FIELD OF THE INVENTION

The present invention relates to polymer composites useful for repair of pipelines such as those carrying gas and oils, suitable nano-filler and more specifically to reinforced polymer composite wrap system to repair and reinforce both internal and external corrosion on pipelines operating at elevated temperatures and to method for repair of corroded pipelines at elevated temperatures of upto 300°C involving such reinforced polymer composite wrap system.
Steel pipelines are widely used by oil and gas industries, steel plants, power plants, chemical industries and many more for transportation of fluids across large distances. Generally, these pipelines are exposed to various corrosive environmental conditions which leads to varied damage scenarios which if untreated for long time, reduces the structural integrity of the pipelines. The intensity or acceleration of corrosion is higher at elevated temperatures or it can be said that as temperature increases, the intensity of corrosion increases. So, pipelines operating at elevated temperatures are prone to heavy corrosion.
Earlier days, the conventional repair methodology for rehabilitation of the corroded pipelines was replacing the damage portion by cutting and welding a new pipe section. But this repair methodology is lengthy and tedious and also poses risk of fire and explosion. Recently, FRP based composite repair methodologies have been developed where the damaged portion of the pipe is reinforced by a composite wrap which reinstates the lost structural integrity of the pipeline. These FRP based composite repair methodology are cold repair methodologies thereby eliminating the risk of fire and explosion. For repair of pipelines at elevated temperatures i.e., pipelines operating with fluids at elevated temperatures, FRP based prepregs are used which require lengthy cure cycles (24 hrs to 72 hrs) at high temperatures resulting in larger downtimes when compared with composite repair of pipelines at ambient temperatures. Repair of pipelines at elevated temperatures is manually critical and poses a safety risk if

the repair is to be performed at live conditions. It is also highly expensive. So, there is a requirement of an economical alternative composite repair methodology with shorter cure cycles for repair of pipelines at elevated temperatures and it is still in the developmental phase.
For the repair system to be qualified for repair of pipelines operating at elevated temperatures the composite should be able to sustain the internal pressure of the pipeline at the maximum temperature at which the pipelines is operating and for this an adequate understanding of the thermo-structural behaviour is of utmost importance to execute an appropriate and efficient repair.
BACKGROUND ART
There are a few literatures that discuss the application of polymer matrix composites for repair of pipelines at elevated temperatures.
Da Costa et al, Analysis of a glass fibre reinforced polyurethane composite repair
system for corroded pipelines at elevated temperatures
doi:10.1016/j.compstruct.2014.04.015 analysed about the performance of Glass fiber reinforced polyurethane composite repair system applied over corroded pipelines which operating at temperature between 60°C and 90°C. They used water activated polyurethane resin pre-impregnated, bi-directional E-glass composite to repair and reinforce corrosion damages. In this study, repair system is applied to a pipe specimen with 70% wall loss defect created by machining. Hydrotests are conducted at different temperatures between 20°C and 90°C. Tensile tests are also carried out between the same temperature range for the repair system. It was concluded that ultimate strength of composite is strongly temperature dependent in this temperature range while the elastic properties are not affected. Since the elastic properties of pipe and composite sleeve is constant in this temperature range, failure pressure is same for the hydrotests conducted.

J.M.L Reis et al. Effect of rate and temperature on the mechanical properties of
epoxy BADGE reinforced with carbon nanotubes
10.1016/j.compstruct.2017.11.081 studied about the effect of temperature and cross-head rate on the mechanical properties of epoxy diglycidyl ether (bisphenol A) reinforced with CNT. They proposed that 5% by weight of epoxy of multi wall-tube CNT dispersed in epoxy diglycidyl ether matrix exhibits decrease in flexural strength, tensile strength and elastic modulus at the test temperature from 25°C to 75°C. Also higher cross head rates results in increased mechanical properties at all test temperatures.
Swetha et al Preparation and characterization of graphite nano-platelet (GNP)/epoxy nano-composite: Mechanical, electrical and thermal properties DOI:10.1016/i.eurpolymj.2013.10.008 prepared graphite nano-platelet (GNP)/epoxy composites by sonication combined with high speed shear mixing and three roll mill (3RM). They performed mechanical, electrical and thermal characterization of these epoxy nano composites and concluded that 3RM process provides optimum dispersion where electrical and mechanical properties are better. They also observed that l%wt filler loading results in 11% increase in thermal conductivity, 1.8x10 3 S/m electrical conductivity and 43% increase in single edge notch bending fracture toughness.
J.M.L Rein et al, Tensile behavior of glass/epoxy laminates at varying strain rates and temperatures doi:10.1016/j.compositesb.2012.02.005 investigated tensile behaviour of Glass/epoxy laminates at various strain rates and temperature. Analytical expressions modelled to predict ultimate tensile strength (UTS) and elastic modulus as a function of temperature and strain rate. They observed that strain rate affects UTS and temperature affects the GFRP's stiffness especially temperature over glass transition temperature. In this investigation, Closer agreements showed between analytical and experimental results.
No national level publication is available for elevated temperature pipeline repair and rehabilitation using composites.

