Minimising emissions of volatile organic compounds (VOC) from oil tankers during fluctuating ambient conditions is vitally important from environmental and commercial points of view. The release is often undertaken when the gas pressure approaches a pre-set point. However, it is not always clear at what pressure a manually controlled release should be stopped, leading to excess vapour release, air pollution and cargo loss.
To meet this challenge the VOCON Valve and Reporting System controls the vapour pressure in oil cargo tanks to minimise VOC emissions. Complying with the latest international regulations, it is equipped with the most advanced reporting system available.
Central to the system, a venting control valve operated by a Rotork CMA electric process valve actuator is installed on the bypass line between the IG (inert gas) main pipeline and the mast riser. The actuator automatically modulates the valve position in response to a signal from a pressure transmitter to control the vapour pressure in all the cargo tanks. This critical duty reduces VOC loss by maintaining a constant pressure in the cargo tanks during the voyage.
The compact and robust CMA is IP67 environmentally sealed and certified for Zone 1 hazardous areas, providing maintenance-free operation in exposed environments. Accepting a 4-20mA control signal, resolution is 0.2%, delivering accurate, repeatable and backlash-free positional control.
Tel +44 (0)1225 733200 | information@rotork.com | www.rotork.com