Method and device for controlling tank vapors on a petroleum storage tank

摘要

A device and method are shown for controlling tank vapors on a petroleum storage tank of the type having a tank vapor line which runs to a suction scrubber. The scrubber being connected by conduit to a reciprocating compressor which, in turn, is connected to a compressed vapor discharge line for passing compressed vapors to a gas sales line. The reciprocating compressor is operated to draw tank vapor through the suction scrubber and through the reciprocating compressor to discharge vapor through the compressed vapor discharge line. A pneumatic control valve is installed in the tank vapor line for controlling the flow of tank vapors to the suction scrubber. A pilot valve is provided as a part of the pneumatic control valve for controlling the operation of the control valve. The control valve is operated to maintain a vacuum in the tank vapor line between the control valve and the suction scrubber to eliminate the tendency of tank vapor to liquify in the tank vapor line.