The US6276401B1 discloses 'High Temperature composite pipe wrapping system' provides a method and apparatus for providing metal or non-metal vessels, and pressure containing vessels, with an external composite lining of webbing of biaxial or triaxial Weave preferably composed of fiberglass which is pre-impregnated with a high temperature heat curable polymer composition capable of being heat cured at a temperature range of from about 275°F to about 375 °F.
The US5632307A provides for 'Methods for using a high tensile strength reinforcement to repair surface defects in pipe' discloses a methodology to repair Gouges, dents and corrosion pitting damages in pipelines. In this, damaged portions are filled with uncured filler material, then high tensile material over wrapped around the defective portion of pipeline with a layer of curable adhesive. Filler material cures to a rigid state capable of transferring the fluid pressure within the pipeline to the overwrapped reinforcement completely.
The JP2008508417A teaches about 'Carbon nanotube reinforced polymer nanocomposite' provides method for making nano composites in which the compatible surfactant that interacts with both theCNTand the polymer matrix provides initial CNT dispersion and subsequent mixing with the polymer.
The US8585934B2 is an advancement directed to 'Composites comprising Carbon nanotubes on fiber' discloses a composite composition that contains a plurality of CNT infused fibers dispersed in matrix. CNT 0.1% percent by weight to about 60% by weight of the composite is used in the composition. Composite structures made by processes disclosed herein, with CNT infused fibers, have shown improved mechanical properties, including in-plane and in shear interlaminar. Along with this, electrical and thermal conductivity of composite structures have improved, based, in part, control of CNT orientation and good CNT loading.

The US9057473B2 discloses 'Pipe restraining repair method and structure for piping structures using composites' discloses reinforcement structure and method for repairing or reinforcing a pipe, pipeline or other tubular members containing cracks. This invention provides methods for installing one or multiple number of compression straps around the structural member; applying load transfer putty at the edges of straps; applying corrosion resistant coating material on the straps and substrate; providing reinforcement by composite overwrap.
The invention JP4907899B2 discloses 'Resin composition containing carbon nanotube and concentrate for compounding carbon nanotube' discloses a concentrate for blending CNTs that can achieve improved deformation characteristics such as tensile elongation at break and rheological characteristics. This also provides excellent CNT dispersibility, resulting in good crack resistance and dimensional accuracy and providing a production method for producing a resin composition having both conductivity.
OBJECTS OF THE INVENTION
Thus the primary object of the present invention is to provide for a suitable nano-filler reinforced polymer composite wrap system to repair and reinforce both internal and external corrosion on pipelines operating at elevated temperatures.
Another object of the present invention is to develop resin system with improved mechanical and thermal properties i.e, by enhancing its glass transition temperature and thermal stability to make it qualified for repair of corroded structures operating at elevated temperature ranges.
Yet another object of the present invention is to provide for a simple and straight forward economical alternative in-situ composite repair methodology for pipelines operating at elevated temperature ranges with shorter cure cycles.

It is yet further object of the present invention is to provide a simple composite repair methodology for different pipe diameters, also replicable for varied damage scenarios of any dimensions across various diameters of the pipelines.
Another object of the present invention is to facilitate the onsite curing of repair composites using fire resistant, easy to use, low cost band heater based curing setup customizable to different diameters of pipe as high as 48 inches with features to automatically control the temperature according to the cure cycle used.
SUMMARY OF INVENTION
In first aspect of the present invention is provided a system adapted for repair of
corroded pipelines at elevated temperatures of upto 300°C comprising:
on-site wrap able over defective pipe substrate and heat curable polymer
composite composition including selectively,
Epoxy resin selected from modified epoxy resins of low viscosity, with an epoxy
equivalent of 8.00 to 9.09 (Eq/kg), specific gravity of 1.1 to 1.2 and viscosity
12,000 to 18,000 mPas in amounts of 70 to 72 % by wt;
Nano CNT filler in amounts of upto 1 % by wt;
Hardeners selected from modified polyamine based hardeners with specific
gravity of 0.9 to 1.0, viscosity of 10 to 30 mPas in amounts of 28 to 30 % by wt;
and
and optionally including accelerators selected from imidazole based compounds
with chemical name 1- Methyimidazole in amounts of 0 to 1 % by wt,
for generating desired cured polymer composite having tensile strength ranging
from 260 to 290 MPa even at elevated temperatures of upto 300°C and thermal
properties such as thermal stability ranging from 335°C to 345°C.
In another aspect of the present invention is provided the system, wherein said polymer composite composition includes,

from 0.5-1 % by wt nano CNT filler reinforced polymer which is an on-site curable polymer composite having tensile strength ranging from 260 to 290 MPa at elevated temperatures of upto 300°C, preferably in the range of 200°C to 300°C and thermal stability ranging from 335°C to 345°C.
In further aspect of the present invention is provided the system comprising said
polymer composite as a in-situ selectively curable wrap able repair system for
corroded pipelines operating at temperatures from 100°C to 200°C comprising
selectively,
Epoxy resin selected from Bisphenol-A based systems with epoxy equivalent of
5.3 to 5.45 (Eq/kg), specific gravity of 1.15 to 1.2 and viscosity of 10,000 to
12,000 mPas in amounts of 50 To 52 % by wt;
Hardeners selected from anhydride systems with specific gravity of 0.95 to 1.05
and viscosity of 175 to 350 mPas in amounts of 47 to 49 % by wt.;
Accelerator selected from imidazole based compounds with chemical name 1-
Methyimidazole in amounts of 1 to 1.2% by wt;
and CNT in amounts of 0 to 1 % by wt.
In yet further aspect of the present invention is provided the system comprising said polymer composite composition including bisphenol-A based epoxy resin, hardener and accelerator with said CNT which is obtained of selectively cured cure schedules selected from any one of:
(a) 2 hr 120°C + 2 hr 180°C, (b) 2 hr 120°C + 2 hr 160°C + 2 hr 180°C and (c) 4 hr 80°C + 4 hr 140°C and wherein the thermal stability (°C) from 290 to 295, including Glass Transition Temperature (°C) attained in the range of 155 to 160 and with Ultimate tensile strength (MPa) in the range of 230 to 260 MPa, Tensile Modulus (GPa) in the range of 13 to 14 GPa and Tensile Strain to failure in the range of 1.3% to 1.6% and wherein preferably said polymer composite having said bisphenol-A based epoxy resin : hardener : accelerator in ratio of 50% to 52% : 47% to 49% : 1% to 1.2% respectively with select curing schedule of 2 hr

