable than simply affixing a lug to the conductor. The BS7609 standard highlights the code of practice for installation and inspection of uninsulated compression and mechanical connectors for power cables with copper or aluminium conductors.

Conductor Type

Although a lot of focus is given to the crimp lug, die sets, tooling and crimp operation, thought should also be given to the cable and conductor. Even if the best quality electrical lugs and crimping procedures are used, the termination can still fail due to the conductor. Make sure the conductor used is both third-party approved and appropriately marked.

ETS support the work of the Approved Cables Initiative (ACI) Code of Practice in fighting the use of faulty, counterfeit and non-approved cables.

Cable Lug Current Carrying Capacity

The lug should have equal or greater current carrying capacity to that of the conductor. Using lug that have been manufactured with high purity, electrolytic copper allows the maximum level of conductivity with minimal resistance.

Lug manufactured from thin wall copper tube have the potential to cause elevated temperatures when used on conductors carrying high current levels.

Crimp Tooling

Care should be taken to ensure crimp tooling is kept in good working order. The crimp tool should regularly calibrated and serviced when required. All tooling and equipment should be checked for damage or wear before use. To help prevent damage to die sets and tools, they should be stored in the recommended way. E.g. Protective storage case.

Our maintenance guidelines to keep your hydraulic crimping tool in good condition highlight how to keep your tool in top condition and maximise it’s working life.

Die Selection and Number of Compressions

We supply full die set selection charts with all our standard, Cembre and Prysmian lugs. Referring to these guides allows you to match the correct tool, die set and lug, providing the best combination to achieve the best possible compression.

Always follow manufacturers guidelines concerning number of compressions per lug and in which sequence, to assure the performance of the termination after crimping and avoid distorting the lug.

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There is more to crimping a cable than simply affixing a lug to the conductor. The BS7609 standard highlights the code of practice for installation and inspection of uninsulated compression and mechanical connectors for power cables with copper or aluminium conductors.

The purpose of this code of practice is to give guidance to manufacturers and electrical contractors who use compression connectors and terminals to enable cables to be terminated in a safe, consistent and efficient manner following good engineering practices.

The following steps provide simple instructions on how to crimp a cable lug to BS7609.

How To Preform The Perfect Crimp?

1. Choose a supplier that provides crimp tooling, die sets and cable lugs which are compatiable and designed to work together to give the optimum crimping performance.

2. Each lug/terminal should have a reference clearly marked on the palm or barrel which enables the user to easily verify that it is the correct size and type for the conductor it is due to be used on.The crimp lug should also feature the manufacturers name or logo to enable the use of the correct tooling and die set, which can be selected from their published die set selector charts.

3. Prepare the aluminium or copper conductor for crimping by stripping back the insulation to a length equal to that of the lug barrel. This ensures that no insulation can be trapped in the barrel of the lug when assembled.

4. Insert the conductor into the terminal barrel. If applicable, use the inspection hole to check the conductor is fully inserted.

5. Perform the crimp paying careful attention to the positioning of the die on the barrel and, if multiple compression actions are required, in which sequence they should be performed.If using a hydraulic crimping tool, making sure the correct tool is used with a compatible die set is vital. Care should also be taken to keep the tool well maintained, working properly and has an up to date calibration certificate. More information can be found in our hydraulic tool maintenance guide.

6. Once the crimp(s) have been performed, check the completed termination for:

a) No insulation is trapped in the barrel

b) Check the inspection hole to confirm the conductor has been fully inserted

c) Over-crimping – make sure the barrel is not over crimped causing excessive stress on the conductor and flash or burrs on the lug

d) Under crimping – No air voids should be found between the strands of the conductor. They should be tightly compacted to ensure maximum performance

Over Crimped and Under Crimped Lugs

The below image shows an under crimped lug (left) and an over crimped lug (right). Both these incorrectly crimped terminals can cause overheating and ultimately lead to termination failure or fire. The over crimped lug is easily identifiable by the ‘ears’ or ‘wings’ of created on the barrel of the terminal. The under crimped lug is identifiable by inspection of the lug and conductors.

	Under Crimped Lug
	Over Crimped Lug

For more information on our range of hydraulic and battery powered crimping tools, please contact our Tooling Department.

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When specifying products for use within harsh environments, choosing the correct materials is vital. For example, in offshore oil and gas installations, equipment experiences exposure to high levels of seawater and salt-spray, which are highly corrosive due to the dissolved chlorides within. Offshore installations are not the only projects that experience harsh, corrosive environments, other corrosives that affect a wide range of industries include: chlorine, ammonia and hydrochloric acid.

