Cable labelling

Effective labelling of electrical cables and equipment is one of the many practices that contribute to complying with the regulations.

Electrical equipment, wherever possible, needs to be physically identified. Labelling circuits and equipment is part of that process, although all labelling needs to be verified before maintenance work begins by checking it against drawings, diagrams and other written information.

In locations where a range of different services are distributed, labelling is essential in order to conduct maintenance without the potential for confusion or the risk of interrupting the supply of another service. Fixed wire circuits need labels at the following points and equipment within an installation:

• at the origin of every installation;
  
• where different voltages are present;
  
• at earthing and bonding connections and residual current devices.

  With a multitude of cables present in large, industrial environments, positive identification is vital, especially when cabling runs between locations.

Aid to record keeping
In terms of testing and inspection, adequate records need to be kept and labelling can assist this by relating each piece of equipment to a documented test and maintenance record. A securely attached label ensures that a test and inspection history can be verified.

For contractors applying for enrolment with the National Inspection Council for Electrical Installation Contracting, various standards need to be met. A common reason for deferment of an application following inspection of an installation is the lack of a verification system in place. An example of this may be that labels have not been provided to show the purpose of switchgear, control gear or other means of control, resulting in the possibility of confusion.

Writing a label with an indelible pen is still the most common method of identification. But there is no guarantee that another contractor will be able to read it. This issue adds time to the job, as the handwritten identification cannot necessarily be trusted and testing of the equipment is required before any work can take place.

Electronic labelling
For a professional approach to identification, and maximum effectiveness in terms of health and safety, an electronic labelling machine is the best solution.

Research by electronics manufacturer Brother – producer of P-touch electronic labelling systems – has identified important needs for installation professionals.

For on-site labelling, machines need to be durable and simple to operate.

A rubber grip design, belt clip and holster are all considered to be key elements in a hard-wearing and highly portable machine. The tapes used by the labelling system need to be flexible for wrapping and flagging, plus a rotate printing capability. In addition, they should have a backing that is easy to peel off and an adhesive strong enough for coated and textured surfaces.

In response to this research, Brother has designed the P-touch 2480, a labeller for use in tough installation environments.

With a specially designed Rotate Print function, the machine will print text vertically on labels, making it easy to read after wrapping around the cable or wire.

A flexible ID tape enhances this feature (see figure 1.)

Other print options, including repeat, panel, vertical and mirror printing, enable labels to be produced for anything from thin wires to complex switchboards.

A print preview facility allows customisation of the label before printing. Variable elements include font styles and sizes, width, frames, alignment, margins and length. Tapes can be cut manually to any length, and the Tape Cut Pause function simplifies multiple printing of the same label.

The new Custom Template capability is designed specifically for Patch Panel labelling, whereas a new Flash Rom and USB interface allows the user to download images, logos and professional symbols from a PC into the machine's memory before going out on a job.

Ten pre-format keys enable the saving of regularly used labelling formats for quick and easy recall and the ABCD keyboard offers a hard wearing, yet ergonomic, design.

The PT-2480 uses Brother's patented TZ tapes in 6, 9, 12, 18 and 24 mm widths. Its unique construction comprises six layers of material, providing a high level of resistance and wear.

Characters formed with thermal transfer ink are printed on to the underside of a laminate and sandwiched between two layers of PET (polyester) film (see figure 2). They are able to withstand heavy abrasion and electrical resistance, plus lengthy exposure to chemicals, sunlight, water and temperatures ranging from -50°C to 300°C.

Tests of the tapes' dielectric strength show that black characters begin to lose their electrical resistance at an applied voltage of 8 kV.