The Powerful Impact of Preventive Maintenance
Hydraulic fluid acts as the lubricant between moving parts and often the necessary resistance in components, such as brakes or power steering. The most common applications that require regular monitoring of fluid contamination are in heavy equipment, such as off-road earth-moving equipment and agricultural equipment. Industrial machinery that experiences frequent actuation or movement is also more susceptible to contamination than equipment that has infrequent actuation, or is isolated to a clean environment.
Contamination control is integral to ensuring efficient operation of a hydraulic system by identifying and measuring potential types of contamination. Taking the proper steps will extend the service life of hydraulic equipment.
Hydraulic systems are integral parts of a wide variety of equipment including: aircraft flight-control systems, backhoes, excavators, garbage trucks, hydraulic brakes, industrial machinery, lifts, power steering systems, and transmissions.
Hydraulic fluids are individually formulated for specific applications. They are usually comprised of a base stock and an additive package. The additive package consists of chemical compounds designed to protect the base stock, which is primarily made up of natural mineral oil-based fluids. It is essential to have the correct formulation of fluid for the proper performance of the system. Many additives include anti-corrosion, antioxidants, anti-foaming, anti-wear, viscosity-index improvers, and certain extreme pressure (EP) agents.
Water and any foreign particulates will contaminate and adversely affect the chemical properties of the additives and the base stock of hydraulics. The presence of contamination can cause excessive wear on the system or premature failure, sometimes with catastrophic consequences. Imagine an aircraft control system seizing up due to contaminated hydraulic fluid. This is why critical hydraulic systems should be regularly tested for contaminants and variations in pressure.
Fluid Contamination Testing
To avoid contamination of hydraulic fluid, it is important to place filters at regular intervals in the hydraulic system to collect contaminant that may inadvertently get into the line. For certain equipment that is more sensitive or regularly exposed to dirty environments, contamination control procedures should be put into place for periodic testing of the cleanliness of the hydraulic fluid, usually based on the equipment manufacturer’s recommendation. The fluid should also be tested after equipment maintenance that may subject the hydraulic system to outside elements. Fluid testing should be conducted after new fluid is added, new components are placed in line, and replacement of hoses or any other condition that exposes the current fluid. Purging a system from the existing fluid and replacing it with new is a critical time to have the system tested due to exposure to the outside elements and to ensure the new fluid is not contaminated. Suppliers of hydraulic fluids recommend chemically analyzing the fluid on a regular basis to be proactive in eliminating problems before they occur.
The most practical method for regularly testing fluid line systems is to place test point fittings at regular intervals throughout the system, which allows sampling at working pressure without disrupting the system’s operation and avoiding costly shutdowns. Quality test point connections are leak-proof before the ball check is open to minimize contamination and their self-locking metal cap helps protect the system. It is recommended to have a full line of test point components on hand, or a variety of test point kits, which include all styles of connections, test hoses, couplings, pressure gauges, gauge adapters, plugs, and probes. These kits provide all of the components necessary for periodic testing of a wide variety of equipment from different manufacturers.