120°C + 2 hr 180°C for repair of pipelines operating at elevated temperature ranging from 100°C to 200°C.
In another aspect of the present invention is provided the system comprising polymer composite composition including bisphenol-A based epoxy resin, hardener with said CNT which is obtained of selectively cured cure schedules selected from any one of:
(a) 2 hr 80°C + 4 hr 160°C + 4 hr 200°C and (b) 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C and wherein said polymer composite having said resin: hardener in the ratio of 70% to 72% : 28% to 30% have the thermal stability (°C) from 335°C to 345°C including Glass Transition Temperature (°C) attained in the range of 225°C to 235°C and with ultimate tensile strength (MPa) in the range of 260 MPa to 280 MPa, Tensile Modulus (GPa) in the range from 13 GPa to 14 GPa and Tensile Strain to failure in the range of 1.4% to 1.6% and wherein preferably said polymer composite preferably included loading of 1% CNT with cure cycle of 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C, for significant improvement of 42% of the tensile strength with respect to polymer composite free of CNT suitable for composite repair of pipelines at elevated temperature range of 200° to 300°C.
In further aspect of the present invention is provided the system wherein said on-site wrap able over defective pipe substrate and heat curable polymer composite composition is operatively connected to custom operable band heater system for desired on-site heat curing of the polymer composite overwrap as per desired cure schedule.
In yet further aspect of the present invention is provided the system, wherein said custom operable band heater system includes,
two half units capable of getting mounted with resepct to any pipe substrate involving hinging the two halves by means of a locking mechanism and said units adapted to be oriented concentrically over the pipe substrate, two rigid heaters having respective heating elements mounted on both half units ;

a cooperative power unit supplying power to said heating elements via contactors and a PID temperature controller means adapted to protect over current damages and thermocouple means for measuring temperature operatively connected to said PID controller.
In another aspect of the present invention is provided the system comprising whole set up insulation including glass fabric and teflon based insulation jacket insulating said repair and band heater set up.
In further aspect of the present invention is provided the system, wherein said custom operable band heater system setup is customizable to different diameters of pipe as high as 48 inches.
In another aspect of the present invention is provided a method for repair of corroded pipelines at elevated temperatures of upto 300°C involving the system of the present invention, comprising the steps of,
(i) providing on the defected location of the pipeline substrates interface adhesive;
(ii) reinforcing the defected portion with said polymer composite wrap;
(iii) setting up the custom operable band heater system with said two half units mounted with respect to any pipe substrate and locking for desired heat curing;
(iv) subjecting the polymer composite wrap to controlled heat curing by operation of the custom operable band heater system such as to achieve desired curing schedule based developing of controlled on-site curing of the composites; and finally
(v) removing the custom operable band heater system.

In further aspect of the present invention is provided the method, wherein the polymer composite used includes nano CNT filler reinforced polymer which is an on-site curable polymer composite having tensile strength ranging from 260 to 290 MPa at elevated temperatures of upto 300°C, preferably in the range of 200°C to 300°C and thermal stability ranging from 335°C to 345°C
In yet further aspect of the present invention is provided the method, wherein said polymer composite composition used includes bisphenol-A based epoxy resin, hardener and accelerator with said CNT, which is obtained of selectively cured cure schedules selected from any one of:
(a) 2 hr 120°C + 2 hr 180°C, (b) 2 hr 120°C + 2 hr 160°C + 2 hr 180°C and (c) 4 hr 80°C + 4 hr 140°C and wherein the thermal stability (°C) from 290°C to 295°C, including Glass Transition Temperature (°C) attained in the range of 155°C to 160°C and with Ultimate tensile strength (MPa) in the range of 230 to 260 MPa, Tensile Modulus (GPa) in the range of 13 GPa to 16 GPa and, Tensile Strain to failure in the range of 1.3% to 1.4% and wherein preferably said polymer composite having said bisphenol-A based epoxy resin : hardener : accelerator in ratio of 50% to 52% : 47% to 49%: 1% to 1.2% respectively with select curing schedule of 2 hr 120°C + 2 hr 180°C for repair of pipelines operating at elevated temperature ranging from 100°C to 200°C.
In another aspect of the present invention is provided the method, wherein said polymer composite composition used includes modified epoxy resin, hardener with said CNT which is obtained of selectively cured cure schedules selected from any one of:
(a) 2 hr 80°C + 4 hr 160°C + 4 hr 200°C and (b) 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C and wherein said polymer composite having said resin : hardener in the ratio of 70% to 72% : 28% to 30% have the thermal stability (°C) from 335°C to 345°C, including Glass Transition Temperature (°C) attained in the range of 225°C to 230°C and with Ultimate tensile strength (MPa) in the

