Abstract:
An air inversion and steam cure apparatus for installing a flexible resin impregnated cured in place liner in an existing conduit is provided. The apparatus has a low friction seal between a moving liner and the stationary apparatus gland. The gland is operated and adjusted by displaceable members that move substantially perpendicular to the liner being inverted to engage the moving liner as it passes through the gland. No part of the gland extends into the chamber so that once a pre-shaped gland is adjusted, the pressure on the moving liner is not increased. As the liner reaches the distal end, it enters a sample and porting pipe with an exhaust pipe gland and exhaust pipe and is pierced by a rigid porting tool. Steam is then introduced into the liner to cure the resin and is exhausted through an exhaust hose connected to the porting tool. After cure, steam is replaced with air to cool the liner and the ends are cut to restore service through the existing conduit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based on and claims the benefit of pending provisional application Ser. No. 60/674,420 and No. 60/700,632, filed on Apr. 25, 2005 and Jul. 19, 2005, respectively. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to a method for installation of a cured in place liner into an existing conduit by air inversion of a resin impregnated liner with an apparatus having a low friction seal between the everting liner and a gland. The resin may be cured with continuous flow-through steam without loss of pressure and to the apparatuses for practicing the method. The method and apparatuses are particularly well suited for lining small to medium diameter conduits.  
         [0003]     It is generally well known that conduits or pipelines, particularly underground pipes, such as sanitary sewer pipes, storm sewer pipes, water lines and gas lines that are employed for conducting fluids frequently require repair due to fluid leakage or deterioration. The leakage may be inward from the environment into the interior or conducting portion of the pipelines. Alternatively, the leakage may be outward from the conducting portion of the pipeline into the surrounding environment. In either case, it is desirable to avoid this leakage.  
         [0004]     The leakage may be due to improper installation of the original pipe, or deterioration of the pipe itself due to normal aging or to the effects of conveying corrosive or abrasive material. Cracks at or near pipe joints may be due to environmental conditions such as earthquakes or the movement of large vehicles on the overhead surface or similar natural or man made vibrations, or other such causes. Regardless of the cause, such leakage is undesirable and may result in waste of the fluid being conveyed within the pipeline, or result in damage to the surrounding environment and possible creation of a dangerous public health hazard. If the leakage continues it can lead to structural failure of the existing conduit due to loss of soil and side support of the conduit.  
         [0005]     Because of ever increasing labor, energy and machinery costs, it is increasingly more difficult and less economical to repair underground pipes or portions that may be leaking by digging up and replacing the pipes. As a result, various methods had been devised for the in place repair or rehabilitation of existing pipelines. These new methods avoid the expense and hazard associated with digging up and replacing the pipes or pipe sections, as well as the significant inconvenience to the public. One of the most successful pipeline repair or trenchless rehabilitation processes that is currently in wide use is called the Insituform® Process. This Process is described in U.S. Pat. Nos. 4,009,063, 4,064,211 and 4,135,958, all the contents of which are incorporated herein by reference.  
         [0006]     In the standard practice of the Insituform Process an elongated flexible tubular liner of a felt fabric, foam or similar resin impregnable material with an outer impermeable coating that has been impregnated with a thermosetting curable resin is installed within the existing pipeline. Generally, the liner is installed utilizing an eversion process, as described in the later two identified Insituform patents. In the eversion process, radial pressure applied to the interior of an everted liner presses it against and into engagement with the inner surface of the pipeline. However, the Insituform Process is also practiced by pulling a resin impregnated liner into the conduit by a rope or cable and using a separate fluid impermeable inflation bladder or tube that is everted within the liner to cause the liner to cure against the inner wall of the existing pipeline. Such resin impregnated liners are generally referred to as “cured-in-place-pipes” or “CIPP liners” and the installation is referred to a CIPP installation.  
         [0007]     The CIPP flexible tubular liners have an outer smooth layer of relatively flexible, substantially impermeable polymer coating the outside of the liner in its initial state. When everted, this impermeable layer ends up on the inside of the liner after the liner is everted during installation. As the flexible liner is installed in place within the pipeline, the pipeline is pressurized from within, preferably utilizing an eversion fluid, such as water or air to force the liner radially outwardly to engage and conform to the interior surface of the existing pipeline.  
