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Special KABELSCHLEPP cable carrier chain for ATEX applications

A cable and hose management solution was needed for an automated drill rod handler on a Bauer deep drilling rig. Other than performance and ATEX-conformity, longevity and service life were of importance. A Kabelschlepp hybrid energy drag chain now delivers all requirements.

We all experienced static energy at some point. Step out of your car after a long drive, touch the door handle and get an electric shock. Often, sparks are visible proof of this static discharge. The cause of this is friction between different materials, such as clothing and car upholstery or of soles on the carpets, resulting in a static charge. These electrostatic discharges are only hazardous to men due to the shock reaction, but they can ignite flammable materials. This needs considering when handling liquids and gases.

This also applies to machinery, tools and equipment in industrial applications such as in civil engineering and mining, refining or chemical processing. Movement and friction create a static charge, and the inevitable discharge will have devastating consequences in oil or gas production. Bauer Maschinen GmbH knows this is only too well. In product development of deep drilling device, there are strict requirements for explosion prevention.

Safe abyss
The new generation deep drilling rigs TBA 200 and 300 were developed focusing oil and gas drilling, but also for future geothermal technology. For the latter, a load of 300 tons can be lowered to depths of 5,000 meters (16000 ft). For comparison, the average depth of the North Sea is 93 meters and 725 meters at its deepest. Because of the inflammatory nature of the operating environment that prevails in these applications in general, the design and development of drilling rigs needs to follow the ATEX Explosion Protection Directive. It basically applies for all assemblies and components used throughout a system. This includes the drag chain with electrical and hydraulic lines of the laterally mounted for the rod handling system. A fully automated manipulator feeds rods straight from (horizontal) storage into the drilling axis and the drive. As a result, manpower is limited to supervision. Work hazards are eliminated, and the difficult and dangerous work of derrick men above the top drive is no longer required.

The required electric and hydraulic feeds on the mast of TBA 300 are managed by a vertically fitted MC 1300 type KABELSCHLEPP drag chain. The previous solution of grouping hose and cable in festoon bags needed replacement to fast movements in operation, and the variety of lines to be handled. The MC 1300 chain was chosen as the inner height of 87 mm and the bespoke compartment width of 650mm "We now have hall cable and hose neatly organized and separated" explains Dreier, engineer in design and development at Bauer. Assembly and maintenance of components is easier and quicker. The chain easily manages the required operation speed of one meter per second without problems – according to Dreier already a high value for this type of operation, as it is designed for travels up to 5 m per second.

Reliable in any case
Whether desert climate in the Far East or permafrost in Alaska – for outdoor use in different environments, the multi-variable chain is designed for tough conditions on construction sites. A rigid link design makes it extremely robust, and it is equipped with an enclosed and dirt-resistant stop system.
This stability achieved by the combination of GRP side band and aluminum cross stays, also offering good conductivity to avoid excessive static charge.
The ATEX Directive stipulates that all components must have controlled discharge properties. To follow the directive, and essential for ATEX applications, the chain band is made of a special, conductive material. "If a cable chain is made of a material that does not allow controlled discharge the result was spark – for example by just touching a steel cable. In highly explosive environments, this can lead to a major accident, to be avoided in the first place." says Dreier. The special material for this design delivers the required properties while retaining the abrasion resistance and stability. This is particularly important for the TBA 300: it is not only more cable to handle, but also larger diameters. The result is higher loads on the chain, and the separators.

Apart form increased torosinal stiffness and conductivity, the properties aluminum cross stays reduce friction. Even if cables do have appropriate sheathing and modern plastics are less abrasive, aluminum by far copes better with heavy cable. In addition, KABELSCHLEPP´s diverse offering of stay and shelving systems covers includes hole stays (LG type). Enclosing cable and hose they feature identical advantages in terms of conductivity and stability as other cross stay designs. In a vertical application though they have the additional advantage of controlling the momentum. The hole stay pattern is designed to suit the OD of cable and hose, friction or twisting is impossible. Holding the media in the centerline of the radius, length variances hence movement and wear is avoided. Hanging cable and hose tends to elongate and needs readjusting from time to time. Bespoke strain relief on both ends with cable and hose clamps secure cable and hose.

Compared to loose lines, invariably subject to reduced service life and chafing due to the relative movements, the service life is extended to a maximum, and cost is prevented.

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