Maintaining Your Insulated Booms: Part 3 – Maintenance of Fiberglass to Steel Joint

In this four-part series, Utility Pros is summarizing four Tech Tips produced by our Product Support Team. Tech Tips cover the most common questions our Terex Services Team receives regarding repairs and replacements and is meant to provide service personnel with information to make their jobs easier. In this series, we cover tips related to maintaining insulated booms, including: 

• Damage classification and measurement,  

• Correctly taking photos of the damage, 

• Performing maintenance on the caulking or sealant at the fiberglass to steel joint, and 

• Repairing gel damage or refinishing the fiberglass boom.  

One of the most common fiberglass maintenance points on a unit is the caulking or sealant at the fiberglass to steel joint. Improperly maintained joints can lead to corrosion of the steel boom section, moisture and rust damaging the fiberglass to steel bond, or allow water and other contaminants to wick into the fiberglass. Rust or dirt that track along the boom can cause dielectric failure. In addition, when moisture penetrates fiberglass windings, the dielectric strength of the fiberglass can be reduced.  

How to Seal the Joints 

To properly seal fiberglass to steel joints, first remove the sealant all around the boom to allow for thorough inspection. Clean the steel to remove any rust. Naval Jelly or Evapo-Rust are two commercially available products that are suggested for this task. Do not use a rust converter product. Sandblasting may be necessary if minor pitting exists; however, if pitting is extensive, contact the manufacturer to determine if it is safe to repair the boom or if the boom must be replaced. 

After priming and painting the area, apply a urethane caulk at the joint, ensuring that it adheres to both surfaces. Once you’ve addressed the issues causing wear or damage to the fiberglass, then take proper steps to repair the fiberglass.