Cables mechanical protection

Even if the receptor by itself has high accuracy, the sensor may be unable to execute the measurement in a defined place. Quality and total accuracy depend on the combination of receptor, the converter for measured values, and mechanical protection. Mechanical protection can take the form of pockets in water and fluid and also assembly boxes which protect against pollution, humidity, and temperature in the surroundings or against electromagnetic transmissions and noise from power-supplied pipes and cables. 

Development work in the pilot-plant production of the vinyl ether intermediate was performed on a Mettler Toledo ReactlR MP m. This instrument was the hrst generation of explosion-proof manufacturing technology available from Mettler Toledo. Setup requirements for the incorporation of the ReactlR monitoring system into the vinyl ether process in the pilot plant were minor. Installation of a fiber optics cable and protective conduit from the pilot-plant operations area to the control room, allowing communication between the acquisition computer (contained within the ReactlR MP ) and the monitoring station, was the most extensive mechanical modification. ... 

If the protective conductor is a separate conductor, that is, it does not form part of a cable as in this example and is not enclosed in a wiring system as in Example 1, the cross-section of the protective conductor must be not less than 2.5 mm where mechanical protection is provided or 4.0mm where mechanical protection is not provided in order to comply with lET Regulation 544.2.3. 

PVC insulated steel wire armour cables are used for wiring underground between buildings, for main supplies to dwellings, rising sub-mains and industrial installations. They are used where some mechanical protection of the cable conductors Is required. 

Part 5 of the lET Regulations tells us that electrical equipment and materials must be chosen so that they are suitable for the installed conditions, taking into account temperature, the presence of water, comosion, mechanical damage, vibration or exposure to solar radiation. Therefore, PVC insulated and sheathed cables are suitable for domestic installations but, for a cable requiring mechanical protection and suitable for burying underground, a PVC/ SWA cable would be preferable. These two types of cable are shown in Figs 3.38 and 3.39. 

Ml cables are waterproof, heatproof and corrosion-resistant with some mechanical protection. These qualities often make it the only cable choice for hazardous or high-temperature installations such as oil refineries, chemical works, boiler houses and petrol pump installations. An Ml cable with terminating gland and seal is shown in Fig. 3.40. 

Where PVC insulated and sheathed cables are concealed in walls, floors or partitions, they must be provided with a box incorporating an earth terminal at each outlet position. PVC cables do not react chemically with plaster, as do some cables, and consequently PVC cables may be buried under plaster. Further protection by channel or conduit is only necessary if mechanical protection from nails or screws is required or to protect them from the plasterer s trowel. However, lET Regulation 522.6.101 now tells us that where PVC cables are to be embedded in a wall or partition at a depth of less than 50 mm they should be run along one of the permitted routes shown in Fig. 3.45. Figure 3.44 shows a typical PVC installation. To identify the most probable cable routes, lET Regulation 522.6.201 tells us that outside a zone formed by a 150mm border all around a wall edge, cables can only be run horizontally or vertically to a point or accessory if they are contained in a substantial earthed enclosure, such as a conduit, which can withstand nail penetration, as shown in Fig. 3.45. 

A conduit is a tube, channei or pipe in which insuiated conductors are contained. The conduit, in effect, repiaces the PVC outer sheath of a cable, providing mechanicai protection for the insuiated conductors. A conduit instaiiation can be rewired easiiy or aitered at any time, and this flexibility, coupled with mechanical protection, makes conduit installations popular for commercial and industrial applications. There are three types of conduit used in electrical installation work steel, PVC and flexible. 

Steel wire armoured PVC insulated cables are now extensively used on industrial installations and often laid on cable tray. This type of installation has the advantage of flexibility, allowing modifications to be made speedily as the need arises. The cable has a steel wire armouring giving mechanical protection... 

The cables are available with bare sheaths or with a PVC oversheath. The cable sheath provides sufficient mechanical protection for all but the most severe situations, where it may be necessary to fit a steel sheath or conduit over the cable to give extra protection, particularly near floor level in some industrial situations. 

MI cables are waterproof, heatproof and corrosion resistant with some mechanical protection. These qualities often make it the only cable choice... 

Mass market applications of SMP are foils for packaging and tubes for cables. When being heated these materials shrink and are able to adapt to virtually any shape, providing mechanical protection and insulation. Further examples for different fields of applications are illustrated in Fig. 3. Another early technical application of SMP was a choke system in automobile engines, which was applied before electronic fuel injection became affordable for mass application. Other technical... 

Cable jacketing affords mechanical protection during installation and service. Semiflexible cables typically are supplied with a jacket consisting of low-density polyethylene blended with 3% carbon black for protection from the sun s ultraviolet rays, which can degrade plastics over time. This approach has proved to be effective, yielding a life expectancy of more than 20 years. Rigid transmission line has no covering over the outer conductor. 

One way to improve the efficient use of premium duct space is to subdivide the ducts using bundles of miniature ducts, each one of which can house a separate mini-cable. Because the primary source of locomotion for such installations is the force of a high velocity fluid acting on the cable jacket, the forces placed on the cable during installation are minimal. The ducting also provides additional mechanical protection for individual cables and isolates them from one another. For such applications, the size of the... 

Polyesters in wire and cable applications include Hytrel (Du Pont), a thermoplastic polyester elastomer for the offshore industry Kapton (Du Pont), a polyimide film offering weight saving and chemical resistance and Mylar (Du Pont), used in primary insulation, shield isolation, chemical barrier, and mechanical protection. 

Ethylene-Propylene-Diene Terpolymer (EPDM) is used for weather protection, tire sidewalls and coverstrips, wire, cable, mechanical goods, sheeting, hoses, tubing, and plastics modification and TPO. EPDM can be modified with silicone to reinforce high temperature performance of silicone and mechanical and physical strength of EPDM. Maleated EPDM (0.5 to 1.0%) is used to toughen nylon (impact modifier of nylon) and polyester thermoplastics (impact modifier for polycarbonate and polyester/carbonate alloys, PVC). Typical EPDM recipes are... 

Heat loss from the reactor coolant segment must be minimized in order to minimize loss of power and to avoid excessive temperatures for nearby electronic components, cabling, mechanisms, and other components which would benefit from lower temperatures. In order to accomplish this, effective multi-layer insulation must be demonstrated to satisfy isolation requirements at high temperatures and elevated radiation levels. Further evaluation would be necessary to assess the degree of micrometeoroid protection provided by the multi-layer insulation. 

A single or multicored plastic-coated cable of the type NYY or NYY-O is used as the connecting cable between a protected object and an anode in soils and fresh water, and particularly in seawater, medium heavy or heavy rubber-sheathed connections of an NSHou or NSSHou type are used. Heavy welded connections of type NSLFSou are used for severe mechanical loading. In addition to these, for ships, marine cable of type MGCG or watertight cables must be considered. 

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