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Safety Circuits on machinery need to be 'Control Reliable which requires redundancy and monitoring (Self Checking). But how much redundancy is required? I have seen many designs and ideas demonstrating electrical redundancy but not too much regarding pneumatic redundancy. The system I am working on is a small pneumatic press (1400 lbs force, ine inch stroke) controlled by a solenoid valve with the parts loaded/onloaded manually. A light curtain is between the operator and press.
First, is a dual valve (i.e Ross Controls or Herion) needed to control the press? A regular 5/2 solenoid valve does not have redundancy.
What about a pilot operated check valve to prevent the press from moving/drifting down?
Second, I have seen many machines that incorporate a dump valve that exhausts all air pressure when the E-stop is pressed. To make the system 'Control Reliable', shouldn't the dump valve have redundancy built-in or two dump valves being used?
And how does the E-stop safety relay monitor the dump valve for proper operation. Auxillary contactors are monitored using NC contacts.
Please respond with any ideas and comments.
Adrian
First, is a dual valve (i.e Ross Controls or Herion) needed to control the press? A regular 5/2 solenoid valve does not have redundancy.
What about a pilot operated check valve to prevent the press from moving/drifting down?
Second, I have seen many machines that incorporate a dump valve that exhausts all air pressure when the E-stop is pressed. To make the system 'Control Reliable', shouldn't the dump valve have redundancy built-in or two dump valves being used?
And how does the E-stop safety relay monitor the dump valve for proper operation. Auxillary contactors are monitored using NC contacts.
Please respond with any ideas and comments.
Adrian