         [0008]     Typically, an eversion tower is erected at the installation site to provide the needed pressure head to evert the liner or a bladder. Alternately, an eversion unit as shown and described in U.S. Pat. No. 5,154,936, No. 5,167,901 (RE 35,944) and No. 5,597,353, the contents of which are incorporated herein by reference. Cure may be initiated by introduction of hot water into the everted liner through a recirculation hose attached to the end of the everting liner. Inversion water is recirculated through a heat source such as a boiler or heat exchanger and returned to the inverted tube until cure of the tube is complete. The resin impregnated into the impregnable material is then cured to form a hard, tight fitting rigid pipe lining within the existing pipeline. The new liner effectively seals any cracks and repairs any pipe section or pipe joint deterioration in order to prevent further leakage either into or out of the existing pipeline. The cured resin also serves to strengthen the existing pipeline wall so as to provide added structural support for the surrounding environment.  
         [0009]     The eversion tower, which was time consuming to construct, caused workers to be 30 feet above the ground often near trees and electrical wires. This method was improved by an apparatus, which allowed Insituform to create a hydraulic head by the use of a sphincter valve. The tube was fed into the top of the apparatus and pulled through the sphincter valve by pressurized water below the valve. The pressurized water applied a force on the nose of the tube causing it to invert into the pipe being rehabilitated. These apparatuses for the rehabilitation of small diameter pipe have been in use for about fourteen years.  
         [0010]     The major disadvantage to the use of these apparatuses with water is the quantity and availability of the inverting water. Water must be heated typically from 55° F. to 180° F. in order to affect the cure, and then cooled by the addition of more water to 100° F. before being released to an acceptable disposal system.  
         [0011]     This disadvantage may be overcome by using air in lieu of water to create the inverting force. Once the impregnated tube is fully inverted, it then can be cured with steam. Although water is necessary to produce steam, the quantity of water in the form of steam is only 5-10% of that required for water inversion, cure and cool down. This means that steam can be used even if water is not readily available on site. This drastic reduction in the quantity of water is the result of the higher energy available from one pound of water in the form of steam versus one pound of heated water. One pound of steam condensing to one pound of water gives off approximately 1000 BTUs while one pound of water gives off only one BTU for each degree in temperature drop. This reduced water requirement plus virtual elimination of the heat up cycle greatly reduces cure cycle and installation time.  
         [0012]     With this apparent advantage in using air inversion and steam cure why has the industry been slow to abandon water inversion and hot water cure? 
         [0013]     When water is used to invert the resin-impregnated tube, the uninverted portion of the tube from the inverting nose to the inverting apparatus is buoyed up by a force equal to the quantity of water displaced by the tube. In the case of CIPP tubes, this mean the effective weight of the tube is substantially reduced, as is the force necessary to pull the uninverted tube forward to the inverting nose. When air is used to create the inverting force, the uninverted tube lies on the bottom of the pipe and the air pressure acting on the inverting nose of the tube must pull the full weight of the tube forward.  
         [0014]     Three forces must be over come to invert a CIPP tube no matter what is used to create the inverting energy. These forces are:  
         [0015]     1. Force required to invert the tube (turn tube inside out). This force varies by tube thickness, material type and relation of tube thickness to diameter.  
         [0016]     2. The force necessary to pull the tube from the inverting apparatus to the inversion nose.  
         [0017]     3. The force necessary to pull the tube through the inverting apparatus.  
         [0018]     Force number one (1) above is generally the same for both air and water inversions.  
         [0019]     Force number two (2) varies greatly between air and water and can limit the length of air inversions. There is limit on how much pressure can be used to invert a tube without adversely affecting the quality of the installed CIPP tube and/or damaging to the existing conduit. Lubricant can be used for both water and air inversion to reduce the required pulling force.  
