Conversion EFRT to CFRT

[dunedin]

Our company (VACONO) design and manufacture the aluminium dome roof (VACONODOME) for converting External Floating Roof Tanks (EFRT) to Covered Floating Roof Tanks (CFRT). We are gathering information in connection with the operating and design implications of converting EFRT to CFRT. In particular we are concerned about the comments that operators do not convert because they are concerned about the increased safety requirements for inspection of the valves on the EFRT after conversion because they now have a Fixed Roof Tank..

Have you any comments or observations on this matter, i.e would you suggest removal of the pressure relief valves and allowing the vapour under the EFRT to escape into the now free vented CFRT?

Any comments you may have would be appreciated at quinn@vacono.fsbusiness.co.uk.

 

[25362]

From what I've heard, in the UK and USA it is more general to use ventilating slits or vents. Others may still prefer P/V valves. Users of vents claim these are more effective in reducing gas concentrations to below the lower flammable limit. It is recommended that the cover should be electrically bonded to the tanks' structure.

As for losses through "penetration" fittings, such as deck fittings, roof column supports, or other openings, they are considered in the same range as for EFRTs. Aluminum (paint) finishings, and roof finishing in particular, are meant to minimize solar gain and thus the expansion of vapours by their rise in temperature. The temperature in the vapour space being found (by the API?) to be more significant than changes in tank liquid temperature.