Fiberglass and Insulated Boom FAQs

A filament-wound boom is a fiberglass structural component used in aerial lifts, cranes, digger derricks, and similar equipment. It's built by precisely winding continuous fiberglass filaments around a mandrel under controlled tension, then curing the result with an epoxy resin system. The finished boom provides electrical insulation, protecting workers, the public, and property from the risk of electrocution near energized power lines.

Filament wound booms are purpose-built for work performed on or near electrical lines. Because fiberglass is non-conductive, it provides a layer of protection that steel and other metals cannot. To understand why insulation matters, it helps to look at the real risks of working near live power lines across utility, tree care, construction, and crane applications.

Filament wound booms offer high rigidity and strength, reliable electrical insulation, a lightweight profile compared to steel alternatives, and strong resistance to corrosion. Together, these properties make them durable in the field while keeping equipment weight manageable.

Filament wound booms show up anywhere workers need to operate safely near energized power lines, from utility crews restoring service after a storm to crews clearing vegetation along a right-of-way. That versatility is why Waco Boom's booms are found across a wide range of industries. Common applications include:

• Distribution
• Transmission
• Tree care
• Construction
• Agriculture

Beyond the industries they serve, filament-wound booms also take shape as specific components built into the equipment itself, engineered to fit the exact dimensions and load requirements of each platform. Filament wound booms are used to build jibs, upper booms, and lower booms across a range of aerial platforms and lift types, including:

• Cranes
• Bucket trucks
• Digger derricks
• Compact lifts
• Tree trimmer lifts

Insulated fiberglass sections attach to cranes as jib booms, giving facilities maintenance and equipment rental fleets the ability to outfit a standard crane for work near energized lines. This lets a single crane serve both general lifting and insulated utility applications without needing a dedicated insulated unit.

Construction sites frequently work near live power infrastructure during power and lighting installation, so insulated boom sections protect operators from contact-related damage or injury. This is especially relevant for digger derricks setting utility poles and bucket trucks accessing overhead lighting or signage, both common on construction sites.

Filament winding uses multi-axis, CNC-controlled winders to precisely control fiber orientation and tension throughout the laminate, tailoring the boom to its specific end-use stresses. This precision-controlled process, combined with an external molding system, produces a higher fiber-to-resin ratio (typically over 75% fiberglass by weight) than hand lay-up or centrifugal casting can achieve, resulting in a stronger strength-to-weight ratio and more consistent wall thickness.

An insulated boom has a fiberglass section built into the upper boom, lower boom, and bucket liner that prevents electrical current from traveling through the equipment. A non-insulated boom is typically all-steel and will conduct electricity freely. Insulated booms are required whenever there's a realistic chance of contact with energized lines; non-insulated booms are suited to general lifting, tree work, or signage where that risk doesn't apply.

A qualification test is performed at the factory to establish a new boom's voltage rating, and must be redone using AC test equipment any time a boom is replaced or the insulated section is modified. The original qualification no longer applies once that happens. A periodic (or maintenance) test is the recurring annual test performed once equipment is in service, done using AC or DC equipment to confirm the boom still performs to its rated insulation level.

Fiberglass booms are electrically tested during manufacturing to confirm performance and safety. Shorter sections are typically tested at 50 kV per 12 inches, while longer sections are tested at 100 kV end-to-end. The final voltage rating for a piece of equipment depends on its complete design, including insulation gaps, platform materials, and overall configuration, not the fiberglass boom alone.

Yes, but above approximately 100 kV, the fiberglass boom alone isn't sufficient on its own. Safe operation at transmission-level voltages requires integrating the boom with additional system components, including corona rings, gradient control devices, and proper system-level insulation design. These features work together to manage electrical fields and prevent corona discharge.

Dielectric testing verifies that the insulating properties of a finished boom meet the required voltage rating. Waco Boom submerges lower booms in water for an hour prior to testing to rule out moisture wicking or entrapment, then tests using a 100KV unit. It's required because insulation can only be trusted for safety once it's been verified.

Under ANSI A92.2 and A10.31, insulated equipment must be periodically (annually) dielectric tested. Testing is also required any time repairs are made to components within the insulated sections, whenever there's reason to question the boom's dielectric properties (such as contamination or visible damage), or after any incident involving contact with an energized line.

We don't assign a single universal voltage rating to our booms, since insulation performance depends on the complete machine design rather than the fiberglass component alone. We recommend designing in accordance with ANSI standards to ensure proper insulation spacing and safe operation.

Insulated booms are governed primarily by ANSI A92.2 (aerial devices) and ANSI A10.31 (digger derricks), which set qualification and periodic testing requirements. You can find technical documentation and reference materials covering these standards in more detail. OSHA references these standards directly in its aerial lift regulations (29 CFR 1926.453).