         [0020]     Force number three (3) can vary based on the apparatus design. In most apparatus presently in use, the force required to pull the tube through the apparatus will increase when either or both forces one and two increase. This is caused by the fact that in order to increase available inversion energy, typical apparatus in use today restrict loss of pressurized fluid from the pressure chamber below the tube entry point into the apparatus and the cuff and banded end of the tube being inverted. This restriction is typically accomplished by increasing the air pressure in a pneumatic gland (i.e. Insituform&#39;s CHIP Unit) or by using a gland that is energized by the inverting fluid (i.e. The Shooter cup seal). The movement inward in both cases is restricted by the gland material and compression of the inverting CIPP tube. This in turn causes an increase on the friction between the inverting CIPP tube and gland.  
         [0021]     In view of these apparent benefits of steam cure compared to hot water cure, the use of steam has been proposed in view of the energy it carries. Air inversion of an inflation bladder and flow-through steam to cure has been disclosed in Insituform U.S. Pat. No. 6,708,728 and No. 6,679,293, the contents of which are incorporated herein by reference. The processes disclosed in these recently issued patents utilize pull in and inflate technology and are currently in use for small diameter liners. They provide advantages over water eversion for small diameters. Moreover, use of a puncturing canister disclosed in these patents is not suitable for medium and large diameter liners. Medium size liners are those between about 18 and 45 inches in diameter. Large diameters are those in excess of about 45 inches and larger in diameter.  
         [0022]     Accordingly, it is desirable to provide an improved apparatus for an air inversion and porting assembly for flow through steam cure CIPP installation.  
       SUMMARY OF THE INVENTION  
       [0023]     Generally speaking, in accordance with the invention, an apparatus for inverting a resin impregnated cured in place liner with air having a low friction seal between the moving CIPP liner and a stationary inverting gland is provided. Unlike other inverting apparatus in use today, this pre-shaped adjustable gland, once adjusted, does not increase friction on the tube when inverting fluid pressures are increased. A sample and porting pipe having an exhaust pipe with a porting gland receiving a porting tool is positioned in the distal access point. Once the inversion is completed, the porting tool is inserted into the inflated liner and an exhaust hose is connected.  
         [0024]     The gland includes a slit with an adjustable gap in at least its thickness. The adjustment of the gap across the gland is made by moving rigid members substantially perpendicular to the liner passing through the gland. The gland may have one stationary side and one adjustable side. In this case, the stationary side has a steel backing plate with a temperature resistant ˜¼″ thick compressible layer of material, such as a resilient silicone rubber and a thin absorbent layer (⅛″ or less) such as polyester felt facing the impermeable layer of the liner. This allows one to apply lubricant to the surface of the inverting CIPP liner. In this embodiment, the adjustable side of the gland has a substantially rigid one-inch thick shaped block of Nylon or the like, faced with a similar compressible and absorbent layer. The shaped block is sized and shaped specifically for the size and thickness of the CIPP tube to be inverted. The shaped block may be a one-piece member or be formed in sections, such as three or four depending on the layflat size of the CIPP liner to be installed. A separate adjustment bolt is provided for each section of the block.  
         [0025]     In another embodiment the gland is formed by a plurality of opposed fingers across the opening in the apparatus. Each finger is an air driven piston or rod sealed in a cylinder extending from a manifold positioned about the opening. The fingers may be positioned on one side facing a stationary opposed side or surround the liner on both flattened surfaces.  
         [0026]     In a preferred embodiment, the gland has one stationary side and one adjustable side. The stationary side has a steel backing plate faced with a temperature resistant ˜¼″ thick compressible layer of material such as silicone rubber and a thin absorbent layer (⅛″ or less) such as polyester felt to apply lubricant to the surface of the CIPP tube. The adjustable side has a one-inch thick shaped Nylon blocks faced with a similar compressible and absorbent layer. The shaped block is sized and shaped specifically for the size and thickness of the CIPP tube to be inverted. Typically CIPP tubes intended for inversion are manufactured with the layers sized for final position. This means that prior to inversion the biggest circumference layer is on the inside and the smallest circumference coated layer is on the outside. This results in the inner layer having a folded area or thick spot in the tube cross-section. The compressible layers on each side of the gland accommodate this and any other tube cross-section irregularities. The folded area may move back and forth across the surface of the CIPP tube therefore a fixed accommodation for this change in tube spot thickness would be ineffective. The compressible layer, which surrounds the CIPP tube, is well suited to accommodate any tube spot thickness regardless of location. The limited area of increased friction caused by these thick spots helps to assure the low friction performance of this gland design.  
