Method and apparatus for determining proper curing of pipe liners using distributed temperature sensing

Abstract

The present invention relates to method and apparatus utilizing distributed temperature sensing (DTS) to monitor the temperature of a cured-in-place pipe liner to determine if proper curing temperatures and times are achieved. More particularly, an optical fiber is placed in the pipe between the original pipe and the liner running the entire length of the liner. The optical fiber is coupled to a DTS unit at neo end. During curing of the liner, the DTS unit sends light pulses down the fiber from one end and detects the characteristics and time delay of light backscattered to the unit. The characteristics of the backscattered light is indicative of the temperature of the optical fiber, while the time delay between the sending of the light pulse and the detection of any portion of the backscatter signal is indicative of the round trip time of the light within the fiber, and thus the distance down the fiber from the DTS unit from which that particular backscatter signal originated.

1 . A method of curing a cured-in-place liner within a tube segment, the tube segment having a first longitudinal end, a second longitudinal end and a length between the first and second longitudinal ends, the method comprising:
 placing an optical fiber within the tube segment extending longitudinally from at least the first end to the second end of the tube segment, the optical fiber having a first longitudinal end, a second longitudinal end and a length between the first and second longitudinal ends;   positioning a liner within the tube segment extending longitudinally from the first end to the second end of the tube segment, the liner comprising a curable material for lining the tube;   coupling the first longitudinal end of the optical fiber to a distributed temperature sensing unit;   heating the liner to cure the curable material; and   measuring the temperature of the optical fiber continuously along its length via distributed temperature sensing using the distributed temperature sensing unit.   
     
     
         2 . The method of  claim 1  wherein the measuring comprises measuring the temperature at periodic time intervals. 
     
     
         3 . The method of  claim 1  wherein the tube is a sewer, water, or gas pipe. 
     
     
         4 . The method of  claim 1  wherein the placing occurs prior to the positioning. 
     
     
         5 . The method of  claim 1  wherein the placing occurs simultaneously with the positioning. 
     
     
         6 . The method of  claim 5  further comprising the step of attaching the optical fiber to the liner prior to the positioning of the liner within the tube segment. 
     
     
         7 . The method of  claim 5  further comprising ceasing the heating responsive to measurements taken during the measuring reflecting one or more predetermined conditions. 
     
     
         8 . The method of  claim 7  wherein the one or more predetermined conditions comprise the entire length of the optical fiber that is within the tube being above a first predetermined temperature for at least a first predetermined period of time. 
     
     
         9 . The method of  claim 1  wherein the heating further comprises pressurizing the liner. 
     
     
         10 . The method of  claim 1  wherein the curable material of the liner is disposed on the inside of a tubular backing sheet and wherein the positioning comprises inverting the liner as it is being positioned within the tube so that the curable material is on the outside of the backing sheet at the end of the positioning. 
     
     
         11 . The method of  claim 1  wherein the placing comprises placing the optical fiber along the bottom of the tube. 
     
     
         12 . The method of  claim 1  wherein the placing comprises placing a plurality of optical fibers in the tube substantially parallel to each other and substantially evenly radially spaced from each other. 
     
     
         13 . The method of  claim 1  wherein the placing comprises placing the optical fiber such that the second end of the optical fiber extends at least ten meters beyond the end of the tube segment. 
     
     
         14 . The method of  claim 1  wherein the measuring comprises:
 issuing a light pulse into the optical fiber form the first end of the fiber; 
 detecting light backscattered from the optical fiber at the first end of the optical fiber; and 
 calculating the temperature of the optical fiber continuously along its length as a function of one or more characteristics of the backscattered light and the delay time of the backscattered light since issuing the light pulse. 
 
     
     
         15 . The method of  claim 1  further comprising:
 determining if the temperature of the optical fiber has been within a predetermined temperature range continuously during a predetermined time range. 
 
     
     
         16 . The method of  claim 15  further comprising:
 measuring the pressure within the tube liner contemporaneously with the measuring of the temperature. 
 
     
     
         17 . A system for curing cured-in-place pipe liner in a pipe segment having a first longitudinal end, a second longitudinal end and a length between the first and second longitudinal ends comprising:
 an optical fiber disposed within the pipe segment extending longitudinally from at least the first end to the second end of the tube segment, the optical fiber having a first longitudinal end, a second longitudinal end and a length between the first and second longitudinal ends;   a pipe liner within the tube segment extending longitudinally from the first end to the second end of the tube segment, the liner comprising a curable material for lining the tube;   a distributed temperature sensing unit coupled to the first end of the optical fiber adapted to measure the temperature of the optical fiber continuously along its length via distributed temperature sensing.   
     
     
         18 . The system of  claim 17  further comprising:
 a source of heat and pressure; and 
 a coupling mechanism for coupling the source of heat and pressure to the liner for heating and pressurizing the liner. 
 
     
     
         19 . The system of  claim 18  further comprising a computer program product recorded on computer readable medium comprising computer executable instructions for generating a report of temperature of the fiber as a function of one or more of time and longitudinal position within the fiber. 
     
     
         20 . The system of  claim 17  wherein the optical fiber is contained within an encasement and wherein the optical fiber is capable of movement relative to the encasement.