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plc program and safety

Created by: saeedplc at: 7/10/2014 8:05 AM (4 Replies)

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7/10/2014 8:05 AM	Rate (0)
saeedplc Posts: 288 Rating: (4)	hello dear friends. i am curious to know that what safety precedure i should consider when i write plc program. i mean that for example if i press emergency stop button on the machine what should happen in plc program. should all outputs be turned off? should the hydraulic motor be turned off and it should be independent of plc program? please tell also about electrical wiring of emergency stop and power on the machine. best regards.
saeedplc Posts: 288 Rating: (4)
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7/10/2014 8:32 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 12/31/2023 Posts: 8092 Rating: (878)	Hello, It depends upon the machine logic & functional or operational requirements. There is no any rule but generally, when emergency stop is pressed, "in emergency conditions", all power deviceslike motors, solenoid valve, pumps, etc are STOPPED i.e. out puts are cutt off. HTH

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7/10/2014 10:00 AM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 10/17/2024 Posts: 5697 Rating: (715)	Hello, The reaction to a emergency stop should be stop all movement as fast as possible and then put the machinne in a save state to prevent moving without some kind of reset. For in example a big motor with Fc you first have brake as fast as possible and then cut the power to the Fc or put the fc in safe torque off mode. Off course every country has it's own regulations, so check that first. Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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7/24/2014 9:33 AM	Rate (0)
olloy Silver Member Joined: 8/27/2010 Last visit: 4/13/2024 Posts: 417 Rating: (37)	Hi! My little addition: An Emergency Stop is a fail-safe control switch or circuit that, when de-energized, will stop the operation of associated equipment and will shut off all potential hazards outside the main power enclosure. An overview of the European standards applicable to Emergency Stops: ISO 13850 / 4.4.4 Gives requirements for the emergency stop function of a machine, whatever the energy used may be: Once the emergency stop command has been generated during actuation of the Emergency Stop device, the command shall be maintained by latching means. The emergency stop command shall be maintained until the device is reset (disengaged). It shall not be possible for the device to engage without generating the stop command. In case of a failure in the emergency stop device (including the engagement means), generation of the stop command shall have priority over the engagement means. EN418 / 4.1.11 Gives requirements for the emergency stop function of a machine In addition to the ISO 13850 requirements above, EN418 more specifically states: Any action on the device which results in generating the emergency stop command shall also result in the latching-in of the device so that when the action on the device is discontinued, the emergency stop command continues to be maintained until the control device is reset (unlatched). IEC 60947-1 Low Voltage Switchgear and Control Gear: General Rules IEC 60947-5-1 Control-Circuit Devices and Switching Elements, Electromechanical Control Circuit Devices IEC60947-5-5 Control-Circuit Devices and Switching Elements, Electrical Emergency Stop Device with Mechanical Latching Function IEC 60204-1 Gives additional requirements for an emergency stop function realized by the electrical equipment of a machine, specifically installation methods and location requirements. Andhereis a few emergency stop circuit examples (be aware, that standards mentioned that site is Australian). Hope it helps.

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7/15/2017 11:04 PM	Rate (0)
GuyBrows of the Brow Posts: 7 Rating: (0)	Hi The removal of power to actuators etc are normally carried out with a separate safety relay unless of course you are using a safety plc. In the UK we carry our a risk assessment according to BS EN 13849-1 to determine how we will stop the machine and in some rare cases it is even necessary to have an actuator carry out a special function when an estop is pressed as the instant stop could create a more dangerous state. Check out this book for some great info regarding safety design. https://www.sick.com/de/en/we-guide-you-to-safe-machinery-in-six-steps/w/safety-know-how/
GuyBrows of the Brow Posts: 7 Rating: (0)
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