Provides safe access
February 1st 2006 Trapped-key interlocks from Castell are protecting maintenance workers at an underground liquid hydrogen bus refuelling station near Hornchurch.
To combat any fire risk, the site's three-level, 55 000L storage vessel is protected by a CO2 deluge system. In addition to electrical safety measures, BOC (responsible for the project on behalf of BP) opted for a mechanical safety guard to ensure noone could access the storage chamber while the CO2 supply is active.
When entering the chamber, a three-way MBV ball valve interlock must be set to discharge to atmosphere.
The interlock releases a coded key, which is inserted into the lock, allowing the door to be opened. The key is trapped in the lock, while a second key is released.
Retaining the key, the worker is sure the CO2 supply cannot be re-established. More articles from Castell Safety International Ltd: | 
