Tattle-tale apparatus
An electro-mechanical indicator system for signaling when a droppable object (such as, for example, a dart, plug or ball) is released during well cementing operations. A body section has first and second chambers divided by a fluid and pressure sealing barrier. A mechanical trigger mechanism is situated in the first chamber, which is exposed to elevated pressures and harsh wellbore fluids. Less robust components, such as sensor(s), power source(s), and signal device(s) located in the second chamber, remain isolated from the wellbore environment and elevated pressures.
1. An indicating device for signaling passage of a launched object through a central flow bore of a tool comprising:
a. a body member connected to said tool having a first chamber in pressure communication with said central flow bore, a second chamber at substantially atmospheric pressure, and a substantially solid and non-magnetic pressure sealing barrier disposed between said first and second chambers, wherein said barrier isolates said first and second chambers from each other;
b. a mechanical trigger pivotally mounted within said first chamber, wherein said mechanical trigger does not extend beyond said barrier, is rotationally displaced when said launched object passes through said central flow bore, and causes a change in magnetic field across said barrier when displaced;
c. a sensor wholly disposed within said second chamber, adapted to sense when said magnetic field changes across said barrier resulting from displacement of said mechanical trigger, wherein only said magnetic field is transmitted between said first and second chambers; and
d. a signal device that produces a signal when said sensor senses said change in magnetic field across said barrier.
2. The indicating device of claim 1 , wherein said pressure sealing barrier is capable of withstanding a pressure differential across said barrier that is greater than or equal to the working pressure rating of said tool.
3. The indicating device of claim 1 , wherein said mechanical trigger comprises a spring wire tongue that when displaced by passage of said launched object causes displacement of a magnet in proximity of said pressure sealing barrier.
4. The indicating device of claim 1 , wherein said electronic sensor comprises a Hall-effect sensor that produces either an on or off signal.
5. The indicating device of claim 1 , wherein said electronic sensor comprises a wire coil positioned in said second chamber so that movement of a magnet in said first chamber produces an electrical voltage in said wire coil.
6. The indicating device of claim 1 , wherein said mechanical trigger comprises a spring wire tongue that when displaced by passage of said launched object causes displacement of a ferrous metal member in proximity to said pressure sealing barrier.
7. The indicating device of claim 1 , wherein said electronic sensor comprises a Hall-effect sensor having a biasing magnet incorporated in said Hall-effect sensor.
8. The indicating device of claim 1 , wherein said signal device generates an audible sound when said launched object passes through said central flow bore.
9. The indicating device of claim 1 , wherein said signal device comprises at least one light emitting diode to provide a visual alert when said launched object passes through said central flow bore.
10. The indicating device of claim 9 , wherein said signal device further generates an audible sound when said launched object passes through said central flow bore.
11. The indicating device of claim 1 , wherein said trigger comprises a wire configured such that all objects at least 3 inches in diameter will displace said trigger, while loss circulation material will not displace said trigger.
12. An indicating device for signaling passage of a launched object through a central flow bore of a tool comprising:
a. a body member connected to said tool having a first chamber in pressure communication with said central flow bore, a second chamber at substantially atmospheric pressure, and a substantially solid pressure sealing barrier disposed between said first and second isolating said first and second chambers from each other;
b. a mechanical trigger having a first end and a second end, wherein said mechanical trigger is pivotally mounted to within said first chamber, said first end of said mechanical trigger extends into said central flow bore substantially perpendicular to the longitudinal axis of said central flow bore, and said second end of said mechanical trigger is disposed within said first chamber and is rotationally displaced when said launched object passes through said central flow bore, thereby causing a change in magnetic field across said barrier;
c. an electronic sensor disposed within said second chamber adapted to sense said change in magnetic field across said barrier caused by displacement of said trigger upon passage of said launched object through said central flow bore, wherein only said magnetic field is transmitted between said first and second chambers; and
d. an electrical signaling device disposed within said second chamber adapted to signal when said mechanical trigger is rotationally displaced by said launched object passing through said central flow bore, and selected from a group comprising light emitting diodes and audible alarms with indicia means.
13. The indicating device of claim 12 , wherein said pressure sealing barrier is capable of withstanding a pressure differential between said chambers that is greater than or equal to the working pressure rating of said tool.
14. The indicating device of claim 12 , wherein said mechanical trigger comprises a spring wire tongue that when displaced by passage of said launched object causes displacement of a member from a group comprising magnets and ferrous metals in proximity to said pressure sealing barrier.
15. The indicating device of claim 12 , wherein said electronic sensor is positioned in said second chamber, and movement of a magnet in said first chamber produces an electrical voltage capable of being sensed by said sensor.
16. The indicating device of claim 15 , wherein said electronic sensor comprises a member selected from a group comprising wire coils and Hall-effect sensors that produce either an on or off signal.
17. The indicating device of claim 12 , wherein said trigger comprises a wire configured such that all objects at least 3 inches in diameter will displace said trigger, while loss circulation material will not displace said trigger.