range of 260 MPa to 290 MPa, Tensile Modulus (GPa) in the range from 13 GPa to 16 GPa and Tensile Strain to failure in the range of 1.3% to 1.4% and wherein preferably said polymer composite preferably included loading of 1% CNT with cure cycle of 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C for significant improvement of 42% of the tensile strength with respect to polymer composite free of CNT suitable for composite repair of pipelines at elevated temperature range of 200° to 300°C.
In further aspect of the present invention is provided the method comprising involving said thermocouple means for measuring temperature of the polymer composite for curing and controlling the curing process involving the operatively connected PID controller.
BRIEF DESCRIPTION OF THE NON LIMITING ACCOMPANYING DRAWINGS
Figure la shows 1AC0: Tensile strength test specimens before testing
Figure lb shows 1AC0: Tensile strength test specimens after testing at room temperature (RT) conditions.
Figure lc shows 2AC0: Tensile strength test specimens before testing
Figure Id shows 2AC0: Tensile strength test specimens after testing at room temperature (RT) conditions
Figure 2 shows 1AC0: Tensile strength test specimens of (A) before testing and (B) after testing at elevated temperature (ET) conditions
Figure 3 shows 4BC0: Tensile strength test specimens (A) before testing and (B) after testing at room temperature (RT) conditions
Figure 4 shows 4BC0.5: Tensile strength test specimens (A) before testing and (B) after testing at room temperature (RT) conditions

Figure 5 shows 4BC1: Tensile strength test specimens (A) before testing and (B) after testing at room temperature (RT) conditions
Figure 6 shows 4BC0: Tensile strength test specimens (A) before testing and (B) after testing at elevated temperature (ET) conditions
Figure 7 shows 4BC0.5: Tensile strength test specimens (A) before testing and (B) after testing at elevated temperature (ET) conditions
Figure 8 shows 4BC1: Tensile strength test specimens (A) before testing and (B) after testing at elevated temperature (ET) conditions
Figure 9 shows elevated temperature repair of test pipe specimen
Figure 10 shows (A) Repaired pipe specimen (B) sustained more than 500 bar
Figure 11 shows (A) Repaired pipe specimen exposed high temperature using hot airgun, (B) sustains up to 300 bar pressure
Figure 12 shows isometric view of the repair over a defected pipe substrate with pipe substrate (1) and composite overwrap (3)
Figure 13 shows front cut-sectional view of the repair over a defected pipe substrate with pipe substrate (1), interface adhesive (2) and composite overwrap (3)
Figure 14 shows side cut-sectional view of the repair over a defected pipe substrate with pipe substrate (1), interface adhesive (2) and composite overwrap (3)
Figure 15 shows schematic circuit diagram for the band heater setup with pipe substrate (1), composite overwrap (3), Heating element (4), contactor (6), temperature controller (7) and thermocouple (8)
Figure 16 shows isometric view of the band heater mounted over the composite repair with pipe substrate (1), Heating element (4) and band heater (5)

Figure 17 shows front cut-sectional view of the band heater mounted over the composite repair with interface adhesive (2), composite overwrap (3), Heating element (4), and band heater (5)
Figure 18 shows side cut-sectional view of the band heater mounted over the composite repair with pipe substrate (1), interface adhesive (2), composite overwrap (3), Heating element (4), and band heater (5).
DESCRIPTION OF THE INVENTION
As discussed hereinbefore the present invention describes such polymer composite wrap system to repair and reinforce both internal and external corrosion on pipelines operating at elevated temperatures and for that an adequate understanding of the thermo-mechanical behavior is of utmost importance to execute an appropriate and efficient repair. The main motivation for the invention is the rehabilitation of corroded pipelines operating at two different temperature ranges viz. low temperatures (100°C to 200°C), medium temperatures (200°C to 300°C). ASME and ISO codes suggests few empirical relations for glass transition temperature and heat deformation temperature of such polymer composite wrap systems depending upon the operating temperature to be qualified for repair and rehabilitation of corroded pipelines.
So, in the present invention, the main focus is on the development of a suitable nano-filler reinforced polymer composite wrap system qualified for the repair and rehabilitation of corroded pipelines at elevated temperatures. The most economical and viable choice for the reinforcement and polymer are glass fiber and epoxy. Out of these two, epoxy has relatively lower thermal properties when compared with glass fibers. So, special importance is given to improve the thermal properties (specifically glass transition temperature, initial decomposition temperature and thermal stability) of the epoxy polymer and various methods for

doing the same has been explored and applied. A suitable epoxy-based polymer has been developed using different curing agents, various curing schedules and CNT nanofiller for the above-mentioned applications. The effect of variation in temperature on mechanical behaviour of the developed CNT nano-filler reinforced polymer composite wrap system is analysed. Hydrostatic tests are performed to evaluate the failure burst pressure of the pipeline repaired with the developed polymer composite wrap system as per the ASME and ISO codes.
The standards followed for specimen preparation and testing are as follows:
• Glass transition temperature test specimen fabrication - ASTM D6604
• Glass transition temperature test - ASTM E1356
• Tensile Strength - ASTM D3039
• Short term pipe spool survival test - Annexure C of ISO 24817
Example 1
i) Development of a composite repair system for corroded pipelines which are operating at temperature 100°C to 200°C
Materials used:
The epoxy resin used is a bisphenol-A based resin commercially available under the name Araldite LY556 and the anhydride-based hardeners are commercially available under the name Aradur HY906 and Aradur HY917 and amine-based accelerator is commercially available under the name Accelerator DY070. The factors varied are Curing agent (Aradur 906 and Aradur 917 (1&2)), curing schedules (A & B) and percentage of CNT (0%, 0.5% & 1%). The experimental plan is as given in Table 2.