         [0027]     Accordingly it is an object of the invention to provide an improved apparatus and method for inverting a CIPP liner with air.  
         [0028]     It is another object of the invention to provide an apparatus for air inversion of a CIPP liner with an adjustable gland that does not increase the friction on the liner when the everting fluid pressure increases.  
         [0029]     It is a further object of the invention to provide an apparatus for air inversion of CIPP liner and steam cure.  
         [0030]     It is yet another object of the invention to provide a method for air inverting a CIPP liner and porting the downstream end of the inverted liner to allow flow-through of steam for curing the resin.  
         [0031]     It is yet a further object of the invention to provide for air inversion and steam cure of a CIPP liner without allowing the inverted liner to collapse prior to steam cure.  
         [0032]     Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.  
         [0033]     The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to the others, and the apparatuses possessing the features, properties and relation of elements which are exemplified in the detailed disclosure and the scope of the invention will be indicated in the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]     For a fuller understanding of the invention, references had to the following description taken in connection with the accompanying drawings in which:  
         [0035]     FIGS.  1 ( a ) and  1 ( b ) are an elevational view of an air inversion unit and a plan view of a gland to seal against a cured in place liner constructed and arranged in accordance with the invention;  
         [0036]      FIG. 2  is an enlarged top plan view of the gland of the air inversion unit of  FIG. 1 ;  
         [0037]      FIG. 3  is an enlarged top plan view of a gland having a segmented shaped block in accordance with a preferred embodiment of the invention;  
         [0038]      FIG. 4  is an elevational view of an air inversion and steam cure apparatus with a CIPP liner ready for inversion constructed and arranged in accordance with the invention:  
         [0039]     FIGS.  5 ( a ) and  5 ( b ) are plan views in schematic showing a plurality of fingers of the gland of the apparatus of  FIG. 1  in an open and an operating position, respectively;  
         [0040]      FIG. 6  is an elevational view in cross-section of the air inverter and steam cure apparatus of  FIG. 4  in accordance with the invention; and  
         [0041]     FIGS.  7 ( a ) and  7 ( b ) are schematic views of an inverting cured in place liner entering a sample and porting pipe, before and after porting with a porting tool.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]     The following disclosure will describe an improved method and apparatus for air inverting and steam curing a CIPP tube in compliance with ASTM F1216  Standard Practice for Rehabilitation of Existing Pipelines and Conduits by the Inversion and Curing of a Resin - Impregnated Tube . The method and apparatus as described are well suited for working from the surface through structures, such as manholes to rehabilitate existing buried pipelines and conduits.  
         [0043]     Referring now to  FIG. 1 , an air inversion and steam cure unit  11  constructed and arranged in accordance with the invention is shown in elevation. Unit  11  is constructed of a rigid material, typically a metal such as a steel or aluminum, and the like. Composite materials or plastics are also suitable so long as they can withstand the internal pressures and temperatures to be generated during use.  
         [0044]     Unit  11  includes a substantially cylindrical hollow pressure chamber  12  having an upper flange  13  and a bottom flange  14 . A hollow inversion inversion boot  16  is mounted to bottom flange  14 . Inversion boot  16  includes an upper frusto-conical section  17  with a larger opening  17   a  and a smaller opening  17   b  and an annular flange  18  for securing boot  16  to bottom flange  14 . This allows different diameter boots to be readily installed in unit  11 . Smaller opening  17   b  of frusto-conical section  17  includes a substantially cylindrical banding boot  19  with external ribs  21  for securing a folded back portion of a cured in place liner  20  to be fed therethrough. Inversion boot  17  is also fitted with an air/steam inlet fitting  25 .  
