VRWII robotic welding deep well repair
The aging deep well infrastructure is in need of repairs. Current repair capabilities are limited, difficult, expensive, and many times impossible. New permanent repair solutions are needed to maintain the existing deep wells. A proposal for adapting the Visual Robotic Welding system (VRW) for deep well piping is presented here.
The need for a potential means of repair of existing deep wells for both economic and ecological reasons, is an essential consideration in the determination of the viability of this innovative design. This need has been addressed by the proposed design and development of a robotic welding system called VRW II, which can be used in 6 to 8 diameter deep wells at depths up to 5000 feet. During the design process, considerations will be made to extend the repair capability to over 10,000 feet.
VRW II is a free hand remote welding process for the first time combining the best components of human welding and robotic control to the deep well industry. The VRW II process combines closed loop control of a specially developed robotic welding arm and weld monitoring camera designed for internal pipe repair. The design allows an operator to naturally perform welded repairs in inaccessible locations. The operator monitors the welding process visually, from an internal camera. The weld monitoring camera will be modified to provide a detailed image of the weld process superior to the image available through conventional welding hoods and to withstand the extreme pressures generated at the proposed working depths. This process allows for free hand welding in areas inaccessible to a welder and where computer controlled welding is not capable of responding to changing weld conditions. In addition to the VRW II welding arm, an additional surface preparation arm will be developed to allow for surface cleaning of the pipe before and after repair. This arm has the ability to grind and wire brush the pipe applying the same axis of motion as the welding arm.
Key design criteria for the Visual Robotic Welding system (VRW II) are to establish a repair capability for deep well piping which has a high degree of reliability, provides a permanent welded repair, and is cost effective. These criteria include:
- Remote welding to depths of 10,000 feet with or without the presence of water in 6 to 8 inch diameter pipes.
- Surface preparation capabilities for both pre and post repair.
- Internal sleeve installation capabilities for excessively damaged pipes.
- Continuous video monitoring of welding, grinding, and transport operations.
At Fermi National Accelerator Laboratory, the design team has obtained considerable experience in developing remote controlled hardware to work inside pipes. During the experimental run of 1991 a major vacuum leak developed in the buried beam transport pipe linking the Proton experimental area to the beam Switchyard. The leak rate increased rapidly, and water leaking into the pipe threatened to shut down the run for all experiments in the Proton area. Working on a time scale of a few weeks, a device was developed which could be operated remotely within the several hundred foot long pipe, find the leak, clean the surrounding surface area, and install an epoxy patch especially designed to seal under water. This was accomplished successfully, and the pipe remained leak tight for the remaining months of the experiential run. The figure below is a photograph of this hardware being inserted into a test pipe matching the beam transport pipe diameter.
During the extended downtime prior to the next Fixed Target experimental run, this development effort continued to acquire a permanent remote repair capability for the large laboratory network of buried beam transport pipes. No commercial system was available which could accomplish the task of welding at distances thousands of feet inside a 12-inch diameter pipe. Hence, the first of such a system was developed, called Visual Robotic Welding.
The VRW process, illustrated in the figure above, allows for free hand welding in areas inaccessible to a human. It combines closed loop master / slave control of a specially developed robotic welding arm and also includes an adjacent robotic camera arm. Both arms articulate and have the ability to move about five independent axes. An operator, who may be located at considerable distances away, remotely controls each arm. Welding can be accomplished several thousand feet inside a pipe; the remote control was tested at much greater distances.
An additional surface preparation robotic arm was also developed for treatment of the pipe surface before and after repair. This arm is equipped to grind and wire brush the surface, and is articulated about the same five axes of motion as the welding arm. A separate camera arm also monitors the surface preparation process.
Some considerable challenges have been met in welding inside beam transport pipes at the Fermi National Accelerator Laboratory. Typically, the pipes are located in the underground aquifer and are frequently also coated with tar. Welds have been performed with water and tar pouring though the hole being repaired. The robotic arms on VRW must operate accurately and in real time to make precise welded repairs, which consistently test as helium leak tight in quality. Overall cost of VRW was less than $250.000.00 including materials and labor. The system was completely designed and constructed at Fermilab.
In comparison of the challenge presented by previous development efforts with the robotic repair of deep wells, we believe the overall level of difficulty to be similar, although details are quite different.
Design plans have been presented for a robotic system, which can perform a permanent welded repair inside deep wells. We believe the capability for welded pipe repair is fundamental to maintaining the aging deep wells at reasonable cost. Extensive experience of the design team with other challenging remote controlled systems should provide a solid base for successful development of the VRW II system.
John Anderson - Electronic Engineer Cary Kendziora - Mechanical Engineer