Safe electrical installations

Richard W. Scott, Safe Electrical Installations in Atmospheres Containing Hydrogen, Chemical Engineering, pp. 79-82, March 2, 1964. 

Safe electrical installation To meet electrical classification imposed by conveyed materials and the surroundings. 

First, once designed, evaluated, and installed, the safety of the system cannot easily be degraded because the safety is in the design, not protection added afterward. In fact, the intrinsically safe electrical circuit will cease to fulfill the function for which it was designed long before it can become a hazard. This is due to the consideration which must be given to fault conditions. The only possible way for the circuit to become hazardous is if an unapproved or unauthorized component is substituted into the circuit. 

Figure 6.10 shows a typical example for a q-apparatus. It is a power supply for intrinsically safe electric circuits to be installed in zone 1 (and zone 2). The power input (at 24 V AC/DC level) is fed via flameproof plug-and-socket connectors to the apparatus. So, the power supply can be replaced under load without conflicting with the requirements of explosion protection. 

The inherent disadvantages of the underground system are high first cost, inconvenience, and excessive cost of maintenance. Overhead construction is often used since it can be installed at about one-third the cost of the underground system, and repairs can be quickly made. However, such lines are exposed to impairment by weather, lightning, trucks, cranes, and corrosion, so that overhead construction should be avoided in congested areas where a reliable and safe electrical system is necessary. 

Before expecting a change in safety culture, the physical workplace must be put in order. This includes the guarding of all machinery, the erection of handrails where necessary, and any other modification or repair required to bring the workplace up to compliance with safety legislation. The electrical installation must be safe, and all electrical switches and circuit breakers must be clearly labeled in a standardized... 

Colours play an essential safety role in giving information for use in tbe prevention of accidents, for warning of health hazards, to identify contents of gas cylinders, pipeline and services, the identification and safe use of cables and components in electronic and electrical installations as well as the correct use of fire-fighting equipment. 

When the Electricity at Work Regulations (EWR) tell us to ensure that all systems are constructed so as to prevent danger they do not tell us how to actually do this in a specific situation. However, the lET Regulations tell us precisely how to carry out our electrical work safely in order to meet the statutory requirements of the EWR. In Part 1 of the lET Regulations, at 114, it states the Regulations are non-statutory. They may, however, be used in a court of law in evidence to claim compliance with a statutory requirement. If your electrical installation work meets the requirements of the lET Regulations, you will also meet the requirements of EWR. 

The provision of a safe eiectrical system is fundamental to the whole concept of using eiectricity in and around buildings safely. The electrical installation as a whoie must be protected against overload and short-circuit damage, and the peopie using the instaiiation must be protected against electric shock. 

All electrical installations and installed equipment must be safe to use and free from the dangers of electric shock, but some installations or locations require special consideration because of the inherent dangers of the installed conditions. The danger may arise because of the corrosive or explosive nature of the atmosphere, because the installation must be used in damp or low-temperature conditions or because there is a need to provide additional mechanical protection for the electrical system. Part 7 of the lET Regulations deals with these special installations or locations. In this section we will consider some of the installations which require special consideration. 

In this chapter City Guilds asks us once again to look at a safe isolation procedure as a preparation for inspecting and testing an electrical installation. 

In this chapter we have looked at many different types of electrical installations and wiring systems. Most of this type of work is carried out alongside other trades as a part of the construction process. Electricians have an important part to play in any construction project. However, a construction site has the potential to be hazardous because of the temporary and changing nature of the building environment. We have looked at the common causes of accidents at work and how to control the risks associated with various hazards in earlier chapters of this book. To make your work environment safe always ... 

Ignition sources also result from improper installation of electrical equipment. Besides observing safe operating practices, the process plant operator should verify that electrical systems are properly installed and enclosed or are intrinsically safe. Such installation should always be in accordance with NEC codes and NEMA standards [11,12]. Instrument systems are covered in ISA standards and are discussed in Section 3.12. Other sources include ... 

A variety of raceways is available for distribution wiring. Rules governing the application and installation of raceways are discussed in various sections of the National Electrical Code. Adhering to these rules w l help assme a safe, reliable installation. 

Section 4 applies to persons in charge of premises where people work and who are not their employees. They must ensure that the premises, any plant (including the fixed electrical installation) and the means of ingress and egress are safely maintained. An obvious example of the application of this duty is a construction site where the main contractor is the person in charge and in control of the site and who is responsible, therefore, for ensuring that the site is safe for the subcontractors labour forces. 

Section 7 imposes duties of care on employees for their own and other s safety. They have to cooperate with their employer and anyone else to fulfil their obligations. An example would be when an electrician ignores the instructions and procedures put in place by his employer to work on an electrical installation once it has been isolated and made safe and, instead, carries out the work live. Such behaviour would probably be a contravention of section 7 and it is not unusual for cases to be brought before the courts when employees behave in this way and where somebody is harmed as a result. 

The Construction (Health, Safety and Welfare) Regulations 1996 were made on 14 June 1990 and came into force on 2 September 1996 to implement part of Directive 92157/EC and should be read in conjunction with the Construction (Design and Management) Regulations. There are no specific electrical requirements, but Regulation 17 states that plant and equipment has to be safe and maintained in a safe condition. This would include the electrical installation. Standards for electrical installations on construction sites are explained in Chapter 11. 

The principal contractor normally provides the temporary electrical installation. If he has an in house electrical department, he may well install and maintain the installation and, in such a case, he is responsible for its safety. The electrical staff member in charge of the site installation will exercise the technical responsibility. This official should ensure that the planned maintenance is done and that defects and breakdowns are reported and rectified immediately. Some main contractors hire the distribution equipment and arrange for the hirer to install and maintain it. As the occupier, they still retain responsibility for the safe use of the electrical installation, but responsibility for its maintenance in a safe condition rests on the hirer who should appoint competent, electrically qualified persons to do the work. 

There is often a demand for reports on the condition of tenants electrical installations in rented accommodation. This arises because some landlords fail to maintain the accommodation in a safe and serviceable condition and ignore their tenants complaints. In many circumstances such as this, a tenant will approach a local authority or solicitor for assistance in resolving the matter, and this will frequently result in a building surveyor or an environmental health consultant being asked to inspect the accommodation and to produce a report. If the tenant indicates that he or she has had electrical problems or suspects that the electrical installation is faulty, an electrical engineer will often be asked to inspect and test the installation and submit a report. 

Legislation dealing with landlord and tenant relationships does not have any specific electrical safety requirements however, if landlords provide an electrical installation as part of the rented accommodation (which will invariably be the case), they have a responsibility to maintain it in a safe and serviceable state. Failure to do so constitutes negligence, which is actionable. 

In the case of houses in multiple occupancy, the Housing (Management of Houses in Multiple Occupation) Regulations 1990 stipulate that a landlord has a duty to ensure that the electrical installation in the common and accommodation areas is in and is maintained in a state of repair and proper working order. It is a moot point whether this can be interpreted as requiring the installation to be safe. Local authorities who license such houses will usually require evidence to be produced to show that this duty is being satisfied before they will issue licences. 

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