What are hydraulic pumps and where are they used?
Hydraulic pumps convert mechanical power or energy into hydraulic power/energy
They are used at the power input end of the system
What are the three main types of pumps?
Gear, vane, piston
What are the 6 types of piston pumps?
- Simple piston pump
- Swash plate piston pump
- Bent axis pump
- Wobble plate pistion pump
- Simplex piston pump
- Duplex piston pump (double acting reciprocating steam pump)
What are accumulators and where are they used?
They are an isolated energy store obtaining a volume of hydraulic fluid under pressure from a spring, dead weight, or compressed air.
What are brake power boosters?
Accumulator (pressure intensifier) to add thrust to brake actuation. Located between the footbrake linkage and the master cylinder.
What are the four types of brake boosters?
- Vacuum suspended
- Air suspended
- Hydraulic
- Electro hydraulic
What are pressure converters and what do they do?
- Also known as pressure intensifiers or de-intensifiers
- Displacement devices peforming as simple pumps
- Low pressure -> larger piston area, vice versa.
What are hydraulic actuators and what to they do?
- Convert hydraulic power or energy back into mechanical power or energy.
- Similar to a power input device (ie pump)
- Rotary actuators - hydraulic motors
- Linear actuators - hydraulic cylinders
What are the three types of control valves?
Pressure control
Flow control
Directional control
Why is pressure control necessary?
Fluid is essentially trapped, so in the interest of the equipment and safety, we must incorporate a relief valve
What are the five types of pressure control valves?
- Direct acting/single stage relief valve
- Pilot controlled or two-stage relief valve
- Pressure-reducing valve
- Differential pressure regulator
- Proportioning pressure regulator
When are direct-acting/single-stage relief valves used?
When the power being transmitted is comparatively small
When are pilot controlled/two-stage relief valves employed?
When sensitive control of the system is required
Why are pressure-reducing valves used?
Different maximum pressures exist in the same system, thus pressure reducing valves must be used
What are pressure regulators used for?
Used to control a pressure within a certain fixed amount of another pressure (differential and proportioning)
What do differential pressure regulators do?
ensures that there is a fixed difference between inlet and outlet pressure at all times, where the difference in pressure will usually correspond to the spring setting.
What does a proportioning pressure regulator do?
It maintains a fixed ratio between inlet and outlet pressures
How can flow control be achieved?
- Variable pump delivery or throttling valves
What are the three types of directional control valves?
Flow divider
Non-return valve
Multi-way directional control valve
What is the purpose of a flow divider?
It is used to divide the hydraulic flow into two or more equal parts
What is the purpose of a non-return/check valve?
It is used to restrict flows only in one direction?
What is a shuttle valve and what is it used for?
It connects two pressure sources to a common outlet.
What are multi-way directional valves used for?
Where a double-acting actuator is used, it is necessary to reverse the direction of flow into the actuator so as to obtain reverse motion.
