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For a medley of innovative designs
THE CHARACTERISTICS AND MECHANICS OF EVERTING LINERS

The everting/inverting flexible liner is a simple, albeit subtle device with many attractive characteristics.  The first video shows how a liner is everted into and then inverted out of a vertical borehole.  As the everting liner propagates down the borehole, it displaces the borehole water into the formation.  The inverting liner, during removal, draws the formation water into the borehole.  The liner is driven into the borehole by the pressure of the water inside the liner.  That water pressure is produced by the water level inside the liner being above the water level in the formation.  Gravity maintains that pressure difference.  This is a very simple method for pressurizing the liner to provide a seal of the borehole.  In some situations, the liner is everted with air pressure or a heavy mud or other driving fluid.  With air pressure, the liner must be everted from a reel within a pressurized canister. The liner removal is effected by the tension of the tether on the liner, but the interior pressure is still required to cause the liner to invert instead of buckling. The second video below shows the high quality sealing capability of a FLUTe liner.

Carl Keller, on the high quality sealing of a FLUTe liner


The FLUTe everting liners can:
• Provide a continuous seal of a borehole or pipe, and prevent migration of formation fluids through the open hole. No sealing grouts or bentonite seals are needed.

• Carry many useful devices such as tubing, instruments, absorbers, reactive covers, etc.. into place in the borehole while maintaining a continuous seal of the borehole.

• Be used as a flow meter while displacing the borehole water into the formation.

• Support the borehole wall against collapse.

• Propagate through tortuous passages of varying diameters inaccessible to rigid piping or push rods.

• Tow geophysical sondes of many kinds along the interior of the borehole while supporting the borehole against collapse onto the sonde.

Be removed by inversion without the inverted liner touching any other portion of the borehole wall except where the liner was everted into place against the borehole wall.

Be fabricated in many different diameters for many applications.
These capabilities are utilized in the many FLUTe uses of flexible liners. The FLUTe liners are made of high strength fabrics coated with urethane to make them impermeable to the pressurizing interior fluids.

The larger the borehole, the more easily it is everted into place. Methods have been developed to evert liners into difficult boreholes such as those with artesian flows, large vertical pressure gradients, sharp rocks, or nearly impermeable formations. The liner eversion can propagate through large caverns and washouts such as in karst formations.

With these liner characteristics and special construction techniques, FLUTe has devised methods for sealing of boreholes while mapping in great detail, and very quickly, the transmissivity distribution in open boreholes. Other methods are multi-level sampling of water quality and head measurements, mapping of LNAPLs and DNAPLs, measurement of flows between boreholes, wicking of vadose zone pore water samples, collection of vadose gas samples, pressing activated carbon felt against the borehole wall to obtain a replica of the contaminant distribution, propagating horizontally beneath landfills and buildings to obtain ground water samples, and many other methods. FLUTe has also relined with cure-in-place liners the cast iron piping in the walls of the Smithsonian Museum of Natural history.

As an aid to the use of these flexible liners, FLUTe has designed unique machines for the liner construction and for the field installations. Some of the
ancillary equipment is described on this website for rental or for purchase.

The liner fabrication is done with unique FLUTe devices, and a wide range of liner materials have been developed for different situations. Liner sizes range from 2 inch diameter to more than 30 inches. Liners have been installed to 1400 ft in 4 inch diameter boreholes and can be installed much more deeply under favorable circumstances. Because of the high strength fabrics used, liners are surprisingly puncture resistant. However, most liners should not be dragged on abrasive surfaces such as concrete pavement. Liners have been fabricated which have over 100 psi burst pressure capability in 6 inch diameter.

Most borehole liners are installed in uncased open stable holes in fractured rock, but they are often installed in cased holes with multiple screens. Liners under landfills are usually installed in lined holes, but have been installed under landfills in uncased holes via a technique called
liner augmentation of horizontal drilling. Liners can be installed vertically upward from underground tunnels. Liners can be propagated across the surface of a lake or along the bottom of the lake bed depending upon the design and the driving fluid. With air pressure, liners can be even be everted vertically upward in the open air. An everting liner is a simple means of deploying a light weight “pipe line” quickly under difficult circumstances.

For ordinary or extraordinary applications, contact us with any questions.