Hydraulic Systems Components and Operation
1) Basic Components of a Pond and Their Functions
1. Vent: Since the oil inside the tank comes and goes, you need a vent to allow air to enter or exit when the oil level changes, preventing a vacuum.
2. Oil Level: The level indicator is used to verify the current oil volume in the tank, which should ideally be twice the amount used by the circuit.
3. Thermometer: This checks the oil temperature in the reservoir, as each type of oil has specific operating temperature limits.
4. Oil Output: This is where the pump draws oil from the tank. A filter can be placed between the pump and the oil output.
5. Diverter Plate: This separates the incoming fluid from the outgoing fluid, preventing the oil output from mixing with the input and carrying impurities, temperature variations, etc.
8. Filling the Tank: This is where you add oil before a task or when the low-level indicator signals the need.
9. Return of the Oil: This is where the oil returns to the tank. It often consists of a rod cut at 45 degrees, aimed at the opposite wall of the aspiration point to minimize the spread of fluid with impurities, bubbles, etc.
10. Empty Tank: This allows for periodic cleaning of the pond and removal of the remaining oil.
2) Filter Placement in a Hydraulic Drive and Their Characteristics
Hydraulic systems typically use three types of filters:
- Suction Filter: Located between the pump and the tank, it removes particles from the reservoir.
- Pressure Filter: Traps particles generated by the pump during normal operation and is located after the pump.
- Return Filter: Situated before the tank, it prevents wear particles from reaching the circuit components.
3) Types of Oil Hydraulic Pumps
Gear Pump:
The oil is carried between the teeth of the gears. They are cost-effective and tolerant of impurities in the oil, but they can be noisy.
Internal Gear Pump:
Suitable for low speeds and low inlet pressures, they provide a constant and even flow discharge despite pressure variations.
Gear Pump Type Lobes:
Similar to gear pumps, but with lobes instead of gears.
Vane Pump:
These pumps have a slotted rotor revolving inside a chamber. Vanes within the rotor slots move in and out due to centrifugal force, creating suction and discharge. They are compact, and the blades can be replaced.
Balanced Vane Pump:
With two inlets and two outlets, radial forces are balanced, and oil is expelled every half turn. They are more expensive than gear pumps but quieter, and their efficiency decreases with wear.
Axial Piston Pump:
Widely used, they consist of a rotating drum with pistons and a pressure cap with input and output connections. They are the most expensive but also the most efficient. They are sensitive to oil contamination and have low tolerances.
4) Variable Flow Pumps: Methods for Flow Change
While all pumps can adjust flow output by changing their speed, variable displacement pumps can alter the output flow by modifying the geometry or volume of the internal chambers.
5) Technical Details of a Pump
Typical technical details include: maximum and minimum pressure, flow rate (L/min), displacement volume, oil type, dimensions, weight, permissible temperature, pressure multiplication, and maximum RPM.
6) Primary Functions of Hydraulic Components
- Relief Valve: Protects equipment and piping from excessive pressure.
- Flow Reducing Valve: Allows for precise adjustment of oil flow. It can be used in both directions and opens when the pressure exceeds the set value.
- Piloted Check Valve: Prevents leakage in specific parts of the system, such as hydraulic cylinders or motors.
- Flow Divider: Splits the flow into two or more streams. Used in applications like wastewater treatment to avoid overloading treatment tanks.
- Circuit Selector Valve “O”: (Further information needed on this specific valve type.)
7) True or False Statements
- F: Controlling the flow rate alters the pressure applied to the actuator (motor or cylinder).
- V: Controlling the pressure alters the force exerted by the actuators.
- V: Reducing the diameter of a pipe increases the velocity of the fluid.
- F: The torque generated by a hydraulic motor depends on the flow.
- V: The speed of an actuator depends mainly on the flow it receives.
9) Flow Control Valve Installation
Flow control valves can be installed in the actuator’s work and unloading lines to regulate its speed.
10) Check Valve Identification
Based on the description, it’s a bidirectional check valve with an adjustable back check feature.
15) Cartridge Type Valves
These valves operate similarly to spool valves. By combining various commands, they can regulate pressure, flow, and act as directional valves.
16) Servo Valves
Servo valves, or proportional valves, are actuated by electrical signals. A solenoid, typically located at each end of the valve, moves the spool based on the strength of the signal, allowing for precise control.