What is the difference between proactive and reactive inhibit functions and when should they be used?
Inhibit functions could be used to prevent unexpected start-up any time someone could be undetected or unobservable inside a safeguarded space. Proactive inhibit functions give individuals control to prevent a machine from being reset while they are inside the safeguarded space, whilst reactive inhibit functions allow them to escape the area or stop a reset that has been initiated.
Below more information on what proactive and reactive inhibit functions are, as well as some examples.
In whole body access applications – any situation where a person can be completely inside a safeguarded space – it is important to make sure that the machine cannot be reset while personnel is still inside the space.
The method chosen to prevent unexpected start-up will be dependent on the risk assessment. This could include placing 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.
However, these options are not always possible or practical due to the size, layout, or environment of the safeguarded space. In such situations inhibit functions should be considered.
The two types of inhibit functions are proactive and reactive inhibit functions.
Proactive Inhibit Functions
Proactive inhibit functions give an individual control to prevent a machine being reset while they are inside the safeguarded space.
An example is interlock blocking, preventing an interlock from being closed. This can be achieved by applying a personal padlock onto the interlock (or its actuator), or with a personnel (safety) keys where the operator takes a personnel key from the interlock into the safeguarded space.
In both cases the guard cannot be locked while personnel are inside and the machine cannot be reset or restarted.
Reactive Inhibit Functions
Used in the event of inadvertent restart, reactive inhibit functions give personnel the ability to avoid exposure to hazards if they become trapped.
The most common example is an escape release function, used in conjunction with an initiation warning system. The interlock must be easily openable from inside the safeguarded space in all modes of operation, even if the power has failed.
Operating the interlock with an escape release function must initiate a stop command and unlock the device allowing personnel to exit.
Examples of Inhibit Functions
Each person takes a personnel key from the interlock into the safeguarded space. While that key is with the person the interlock cannot be relocked and the machine cannot be reset.
Fortress offers several different options to give personal control and reduce risk to personnel entering a safeguarded space, including forced extraction and retrofittable solutions (either mechanical or RFID coded).
Each person entering the space attaches a personal padlock onto the interlock or its actuator to stop it being closed, ensuring the machine cannot be reset until every person has left and removed their personal padlock.
The most common example of a reactive inhibit function. An escape release will allow personnel to escape when a reset that has been initiated unintentionally or when they have become trapped in the safeguarded space.
Examples of Inhibit Functions
Personnel (Safety) Keys
Each person takes a personnel key from the interlock into the safeguarded space. While that key is with the person the interlock cannot be relocked and the machine cannot be reset.
Fortress offers several different options to give personal control and reduce risk to personnel entering a safeguarded space, including forced extraction and retrofittable solutions (either mechanical or RFID coded).
Interlock Blocking
Each person entering the space attaches a personal padlock onto the interlock or its actuator to stop it being closed, ensuring the machine cannot be reset until every person has left and removed their personal padlock.
Escape Release
The most common example of a reactive inhibit function. An escape release will allow personnel to escape when a reset that has been initiated unintentionally or when they have become trapped in the safeguarded space.
Case studies
Enhancing Lockout / Tagout Procedures – How Do I Perform Full Power Isolation?
Case studies
Example of a Trapped Key Interlock System in the Control of Multiple Energy Sources
Unexpected Start-Up Prevention with Proactive Inhibit Functions
Proactive inhibit functions such as the safety key prevent unexpected restart whilst operators enter safeguarded spaces.
RFID Safety Key (RSK)
RFID Safety Keys remove the risk of on-site duplicates of lost keys with integrated re-teachability when protecting from unwanted restart.
Case studies
Design to Minimize Motivation to Defeat Possibilities of Interlocking Devices
EN 528:2021 – Designing a Safeguarding Solution
Automated Storage and Retrieval Systems – How to Design your Safeguarding Solution to Meet EN 528
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