         [0045]     The top of pressure chamber  12  is closed by a top cover  22  formed of a first semi-circular section  23  and a second semi-circular section  24 . Both semi-circular top sections  23  and  24  are secured to upper flange  13  and facing cut-out regions  23   a  and  24   a  to form a gap  26  therebetween to allow passing liner  27  into unit  11 . The details of construction of gap  26  to form a gland  28  so that sufficient inversion pressure can be generated in pressure chamber  12  and inversion boot  16  will be described below.  
         [0046]     Semi-circular portions  23  and  24  with cut-outs  23   a  and  24   a  are secured to upper flange  13  to form a gap  26  along the centerline between them. Semi-circular portion  23  includes a horizontal portion  37  of stationary gland bracket  31  with a horizontal mounting portion  32 , a substantially vertical section  33  across the diameter of pressure chamber  12  and a flared section  34 . Semi-circular section  23  includes cut-out region facing semi-circular portion  24 .  
         [0047]     Matching adjustable semi-circular portion  24  also includes an adjusting bracket  36  with a horizontal mounting section  37 , a substantially vertical section  38  and a flared portion  39 . Adjustment bracket  36  also presents cut-out region  24   a  to ???????. Here, moveable adjustment bracket  36  includes a cut-out or drawer region  41  for mounting at least one substantially rigid shaped block  42 . Block  42  includes a tube inlet cut-out  43  facing the vertical section  33  of stationary bracket  31 . Tube cut-out  43  is formed by an indentation in shaped block  42 . Three gap adjustment screws  44  are mounted behind shaped block  42  for adjusting the position of block  42  to vary the size of gap  26  so as to engage liner  26  in use.  
         [0048]     Two sheets of a compressible compressible member  46  are positioned between both sections of top cover  22  and upper flange  13 . Compressible material  46  is pulled up along the facing surfaces of gland brackets  31  and  36  and secured to bracket flared sections  34  and  39 . This provides a smooth compressible and resilient path for liner  27  to be engaged in gland  28  as it passes through. In addition to compressible material  46 , an absorbent layer  47  is positioned to the outside of compressible material  46  facing gland  28 . This material may be an absorbent material such as a layer of felt  47  that can be oiled to provide lubricating for inverting liner  27 . Alternatively, a layer of low friction material such as FEP, PFA or PTFE can be used to facilitate passage of liner  27  through gland  28 . Use of compressible material  46  helps gland  28  conform to the cross-section and profile of liner  27 . Gap adjustment screws  44  are mounted on adjustable bracket  36  to displace shaped block  42  towards opposed vertical section  33  to adjust the opening of gland  28 .  
         [0049]     In the embodiment illustrated in  FIG. 3   a , shaped block  51  is formed in three individual segments, including two outer sections  52  and  53  with curved cut outs  52   a  and  53   a  and a straight mid-section  54 . Here, bracket  36  includes individual pockets to hold blocks  52 ,  53  and  54  with opening in bracket vertical section  38  to allow movement towards stationary bracket  31  in response to tightening adjustment gap screws  44 . Block mid-section  54  presents a straight edge, whereas outer sections,  52  and  53  form curved openings to conform to the layflat shape of liner  27 .  
         [0050]     Unit  11  includes three leg mounting brackets  56  welded to the sidewall of pressure chamber  12  for fixing legs  57  for supporting unit  11  over an installation access opening. Unit  11  is constructed of a rigid metallic material, such as steel or aluminum. Once assembled, semi-circular sections  31  and  36  with shaped block  42  and compressible material  46  form adjustable gland  28  for allowing liner  27  to pass therethrough when air pressure is introduced into air steam inlet  20 .  
         [0051]     Shaped block  42  may be a single member as shown in the embodiment of  FIG. 2  or included three sections,  52 ,  53  and  54  as shown in the embodiment in  FIG. 3 . Additional sections can also be formed which provide greater flexibility in adjusting gap for dealing with location of folds and variations in cross-sectional dimensions of liner  27  as it passes therethrough.  
