Portable apparatus

Tafe plots The linear part of the anodic or cathodic polarisation log-current and potential plot is extrapolated to intersect the corrosion potential line ". Low corrosion rates can be measured relatively quickly. Note that resultant oxide films may be of different composition from those occurring in practice owing to the several decades of current applied which may not relate to actual plant practice. Portable apparatus including computing facilities is commercially available for plant testing. 

Cross-linked wre and cable, foam tubing, weather protection, and moisture barriers (e.g., powercable, building conduit, portable apparatus building control, instrument, shipboard, automotive, marine appliances, insulation of heating tubes)... 

FIGURE 53.5. GC-MS data of portable apparatus, Hapsite. Left total ion chromatogram right electron ionization mass spectra. GB, GD 1 mg/m GA 3 mg/m HD 0.5 mg/m. IS internal standard. 

Figure 12.4 Miniature size X-ray generator and detector. These probes are used with portable apparatus though their control modules or power units are nevertheless more bulky (reproduced courtesy of Amptek Inc.).

Circumstances of the accident One day in Autumn 1993 Rhys was participating in a gymnastics lesson when he fell from a ladder supported by a fixed and portable apparatus frame and broke his arm. At the time, Rhys was performing what is known as a low impact movement, which involved climbing the apparatus. The medical report indicates that when climbing the ladder Rhys s hands were somewhat slippery and he slipped off the climbing ladder. Rhys claims that he was at the top of the ladder and intended to climb over the top of the frame to the other side. Mr C claims that the general policy is that children do not climb over the top of the frame because of the wires. 

The British pendulum was designed with the aim of providing a low-cost and portable apparatus for stationary measurements of slip/skid resistance of a surface in the field or in the laboratory. This test method provides a measure of frictional property, micro-texture in particular, of surfaces and may be used to determine the relative effects of various polishing processes on materials or material combinations. 

Tests to measure the bond which can be obtained with the concrete of the structure to be strengthened are best carried out on the structure itself. A possibility is to utilise a pull-off test as developed for the non-destructive testing of concrete(21). A circular steel probe is bonded to the concrete surface and specially designed portable apparatus is then used to pull off the probe, along with a bonded mass of concrete, by applying a direct tensile force. Any defects in bond would be revealed by the occurrence of failures at the adhesive-concrete interface. 

A portable apparatus has been developed for the determination of chloride in water (0.001%) by precipitation with silver labeled with "Ag. A rapid and routine method for the determination of sulfate in soils is based on its precipitation with barium salt labeled with... 

Portable apparatus should be controlled by efficient means, or easily accessible, within reach and near the apparatus for cutting off the electricity supply. For 240 V tools the plug itself, if it can be pulled out of the socket easily enough and without danger, will meet this requirement. However, for voltages above 240 V an isolating switch will be required. 

It is essential that portable apparatus is properly maintained, with the earth core of the flexible cable and associated earth connections being tested regularly by a competent person using a substantial current (special test sets are available) to ensure continuity and strength of the earthing. 

Apparatus of the double-insulated or all-insulated types need not be earthed provided it complies with the Electricity Regulations 1908 (Portable Apparatus Exemption) Order 1968. This order, in exempting such apparatus from the earthing requirements, makes it a condition that the apparatus is clearly marked (i) with maker s name, model and type number (ii) with an indication that it has been certified, by an approved body, as being apparatus conforming to the approved standard for such apparatus. It is also a condition that the insulation of the apparatus is maintained so as to prevent danger. ... 

Additional back-up protection can be provided by residual current devices that ensure that in the event of an earth fault the current is cut off before a fatal shock is received. This form of protection works on the principle of monitoring any differential between (i) the current entering a circuit to supply power to the portable apparatus and (ii) the current returning to the supply point. For normal safe operation this current differential is zero but if there is a fault, such as leakage to earth, a differential current occurs which the device rapidly senses, tripping its contacts to cut off the supply to the apparatus. 

Electricity Regulations 1908 (Portable Apparatus Exemption) Order 1968 620... 

