Health Canada – Dosimeter
Health Canada – National Dosimetry Service – Auto Load and Unload Machines
Auto Load and Unload Machines are being used by Health Canada to record the amount of radiation, a person working within the parameters of radioactive equipment, has contracted over a period of time. Each holder, which is identified by name and number, has a TLD card insert which absorbs the radiation. Both the machines have a rotary indexing system where six workstations are positioned around a circular table to:
- Remove a full plaque holder from a magazine
- Extract the insert and plaque from that holder
- Scan the barcodes on the plaque and holder simultaneously
- Extract the plaque from the insert pocket and place it in a magazine
- Replace the insert back in its magazine
- Place the holder and empty insert back into a magazine
The each machine has 6 stations lettered A-F and individual parts of the machine indicated by numbered balloons. It is bench mounted with a footprint of approximately 30″ hexagonal square and a table height of 8″. Mounted above the rotary table are three removable magazines located in guides to position them over the appropriate stations and various pneumatic actuators.
The two larger magazines for holders are 24” long (capacity 60 holders each) and a single magazine for the plaque is 15″ long (capacity 240 plaques).All the actuators of the Auto—Load/Unload Machine are pneumatically operated, utilizing existing compressed air supply. The control system is operated on 24VDC from a built in switching power supply working off existing mains at 115V, 1Ph, 60 Hz.
Adjacent to the rotary table there is a control panel mounted in a suitable enclosure for the power supply, programmable logic controller (PLC), pneumatic solenoids and filter—lube—regulator units etc. Emergency stop buttons are strategically located around the table and on the control panel. Where applicable, machine guards prohibit access to moving parts.
The cycle time of the machine is 4 seconds, which gives a theoretical output of 900 plaques extracted from their holders every hour. Allowing time for magazine changes and normal operating service factors the expected output is 765 plaques/hr and assuming a 6.5 hour working day this comes to approximately 4900 plaques extracted per Auto-Load/Unload Machine per day.
About every 4 minutes the operator must replace the empty holder magazine at station “A” with a full one. Similarly, every 4 minutes the full magazine at station “F” must be replaced with an empty one, and these two operations should staggered by starting with one of the magazines half full. Every 16 minutes the full plaque magazine at station “D” must be replaced with an empty one. Sensors are fitted to detect magazines full or empty states to ensure the system stays in sequence should the operator not do a magazine change.