Preparation:
Nano fillers cannot be dispersed iso-tropically into the resin system by hand stirring technique. So a magnetic stirrer is used for dispersing CNT in the epoxy resin. Epoxy resin of weight lOOg is taken in a beaker and then acid functionalized CNT of outer diameter 20-40 nm and length 10-30 micron is dispersed in the epoxy resin using a magnetic stirrer with a hot plate. As the resin is slightly viscous, mixing a high volume of CNT becomes slightly difficult on the magnetic stirrer. Adding solvent such as acetone, 50% by weight of epoxy resin as a diluent to the system can be an added advantage, since solvent gives no reaction with any hardener and being volatile, it evaporates at high temperatures from solution completely. The purpose of the diluent is to decrease the viscosity of the solution, thus increasing the feasibility of magnetic stirring. The mixing is initiated at room temperature at the speed of 600 RPM. Then the following schedule given in Table 1 is followed. The hardener and accelerator are added while stirring after the temperature of the solution is brought down to room temperature. For example, in the case of preparing 1AC0.5 (refer Table 2), lOOg epoxy resin and 0.5g of CNT (0.5% by weight of epoxy resin) are taken in the beaker and 50g acetone is added. The mixing is initiated at room temperature at the speed of 600 RPM, then the following schedule given below in table 1 is followed. The temperature is then brought down to room temperature and then 95g of hardener Aradur 906 and 2g of accelerator DY070 are added while stirring is continued.
Table 1. Stirring schedule

Temperature (°C) Speed (RPM) Time (min)
30 1200 15
45 1200 15
75 1200 15
100 1200 15
The above process can still be extended if the mixture is still very less viscous which means that the diluent is not completely evaporated.

In case of no CNT presence (0%), epoxy resin, hardener and accelerator can be mixed one by one using hand stirring method.
Two different curing schedules chosen for each of the resin systems. Cure schedules '2 hr 120°C + 2 hr 180°C (A)' and '2 hr 120°C + 2 hr 160°C + 2 hr 180°C (B)' for Araldite LY556 + Aradur 906 + DY070 resin system and cure schedules M hr 80°C + 4 hr 140°C (A)' and M hr 80°C + 4 hr 160°C (B)' for Araldite LY556 + Aradur 917 + DY070 resin system. These cure schedules follow 20°C /10 minutes ramp for each step temperature increment.
Table 2. Experimental Plan for 100°C to 200°C application

s.
No. Specimen Code Curing Schedule % CNT
[1] Araldite LY556 (100) : Aradur 906 (95) : Accelerator
DY070 (2)
1 1AC0 2 hr 120 °C + 2 hr 180 °C (A) 0
2 1AC0.5 2 hr 120 °C + 2 hr 180 °C (A) 0.5
3 1AC1 2 hr 120 °C + 2 hr 180 °C (A) 1
4 1BC0 2 hr 120 °C + 2 hr 160 °C + 2 hr 180 °C (B) 0
5 1BC0.5 2 hr 120 °C + 2 hr 160 °C + 2 hr 180 °C (B) 0.5
6 1BC1 2 hr 120 °C + 2 hr 160 °C + 2 hr 180 °C (B) 1
[2] Araldite LY556 (100) : Aradur 917 (90) : Accelerator
DY070 (2)
7 2AC0 4 hr80 °C + 4 hr 140 °C (A) 0
8 2AC0.5 4 hr80 °C + 4 hr 140 °C (A) 0.5
9 2AC1 4 hr80 °C + 4 hr 140 °C (A) 1
10 2BC0 4 hr80 °C + 4 hr 160 °C (B) 0
11 2BC0.5 4 hr80 °C + 4 hr 160 °C (B) 0.5
12 2BC1 4 hr80 °C + 4 hr 160 °C (B) 1
Glass Transition Temperature (Tg) test specimens are prepared as per ASTM E1356 for all test cases mentioned in Table 2 and the DSC test for the same has

been performed as per ASTM D6604 and the results of the same are as shown in Table 3.
Table 3. DSC Analysis Results for 100°C to 200°C application

S. No. Specimen Code Curing Schedule % CNT Glass
Transition
Temperat
ure (°C)
[1] Araldite LY556 (100) : Aradur 906 (95) : Accelerator DY070 (2)
1 1AC0 2 hr 120 °C + 2 hr 180 °C (A) 0 157
2 1AC0.5 2 hr 120 °C + 2 hr 180 °C (A) 0.5 143
3 1AC1 2 hr 120 °C + 2 hr 180 °C (A) 1 140
4 1BC0 2 hr 120 °C + 2 hr 160 °C + 2 hr 180 °C (B) 0 111
5 1BC0.5 2 hr 120 °C + 2 hr 160 °C + 2 hr 180 °C (B) 0.5 133
6 1BC1 2 hr 120 °C + 2 hr 160 °C + 2 hr 180 °C (B) 1 100
[2] Araldite LY556 (100) : Aradur 917 (90) : Accelerator DY070 (2)
7 2AC0 4 hr80°C + 4 hr 140 °C (A) 0 114
8 2AC0.5 4 hr80°C + 4 hr 140 °C (A) 0.5 133
9 2AC1 4 hr80°C + 4 hr 140 °C (A) 1 114
Thermogravimetric analysis (TGA) test specimens are prepared for all test cases mentioned in Table 2 and the TGA test for the same has been performed as per ASTM E2550 and the results of the same are as shown in Table 4.
Table 4. Thermogravimetric Analysis Results for 100°C to 200°C application

s.
No. Specimen Code Curing Schedule % CNT Initial
Decomposition
Temperature
(°C) Thermal
Stability
(°C)
Hi } Araldite LY556 (100) : Aradur 906 (95) : Accelerator DY070 (2)
1 1AC0 2 hr 120 °C + 2 hr 180 °C (A) 0 380.9 293.0

