The effectiveness of a cable connection is often dependent on the quality of the cable gland. Also known as a connector or fitting, cable glands are devices that attach the end of an electrical cable to its equipment. Its purpose is to provide a secure connection. The connection depends on the type of cable, since it is specifically designed as per the type. It will also provide for armour or sheath of the cable.
Cable glands are commonly found in industries that deal with instrumentation or automation. Cable glands are made of different types of metals like steel, aluminium and brass. Of these brass cable glands are the most preferred because of the unique properties of brass.
Selecting the Right Cable Gland
Cable glands are responsible for the secure connection of the cable to its instrument. The strength of the connection has a direct impact on the quality of the quality of the transmission. In instrumentation and automation industry this is a critical aspect because without a high quality gland connection, the entire product can fail to perform no matter how superior its design and production. This small device is crucial to create a secure and high quality transmission.
So, it’s important that the cable gland is selected carefully. There are no one size fits all when it comes to cables. There are multiple factors that determine the most suitable gland. This selection should be done at the planning stage. Here are a few pointers you can follow:
Type of cable
Since all cables are not the same, their attaching gland cannot be the same. The type of cable is the most important factor when selecting the gland. So, you have to start by identifying the type of cable to be used. Every facet matters here. So, check its construction, diameter, material properties and size. For instance, glands for armoured cables are different from unarmoured cables. This is because an unarmoured cables typically has no seal. In rare cases it may have a single seal. Armoured cables, however, have extra seals for protection. This changes its construction and gland requirement.
The construction of the cable is very important. To select the right gland we have to understand the cross-section of the cable that attaches to the gland. For instance, is it screened or braided? Only a good fit will ensure a secure connection. Details like diameter of the inner bedding or the lead covering and the type of the armour or shield have to be considered.
The effectiveness of the gland also depends on its working environment. Factors like space availability, electromagnetic disturbances and the environment are very important. Cable glands are available in indoor, outdoor and weather proof categories. Space restrictions means that we have to select a gland that can fit in small space.
A high requirement to screen electromagnetic disturbances require special brass cable glands. Similarly, other conditions like presence of water and dust will again change our requirements. We can find cables suitable for wet conditions that are able to withstand water pressure. Cables used in hazardous areas have to contain additional protection. Where the cable is likely to be used in a corrosive environment, special protective plating should be considered.
Cable glands are often bought as per the accessories offered and as a result, most manufacturers have all the standard add-ons. These are provided either separately or as part of the cable gland package. Accessories include sealing washers, earthing washers, locking washers, lock nuts, clamping modules, earth tags, shrouds, adapters and reducers and stopping plugs.
Like location, the application is also crucial. We have to decide beforehand how the instrument will be used, since it will have a direct relevance on the type of gland. For instance, if we need cable glands for complicated instrumentation, it should be able to deal with electromagnetic disturbances.
Cable glands are not very expensive, but their cost can vary. Additional accessories like extra protection, stopper plugs, addition of entry thread sealing washer and earth tag can drive up the cost. When designing an equipment, the cumulative cost of all the brass cable glands can be a significant factor. However, keep in mind that certain additions are critical for the overall functioning of the instrument and should not be compromised with.