Rail Dependent Storage And Retrieval Equipment

Using the Safety Mosaic safety speed monitoring Mosaic MVx modules or the speed monitoring Interface SV MR0 in applications using stacker cranes and rail dependent retrieval and transfer equipment. Monitor the movement speed of stacker cranes for collection and storage of material and transfer equipment between aisles in logistics systems ASRS (Automatic Storage and Retrieval Systems), vertical automated warehouses and warehouses with satellites.

These equipments are typically used in ASRS (Automatic Storage and Retrieval Systems) applications, vertical automated warehouses, and warehouses with satellites.

The accidents with storage and retrieval are infrequent, but when they occur the consequences can be very serious. The main dangers are:

• Shearing and crushing,
• Falling from a height in correspondence with the loading/ unloading points of the material and of the accesses,
• Injury during the maintenance procedures.

The standard reference for this type of application is EN ISO 528 of February 2009 “Rail dependent storage and retrieval equipment Safety requirements”.

This standard is applicable to all types of machines which are restricted to rails for travelling within and outside the aisles. They also include lifting means and possibly lateral handling facilities, to store and retrieve unit loads and/or long goods eg. bar materials and/or order picking or similar duties.

NOTE: The requirements of 9.2.4 of EN 60204-32:1998 will be applied for maintenance, fault clearance, inspection and setting:

1. Control devices for dangerorus movements shall be hold-to-run devices;
2. Relevant movements shall be with reduced speed;
3. Emergency stop device shall be provided at the control station.
4. If the nature of the work to be done does not give space enough to escape, the travel distance of the powered movement has to be limited or the enabling devices shall be a three-position type

As an example, consider the following functional diagram of a plant.
The operator access into the machine is regulated by procedures and specific controls, for example:

1. The machine operating mode must be switched from the automatic operating mode (A) to the manual mode (M) through an external key selector switch (1). The key can be removed only when the selector is in the manual position.
2. The door (2) can be opened only with the key removed from the selector switch. The door is monitored, so the system is in manual operation.
3. To proceed with the operations requiring, the presence of an operator, also the key selector switch inside the machine (3) must be brought in the manual position (M).
4. The plant can be activated through a “Start” button (4b) and eventually controlled by means of suitable devices such as the three-position type enabling switch.
5. In this phase the movement speed of the material handling devices must be monitored and must not exceed the safe speed. For this safety function the ideal solution is the safety speed monitoring interface SV MR0 or Mosaic MVx modules.
6. To reactivate the automatic operating mode, you need to move the internal key selector switch (3) in Automatic (A) position. The key can only be removed with the selector in automatic position.
7. The machine will start again in automatic operating mode (A) only when the door (2) is closed, and the external selector is in automatic mode (A) position.
8. At this point the plant will be started with the outside “start” button (4a).

With reference to section 5.7.6 of the ISO EN 528 standard is clear the need to monitor the movement speed of the stacker and stacker cranes during maintenance, trouble shooting, machine inspection and configuration.

The standard does not specify the speed considered safe. We will assume a speed of 2 m per minute as safe speed for the maintenance operations.

At this speed, we should be able to avoid:

• The problem of the projection of material from great heights
• Slippage problems in case of emergency braking.

For the safe monitoring up to PL d of speed you can use an SV MR0 module and 2 proximity switches, that perform the dual channel. Other solution with Mosaic MV1S with a safety encoders.

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