In May we reviewed the effects of galvanic-corrosion between two dissimilar metals, in that example we explored the use of stainless steel cleats with galvanised steel support structures. Corrosion can take many different forms and choosing the correct materials and finishes is key to minimising its effects. We have outlined common corrosion control methods, explaining how and where they should be implemented.

Choosing materials based on their galvanic characteristics

Different metals have different electrode potentials, therefore when two different metals are electrically connected in the presence of an electrolyte, such as seawater, the more active metal will become anodic leading to loss of electrons and increasing oxidisation in a process known as galvanic-corrosion.

Metals and alloys are ranked in order of noble to active, in what is called the galvanic series. A more noble metal, such as stainless steel, will have much better corrosion-resistance than a more active metal such as cast iron.

Galvanic Series of Metals

Galvanic corrosion can be controlled and minimized by selecting metals in similar positions within the galvanic series. A more active metal can also be used as a sacrificial anode, attracting corrosion in order to protect the more noble metal from corrosive attack. Alternatively, depending on the installation, a cleat separation washer can be installed between the dissimilar metals increasing the distance between each metal and removing the electrical and physical contact points, critical to causing corrosion.

Passivation

During manufacturing, certain metals form a layer of metal oxide on the surface in a process known as passivation. Although the process occurs naturally, it can be enhanced through chemical passivation treatments and anodising. The layer protects against corrosion as it is tightly bound to the surface, preventing further penetration of oxygen and corrosive molecules.

The most common examples include aluminium and stainless steel. Usually, if these metals are damaged the layer reforms quickly, however this process is not without its faults. Pitting corrosion can occur in aluminium when chloride ions interfere with the reforming process and high chromium carbides can affect welded stainless steel.

If the products are properly selected for the intended application, passivated metals can provide high levels of corrosion-resistance. This is why stainless steel cleats are the preferred product within offshore installations.

Protective Finishes and Coatings

Various protective coatings can be applied to metals to help shield metallic surfaces from the surrounding environment, including epoxy power coating, oven-baked enamel, hot-dipped galvanisation and PVC-type coatings. Care must be taken when installing products with these coatings as any damage during installation and fitting, drilling and cutting etc. must be re-protected to ensure the integrity of the rest of the coating.

Hot-dipped galvanised products offer two forms of protection as the zinc coating protects the surface of the steel and becomes a sacrificial anode if damaged.

Non-metallic components

In highly corrosive environments, where metals are not suitable due to high levels of corrosion, non-metallic products are commonly being specified as an alternative. It is important to remember that plastics are not completely impervious to chemicals and often suffer from UV exposure, which should be taken into consideration when specifying project materials.

The possibility of corrosion may not be at the forefront of material specifications and in times of economic hardship, may be over looked. However, with the World Corrosion Organisation estimating the annual cost of corrosion, throughout all industries, at $2.2 trillion, it truly is a global issue. We believe any short-term savings made from overlooking the extensive effects of corrosion will be more costly in the future and the figure from the WCO backs this up.

If you are concerned about potentially corrosive environments affecting products you may be specifying, we are able to offer expert advice on the best product to suit your specific requirement.

Have you had any experience with corrosion and would like to share your experiences then please leave a comment below. Learn more about our offer of electrical lugs.

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In recent years there has been a large influx of European switchgear. This has often lead to confusion about the type of switchgear being used and the switchgear bushing to which the cables are to be terminated.

Correct cable terminations

This has led to the discovery of conventional heat shrink terminations being used incorrectly in instances where the bushings were compatible with CENELEC style separable connectors, E.g. Pfisterer CONNEX and Euromold connectors. This can lead to delays on site in sourcing the correct cable termination type, not to mention the practical difficulties and increased costs in re-terminating the cables.

Specify the correct equipment

One of the ways to avoid this issue is to cross check the cable termination specified with a database of equipment manufacturers, ensuring that the termination type sourced is completely suitable for your switchgear bushing. This can be a lengthy process if the relevant information isn’t readily available.

Therefore, ETS Cable Components are able to offer this service using our expansive database of switchgear and bushing equipment and equipment manufacturers to insure the correct equipment is matched at tender stage.

The advantages of this bushing selection service being:

• Correct costs for termination materials.
• Compatibility with the cables being used.
• Accurate installation costs.
• Reduction in lost time on site.
• Happier clients!

Switchgear Familiarisation Training

Additionally, we are able to offer familiarisation training for your installation team, on-site support and the technical expertise you would expect from one of the UK’s leading cable accessory distributors.

Please contact Nick Timms for more information on sourcing the correct terminations and connectors.

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