THE LINEAR CAPSTAN

"Linear capstan" is the name we have given to the FLUTe device that is used for installing liners under special circumstances. The special circumstances are:

• very deep water tables with associated large hanging loads of the liner in the hole,
• removing liners from deep holes (>500’) which require a large tension on the liner or tubing bundle, or,
• when the liner installation/removal parameters of tension, speed, water depth, liner depth need to be measured and recorded continuously.

A linear capstan performs much the same function for a liner that a sailboat winch provides for a line (rope) on a sailboat. A linear capstan purchased by Boeing, for use in deep holes for 25 Water FLUTe systems, is shown in the photograph.

The main purpose of the original linear capstan was to pull blank liners out of deep holes with deep water tables. The linear capstan is a series of rollers with a constant surface velocity driven by an electric motor. By wrapping the liner in a zigzag manner over the rollers, a large amount of surface friction is developed. The rollers alternate in their direction of rotation, so that the liner is pulled smoothly from the hole. A very small tension on the liner at the back end of the capstan (distant from the hole), allows up to 1000 lbs to be lifted from the hole. The speed of the capstan is controlled as needed.

As the liner is pulled continuously from the hole, it is rolled onto a shipping reel. The removal of blank liners on a daily basis has been greatly eased by the use of the linear capstan instead of a simple winch system.

During installation, the liner feeds from the shipping reel through the linear capstan and into the hole. The capstan is instrumented to monitor and record tension, speed and the level of water in the liner.

The linear capstan has been used to install Water FLUTe systems to 880 ft. with a water table at about 500 ft. This device allows one to install flexible liners to much greater depths and very large diameter holes safely and without damage to the liner system.

A smaller version of the linear capstan has been built for use (rental) at many other sites. It is shown below, and can fit in the back of a small pickup truck. Other linear capstans are being built for rental and sale. Each is designed for the particular circumstances required. However, for the installations and retrievals from holes with shallow water tables, the simple wellhead roller and winch system are usually adequate.

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