         [0052]     Compressible material  46  is a temperature resistant ˜3 to 20 mm, resilient layer of material, such as silicone rubber. A thin absorbent layer (2 to 8 mm) polyester felt to apply lubricant to the surface of CIPP liner  27  is placed on the outer surface of compressible layer  46 . As noted above, a low friction material such as a PTFE scrim can be use in place of oiled felt. Gland  28  formed by gap  26  in top sections  23  and  24  may be infinitely variable by utilizing an embodiment having a plurality of hydraulic fingers such as shown in  FIGS. 4 and 5 .  
         [0053]     Unit  11  is particularly well suited to install a small diameter CIPP liner in an existing conduit utilizing air to invert the liner and steam to cure. Small diameter liners are those having a diameter between about 6 and 12 inches (15 to 30 mm).  
         [0054]     The following procedures are followed to install a cured in place liner by air inversion and steam cure using unit  11 .  
         [0055]     1. Adjustment screws  44  on adjustable bracket  36  of gland  28  are opened and a wet out CIPP liner  27  is threaded through gland  28  into pressure chamber  12  and banding boot  19 . Liner  27  is cuffed back over the end of banding boot  19  and secured with two stainless steel bands. An air/steam hose is attached to steam air inlet  20  on inversion boot  16 .  
         [0056]     A hold back rope or cable is attached to the other end of CIPP liner  27 . A suitable lubricant is placed on absorbent felt layers  47  at the inlet to air inverter unit  11 . Gland  28  is adjusted with adjustment screws  44  to uniformly close gland  28  about CIPP liner  27 .  
         [0057]     2. The other end of the air steam line is connected to the air steam manifold. A steam supply line and air supply line are connected to the air steam manifold. All air and steam connections are checked for safety pins or whip checks installed. Once the air valve on the manifold is closed and the air regulator has been backed off to prevent air flow through it, the air supply line is connected to an air compressor. The air discharge line at the compressor is closed and the air compressor is then started.  
         [0058]     3. When the air/steam operator has been checked to make sure that everything is safe and ready to proceed to send air to the air/steam manifold. The air/steam manifold operator then opens the air/steam supply line to the air inverter and slowly screws down the adjustment screw on the air regulator to increase the air supply to the desired air inversion pressure. The air inverter operator will simultaneously pull CIPP liner from the refrigerated storage truck or bin to feed into air inverter  11 .  
         [0059]     The inversion is continued until the trailing end of the liner is near air inverter unit  11 . At this time the hold back rope up is threaded over rollers above the air inverter. Just prior to the end of the liner going into the air inverter, the hold back rope is wound around a capstan so that there is tension on the rope leading into air inverter  11 .  
         [0060]     Once the end of the liner goes through the gland in the top of the air inverter, the gland is adjusted to reduce air leakage. The hold back rope and inversion air pressure are controlled to maintain the same inversion speed and pressure used on the first half of the inversion.  
         [0061]     As shown in FIGS.  7 ( a ) and  7 ( b ) a PVC or rigid pipe sample mold of metal with an exhaust pipe assembly  61  with a mold  62  and steel pipe  63  in the far manhole and align it to receive an inverting tube. As the inverting nose nears the far manhole, the inversion is slowed to allow the liner to enter sample mold  62  and steel pipe  63 . The inversion is stopped when the nose of the inverting liner is about one diameter past the end of sample mold  62 .  
         [0062]     The hold back rope is tied off and the inverted liner is ported by inserting a steel-porting pipe  64  with a piercing point  66  at the lower end and a valve  67  at upper end. A flange or o-ring  68  is provided a point on porting pipe  64  to prevent pipe  64  from piercing the opposite side of the liner.  
         [0063]     A crewmember who is responsible for porting notifies the inverting end that he is preparing to port the inverted liner so that they will be prepared to adjust the supply air to maintain pressure on the inverted liner once it has been ported.  
