The “Autolock” function was developed at the request of the operators to allow for safer and more timely tripping. By locking the tool in the open position, the drill string can easily drain and fill during tripping operations. This “Autolock” feature of the PBL Bypass System is reliable and very effective.
|The unique “Autolock” function works as following:|
To lock the tool open:
1. With the activation ball dropped and the tool open, drop the smaller locking ball. When the locking ball reaches the tool it will move through the open port in the sleeve and lodge in the nozzle in the main body. When pressure/flow is reduced, the sleeve will start to close, wedging the locking ball against the nozzle, holding the sleeve open. The top of the activation ball is level with the ports, so that no debris can be accumulated above it; all debris is simply flushed out of the port. (see Figure 1)
To unlock the tool:
1. With the tool in the locked open position (activation ball in the seat, and the locking ball in the port nozzle), drop the two deactivation balls. The operator then pressures up past the shear pressure rated for the tool (stamped on the OXD). The following series of events occurs, releasing the tool to the closed position.
A) The first deactivation ball will close the remaining open port, dead-ending the tool.
B) At approximately 1/2 - 2/3 of the rated shear pressure for the tool, the locking ball will blow through into the annulus (approximately 1000psi below activation ball shear pressure).
C) The second deactivation ball will then close this second port, again dead-ending the tool.
D) As the pump pessure exceeds the shearing specified for the tools, the activation ball will blow through the seat, and be caught in the cage below. The two deactivation balls will follow.
E) The tool is now closed and ready for drilling. This sequence can be repeated up to 3 - 5 times (depending on the tool size).
Extended catcher cages to accommodate up to 10 sets of balls (10 cycles) are available on request.