Exxon Mobil highlights the essential key-points that should be considered while performing the hydraulic system check. Hydraulic machines provide power to moving parts of various industrial machines by applying the force of a fluid under pressure.Systems vary from small, simple and straight-forward to large, high pressure systems with a complex array of servo valves and pumps. No matter the size or complexity, proper maintenance of both the system and the hydraulic oil is crucial in maximising uptime and reducing repair costs. Hydraulic fluid care Hydraulic fluids are the lifeline of the hydraulic system. The fluid transmits pressure and energy, seals close-clearance parts against leakage, minimises wear and friction, removes heat, flushes away dirt and wear particles and prevents rusting. Conventional petroleum (mineral) oils are used in hydraulic systems, but fire-resistant, synthetic, and biodegradable fluids are used in other situations. Some of the key objectives essential to gain optimum service life of hydraulic fluids-controlling temperature, keeping systems and fluid clean and lastly, keeping an oil analysis programme. Ten point check A lubrication technician responsible for hydraulic system maintenance should perform the following 10 point checklist as part of a routine weekly of a hydraulic system. Check fluid levels. Inspect breather caps, breather filters and fill screens. Check filter indicators or pressure differential gages. Visually inspect all system hoses, pipes, pipe connections for leaks and frays. Check system temperature via built-in thermometers or hand-held infrared detectors. Normal temperature range for most systems is 110-140¦f. If temperatures are high, check cooler operation and relief valve settings. Visually inspect the inside of the reservoir for signs of aeration (via the fill hole using a flashlight). Listen to the pump for the signs of cavitation. Cavitation is slightly more complicated than aeration, but bares some similarities. Cavitation occurs when air is released from the hydraulic oil during momentary depressurisation at the pump suction and then imploded onto metal surfaces upon discharge. These implosions are extremely destructive to pump surfaces. A cavitating pump will emit a high-pitched whine or scream. Causes of cavitation are the same as those of aeration with the exception of suction side air leaks. How do you discern aeration from cavitation? One way is to install a vacuum gage on the suction side and make sure the pressure is equal too or greater than that prescribed by the pump manufacturer. Foaming in the reservoir is usually the telltale sign of aeration. Inspect a small sample of fluid for colour, signs of contamination and odor. Keep in mind that visual inspection is limited and it will only detect signs of excess contamination. Scan electrically controlled servo valves with an infrared thermometer. High valve and solenoid temperatures (over 150¦f) usually indicate the valve is sticking. Scan the electric drive motor for housing hot spots and rotor bearing temperatures using an infrared thermometer. Fluid change-out recommendations  Drain the system while the fluid is hot to keep contaminants in suspension. Empty fluid from cylinders, accumulators and lines that might not drain properly. Mop, siphon, or pump out oil left in the reservoir. Wipe reservoir clean with lint free rags and remove rust and free paint. Replace or clean filter elements and strainers and clean filter housings. Refill the system with new fluid making sure to vent high points. Restart and check system for proper operation. For systems that exhibit high deposit, sludge or varnish formation: a petroleum based cleaner (such as Mobil System Cleaner) may be required. Safety precautions Hydraulic systems operate under very high pressures. Shut the system down and relieve system pressure before opening any part of the system that is under pressure. Do not allow spray from any high pressure leak to contact any part of the body, as it may result into serious injection injuries. Pumps, valves and motor may become hot; be cautious of incidental contact between bare skin and hot surfaces. Keep hands and clothing away from moving parts of the system. (Communication by the management of the company)