Plugging pinhole leaks in flowlines

A method to plug a leak in a flowline, the method comprising:

• detecting a location of a leak on a circumferential surface of a flowline comprising a longitudinal axis;
• attaching a chain-operated rotational positioning subassembly to the circumferential surface of the flowline near the location of the leak, wherein the rotational positioning subassembly carries an axial positioning subassembly that can move along the longitudinal axis, wherein the axial positioning subassembly supports a plug insertion subassembly that supports a plug that is configured to plug the leak in the flowline;
• adjusting a circumferential position of the rotational positioning subassembly such that a location of the plug is axially in-line with the location of the leak on the circumferential surface of the flowline;
• adjusting an axial position of the axial positioning subassembly such that the location of the plug is radially in-line with the location of the leak on the circumferential surface of the flowline;
• and
• moving, using the plug insertion subassembly, the plug into the leak in the flowline.

An assembly comprising:

• a chain-operated rotational positioning subassembly configured to be wrapped around a flowline, the rotational positioning subassembly comprising:
• a body comprising an arcuate surface shaped to match a circumferential surface of the flowline,
• a plurality of wheels attached to the arcuate surface and directly contacting the circumferential surface of the flowline, and
• a chain attached to the body, the chain configured to be wrapped around the flowline to retain the rotational positioning subassembly against the circumferential surface of the flowline;
• a control wheel supported by the body, the control wheel connected to the chain and to the plurality of wheels, wherein a rotation of the control wheel causes a translation of the chain which causes the plurality of wheels to rotate on the circumferential surface of the flowline, wherein the chain-operated rotational positioning subassembly further comprises a chain holder comprising a lock connected to the chain, wherein when the lock is in a locked position, the chain holder is configured to lock a rotation of the rotational positioning subassembly on the circumferential surface of the flowline, and when the lock is in an unlocked position, the chain holder is configured to permit free rotation of the rotational positioning subassembly on the circumferential surface of the flowline;
• an axial positioning subassembly attached to the rotational positioning subassembly, the axial positioning subassembly configured to move along a longitudinal axis of the flowline, the axial positioning subassembly comprising:
• a plurality of arms, each arm attached to the body of the rotational positioning subassembly, each arm extending along the circumferential surface of the flowline parallel to the longitudinal axis of the flowline,
• a plurality of sleeves, each defining a hollow portion through which a respective arm of the plurality of arms passes, wherein the plurality of sleeves are configured to slide parallel to the longitudinal axis of the flowline on the plurality of arms, and
• a plate connecting the plurality of sleeves;
• and
• a plug insertion subassembly attached to the axial positioning subassembly, the plug insertion subassembly comprising:
• a plugger body attached to and resting on the plate of the axial positioning subassembly,
• a threaded shaft passing through the plugger body and comprising a plug holder configured to hold a plug to plug a leak in the circumferential surface of the flowline, and
• a control wheel attached to the threaded shaft.