Portable apparatus may be of Class I construction, in which case the metalwork is earthed by a protective conductor which is a separate core in the flexible supply cable, or it may be of Class II construction, having no protective conductor terminal as its metalwork is not earthed. The essential safety feature of Class II apparatus is that the basic insulation is supplemented by additional insulation to provide a further safety barrier and danger arises only if both insulating layers fail. There are two types all insulated where the supplementary insulation is a plastic case, and double insulated where there is a metal case but live parts are separated from it by two layers of insulation. It is not advisable to use enclosed ventilated Class II apparatus in wet environments, because moisture may penetrate and provide a conductive film between the touchable surfaces and internal live conductors. 

Regulation 471-08-03 refers to locations where the installation supplies fixed equipment outside the equipotential zone, e.g. an outside motor-driven pump for a garden fountain, and the equipment has exposed conductive parts. In such cases. Table 41A applies and the maximum interruption time is 0.4 s for 230 V equipment. 230 V outdoor portable apparatus, such as an electric hedge trimmer, requires sensitive RCD protection see Regulation 471-16-01. There are similar protection requirements for circuits in locations of enhanced shock risk such as those in Part 6 see Regulation 471-08-01. 

Regulation 553-01-07 is a plea to avoid the tripping hazard of long, flexible cables and cords trailed across the floor. As portable apparatus may be used anywhere, socket outlets need to be fairly closely spaced, and where there is much portable apparatus to be used at one location, multi-way socket outlets are preferable to the use of adapters. 

The Regulations do not cover locations outside the equipotential zone. In such locations it is suggested that it should be possible to separate livestock from mains voltage electrical equipment or use SELV apparatus operating at not more than 25 V a.c. or 60 V d.c. Where persons only are at risk, the SELV voltages may be increased to a maximum of 50 V a.c. or 120 V ripple-free d.c. Users of mains voltage portable apparatus should be protected by a sensitive RCD, and Class II apparatus is to be preferred. 

There is only limited use of Class II equipment in the fixed installation because in most cases it has to include the protective conductor for use elsewhere in the circuit to connect Class I equipment and this usage negates the Class II classification. Class II is more prevalent in portable apparatus. Protection by non-conducting location is not much used in the UK except for special locations such as test facilities. Earth-free local bonding, again, is used only in special locations where the necessary precautions can be taken to avoid importing an earth. Electrical separation s main application is also in electrical testing areas. 

The safety philosophy is based on dividing the site installation into two distribution systems the 400/230 V system where there is a comparatively high shock risk because the voltage to earth is 230 V, and the comparatively safe 110 V system where the voltage to earth does not exceed 64 V. The 400/ 230 V system is intended to be installed and maintained only by authorised and competent persons, i.e. those who are electrically qualified. The construction workers role is confined to operating the distribution equipment, which is metalclad, weatherproof and earthed. The portable apparatus which they constantly handle is all connected to the llOV system (see Fig. 11.1). 

The term intrinsically safe applies to the apparatus and to the circuit in which is connected. It is normally associated with instrumentation circuits and some portable apparatus. This type of equipment may arc or spark... 

BS 7671 specifies that d.c. test voltages should be used for insulation resistance tests, and that the minimum acceptable insulation resistance values should be in accordance with Table 17.1. The instruments used should be capable of providing an output of not less than 1 mA. For installations designed to operate at voltages up to 500 V, e.g. those connected to the 400/ 230 V public supply and the 110 V systems supplying portable apparatus, a 500 V d.c. insulation tester is adequate and suitable for the prescribed test. A 1000 V tester should be used to test systems over 500 V up to 1000 V. Large installations should be tested in sections, each of not more than 50 outlets. An outlet, for example, consists of a lighting point, a switch or a socket outlet. 

Between inspections, some equipment will become defective and may become dangerous so the users should be encouraged to look for and report such defects as soon as they are aware of them, preferably as part of a pre-use inspection. They should cease to use the equipment imtil the defect has been repaired. Portable apparatus with flexible cables and plugs is more likely to be damaged than fixed equipment. It is also more likely to be hazardous to the user, who should be reminded periodically of the danger and the need to report incipient defects before they become dangerous. 

Work is being carried out on new on-line monitoring systems of CP effectiveness. The start of production by some firms of complicated portable apparatus for electrochemical investigations, allowing measurements in field conditions, should be mentioned. The SOLARTRON SI 1280 corrosion monitor and Gamry Instruments apparatus can be mentioned here. The development of apparatus in this direction holds... 

For surveys, a small portable apparatus weighing less than 10 kg is convenient. Images provided with such an instrument are excellent in spite of the small size. 

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