Dielectric Testing

Dielectric Tester

Dielectric testing is an evaluation process performed by applying voltage to an aerial device that exceeds the normal operating voltages surrounding the working area. The purpose of the test is to determine if a component’s insulation is adequate enough to protect the user from electric shock. This testing procedure is performed on all insulated aerial devices. The manufacturer of an aerial device typically conducts dielectric testing at the end of the production process. A special device known as a dielectric tester is used to perform this type of test.

Almost all aerial devices leak a certain amount of electrical current due to a variety of different factors. This very small amount of current is considered to be safe for users of these components. Under certain conditions the insulating materials or mechanisms can breakdown and allow dangerous amounts of electrical current to come into contact with the user. This type of insulation failure can sometimes cause serious injury or death. Dielectric testing is necessary to ensure that the insulating mechanism of an aerial device will withstand voltage variations under normal operating conditions.

Dielectric Testing

A dielectric test is performed before the vehicle is delivered new to a customer.  An additional dielectric test is required to be performed once a year for the aerial’s yearly inspection.  Also anytime an aerial’s insulated section has been repaired or any component on that unit has been replaced.  Some end user’s have higher safety standards and require a test done more frequently.  Check with your manufacturer or your service center to see if your aerial device is due for an inspection and dielectric test.

Care of Fiberglass Booms

Fiberglass booms should be wiped down daily with a lint free cloth. This practice both cleans the boom and allows the operator to inspect the boom for any damage or items requiring repair. In the event any chips, scrapes or abrasions are found, that would permit water to be absorbed into the fiberglass, the boom should be repaired in accordance with the manufacturers requirements.

Fiberglass booms should never be steam cleaned. This practice may actually damage the boom by allowing the high-pressure water and steam to penetrate the fiberglass. Booms should be washed with a mild dish-washing detergent. Never use an abrasive type cleanser or anything that will compromise the dielectric value of the boom.  The boom will need to be elevated and allowed to air dry after the unit has washed.

If the boom does have deposits of creosote or grease a more aggressive chemical, such as Donar Chemicals Electra Clean, may be used. The booms need to be thoroughly rinsed and allowed to air dry after the use of any type of cleaner.

Once booms have been cleaned, it should be coated with a good quality fiberglass wax. Boom wax is available from companies such as Hastings, Kearney and Donar. This coating of wax will help to keep the booms clean and shiny, preventing grease, road salts and creosote from adhering to the boom. This will also assist the boom with shedding water during storm work.

Fiberglass booms should be dielectrically certified after the booms have been cleaned to insure the dielectric values of the boom have not changed. A dielectric test should also be performed anytime a boom has been repaired or a component that passes thru an insulated portion of the boom has been replaced. This test will insure the repair procedure and the replacement items used, have not affected the insulated value of the boom.

Items such as saw scabbards should be removed for any dielectric tests. These items should also be washed periodically to insure they do not track any residue across an insulated portion of the booms. It is important not to place any aerial accessories in a manner that may affect the dielectric value of the boom.

If you have any questions about boom maintenance or repairs, you should contact your aerial service center or the aerial manufacturer for assistance.