Position instrumented blowout preventer

The method of determining the location of a ram in a well head blowout preventer, which comprises

• positioning a longitudinally magnetized magnetostrictive waveguide tube alongside and parallel to the travel path of a piston that drives a preventer ram,
• affixing to the driving piston a plurality of permanent magnets evenly spaced around and in a plane transverse to the waveguide tube so that as they travel forward and back with the closing and opening of the driving piston they longitudinally magnetize a small area of the waveguide tube,
• pulsing a conductive wire located inside the waveguide tube to generate a moving toroidal magnetic field around the wire to produce a helical return signal in the tube when the toroidal field encounters the longitudinally magnetized area of the tube,
• continuously magnetostrictively sensing the helical return signal to absolutely determine the location of the driving piston as it closes and opens.

The method of determining the velocity of a ram in a well head blowout preventer, which comprises

• positioning a longitudinally magnetized magnetostrictive waveguide tube alongside and parallel to the travel path of a piston that drives a preventer ram,
• affixing to the driving piston a plurality of permanent magnets evenly spaced around and in a plane transverse to the waveguide tube so that as they travel forward and back with the closing and opening of the driving piston they longitudinally magnetize a small area of the waveguide tube,
• pulsing a conductive wire located inside the waveguide tube to generate a moving toroidal magnetic field around the wire to produce a helical return signal in the tube when the toroidal field encounters the longitudinally magnetized area of the tube,
• continuously magnetostrictively sensing the helical return signal to absolutely determine the location of the driving piston as it closes, and
• determining the velocity of the driving piston from the locations of its positions over a period of time as the driving piston closes.

The method of determining the closure rate of a ram in a well head blowout preventer, which comprises

• positioning a longitudinally magnetized magnetostrictive waveguide tube alongside and parallel to the travel path of a piston that drives a preventer ram,
• affixing to the driving piston a plurality of permanent magnets evenly spaced around and in a plane transverse to the waveguide tube so that as they travel forward and back with the closing and opening of the driving piston they longitudinally magnetize a small area of the waveguide tube,
• pulsing a conductive wire located inside the waveguide tube to generate a moving toroidal magnetic field around the wire to produce a helical return signal in the tube when the toroidal field encounters the longitudinally magnetized area of the tube,
• continuously magnetostrictively sensing the helical return signal to absolutely determine the location of the driving piston as it closes, and
• determining the rate of closure of the driving piston from the locations of its positions over a period of time as the driving piston closes.