2 1AC0.5 2 hr 120 °C + 2 hr 180 °C (A) 0.5 379.7 292.1
3 1AC1 2 hr 120 °C + 2 hr 180 °C (A) 1 378.8 291.4
[2] Araldite LY556 (100) : Aradur 917 (90) : Accelerator DY070 (2)
7 2AC0 4 hr80 °C + 4 hr 140 °C (A) 0 380.0 292.3
8 2AC0.5 4 hr80 °C + 4 hr 140 °C (A) 0.5 379.7 292.1
9 2AC1 4 hr80 °C + 4 hr 140 °C (A) 1 381.3 293.3
It can be observed from table 3 and table 4 that no significant improvement in thermal properties is observed by dispersing CNT in resin. So it has been decided to study the mechanical properties of combinations without CNT dispersion, with curing schedule 'A', for which the best thermal properties are observed.
Tensile strength test specimens are prepared for 1AC0 and 2AC0. The tensile strength test is performed at room temperature as per ASTM D3039 and the results of the same are as shown in Table 5 and the specimens before and after testing are as shown in Figure l(a-d).
Table. 5. Tensile strength test results of 1AC0 & 2AC0 performed at room
temperature

s.
No. Specimen Code Ultimate Tensile Strength (MPa) Tensile Modulus (GPa) Tensile Strain to failure (%)
■I-I 1AC0 243.54 15.23 1.59
2 2AC0 221.53 13.85 1.6
From the above results, 1AC0 has the best thermal and mechanical properties and is qualified for composite repair of pipelines at elevated temperatures ranging from 100°C to 200°C. To validate this, tensile strength test specimens are prepared for 1AC0 test cases and the tensile strength test is performed as per ASTM D3039 at live temperatures of 175°C, 200°C, 225°C and 250°C and

the results of the same are as shown in Table 6 and the specimens before and after testing are as shown in Figure 2.
Table 6. Tensile strength test results of 1AC0 performed at elevated temperature

S. No. Specimen Code Testing Temperature (°C) Ultimate Tensile Strength (MPa)
1 1AC0 RT 243.54

175 234.69

200 199.27

225 268.10

250 240.58
From the results in table 6, it can be seen that there is no significant degradation in the ultimate tensile strength of 1AC0 system which is a desirable quality and it qualifies as a promising candidate for the repair of pipelines operating at elevated temperature ranging from 100°C to 200°C.
Example 2
ii) Development of a composite repair system for corroded pipelines which are operating at temperature 200°C to 300°C
Materials used:
The epoxy resin used is a modified epoxy resin commercially available under the name Lapox ARL140 and hardener commercially available under the name Lapox AH419. The factors varied are curing schedules (A & B) and percentage of CNT (0%, 0.5% & 1%). The experimental plan is as given in Table 7.
Preparation:
lOOg epoxy resin ARL 140 and appropriate amount of CNT (0.5g = 0.5% of epoxy resin for 4AC0.5 and 4BC0.5 and lg = 1% of epoxy resin for 4AC1 and 4BC1) is taken in a beaker. Then 50g of solvent like acetone (50% weight of epoxy resin) as diluent is added. Using a magnetic stirrer, mixing is initiated at

room temperature at the speed of 600 RPM. The mixing schedule given in table 1 is followed. 42g of hardener AH419 is added after the temperature of the solution is reduced to room temperature. Two different cure schedules '2 hr 80°C + 4 hr 160°C + 4 hr 200°C (A)' and '2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C (B)' chosen for curing to evaluate the effect of cure schedule in composite repair system. This cure schedules consist of ramps and flats to avoid sudden temperature change. For example, cure schedule A has ramp of 20°C /10 minutes which means to increase temperature from 80°C to 160°C it would take 40 minutes.
Table 7. Experimental Plan for 200°C to 300°C application

Lapox ARL140 (100) : La pox AH419 (42)
s.
No Specimen Code Curing Schedule %CNT
1 4AC0 2 hr 80 °C + 4 hr 160 °C + 4 hr 200 °C (A) 0
2 4AC0.5 2 hr 80 °C + 4 hr 160 °C + 4 hr 200 °C (A) 0.5
3 4AC1 2 hr 80 °C + 4 hr 160 °C + 4 hr 200 °C (A) 1
4 4BC0 2 hr 80 °C + 4 hr 120 °C + 2 hr 160 °C + 4 hr200°C (B) 0
5 4BC0.5 2 hr 80 °C + 4 hr 120 °C + 2 hr 160 °C + 4 hr200°C (B) 0.5
6 4BC1 2 hr 80 °C + 4 hr 120 °C + 2 hr 160 °C + 4 hr200°C (B) 1
Glass Transition Temperature (Tg) test specimens are prepared as per ASTM E1356 for all test cases mentioned in Table 7 and the DSC test for the same has been performed as per ASTM D6604 and the results of the same are as shown in Table 8.
Table 8. DSC Analysis Results for 200°C to 300°C application

Specime n Code
S. No

Lapox ARL140 (100) : Lapox AH419 (42)
Curing Schedule

%CNT

Tg(°C)

