Designing a Safeguarding Solution to EN 528

 

Automated Storage and Retrieval Systems (AS/RS)

 

Rail dependent storage & retrieval has seen huge growth over the past decade with the transition to automated online retail. Whilst automation has dramatically reduced human interaction, hazards remain present when interaction is required. Fast moving automated picking and handling equipment in narrow aisles provide limited means for operators to avoid impact from approaching equipment.

 

EN 528: 2021 Rail Dependent Storage and Retrieval addresses all significant hazards relevant to rail dependent storage and retrieval equipment. Three key mitigations this standard requires are:

 

  • Prevent the risk of being trapped inside during Whole-body Access
  • Provide means of Escape Release at the end of aisles
  • Prevent Machine movement whilst access is performed by operators and the door is open
  • Prevent Unauthorised Access to the AS/RS system

 

Whole Body Access

 

To mitigate the risk of being of being trapped inside:

“Access doors […] shall be interlocked so as to open only when the machine is in the correct position for access” & “door […] opened only with key from the outside.

 

Escape Release – to escape the hazardous space in an emergency

 

In the event of being trapped inside:

“escape facilities” must be provided “in case of emergency” & allow the door to “always [be opened] from the inside.” 

 

Prevent Unintended Machine Motion

 

“Whilst the door is open (with solenoid-controlled guard locking), “interlocks movable guards… shall prevent any movement of the [Storage and Retrieval] machine when they are not fully closed.” 

 

 

Let’s take a look at EN 528…

A – Automatic      B – Manual    1 – Mode Switch    2 – Access Point    3 – Mode Switch    4 – Start Device    5 – Escape Release Door

 

 

 

The Fortress Solution

 

 

1. Outside of the safeguarded space, a key switch allows you to change the mode of the AS/RS from Automatic to Manual. The key can only be removed when in Manual Mode.

2. The door to access the AS/RS ‘safeguarded space’ can only be opened when (a) the key is removed from the switch (now in manual mode) and entered into the key switch of the interlock mounted to the door. Whilst the key is inserted into the key switch (shown in red below), the interlock can unlock and the actuator can be removed from the interlock, opening the access point.

 

 

3. For manual drive, the key is removed from the key switch on the interlock whilst the door remains open and taken inside the AS/RS area. A second Manual/Automatic switch is inside the safeguarded space and labelled opposite to step 1 (i.e. Automatic is key free, Manual is key trapped). The key can be inserted into this switch and rotated to change the mode inside to match that outside to ‘Manual’. In this state the internal mode and external mode will both be ‘Manual’ allowing the user perform manual drive.

 

4. If there is no manual drive and the operator is only performing ‘maintenance’ procedures, step ‘3’ can be skipped by the operator pocketing the key whilst inside the safeguarded space. Whilst this is on their person, the AS/RS cannot restart.

 

5. In the event an operator becomes trapped inside the AS/RS, an escape release provides the mechanism for quick escape at both ends of the aisle.

 

 

 

 

Additional Considerations – How to prevent untrained personnel from entering the safeguarded space

 

RFID features can be designed into the robust solution to set permission based access. Contact our team to learn more.

 

 

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