An automated purge valve for marine salvage

Air filled salvage lift bags have been a problem and danger since their invention due to uncontrolled vertical acceleration as they ascend the water column. This paper presents the design of an automated purge valve to control a lift bag´s ascent. The automated purge valve monitors the changes in pressure to determine the ascent velocity of the lift bag. The resulting velocity is then evaluated by a proportional, integral, derivative (PID) control algorithm that outputs a signal to a purge valve installed on the top of the lift bag. The purge valve opens or closes to control the purge of the expanding air volume allowing for a smooth controlled ascent.