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2017 WINTER

State at least four advantages and disadvantages of pneumatic systems...........................

Advantages of Pneumatic system 1) Infinite availability of the source 2) Easy channeled and Temperature is flexible 3) Safe and clean 4) The transfer of power and the speed is very easy to set up 5) Can be stored and Easy utilized Disadvantages of Pneumatic system ( Four points 02 Marks) 1) Requires installation of air-producing equipment 2) Easy to leak 3) Potential noise 4) Easy condenses 5) Low operating pressure 6) Limited applications.

Explain pneumatic impulse circuit with neat sketch...............

Figure 1 shows a symbol circuit of an impulse-valve controlled double acting pneumatic cylinder (A). The position of the impulse-valve (3), which is controlled by the start/stop-valve (1) and the end position valve (2), determines if the cylinder piston shall make a positive stroke and negative stroke. Positive piston stroke is initiated by manual activation of the start valve (1). Negative piston stroking takes place when valve (2) is activated by the cylinder rod at the position a1.

Explain working of counterbalance hydraulic circuit with neat diagram........

Counterbalance valves are commonly used to counterbalance a weight or external force or counteract a weight such as a platen or a press and keep it from freefalling.Figure1.16 illustrates  the use of a counterbalance or back-pressure valve to keep a vertically mounted cylinder in the upward position while the pump idles, that is, when the DCV is in its center position. During the downward movement of the cylinder, the counterbalance valve is set to open at slightly above the pressure required to hold the piston up (a check valve does not permit flow in this direction).

Explain time delay valve with neat sketch....

Time delay valve is a combination valve used to set the operation time as per the requirement. The time delay can be increased or decreased by adjusting the flow through the non-return flow control valve. The change invariably increases or decreases the time taken to fill and pilot actuates the direction control valve. Time delay valve is a combination of a pneumatically actuated 3/2 direction control valve, an air reservoir and a throttle relief valve. The time delay function is obtained by controlling the air flow rate to or from the reservoir by using the throttle valve.

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