Pig detector

Apparatus for detecting a pig in a pipeline, comprising:

• a housing mounted over an aperture in the wall of the pipeline;
• a hydraulic piston and cylinder mounted on said housing, said piston having a first and second conduit with a common bore extending therethrough, said first conduit extending into said housing and aligned with the aperture and said second conduit extending exteriorly of said cylinder;
• a non-magnetic rod received within said common bore and having a magnet disposed on its upper end;
• a non-magnetic end cap secured to the upper end of said second conduit and receiving said magnet;
• means disposed on said housing for detecting the magnetic field of said magnet;
• means for actuating said piston to move said piston downwardly, said first conduit and rod having a portion thereof passing through the aperture and projecting into the pipeline upon said downward movement;
• said cap being disposed adjacent said detecting means upon said downward movement;
• and
• the downward movement of said rod being arrested by the pressure of a pig in the pipeline with said second conduit continuing to move downward to expose the magnetic field of said magnet to said detecting means.