When fluid moves from an area of high pressure to an area of low pressure without performing useful work (pressure drop), heat is generated. Therefore, check the performance of all cooling circuit components and replace as necessary. The ability of the heat exchanger to dissipate heat is dependent on the flow rate of both the hydraulic fluid and the cooling air or water circulating through the exchanger. It is important to inspect the heat exchanger and ensure that the core is not blocked. Check that there are no obstructions to airflow around the reservoir, such as a build up of dirt or debris. Therefore, the reservoir fluid level should be monitored and maintained at the correct level. Hydraulic systems dissipate heat through the reservoir. High fluid temperature can be caused by anything that either reduces the systemвЂ™s capacity to dissipate heat or increases its heat load. The temperature at which this occurs is dependent on the viscosity grade of the fluid in the system and can be well below 180вЏ. Fluid temperature is too high when viscosity falls below the optimum value for the systemвЂ™s components. This means that the operation of any hydraulic system at temperatures above 180вЏ is detrimental and should be avoided. Flexible intake lines are prone to collapsing with age therefore, replace old or suspect intake lines.ДЇluid temperatures above 180вЏ (82вЊ) can damage seals and accelerate degradation of the fluid. The intake line between the reservoir and pump should not be restricted. This type of isolation device is prone to vibrating closed. If a gate-type isolation valve is fitted to the intake line, it must be fully open. If the pump has an inlet strainer or filter, it is important for it not to become clogged. A clogged inlet strainer or restricted intake line will cause the fluid in the intake line to vaporize. While cavitation can occur just about anywhere within a hydraulic circuit, it commonly occurs at the pump. In extreme cases, cavitation can cause mechanical failure of system components. Cavitation causes metal erosion, which damages hydraulic components and contaminates the fluid. The consequences of cavitation in a hydraulic system can be serious. This results in the formation of vapor cavities within the fluid, which implode when compressed, causing a characteristic knocking noise. This causes the absolute pressure in that part of the circuit to fall below the vapor pressure of the hydraulic fluid. Check the condition of the pump shaft seal and if it is leaking, replace it.Д¬avitation occurs when the volume of fluid demanded by any part of a hydraulic circuit exceeds the volume of fluid being supplied. In some systems, air can enter the pump through its shaft seal. If the fluid level in the reservoir is low, a vortex can develop, allowing air to enter the pump intake.Д¬heck the fluid level in the reservoir, and if low, fill to the correct level. Flexible intake lines can become porous with age therefore, replace old or suspect intake lines. For this reason, it is important to make sure pump intake lines are in good condition and all clamps and fittings are tight. Aeration accelerates degradation of the fluid and causes damage to system components through loss of lubrication, overheating and burning of seals.ДЄir usually enters the hydraulic system through the pumpвЂ™s inlet. Other symptoms include foaming of the fluid and erratic actuator movement. Air in the hydraulic fluid makes an alarming banging or knocking noise when it compresses and decompresses, as it circulates through the system. Aeration occurs when air contaminates the hydraulic fluid. These symptoms are abnormal noise, high fluid temperature and slow operation.ДЄbnormal noise in hydraulic systems is often caused by aeration or cavitation. In the case of hydraulic systems, there are three easily detectable symptoms that give early warning of root cause conditions. Proactive maintenance emphasizes the routine detection and correction of root cause conditions that would otherwise lead to equipment failure.

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