What is the difference between proactive and reactive inhibit functions?
Inhibit functions should be implemented anytime someone could be unnoticed or unobservable in a safeguarded area.
Proactive inhibit functions give an operator the control to stop a machine from being reset while they are in the safeguarded space. Reactive inhibit functions allow them to escape or stop a reset that has been initiated.
Full body access
In “full body access” applications, , any situation where a person can be completely inside a safeguarded space, it is important to make sure that the hazard can not be reset while a person is still inside the space. This can be achieved by putting a manual reset device in a location with a full view of the entire safeguarded space or by using presence-sensing devices to detect people in unobservable locations.
Unfortunately, these options are not always possible or practical due to the size, layout or environment of the safeguarded space. In these situations, and if the risk assessment requires it, one or more inhibit functions should be installed. Inhibit functions can be divided into two types. Either proactively stopping the hazard from being able to be reset while personnel are inside the space, or reactively allowing them to escape and stopping the hazard if they become trapped.
Pro-active inhibit functions
Pro-active inhibit functions provide an operator personal control, the door cannot be locked behind them and the hazard cannot be reset or reset while they are in the safeguarded area – even if they are hidden from view.
Examples of proactive inhibit functions are:
– Using a safety-key function on a safety switch
– Placing a lockout on a safety switch
– A detection system such as radar protection or laser scanners
– Containment protection for doors or light curtains
Re-active inhibit functions
Re-active inhibitfunctions, in conjunction with a warning system, offer the possibility of escape if someone is locked in a safeguarded area. The most common example is an emergency escape release. It should be easy to open from the protected area in all operating states, even if the power has failed. Opening the interlock with an escape and release function should trigger a stop command on the machine.
Examples of re-active inhibit functions are:
– Safety interlock with an all-in-one emergency release function
– Safety switch or safety sensor without interlock function (only when RI&E allows it).
– Signal lights with or without sound signal
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