Click here for a printable version of this article.

January 2005: Electrical Testing

The electrical demands in industrial or commercial buildings vary from simple lighting and heating requirements for an office building to major on-site power distribution centers for a steel mill, semiconductor plant or other large manufacturing operation.

Electrical equipment deterioration is normal, but equipment failure is not inevitable. Theoretically, as soon as new equipment is installed, a process of normal deterioration begins. Unchecked, the deterioration process can cause a malfunction or an electrical failure. Deterioration can be accelerated by factors such as a hostile manufacturing environment, electrical overload or a severe duty cycle. An effective Electrical Preventive Maintenance (EPM) program identifies and recognizes these factors and provides measures for coping with them.

In addition to normal deterioration, there are other potential causes of equipment failure that can be detected and corrected through an EPM program. Among these are load changes or additions, circuit alterations, improperly set or improperly selected protective devices and changing voltage conditions. Without an EPM program, management assumes a greatly increased risk of a serious electrical failure and its consequences, which could be major property damage as well as significant business interruption.

A well-administered EPM program will reduce accidents, save lives, and minimize costly breakdowns and unplanned shutdowns of production equipment. Impending troubles can be identified and corrected before they become major problems requiring more expensive, time-consuming solutions.

Benefits of an effective EPM program fall into two general categories. Direct, measurable, economic benefits are derived by reduced cost of repairs and reduced equipment downtime. Less measurable are benefits that result from improved safety. Although the benefits that result from improved safety are difficult to measure, direct, measurable, economic benefits can be documented by equipment repair cost and equipment downtime records after an EPM program has been implemented.

Types of Inspections

Visual Inspections should be done on a monthly basis to determine the general physical condition of equipment. Inspections can reveal cracked or chipped insulations, loose or cracked components and other mechanical and electrical

defects. Written records should be maintained of all inspections to establish a historical inspection database for all equipment. Any deficiencies noted during the visual inspection should be brought to the attention of management and acted upon promptly.

Infrared Thermal Measurements can detect trouble such as deteriorated insulation or poor physical connections in switchgear before they become major problems. They should be performed at least once for a facility that has electrical equipment considered essential to production or is a significant fire exposure. At smaller locations, a survey may not be economically warranted unless the fire exposure is unusually high. Newly installed equipment should be included in the infrared inspection program.

The frequency of follow-up infrared inspections depends on the number of problems found during the initial survey. At large facilities with a harsh environment, infrared inspections may be required every six months for the first couple of years. This interval may be gradually reduced to every three to five years.

The following table lists some electrical equipment that should be infrared tested as well as the recommended frequency of testing:

Electrical Bus Bars
3 to 5 years
Switchgear
1 to 5 years depending upon electrical rating and type of switch
Rotating Machinery
1 to 3 years
Transformers
Dry: 1 to 3 years. Liquid: 3 to 5 years

For a detailed breakdown of testing frequencies and equipment that should be part of an EPM program, see NFPA Standard 70B, "Recommended Practice for Electrical Equipment Maintenance" or FM Global Data Sheet 5-20, "Electrical Testing."

Risk Logic can assist in developing an EPM program for your facility by determining which electrical equipment is the most critical to production and/or the overall operations at your facility.