Implementation

The aim of the project is to secure the operation of 11 bucket loaders. Bucket loaders are ATEX 20 classified. To meet CARGILL recommendations, it was decided, according to the Critical Safety Devices (CSD) safety document, to record the temperatures at various points on the bucket loaders :

• The actual temperatures at the bearings of the 11 bucket loaders and on two levels :
  • Two at the bottom and two at the top (4 temperature probes per lift, i.e. 44 probes in total).
• The actual ducts temperatures on the 11 bucket loaders and on two levels :
  • Two at the bottom and two at the top (4 temperature probes per bucket loader, i.e. 44 probes in total).
• The temperature of the crusher filter duct, at 2 separate points (i.e. 2 temperature probes).
• The temperatures of the crusher bearings, at 2 separate points (i.e. 2 temperature probes).

To validate the monthly check recommended by CARGILL, it was decided to measure the real speed of the 11 bucket loaders (i.e. 11 rotation controllers):

• Speed ​​is measured on the non-motorized axis.

The measurement acquisition is carried out with analog sensors. The PLC must manage two thresholds per sensor :

• The first threshold indicates a warning, without consequences for the installation.
  • An orange indicator light is on.
  • A horn is activated for a configurable time T1.
    • If the warning remains active for a configurable period T2, the horn is activated again for the period T1
  • The second threshold triggers a fault which immediately stops the bucket loader.
    • A red light comes on.
    • A horn is activated for a configurable duration T3 (longer than for the warning).
      • If the fault remains active for a configurable period T4, the horn is activated again for the period T3..
    • If there is no faul :
      • A green light is activated.
        • It is deactivated as soon as a fault appears.

A jam sensor is installed on each bucket loaders (11 all or nothing sensors).

• When the PLC input of the sensor goes to 1, a fault is raised and the bucket loader is stopped.

A switch is installed on each bucket loaders (11 all or nothing switches)

• When the PLC input of the switch goes to 0, a fault is raised and the bucket loader is stopped.

The restart can only be done once the temperature probes have gone back below the fault threshold. A commissioning request acknowledges the faults of the bucket loader  concerned on the rising edge of the request and authorizes commissioning if there are no new faults. A reset request acknowledges all faults in the installation.