Insulation is built into specific, defined sections of the equipment, typically the lower boom, upper boom, and bucket liner, each carrying its own separate insulation rating. This is especially relevant on telescopic booms, where multiple extending sections each need their own verified insulation. Any part of the boom or bucket outside those insulated sections should still be treated as a potential conduction path.

Lift manufacturers typically bond the fiberglass boom to steel components using a methyl methacrylate (MMA) adhesive, which also acts as a gap-filling shim between the two materials. For more on keeping fiberglass-to-steel joints in good condition, a poorly shimmed or gapped joint can create stress concentrations that lead to flexural cracking in the laminate or gelcoat.

There isn't a fiberglass-specific torque spec, it should follow the fastener manufacturer's recommendation for bolt torque. The real concern isn't torque itself but the stress concentration it creates at the clamping point, since the composite has high compressive strength but can develop flexural stress from sharp-edged washers or gaps between the fiberglass and steel. Flat washers should be installed with the cupped side facing the fiberglass to avoid cutting into the surface.

Delrin/Acetal or UHMW slide pads are recommended based on field experience with other customers. Moly-infused nylons should be avoided, while they perform well against steel, they can act like a grinding compound against the softer gelcoat surface, along with any moly or graphite-based solid lubricants.

Lifespan depends heavily on usage conditions and the specific application the boom is used for, so there's no single fixed number that applies across the board. Industry data on similar FRP booms suggests a typical service life in the 10-15 year range under normal conditions, though actual lifespan varies with load cycles, environmental exposure, and maintenance history. Reach out to discuss your specific application.

Daily and periodic inspections should be performed alongside the required annual dielectric test, following manufacturer guidance. Keeping the boom clean is critical, since debris and contamination can compromise insulating performance. This includes regularly cleaning boom rests to remove embedded dirt or gravel. Fiberglass-to-steel joints should be checked for compromised sealant, and any damaged sealant should be removed back to sound material, then cleaned and resealed.

Failures are usually traced to contamination, carbon tracking (an electrical path burned into the fiberglass), embedded dirt, or moisture entrapment. Technicians typically inspect the interior using mirrors or a camera, clean affected areas, and retest. If carbon tracking has burned too deep into the laminate, the section may need to be replaced rather than repaired, but many failures are resolved through cleaning and recoating with silicone or wax before returning the unit to service.

The design process starts with the dimensions and application requirements you provide, along with any supporting drawings or documentation. From there, standard tolerances and load ratings are established and approved before moving into manufacturing.

Both. Waco Boom maintains stock of common standard boom sizes while also designing and manufacturing fully custom sizes. You can learn more about how this fits into the overall sales process from initial inquiry through delivery.

Requirements vary by design, but general guidelines include approximately 42 inches of insulation gap for applications around 46 kV on the inner boom, and approximately 12 inches (300 mm) on lower boom sections. Actual spacing depends on factors like platform construction, metal components, and capacitance effects once the equipment is energized.

Working height is determined by the overall equipment design and how the fiberglass boom is integrated into that system, factors like boom configuration, number of sections, material distribution, and machine architecture all play a role. Typical applications fall in the 25–60 ft range, though heights of 200 ft or more are achievable when booms are built into specialized, engineered systems. Because Waco Boom supplies components rather than complete machines, final working height is ultimately defined by the equipment manufacturer's design and intended application.

Tolerances and load ratings are established and approved on a per-project basis once your dimensions and application requirements are finalized. Waco Boom performs onsite destructive break testing to verify structural load capacities and dielectric testing to confirm non-conductivity, ensuring each custom design meets the safety and performance needs of its specific end use.

Lead times vary based on the complexity of the design, current production schedules, and whether the size falls within standard or fully custom specifications. Contact the team directly with your application details for a project-specific timeline.

Having your dimensions, load requirements, and any existing technical drawings ready upfront streamlines the process significantly. Waco Boom's request-a-quote form includes an optional boom design module where you can enter your specs directly.

Yes. Waco Boom ships globally, with booms in active use across the Americas, Europe, Asia, Africa, and Australia, serving customers in countries including Pakistan, Italy, China, Taiwan, Australia, Argentina, Brazil, Mexico, and Canada.

Both. While Waco Boom's standard sizing is imperial, metric dimensions are available and commonly requested by international customers, since specifications outside the U.S. are often given in millimeters.

Incoterms are standardized international trade terms that define who is responsible for shipping, insurance, and customs at each stage of a shipment. Waco Boom offers flexibility here, customers can choose to have Waco Boom quote and arrange shipping, or handle their own pick-up and transport arrangements.

International specifications generally mirror U.S. standards, so the core engineering and safety requirements carry over. The main practical difference tends to be measurement units, since international requests are often made in millimeters rather than inches.