Safe access to chamber
March 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 no-one 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 reestablished. More articles from Castell Safety International Ltd: | 
