Problems and Solutions of Insulator Cleaning

The Problem

It is widely known that dirty or defective insulators and bushings are the cause of most flashovers, resulting in down-time and loss of production.

Flashed Over Fuse-Holders

                   Flashed Over Standoff

Atmospheric contamination build-up on electrical apparatus generated from industrial plants and mills as well as some residential and commercial locations contribute heavily to black-outs and brown-outs. This contamination builds up on insulators, bushings, lightning arrestors, current-transformers, potential-transformers, stress cones, potheads, fuse holders, switches, terminators, trificators, and guy-wire insulators. Depending on the resistance values associated with said contamination, tracking, and in extreme circumstances, arcing takes place usually during periods of light to moderate rainfall. When this contamination forms of a bridge of conductive material over your porcelain non-conductor (insulator) the high voltage electricity finds a path to ground (phase-to-ground fault) resulting in a number of possible inconveniences for your firm including, but not limited to: insulator explosion, insulator etching, insulator chipping, circuit-trip, exposed live-lines, damage to transformers and breakers, loss of production, injury to personnel, exposure to electrocution risks to personnel, expensive and time-consuming repairs, and fires. 

Why risk it?

We at Petronol have found a way to keep atmospheric contamination from becoming costly problems for high voltage electrical distribution systems.

The Solution

To prevent flashovers, call for regular maintenance of insulators and bushings. 

Take advantage of Petronol's exclusive “air-mat” technology that allows us to safely and effectively clean high voltage insulator apparatus WITHOUT a power shut down. Cleaning insulators by hand during an outage and/or by massive flooding with water are things of the past and entirely obsolete. Safe, cost-effective live-line insulator cleaning is the solution for today and tomorrow.

                       Before Cleaning

                        After Cleaning

How It’s Done

Petronol Corporation became the first live-line insulator cleaners over fifty years ago with a patented “air-mat” method that allows thorough and complete cleaning of the insulator at hand while maintaining the utmost level of safety for all parties involved.

Our method sets us apart from many of our competitors. We use a system involving compressed air and pulverized limestone (or corn-cobs) in a form of sand-blasting to gently strip away any contamination bonded to the insulator. Sand itself cannot be used in the cleaning process as it is too harsh and gritty for the porcelain surface of the insulator. Our abrasive material has a Mohs’ value of 3 ˝ and the insulator glaze has a value of at least 5 ˝ so the glaze cannot be damaged, even though heavy dirt deposits are being stripped off down to the insulator surface.

                       Insulator Cleaning

                  Cleaning 200ft Up!

The actual cleaning operation of the "air-mat" is simple and safe. The dry abrasive is blown against the insulator in a stream of air with the operator using an insulated "hot-stick". The stick is usually sixteen feet long-varying lengths are provided-so that for safety, the operator can remain more than 10 feet from the energized conductor leading to the dirty, contaminated insulator.

Because the abrasive is so fine-particled and because of the relatively small amount required to be mixed in the stream of air, no noticeable traces are left on the insulators or structures after the cleaning process.

The majority of work performed is done from an aerial insulated bucket-truck. Work is also frequently done from OSHA approved ladders and scaffolding, from climbing the structure supporting the circuit(s), JLG®-like man-lifts (de-energized work only), or simply from the ground.

            34.5kV Insulator Cleaning

                   Tower Climbing

  138kV Cleaning from JLG Man Lift (de-energized)

 Cleaning from an Extension Ladder

   Cleaning from a    Stepladder


Insulator Cleaning from Insulated Bucket Truck (34.5kV Energized)


Silicone Application

When silicone grease first came on the market, many plants began coating insulators and, for a time, it was considered the cure-all for flashovers. However, much of the increased reliability of the now-coated insulators could be traced to the fact that the coating made them appear very dirty after a relatively short exposure to any kind of contamination. So there was a tendency to clean them more often, which alone could have accounted for the reduction in flashovers.

Through years of experience, we at Petronol have discovered when applying a silicone mixture to bare insulators is best.

Silicon Coated Insulator

As a general rule, the following conditions indicate where silicone grease is useful:

  • Where a strong bond forms between contaminants and insulator and cleaning the bare insulators becomes difficult.

  • Where there is only a small amount of contaminant but it is highly conductive.

  • Where there is a continuous exposure to dampness.

  • Where there is little and irregular rainfall.

The following conditions are not suitable for the use of silicone grease:

  • Where there is a high concentration or conductive contamination.

  • Where regular maintenance is difficult.

  • Where regularly maintained, uncoated insulators have performed well in the past.

  • Where cleaning of bare insulators is easy and is good economics.


Silicone Application is Not Recommended for Hard-to-Reach Insulators

Petronol uses crushed corn cobs for the more difficult task of removing silicone grease from coated insulators in the cleaning process, prior to re-coating them with silicone. Petronol applies the coating in the manufacturer's recommended thickness of 3/16", using special spray equipment having a small spray angle so that no grease spreads on to the supporting structure. A "hot-stick" is also used in this work, so it can be carried out on energized equipment.

In general, insulator cleaning can be performed twice as often using pulverized limestone as opposed to silicone grease work for about the same cost.

Ask a Petronol Corporation of Indiana associate if a silicone application best fits your needs.


  • You can have the work done ANY time you choose to have it done-24 hours a day, 7 days a week, 365 days a year!

And remember…
Petronol Corporation of Indiana

  • Submits a firm price quotation for all work (no hidden costs, no escalations).

  • Offers 24 hour emergency services (no appointment necessary).

  • Has experienced operators, familiar with all aspects of hot-line work.

  • Uses proven equipment.

  • Does more than simply clean insulators.

  • Can send IBEW Journeyman Lineman when needed.

  • Supplies a service that has stood the test of time!