Now offering Dielectric Testing in Edmonton

If you own a Digger Derrick or Bucket Truck you probably already know about Dielectric Testing. But for those that are new to it, Dielectric testing is a method used to determine the insulating capabilities of the fiberglass sections of a boom. For equipment that is used near high voltage lines you are required to have your equipment Dielectric Tested at least every 12 months. This is to ensure the insulation quality has not deteriorated.  



What needs to happen before the Dielectric test?

To help the Digger Derrick or Bucket Truck pass the dielectric test there needs to be some things done before hand. Moisture is the enemy when performing this test so therefore we need to be aware of the weather. The unit needs to be dry inside and out, so that means no rain or snow on the boom. We usually recommend the client parks their equipment inside the night before the test, cause you never know what Alberta’s weather will bring. Similar to moisture, humidity can play a factor as well. Our equipment is only rated to 80% humidity. Anything above that and we will have to cancel the test for that day.



The next thing we need to worry about is the cleanliness of the fiberglass boom. If there is debris, such as tree brush, inside the boom it needs to be removed as that could make the boom fail the dielectric test. On the outside of the boom we need to have no oil/grease streaks along the length of the boom. In other words, we need the boom completely clean inside and out in order to have a good chance of it passing the Dielectric Test.



What happens during the Dielectric test?

There are a few factors that determine the testing parameters. For Digger Derricks, all we are testing is the fiberglass boom section. On bucket trucks we dielectric test both the upper boom and the lower boom. Also, we will test the jib, bucket liner and the upper controls on units with High Electrical Resistance handles. Since we are following the Periodic Dielectric testing procedures the voltages we induce into the unit are based on the requirements set out in CSA C225 and ANSI A10.31. 


Safety is critical during this testing, we don’t want anyone touching the unit during the test. In some cases we are pushing 100,000 volts through the unit. Removing people from the work area during the test is necessary to keep them protected. Thankfully, the test only takes 3 minutes at a time, so it’s not too much of an inconvenience.



If the unit fails the test there are a couple things we can do to try and rectify the problem. First we can clean the boom better, most of the time this is the biggest cause of failure. Second, we can start removing components to try and narrow down the component that is causing the failure. If both of those fail then we can discuss further options to inspect the boom and confirm it’s structural and dielectric integrity. Here are the steps Terex recommends when a unit fails a Dielectric test: Failed Dielectric Test


What happens after the Dielectric test?   

Once the unit passes the Dielectric Test, we will provide a full report showing the parameters we used and the results of each test. This report can then be printed out and left in the cab of the equipment for quick reference while out in the field.
If you have any questions about Dielectric Testing please don’t hesitate to contact us.