The Petrostar Ball Seat Circulating Valve is designed to be a reliable closeable circulation port generally ran at the bottom of a tool string in either cased or open hole for vertical or horizontal well completions. Once the tool string is in place and the required circulation operation is complete a ball is circulated onto the seat, an adjustable pre-determined pressure is applied and an internal sleeve shifts downwards which closes the internal circulating ports. Once the sleeve has been shifted a positive locking mechanism ensures it is securely maintained in place.