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DISPLACEMENT AND TORQUE The work output of a motor is called torque. It is the turning force on the drive shaft of the motor. Torque is a measure of force times distance; it does not involve speed. The torque output of a motor is determined by the maximum pressure available and the volume of fluid it can displace with each cycle. The speed of a motor is determined by the amount of input flow. The greater the flow rate, the faster the speed.

Torque is the turning force on the motor driven shaft. Torque equals force x distance (as in kg/m).

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VALVE CLASSIFICATION What are Valves? Valves act as controls in a hydraulic system. These valves control pressure, direction of flow and volume of flow in the hydraulic system. The three major types of valves are : 1. Pressure control valves 2. Directional control valves 3. Volume control valves In the illustrations below you can see quite clearly how these valves work. Pressure Control Valves These valves are used to limit the pressure in a hydraulic system, unload a pump, or adjust the pressure of oil entering a circuit. There are several types of pressure control valves; some of these are relief valves, pressure reducing valves and unloading valves.

Directional Control Valves These valves control the direction of oil flow in a hydraulic system. Typical types of directional control valves are Check valves and spool valves. Volume Control Valves These valves control the flow rate of oil in a hydraulic System; they do this by restricting flow, or by diverting it. Some different types of volume control valves are flow Control valves and flow divider valves. These valves can be controlled in several ways: manually. hydraulically, electrically, or pneumatically.

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DIRECTIONAL CONTROL VALVES

VOLUME CONTROL VALVES

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PRESSURE CONTROL VALVES Pressure control valves are used to do following things 1.Limit pressure inside a system 2.Reduce pressure 3.Adjust the oil pressure entering a circuit 4.Unload pump

RELIEF VALVES Relief valves are sometimes called safety valves because they release the excess oil when pressure reaches the set amount . They prevent system components from damage due to overloading

TWO TYPES OF RELIEF VALVES

1. DIRECT ACTING RELIEF VALVE: Which simply open & close

2.

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2. PILOT OPERATED RELEIF VALVE Which have pilot circuit to operate the main relief valve. Direct acting relief valves are usually used in places where the volume of oil flow is small and for less frequent operations. pilot operated relief valves are necessary in places where large volumes of excess oil have to be released

DIRECTIONAL CONTROL VALVES These valves direct the flow of oil, like a policeman directs traffic. The typical types of these valves are: 1. Check valves 2.Spool valves Each uses a different type of valve element to direct oil. The check valve uses a poppet and a spring to allow oil to flow in one direction. The spool valve uses a sliding spool. The spool slides back and forth, opening and closing paths for oil to flow through.

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SPOOL VALVES

CHECK VALVES

Check valves are very simple they are called one way valves. This means that they open to let oil flow in one direction but close to prevent oil from flowing in the opposite direction This is in line check valve which is designed for straight through flow with pipe connections in line. The poppet of the valve opens when pressure on the inlet side is greater than outlet side. While it is open the oil can flow through the opening freely. The poppet closes when pressure on the inlet side drops. The valve start reverse flow & traps oil under pressure on the outlet side.

INLINE CHECK VALVES

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SPOOL DIRECTIONAL VALVES The sliding spool valve is a typical directional control valve which is used to control the operation of actuators. What is commonly called a control valve is the sliding spool valve. The spool valve directs oil to start, operate and stop actuators. When the spool is moved from neutral to the right or left, it opens some oil channels and closes others. In this way, it directs oil to and from an actuator. The spool lands seal off the inlet from the outlet oil. Spools are usually made extra hard and ground to have smooth, precise, durable surfaces. They are even chrome plated to help them resist wear, rust and corrosion. The spool valve in this illustration shows three positions, neutral, left and right. We call it a four way valve because it has four possible flow paths which go to both ends of the cylinder, to the reservoir and to the pump. When you move the valve to the left, oil flows from the pump to the left side of the cylinder, and oil from the right side of the cylinder flows to the reservoir. As a result the piston moves to the right. If you move the lever to the right, the action is the opposite, so the piston moves to the left. In the central position, neutral, oil flows to the reservoir. The paths for both ends of the cylinder are closed.

