Coiled tubing injector with hydraulic traction slip mitigation circuit and method of use
AssigneeNational Oilwell Varco, L.P.
InventorsTimothy S. Steffenhagen, William B. White
Life of this patent
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Abstract
When one of at least two independently driven gripper chains (102) of a coiled tubing injector (100) begins to turn faster than another one of the injector's other independently drive gripper chains by an amount that indicates slipping of one of the independently driven gripper chains relative to tubing (109) being held between the driven gripper chains, a hydraulic timing circuit (318), which is coupled with the driven chains through hydraulic timing motors (214, 216), generates a pressure signal that causes the injector's hydraulic traction system to increase the hydraulic pressure applied by hydraulic cylinders (220) to generate a normal force applied by grippers on the chains to the tubing.
Claims22
A coiled tubing injector, comprising:
- at least two chains, each with a plurality of grippers for gripping coiled tubing within a gripping zone between the at least two chains;
- a traction system for generating a gripping force applied to the at least two chains, a hydraulic traction pressure circuit comprised in the traction system;
- a supply of hydraulic fluid at a set pressure;
- a supply of hydraulic fluid at a priority pressure, wherein the priority pressure is greater than the set pressure;
- a hydraulic timing circuit coupled with the at least two chains, the hydraulic timing circuit generating a hydraulic pressure signal indicating that a difference in speeds of the at least two chains is greater than a predetermined amount, wherein a pressure differential within the hydraulic timing circuit is used as the hydraulic pressure signal, wherein the traction system increases the gripping force in response to the hydraulic pressure signal;
- and
- a valve, wherein the hydraulic pressure signal actuates the valve to increase pressure of hydraulic fluid supplied to the hydraulic traction pressure circuit, wherein the valve selectively connects the supply of hydraulic fluid at the priority pressure to the hydraulic traction pressure circuit.
A coiled tubing injector, comprising:
- at least two chains, each with a plurality of grippers for gripping coiled tubing within a gripping zone between the at least two chains;
- a hydraulic timing circuit coupled with the at least two chains, the hydraulic timing circuit generating a hydraulic pressure signal indicating that a difference in speeds of the at least two chains is greater than a predetermined amount;
- and
- a traction system for generating a gripping force applied to the at least two chains, wherein the traction system increases the gripping force in response to the hydraulic pressure signal, wherein the traction system comprises a valve for shifting between supplies of hydraulic fluid under different pressures.
A coiled tubing injector, comprising:
- a plurality of skates to press, within a gripping zone, first and second chains toward a coiled tubing;
- at least one hydraulic cylinder coupled to one of the plurality of skates to apply a force to the one of the plurality of skates;
- first and second timing motors, coupled to the first and second chains, respectively;
- a closed circuit hydraulically connecting the first and second timing motors in series to transfer force between the first and second chains;
- a first supply of hydraulic fluid at a first pressure level, the first supply being connected to the at least one hydraulic cylinder;
- a second supply of hydraulic fluid at a second pressure level;
- and
- a valve actuated by a pressure differential within the closed circuit, wherein the valve selectively connects the second supply of hydraulic fluid to the at least one hydraulic cylinder.
A method of using a coiled tubing injector, comprising:
- rotating first and second timing motors in a fixed relationship to the speeds of first and second chains of the coiled tubing injector, respectively;
- transferring force between the first and second timing motors via hydraulic fluid in a closed circuit hydraulically connecting the first and second timing motors in series;
- applying a first pressure level to at least one hydraulic cylinder coupled to one of a plurality of skates of the coiled tubing injector;
- actuating a valve by a pressure differential within the closed circuit to selectively apply a second pressure level larger than the first pressure level to the at least one hydraulic cylinder;
- apply an adjustable pressing force to the one of a plurality of skates coupled to the at least one hydraulic cylinder;
- and
- pressing within a gripping zone, the first and second chains toward a coiled tubing with the plurality of skates.
Dependencies are inferred from the claim text.