Trapped key system
December 1st 2004 A concrete mixing plant at Heathrow Terminal 5 has a trapped key interlocking system from Castell Safety International.
Compactors Belgium supplied a twin plant for the production of paving-quality concrete. It opted to rely on a mechanical means of granting access to the plant as it had previously experienced problems with tongue switches.
The plant has two solenoid-controlled KSSE20 electrical switches and four AI access interlocks. When an operator wants to work on the plant, he switches off the main power supply. Depressing the KSSE20s button energises the switchs solenoid and illuminates an led to confirm that one or both of its trapped keys can be removed.
Rotation and removal of one or both keys alters the condition of the machines electrical supply to a safe condition, while granting access to one or both sides of the plant. More articles from Castell Safety International Ltd: | 
