Methods and apparatus for sensing wellhead pressure

摘要

This invention relates to methods and apparatus for monitoring fluid pressure in a subsea petroleum installation or other similarly inaccessible system while isolating the well fluid from the production control system. In one particular form of the invention, a body of secondary fluid is pressure-responsively coupled to but isolated from the oil or other primary fluid of interest by a piston, which subjects the secondary fluid to the pressure existing on the primary fluid. In addition, a measuring device is connected to the secondary fluid to derive an electrical signal representation of the pressure on the secondary fluid as a correlative indication of the wellhead or other pressure actually sought to be measured. Further, the isolating device is constructed and arranged to effectively seal off the primary fluid from escape into the environment or into the production control apparatus and the pressure of the primary fluid is maintained in the event of damage to any portion of the chamber enclosing and holding the secondary fluid. It is a particular feature of this invention to provide at least a minimum pressure on the secondary fluid of a magnitude such as to effectively limit the further compression of the secondary fluid by the piston, when the piston is initially subjected to the primary pressure.