A Float Shoe

By Author: Joanna Smith
Total Articles: 10
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During make-up or break-out operations, the riser to be rotated is first enclosed in the tong and backup and the tong and backup doors are closed and latched. Then a motor/pump unit (float shoe) consisting of a hydraulically driven motor mounted to the tong housing and a piston pump mounted on the tong rotor produces hydraulic pressure for the clamping cylinders.

The piston pump is equipped with six pistons. Two pump pistons supply the pressure for each clamping cylinder. This ensures that each clamping cylinder gets exactly the same amount of oil to provide symmetrical and centric clamping forces for the jaw grip. The rotor then rotates the riser. Finally, the jaws release and back off from the pipe. Changeover between make-up and break-out operation can be accomplished at every rotor position. The size range of jaws is designed to accommodate all variations in riser and casing diameters within their nominal size range from 9 in. through maximum 21-in. diameter.

With its two different gear shifting systems, a shiftable planetary gear reducer for ...
... the two operation modes (riser and casing mode) and a hydraulic gear, shifting covers a total rotating speed range from 0.2-16 rpm. Three parallel-driven hydraulic motors located on the tong casing
to rotate the riser and to distribute the forces symmetrically from three sides drive the system.

A large rotary gear accomplishes closure and rotation of the riser-gripping jaws. Mechanical power is transmitted from the hydraulic motors to turn the rotary gear in either direction.

The rotary gear is a large-diameter gear that has been segmented into drill rotary table with pivotal hinges and latching mechanism. The smaller rotary gear segments pivot open to encircle the riser being worked and then close and latch while working the riser. The internal diameter of the gear has an insert surface for the clamping unit, which is driven by a separate motor/pump unit on top of the tong case to secure hydraulic pressure during rotation.

Bending and shearing forces are eliminated by the free-floating backup system as these forces are symmetrically distributed into the torque posts, allowing measurement of applied torque to be made very accurately. A torque measuring system combined with a power tong with free floating back-up eliminates oscillations and additional interfering forces. Consequently, make-up and breakout torque can be measured with the same accuracy.

Torque load is measured with an active compression-type load cell. The force is directly measured within the torque reaction system of the free-floating backup. If desired, a make-up or a break-out with the Riser Tong drill pipe joint can be controlled using a torque/turn system that records the torque over turn graph while making-up (or breaking-out) the connection.

That halts the make-up process when the pre-selected optimum torque value is reached. Many of the production riser connectors used today are externally shouldered and require “pre-loading” of those shoulders to ensure they will withstand the bending stresses caused by the environment while not backing out.

The suggested orientation of the sensing head is on a horizontal plane for a horizontal segment of pipe. A vertical segment of pipe is also acceptable if the flow is in the upward direction. A steam purge tube is standard and requires that the adapter be installed with flow in the proper direction for correct operation.

The Prism Purge Pak cleaning system is available and provides pre-mounted and plumbed condensate drain and purge solenoids saving installation time and assuring proper purge action.

A maintenance plug is also available for operation without the sensing head installed.

Available for general service and sour service in compliance with any temperature rating and material requirements specified in API specification 6A

Available with Stainless Steel 316L or Inconel 625 corrosion resistant alloy ring grooves

Tap-end studs and nuts are normally provided with studded end connections

Manufactured in compliance with WeldFit’s ISO 9001:2008 certified quality program

Ordering Information:

Nominal size, pressure rating and configuration for all end and outlet connections

Overall length - if not specified for Drilling and Diverter Spools, WeldFit will minimize length