1 4AC0 2 hr 80 °C + 4 hr 160 °C + 4 hr 200 °C(A) 0 177
2 4AC0.5 2 hr 80 °C + 4 hr 160 °C + 4 hr 200 °C(A) 0.5 174
3 4AC1 2 hr 80 °C + 4 hr 160 °C + 4 hr 200 °C(A) 1 175
4 4BC0 2 hr 80 °C + 4 hr 120 °C + 2 hr 160 °C + 4 hr 200 °C (B) 0 177
5 4BC0.5 2 hr 80 °C + 4 hr 120 °C + 2 hr 160 °C + 4 hr 200 °C (B) 0.5 227
6 4BC1 2 hr 80 °C + 4 hr 120 °C + 2 hr 160 °C + 4 hr 200 °C (B) 1 227
It can be observed that there is significant improvement in Tg (28%) for B series with addition of CNT compared to test case without CNT addition. Either of 0.5 % CNT or 1% CNT loaded B series system is considered to be the best with respect to thermal property namely 'glass transition temperature'.
Thermogravimetric analysis (TGA) test specimens are prepared for all test cases mentioned in Table 7 and the TGA test for the same has been performed as per ASTM E2550 and the results of the same are as shown in Table 9.
Table 9. Thermogravimetric Analysis Results for 200°C to 300°C application

Lapox ARL140 (100) : La pox AH419 (42)
S. No Specimen Code Curing Schedule %CNT Initial
Decomposition
Temperature
(°C) Thermal
Stability
(°C)
■I-I 4AC0 2 hr80 °C + 4
hr 160 °C + 4 hr
200 °C (A) 0 327.47 251.9
2 4AC0.5 2 hr80 °C + 4
hr 160 °C + 4 hr
200 °C (A) 0.5 328.65 252.8
3 4AC1 2 hr80 °C + 4
hr 160 °C + 4 hr
200 °C (A) 1 329.22 253.2
4 4BC0 2 hr80 °C + 4 hr 120 °C + 2 hr 0 331.55 338.6

160 °C + 4 hr 200 °C (B)
5 4BC0.5 2 hr80 °C + 4
hr 120 °C + 2 hr
160 °C + 4 hr
200 °C (B) 0.5 332.50 337.7
6 4BC1 2 hr80 °C + 4
hr 120 °C + 2 hr
160 °C + 4 hr
200 °C (B) 1 330.58 340.4
From table 9, it can be seen that there is no significant change in TGA value in 4BC series with addition of CNT. Based on the thermal properties of both 4AC and 4BC series, 4BC series is better with respect to TGA properties. Moreover, the minor changes in TGA values for 4BC series could be experimental errors. Also, it could be noted that the thermal stability for 4BC series lies well above the intended application temperature range (200°C to 300°C).
Based on the above observation, 4BC series is chosen for mechanical property evaluation. Main objective of CNT fillers addition is to achieve optimal thermal and mechanical properties which makes the repair system suitable for elevated temperature condition.
The mechanical property that governs the repair thickness calculation for composite repair system is its tensile strength and modulus. Hence, tensile property evaluation is performed, the results of which will be used for repair design calculation.
Tensile strength test specimens are prepared for 4BC series. The tensile strength test is performed as per ASTM D3039 and the results of the same are as shown in Table 10 and specimens before and after testing as shown in Figure 3, 4, 5.
Table. 10. Tensile strength test results of 4BC series performed at room temperature

s.
No. Specimen Code Ultimate Tensile Strength (MPa) Tensile Modulus (GPa) Tensile Strain to failure (%)
1 4BC0 189.15 13.52 1.4
2 4BC0.5 170.94 13.49 1.55
3 4BC1 268.42 13.51 1.45
With 1% CNT loading, a significant improvement in tensile strength can be observed (42%) compared to the sample without CNT loading. Hence, it can be concluded that 4BC1 has the best thermal and mechanical properties and is qualified for composite repair of pipelines at elevated temperatures ranging from 200°C to 300°C. To validate this, tensile strength test specimens are prepared for all the 4BC test cases and the tensile strength test is performed as per ASTM D3039 at live temperatures of 250°C and the results of the same are as shown in Table 11 and the specimens before and after testing are as shown in figure 6, 7 and 8.
Table ll.Tensile strength test results of 4BC series performed at
elevated temperature

S. No. Specimen Code Testing Temperature (°C) Ultimate Tensile Strength (MPa)
1 4BC0 RT 189.15

250 168.24
2 4BC0.5 RT 170.94

250 182
3 4BC1 RT 268.42

250 277
In example 1, it is found that CNT addition has no significant improvement in thermal/mechanical properties. It is proposed to use neat resin system 1AC0 (without CNT loading) for the temperature range of 100°C to 200°C with select curing schedule of 2 hr 120°C + 2 hr 180°C for application in site conditions. The workable range for 1AC0 is provided in table 12.

In example 2, based on the thermal and mechanical properties for two different cure cycle systems, with varying CNT filler loading, it is concluded that the best composition for application in site conditions for temperature range of 200°C to 300°C is 4BC1 (1% CNT filler loading with cure cycle of 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C. The workable range for 4BC1 is given in table 12 by involving Lapox ARL140 (100) : Lapox AH419 (42).
Table 12. Workable range of compositions for 1AC0 and 4BC1

SI No. Application temperature
°C Resin % wt Hardener % wt Accelerator
%wt CNT % wt
1 100 - 200 50 - 52 47 - 49 1 - 1.2 0
2 200 - 300 70 - 72 28 - 30 0 0.9 -1.1
Example 3: Hydrostatic Burst Test
A 4" test pipe specimen with 80% wall loss has been repaired with the specified wrap code of 2 layers of 300 GSM Chopped Strand Mat (CSM) glass fiber reinforced epoxy and 4 layers of 610 GSM Woven Roving Mat (WRM) glass fiber reinforced epoxy. The repaired test pipe specimen was cured in a furnace oven according to its cure schedule as shown in figure 9. The test pipe specimen repaired with 4BC0 system is mounted onto the static pressure loading setup and the burst test is performed by incrementally increasing the internal pressure in the pipeline until failure. The pressurized repaired test pipe specimen sustained a pressure of 590 bar and no failure was observed as shown in figure 10.

