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What is priority valve in aviation?
A priority valve gives priority to the critical hydraulic subsystems over noncritical systems when system pressure is low. For instance, if the pressure of the priority valve is set for 2,200 psi, all systems receive pressure when the pressure is above 2,200 psi.
What is a priority valve?
Description. Priority valves are used to provide a hydraulic function in a load sensing system with a priority flow.In principle, they operate like a 3-way flow control valve that always supplies the actuator that has priority with the required flow rate, and passes the remaining flow to other actuators.
What is sequence valve?
A sequence valve is a pressure-operated, normally closed, poppet or spool valve that opens at an adjustable set pressure. Some designs use a spring acting directly on the spool or poppet, others are pilot-operated. A sequence valve always has an external drain port to keep from trapping leakage oil.
What is the purpose of a sequence valve in a hydraulic landing gear system?
Sequence valves control the sequence of operation between two branches in a circuit; they enable one unit to automatically set another unit into motion. An example of the use of a sequence valve is in an aircraft landing gear actuating system.
What is the valve margin?
A valve margin is defined. Between the top of the valve and the edge of the face is the width of the valve head. Preignition and valve damage are caused by too narrow a margin.
What is a poppet type valve?
A poppet valve consists of an orifice that is opened and closed by raising and lowering a sealing surface onto the orifice. It usually has an internal spring that holds the valve in the closed position. When the spring force is overcome, the sealing surface lifts off the orifice and the valve opens.
Which valve is best for flow control?
For flow control applications where a ball valve is possible, such as filling a tank to a reasonable degree of accuracy, a trunnion or v-port ball valve design is usually the best choice.
What is a priority flow control valve?
The model OP51FC is a pressure compensated swing arm adjustable flow control valve. By swinging the arm thru 90 °, the flow out the CF or controlled low port can be varied within the range given in the specification. Any remaining flow is bypassed to the EX or excess flow port.
What is the function of the sequence valve?
The basic function of a sequence valve is to control the sequential operation of multiple actuators. Sequence valves have an actuator that diverts the medium to another part of the system to execute the next command in the programmed sequence.
What is the function of time delay valve?
Time delay valve is used to delay the output signal. The time delay valve is actuated by a pneumatic signal through the tank after a preset time delay has elapsed. The returned to the normal position via return spring when the signal is terminated.
What are sequence valves used for?
Sequence valves can be used to sense pressure (port 1) in one circuit and then open and supply oil to a secondary circuit (port 2) at a predetermined pressure. A typical application would be when maintained clamping pressure is required in the primary circuit while work is being performed in the secondary circuit.
What is the purpose of a valve margin?
The margin for an exhaust valve should be larger to improve heat dissipation—generally around 0.080-0.100 inch. Because the flow path for an exhaust valve is the opposite of an intake valve’s, you will sometimes see a smooth radius on the chamber side to improve airflow into the port.
How is the sequence valve in an aircraft operated?
The mechanically operated sequence valve is operated by a plunger that extends through the body of the valve. [Figure 8] The valve is mounted so that the plunger is operated by the primary unit.
What’s the difference between hydraulic sequence valve and pressure relief valve?
Pressure relief valve will have one pilot line to sense the inlet pressure. Pressure relief valve will be internally drained as the outlet of relief valve will be connected with reservoir. Hydraulic sequence valve is also type of pressure control valve.
How are the valves in an aircraft hydraulic system?
Closed-centered selector valves with four ports are most common in aircraft hydraulic systems. These are known as four-way valves. Figure 1 illustrates how this valve connects to the pressure and return lines of the hydraulic system, as well as to the two ports on a common actuator.
When do you use a pilot controlled valve?
Pilot controlled valves (see below) allow flow in one direction and prevent flow in the reverse direction, until operated by pilot pressure to allow free reverse flow. The specified cracking pressure is required to open the valve to allow free flow direction.