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VOLUME CONTROL VALVES As we said earlier. volume control valves work in one of two ways. They either restrict the flow, or they divert it. Flow control valves are used to control actuator speed by metering the flow. "Metering" means measuring or regulating the flow rate to or from the actuator. Flow divider valves control flow volume, but also divide the flow between two or more circuits. Flow divider valves control flow volume, but also divide the flow between two or more circuits.

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PROPORTIONAL FLOW DIVIDER The purpose of this valve is to divide oil flow from a single source. The flow divider below divides oil flows about 75-25 between its two outlets. This is possible because No.1 inlet is larger than the No.2 inlet.

SLOW RETURN VALVE

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CIRCUIT DIAGRAMS In this text you have seen many simple drawings and illustrations to help you understand hydraulic systems and their parts and principles. We have tried to show you construction in many cases, however, aside from such illustrations, we almost always use a different kind of drawings. The drawings we use are called graphical diagrams. Each part of the system and each line is represented by a graphical symbol and You can see some good examples in the graphical diagrams below. You must remember when you look at these graphical diagrams that their purpose is not to show how the parts are constructed. Graphical diagrams are used to show functions and connections only.

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LINE CLASSIFICATION (RETRACT POSITION) Between all of the components in a hydraulic system there are as each has function each has a different name The main types of lines are: WORKING LINES ARE pressure lines, suction & return lines NON WORKING LINES- Drain lines & pilot lines

ADVANTAGES AND DISADVANTAGES OF HYDRAULIC SYSTEM

We have studied basic principles and have an idea of how hydraulics work. Before closing, let's have a look at the advantages and the disadvantages of hydraulics over other method of power transmission.

ADVANTAGES

1.Flexibility 2. Force Multification

3.Smoothness 4.Simplicity

5.Compactness 6.Economy Safety

1. FLEXIBLITY -Confined liquid is the most flexible source of power and has excellent properties of force transfer. Use of pipe and hoses in place of mechanical elements eliminates location problems.

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2. FORCE MULTIPLICATION -Very small forces can move and control much larger ones.

3. SMOOTHNESS -Hydraulic systems are smooth and quiet in operation. Vibration is kept to a minimum.

4. SIMPLICITY -There are few moving parts and fewer points of wear in such systems, and the system lubricates itself. 5. COMPACTNESS -Design of components is much simpler, when compared with complicated mechanical devices. For example, the size of a hydraulic motor is far smaller than an electric motor that produces equal power. 6. ECONOMY -Simplicity and compactness make such systems economical, while they lose little power in use. 7. SAFETY -Relief valves protect the system against breakdowns from overloading. .

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ALWAYS KEEP GOOD MAINTENANCE PRACTICES -As hydraulic components are precision parts and are used under high pressure, good maintenance is required to protect against rust, corrosion, dirt, oil deterioration and so on, therefore cleanliness and use of the proper ydraulic oil is essential.

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FUNDAMENTALS OF HYDRAULICS

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HYDRAULIC MOTOR

VALVES

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1. MODEL NAME DESIGNATION

EX: Excellent Series

200: Operating weight range Approx. 20,000 kg

LC: Long Crawler undercarriage

For EX 200LC-i

i : Improved

ZAXIS spells Z-AXIS.

It is the third axis, followed by X-and Y-axis, and symbolises the future.

ZAXIS also means creative power drawn in the futures space.

ZX100 M, M: Means Marsh ZX 110 WD, W: Wheeled & D: Four wheel drive

ZX 450H ,H: Heavy-duty model ZX 120H ,H: Heavy-duty model

ZX: ZAXIS

200: Operating weight range Approx. 20,000 kg