In this article you will learn about our ANSI-compliant classifications for fluid leaks, dielectric testing, and comprehensive maintenance services for all aerial equipment and utility vehicles. Keep your specialized fleet operating safely with professional hydraulic system repairs and preventative maintenance.

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Article by USSI Service managers: Tim Salentine – Service Manager, USSI Appleton WI and Kyle Schroeder – Service Manager, USSI Rentals, Romeoville IL – Contact them here for service

One of the primary services our mobile aerial equipment technicians and two specialized service locations in Wisconsin and Illinois provide is identifying and correcting external fluid leaks in aerial lifts and utility industry equipment.

In addition to the effects leaks have on the performance of bucket trucks, boom trucks, digger derricks, and other equipment we service, they also pose environmental threats. These fluids are often petroleum based and/or toxic to the environment, and therefore subject to strict environmental guidelines across Wisconsin and the Upper Peninsula. A leak may result in costly fines, cleanup costs and/or legal liabilities.

Safety Hazards of Hydraulic Leaks in Aerial Equipment

Safety hazards associated with hydraulic leaks include the creation of slippery surfaces on the equipment resulting in the potential for loss of balance, traction and/or grip. This is particularly important for aerial lift trucks, cherry pickers, and other elevated work platforms where operator safety is paramount. Leaked fluid in the general vicinity of the equipment on floors, nearby machinery or walkways can also lead to slips and falls, which are among the most common types of workplace accidents. High-pressure leaks can lead to sudden bursts of fluid under pressure, which may cause burns, eye injuries, or more serious harm.

In cases where fluid comes into contact with hot surfaces, there is also the potential for fire hazards, especially when petroleum-based fluids are involved. This can endanger both equipment and human safety, which is why our ANSI & DOT inspection services include thorough evaluation of hydraulic systems.

Advanced Leak Detection Methods for Hydraulic Equipment

At times it may be difficult to determine the source of an external leak in mobile cranes or service cranes. Adding a compatible dye product to the fluid may assist with this. Typically, the dye is visible under ultraviolet (UV) light, allowing our factory-trained technicians to spot the source of the leak even in hard-to-reach or difficult-to-see areas of sign trucks and cable placers. This method is especially useful for detecting small, slow leaks that may not be immediately visible during routine maintenance; it is commonly used where traditional visual inspection methods aren’t effective. Contact your fluid supplier for more information, as they may be able to provide further guidance as well as the specific dye product required.

Critical Safety Warnings

When searching for a leak in any hydraulic equipment, never use your hand to find the leak; use a piece of cardboard or wood instead. The fluid may be hot and could burn the skin. A pinhole leak, under pressure, could inject fluid under the skin causing poisoning, infection and be a threat to life and limb.

When testing fittings for tightness during hydraulic repairs, shut the machine off and bleed pressure from the line. If the fitting threads were to strip or a connection were to fail under pressure, injury or fire could result from a sudden release of hot fluid. The usual cause of a leak at a fitting is improper assembly or damage. Make sure that:

• Both ends are clean inside and out, and that no physical damage has occurred.
• New seals are used, and they have been cleaned and lubricated before installation.
• Fittings are not over-tightened–which may distort seals and ferrules, causing metal fatigue or cracking flared ends.
• Fittings are compatible. There are many different thread ends, and some may almost, but not quite, assemble correctly.

USSI’s Classification System for Hydraulic Equipment Leaks

The perception of the severity of an external leak often varies and may lead to confusion or inaction. To minimize this during our stability testing and dielectric testing services, USSI has adopted equipment industry-standard classifications for the severity of external fluid leaks. This system defines three classes:

• Class I: External leakage indicated by wetness or discoloration, but not great enough to form drops. Typically, the leak area has a dull finish.
• Class II: External leakage great enough to form drops, but not enough to cause drops to drip from the item being checked/inspected. The leak area may have a dull to somewhat shiny surface.
• Class III: External leakage great enough to form drops that fall from the item being checked/inspected. The leak area finish is shiny and may be clean near the leak itself.

On cylinder rod seals, valve spool seals and pump shaft/motor shaft seals in over center bucket trucks and back yard lifts, some slight discoloration may occur due to the thin film of oil left by the rod wiper seal for lubrication purposes. Although it may be noteworthy, in some circumstances it may be considered normal.

Aerial Equipment Operating Guidelines

According to these guidelines, Class I and II external leaks are considered minor leaks (except fuel leaks) and machine operation may continue under these conditions for bucket trucks and material handling bucket trucks. When operating machinery with these types of leaks, fluid levels must be checked regularly on increased intervals. Corrective action through our hydraulic repair services must be taken for Class III external leaks.

Furthermore, if a Class III external leak is discovered during operation of a tree truck or sign crane, the task may be completed as long as the leak is measured in drops only and not a steady stream of fluid, and the fluid level is maintained within its allowed operating range.

Specialized Services for Aerial Equipment Maintenance

At USSI, our factory-trained technicians provide comprehensive services to prevent and address hydraulic leaks across all types of specialized equipment, including:

• ANSI & DOT Inspections – Regular inspections to ensure your aerial devices and other equipment comply with all safety standards
• Dielectric Testing – Essential for the safety and functionality of bucket trucks and aerial devices
• Stability Testing (ANSI/SIA A92.2) – Ensuring your equipment remains stable and safe during operation
• Hydraulic Repairs – Servicing cylinders, valves, pumps, hoses, and other hydraulic components
• Fiberglass Boom and Basket Repairs – Specialized repairs to maintain the integrity of your aerial devices
• On-Site Aerial Lift Operator Training – Including safety, maintenance, load charts, operation and more

Utility Vehicles & Other Equipment We Service

Our technicians are factory-trained and certified to work on a large number of different service utility vehicles, including:

Contact Us for Expert Service

With utility vehicle service facilities in Appleton, Wisconsin and Romeoville, Illinois, plus our mobile service truck fleet, USSI provides expert hydraulic maintenance and repairs across the region. Our factory-trained technicians are ready to service your equipment on-site or at our specialized repair centers, minimizing downtime and keeping your fleet operational wherever you need us.

Of course, the adage “a picture is worth a thousand words” holds true; photos of fluid leaks are very helpful in determining how to address them. Submit your leaky photos to USSI’s Service Team for assistance/guidance throughout Wisconsin and the Upper Peninsula when you schedule service below:

Schedule Service Here