- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2800) Unit Title: EQUIPMENT OPERATION AND MAINTENANCE ___________________________________________________________________________ (CLF2806) Topic: HYDRAULIC SYSTEM MAINTENANCE Time Year(s) 1 hour 1 / 2 / 3 / 4 ___________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the students will be able to: Learning Outcome #: (Q-3) - Use safe work habits while servicing, maintaining, and adjusting agricultural equipment. (Q-7) - Recognize the personal and financial dangers related to the safe use, replacement, and repair of components used in hydraulic applications. Special Material and Equipment: Clean hydraulic oil, lint-free rags, hydraulic equipment, operator's manuals References: Jacobs, C. O., & Harrell, W. R. (1983).AGRICULTURAL POWER AND MACHINERY. New York: McGraw-Hill. Resources Deere & Company. (1984). PREVENTIVE MAINTENANCE (Fundamentals of Machine Operation (FMO) Series). Available from: John Deere Technical Services Deere & Company. (1987). HYDRAULICS (4th ed.) (Fundamentals of Service (FOS) Series). Available from: John Deere Technical Services, Dept. F, John Deere Road, Moline, IL 61265 (Available in Spanish, German, Dutch, Swedish) Evaluation: Quiz by instructor. TOPIC PRESENTATION: HYDRAULIC SYSTEM MAINTENANCE A. Basic Principles of Hydraulic Power 1. Hydraulic power refers to how a liquid (usually oil) is used under controlled pressure and flow to do work. 2. Two scientific laws state the principle involved in hydraulic power. a. Pascal's law states that pressure applied to the surface of a liquid will be transmitted equally in all directions regardless of the container's shape. 1) Liquids can be classified as flexible solids. 2) Unlike air and other gases, liquids confined in an enclosed space, such as a hydraulic cylinder, cannot be compressed in an appreciably smaller space when pressure is applied. 3) The great advantage of transmitting power by hydraulic force is its flexibility, that is, it is not limited to straight-line action. b. The law of conservation of energy states that energy can be neither created nor destroyed. 1) This means that the output of energy cannot exceed the input of energy. 2) The applied force divided by the area of the cylinder equals the pressure on the liquid. a) A force of 100 pounds divided by the pump cylinder volume of 10 square inches equals a force of 10 pounds per square inch (psi) on the liquid. b) Acting on a 100 square inch cylinder, this pressure will support 1000 pounds. c) Thus, there is a mechanical advantage of 10:1 in that 100 pounds of force can raise 1000 pounds of weight. 3. There are two forms of transmitting power hydraulically. a. A hydrodynamic system uses high speed and low pressure of fluid to do work. b. A hydrostatic system uses high pressure and low speed of fluid to do work. 4. The hydrostatic system is the basic system used in agricultural equipment. a. Its common component parts are as follows: 1) A reservoir to hold a supply of hydraulic fluid 2) A pump to move the fluid in the system against resistance 3) Control valves to direct the flow of the fluid 4) Hoses to channel the flow of the fluid 5) A hydraulic cylinder (ram) or hydraulic motor to convert the liquid pressure to linear or rotary motion necessary to perform work b. Its most common functions are as follows: 1) Power steering 2) Power brakes 3) Transmissions 4) Implement control 5) Remote cylinders 6) Hydraulic motors B. Hydraulic Safety Rules 1. Always wear eye and face protection when servicing hydraulic systems. 2. Always lower elevated hydraulic equipment before leaving the machine. 3. Block or lower elevated hydraulic equipment before servicing or repairing it. 4. Never service a hydraulic system while the engine is running unless it is absolutely necessary, as in the case of bleeding the system. 5. Always tag and remove the key from the machine being serviced or repaired in order to avoid accidental starts while work is in progress. 6. Relieve all the pressure from a hydraulic system before loosening any fittings to avoid escaping high-pressure oil which is a fire hazard and can cause serious injury by penetrating the skin. 7. Search for pinhole leaks in hydraulic lines with a piece of cardboard, not your hand. CAUTION: Hydraulic fluid under pressure can pierce the skin, causing severe injury which can lead to gangrene because body cells are crushed and killed. If this occurs, the surrounding tissue has to be surgically removed. 8. Prevent hydraulic oil from being sprayed, dripped, or leaked on hot engine manifolds or exhausts by routing lines, hoses, and valves away from these heat sources. 9. Avoid using compressed air to disassemble a hydraulic cylinder, which can be turned into a cannon by such pressure. 10. Always wear gloves when handling hot hydraulic equipment. 11. Wear heavy gloves to avoid being cut from the sharp reinforcing wire braid when replacing hose couplings. 12. Use non-volatile cleaning solvent when washing hydraulic parts. 13. Bleed air from the hydraulic system before working with repaired hydraulic equipment to avoid unexpected dropping of heavy equipment supported by cylinders. 14. Fasten hydraulic hoses securely to avoid whipping action which may cause injury. 15. Lock the cylinder stops to hold hydraulic equipment solidly in place when transporting the machine. C. Servicing the Hydraulic System 1. Factors commonly responsible for maintenance problems with hydraulic system are as follows: a. Insufficient oil in the reservoir b. Contaminated oil c. Leaking connections or loose intake lines d. Incorrect oil or filter in the system e. Clogged or dirty oil filters f. Air in the system 2. Checking Hydraulic Oil Level a. Check the hydraulic oil level daily. b. Most systems have either a dipstick or sight glass in the reservoir. 1) Be sure to clean around the dipstick opening before checking the oil level. 2) Use a clean, lint-free cloth to wipe the dipstick. c. If the oil level is not up to the full or safe mark on the dipstick or up to the sight glass in the reservoir, add the recommended hydraulic fluid. 1) Wipe off any dirt or moisture from the refill cap before removing it. 2) Use clean oil that has been stored in closed containers. 3) Avoid using funnels that are not clean. c. While checking the oil level, also check for other malfunctions. 1) Oil bubbles or foaming oil may indicate an air leak in the suction side of the system. 2) Milky oil indicates water in the system or in the oil used. 3) Noticeably different oil levels from day to day may indicate leaks or cracks in the external parts of the system. 4) Metal particles in the oil may indicate mechanical failure. 5) Dirty oil may indicate filter failure. 6) Oil that is dissolved or has a burned odor may indicate kinked pipes, a plugged oil cooler, internal leaks, or the wrong oil viscosity. _________________________________________________________ ACTIVITY: 1. Check the oil level in a hydraulic system. _________________________________________________________ 6/28/91 OLR/tf #%&C