Pneumatic Actuated Rack and Pinion Positioning

Can a pneumatic actuated rack and pinion system can be used to position a 500 kg load through 180 degree

Yes, it's physically possible.

whats the pressure required and whats the design calculations
involved for rack and pinion system.

Force done by actuator = actuator piston area x pressure applied

Is 8 bar is enough for for a cylinder having a stroke length of 175mm and a bore dia of 75mm .

8 bar = 8e5 Pa

dia = 75mm -> area = 4.418 m2

Force = 3534 N = aprox 360 KG. No, it's not enough. Use more pressure or a larger actuator. DOn't forget to use a safety margin because your system will not transfer all the force directly to the load.

Whats the safety precautuions for the rack rack and pinion positioning from inadvertant failure of the pneumatic system.

You can think about duplicated control circuit and maybe an emergency damper to avoid the mass to have a sudden movement. Many actuators come with safety devices that blocks the actuator in case of pressure loss.

what kind of controlsystem can be used to position the pneumatic cylinder.

You can find actuators with position indicators built in, that can be used in a PID control. Or you can control by end of travel switches and solenoid valves... there's a number of options.

Do your homework!

what kind of safety circuit in case of pneumatics can be used to prevent the sudden failure of the positioning system.will the operation of the system be safe if we operate with a pneumatic circuit.can a flow control valve be used to control the position of the cylinder which in turn controls the position of the rack and hence the load on the pinion.

there is no problem. you can contact me.

safety circuits in sudden failure of pneumatic circuit.can u explain it with circuit diagram.