ENHANCING TAMPER RESISTANCE VIA "HIGH" CODING
Are your safety control measures associated with guard door monitoring meeting ISO14119 specifications? Have you taken the necessary steps outlined within ISO14119 to not only select and implement your safety devices but to also reduce the chances of your safety control systems from being bypassed?
There are many factors to consider when designing machine safety control measures which aim to prevent exposure of identify risks. Whether to use hard guard fencing or personnel detection systems; locking or non-locking interlock devices; is the equipment in a heavy debris, cleanroom or hazardous atmosphere environment are just a few of the many factors to consider.
One important aspect which is often overlooked is applying the appropriate measure to help minimize bypassing of the installed safety controls. ISO 14119 is a safety standard which focuses on the principles for design and selection of interlock devices associated with hard guards. Part of this standard looks at what type of interlock you are using and provides different measures to help minimize bypassing if it has been concluded that a motivation to bypass safety exists.
Safety manufacturers of interlocking devices often utilize a default actuator key for a specific series of a switch. One way to prevent bypassing such safety switches is by installing it where it cannot be accessed, such as concealed within the frame of a machine. Another option is to utilize a device which offers High Coding.
ISO14119 categorizes a safety device actuator options by 3 different code descriptions. Low coding means that the safety device has 1 to 9 different possibilities for an actuator. Medium coding means that there are 10 to 1,000 different possibilities and typically applies to a trapped key safety system. For High Coding, there would be over 1,000 possibilities for an actuator. This means that the chances of obtaining a spare key to bypass a safety device which can easily be accessed is extremely rare.
According to ISO 14119, an additional measure to implement when using a High Coded device is to use tamper resistant fasteners on the actuator. This will further prevent the uniquely coded actuator from being removed from a guard to bypass a safety device.
ISO 14119 offers several different principles and measures against defeating safety devices, with High Coding actuator options offering the least number of additional measures for interlocking devices having separate actuators.