         [0064]     Once the liner has been successfully ported, porting pipe valve  67  is closed and an exhaust hose with a valve at the far end is attached to porting pipe valve  67 . Control of the exhaust is now at the far end of the exhaust hose.  
         [0065]     5. The exhaust valve and air inlet regulator is adjusted to maintain good flow and recommended heat up and cure pressure. The boiler is blown down and the steam supply hose is attached to the air steam manifold. The manifold operator is notified that steam is being sent to the air steam manifold.  
         [0066]     The air steam manifold operator notifies the far end that warm-up is starting. The interface temperature at the 6 O&#39;clock position in the far manhole is recorded. The warm-up steam air mixture should be about 180° F. The warm-up is continued until there is a 3° F. increase at the inner-face in the far manhole.  
         [0067]     Once warm-up is completed, air flow is slowly reduced and full steam is used to maintain the recommended cure pressure. Full steam cure is continued for about 1 hour recording inner-face temperatures at 15 minute intervals. And there is an inner-face temperature of 130° F. for at least 30 minutes of the 1 hour cure, cure is complete. If not, cure is extended until there is 130° F. for at least 30 minutes.  
         [0068]     7. Once the cure cycle is completed, steam is slowly shut off while simultaneously adding air. Cure pressure should not be exceeded during cool down. The liner is cooled down for a minimum of 15 minutes or until interface is 130° F. at the far end, whichever is longer. Steam supply at boiler is then shut off. When the boiler supply hose pressure reaches zero, the steam supply hose is disconnected at the manifold. When cool down is complete, the air compressor is shut off and pressure in air hose is released prior to disconnecting air supply hose from manifold.  
         [0069]     Depending upon the particular resin and tube thickness, once the cure is complete, steam flow is turned off while simultaneously adjusting the air flow to maintain cure pressured. The exhaust valve is adjusted while cooling to about 130° F. at the six o&#39;clock position for at least one hour.  
         [0070]     Once the temperature has cooled to the desired level, air flow pressure is reduced to zero, the exhaust valve is fully opened. Any condensate that may have accumulated in the bladder is removed by condensate drain on the exhaust assembly.  
         [0071]     At this time, the confined space entry procedures are followed to remove ends from the lined pipe and reinstate services using standard procedures.  
         [0072]     The flexible cured in place liner is of the type generally well known in the art. It is formed from at least one layer of a flexible resin impregnable material, such as a felt layer having an outer impermeable polymer film layer. The felt layer and film layer are stitched along a seam line to form a tubular liner. A compatible thermoplastic film in a form of a tape or extruded material is placed on or extruded over seam line in order to ensure the impermeability of the liner.  
         [0073]     For larger liner diameters, several layers of felt material may be used. The felt layers may be natural or synthetic flexible resin absorbable materials, such as polyester or acrylic fibers. The impermeable film in the outer layer may be a polyolefin, such as polyethylene or polypropylene, a vinyl polymer, such as polyvinyl chloride, or a polyurethane as is well known in the art. In the initial step in all trenchless rehabilitation installations, the existing pipeline is prepared by cleaning and videotaping.  
         [0074]     Prior to commencing installation pursuant to the method in accordance with the invention, a curable thermosetting resin is impregnated into the felt of a liner by a process referred to as “wet-out.” The wet-out process generally involves injecting resin into the felt layer through the end or an opening formed in the impermeable film layer, drawing a vacuum and passing the impregnated liner through nip rollers as is well known in the lining art. One such procedure of this vacuum impregnation is described in Insituform U.S. Pat. No. 4,366,012, the contents of which are incorporated herein by reference. A wide variety of resins may be used, such as polyester, vinyl esters, epoxy resins and the like, which may be modified as desired. It is preferable to utilize a resin that is relatively stable at room temperature, but which cures readily when heated.  
         [0075]     It can readily be seen that the process in accordance with the invention readily allows one to attain the advantage of curing a resin liner with flow through steam. By practicing the process, a tubular member can be easily everted through an existing pipeline. By providing a low friction gland on an eversion chamber, eversion pressure can be increased without increasing the friction on the moving liner. Steam is then passed through the curing liner to utilize the higher energy available in the steam to cure the resin significantly more efficiently than one can cure utilizing circulating hot water.  
         [0076]     An air inverting unit  110  constructed and arranged in accordance with another embodiment of the invention is shown in  FIG. 4 . Unit  110  includes a rectangular trough or box  111  mounted on a frame  112  to be positioned over the inverting access to the conduit to be lined. A roller  113  is positioned at the top of frame  112  over box  111  to facilitate feeding resin impregnated liner  116  into box  111 . The top of box  111  is partially closed by a pair of opposed plates  121  and  122  forming an opening  123  between the sidewalls of box  111 . The bottom of box  111  is sealed and has an inversion nipple or boot  131  for securing inverted liner  116  thereabout. An air and steam inlet  132  is provided on a sidewall of box  111  to inject air/steam from an air supply line  133  and a steam line  134 . The size of box  111  is selected so that flattened liner  116  does not occupy the full width of opening  123 . This insures that air and steam can flow freely about the full perimeter of the liner to force the liner through inversion boot  131 .  
         [0077]     An elastomeric sheet  136  is folded across the top opening and a plurality of fingers  133  are positioned behind and in the fold of elastomeric sheet  136  to close opening  123  partially as shown in schematic in FIGS.  5 ( a ) and  5 ( b ). This allows flattened liner  116  to pass through opening  123  and for fingers  137  to close opening  123  at the edges of liner as shown in schematic in  FIG. 5 ( b ).  
         [0078]     Fingers  137  are rigid rods seated in individual cylinders  138  connected to an air manifold  139  as shown in the cross-section in  FIG. 7 . Manifold  139  has an air bleeder valve and gauge  141  and pressure relief valve  142 . A rigid donut  146  about 1 to 3 cm. in diameter is mounted at the end of each rod and contacts the back surface of  146  folded elastomeric sheet  136 . Each finger  137  is positioned so that the ends of donuts  146  form a continuously variable profile about liner  116  and close the unoccupied portion of opening  123  in box  111 .  
         [0079]     Elastomeric sheet  136  is a temperature resistant ˜3 to 20 mm. thick compressible layer of material such as silicone rubber with a thin absorbent layer (2 to 8 mm.) such as polyester felt to apply lubricant to the surface of CIPP liner  116 . Extending fingers  137  are positioned behind both sides of elastomeric sheet  136  to urge elastomeric sheet  136  and felt into the opposite sides of CIPP liner  116 . Typically, CIPP liners intended for inversion are manufactured with the layers sized for final position. This means that prior to inversion the biggest circumference layer is on the inside and the smallest circumference coated layer is on the outside. This results in the inner layer having a folded area or thick spot in the tube cross-section. Variable fingers  137  on each side of gland opening  123  accommodate for this and any other cross-section irregularities of liner  116 . The folded area may also move back and forth across the surface of CIPP liner  116  and variably extending fingers  137  accommodate for this change in spot thickness.  
         [0080]     In the illustrated embodiment, apparatus  110  includes 64 fingers  137 , with 32 on each side of gland opening  123 . It is contemplated that any number of fingers, such as from 32 to 128 can be used with donuts that are anywhere from 1 to 5 cm. in diameter. Obviously, the smaller the size of the donut the more fingers that can be included and the finer the variations in the shape or profile of the opening are possible. However, one must be careful that the donuts do not pierce the impermeable coating of the liner. The donuts should not be too large so as to form gaps at the edges of the flattened liner or at regions of changes in thickness.  
         [0081]     Inversion boot  131  or nipple is elongated to accommodate flattened liner  116  passing through box  111  and has ribs or ridges to receive steel bands to secure liner  116 . Clamping plates are provided to secure liner  116  against the elongated sides of the inversion boot  131 .  
         [0082]     The installation procedure utilizing inverter unit  110  is identical to that described for the earlier described embodiment using air inverter unit  11 .  
         [0083]     It will thus be seen that the objects set fort above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made and carrying out the above method and in the construction set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.  
         [0084]     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall there between.