Another hydrostatic burst test is conducted at an elevated temperature condition. The 4" test pipe specimen with 80% wall loss has been repaired with the specified wrap code of 2 layers of 300 GSM CSM glass fiber reinforced epoxy and 4 layers of 610 GSM WRM glass fiber reinforced epoxy. The test pipe specimen repaired with 4BC0 system is heated to an elevated temperature of 250°C to 300°C and the same is mounted onto the static pressure loading setup and the burst test is performed by incrementally increasing the internal pressure in the pipeline until failure. The pressurized repaired test pipe specimen sustained a pressure of 300 bar and no failure was observed as shown in figure 11.
Theoretical burst pressure is evaluated based on analytical equations given in ISO 24817 annexure C for 4BC0 system at room temperature. The theoretical burst pressure obtained is 199.7 bar (refer table 13). The experimental pressure observed in test is higher than the theoretical pressure, which qualifies the system to be capable for repair of pipelines as per ISO 24817. The validated theoretical model is used to predict the theoretical hydrostatic burst pressure of combinations with CNT loading. The input required for the prediction are tensile properties of composite repair material, which is available from the tensile tests conducted. The theoretical prediction of hydrostatic burst pressures are given in table 13.
Table 13. Burst pressure prediction for CNT dispersed compositions.

SI. No Repair system Tensile
modulus
(MPa) Strain
to failure Pipe
size
(mm) Remaining
thickness
(mm) Repair
thickness
(mm) Burst
pressure
(MPa)
1 4BC0 13520 0.014 114.3 1.2 4.5 19.97
2 4BC0.5 13490 0.0155 114.3 1.2 4.5 21.53
3 4BC1 13510 0.0145 114.3 1.2 4.5 20.491

It can be observed from table 13, that the theoretical burst pressure for 0% CNT filled combination (4BC0) is only 199 bar (19.9 MPa), whereas the experimental result is 590 bar (59 MPa). So, it is expected that the combinations with CNT dispersions would yield higher pressure bearing capability than theoretical prediction.
Example 4: Composite repair method for pipelines
In site conditions i.e., application of repair in practical scenario, the defected location is filled with interface adhesive (2) and then the defected portion is reinforced with a composite overwrap (3). The isometric view of the repair over a defected pipe substrate (1) is as shown in figure 12. The front cut-sectional view of the repair over a defected pipe substrate (1) is as shown in figure 13. The side cut-sectional view of the repair over a defected pipe substrate (1) is as shown in figure 14.
The curing of the composite overwrap (3) repaired over the defected pipe substrate (1) is done by means of a custom designed band heater (5) with heating elements (4) that generate heat to increase the temperature of the repair system corresponding to its cure schedule using a PID temperature controller (7) along with a contacter (6) which acts a relay. The band heater (5) is a two half system capable of getting mounted on a pipe substrate (1) by hinging the two halves by means of a locking mechanism using a cyclindrical rod. The band heater (5) is oriented concentrically over the pipe substrate (1) by means of eight bolts and nuts, four on each end of the band heater spaced equally in the circumferential direction. The screw supports were provided to lock the rotation of the heater/metal halves around the pipe by tightening the bolt towards the repair substrate. Two rigid ceramic heaters designed with 8 KW capacity are mounted on both halves of the band heater (5) using bolts nuts. This electronic system works on more than 20 amperes and hence a contactor (6) is used as a relay and both the contacter (6) and the heating elements (4)

are connected to a PID temperature controller (7). The 25 amps contactor (6) is coupled with the controller (7) to protect from overcurrent damage through the use of overload heaters. The temperature is measured by means of a thermocouple (8) and it is also connected with PID controller. And, the schematic circuit diagram for the same is as shown in figure 15.
This band heater setup is mounted onto the repair applied over the defected pipe substrate and the whole setup is insulated by means of a glass fabric and teflon based insulation jacket insulating the repair and band heater setup. The temperature controller is used to achieve the temperatures as per the pre¬determined cure schedule for curing of the composite repair system. The isometric view of the band heater mounted over the composite repair is as shown in figure 16. The front cut-sectional view of the band heater mounted over the composite repair is as shown in figure 17. The side cut-sectional view of the band heater mounted over the composite repair is as shown in figure 18.
Conclusion:
This advancement thus comprises following distinguishing aspects not reported in any article/patent in the related art.
• The present system takes into account the effect of nano filler CNT, curing agents and cure schedules on the mechanical and thermal properties such Glass Transition Temperature, Initial Decomposition Temperature and Thermal Stability of the resin systems such that it qualifies for the repair purposes of corroded structures in oil/gas industries.
• Enhanced glass transition temperature and thermal stability of the resin system makes the resin system qualified for repair of corroded structures operating at temperature ranges of 100°C to 200°C and 200°Cto 300°C.
• Development of advanced custom designed band heater for curing the composite repair system as per its cure schedule.

• The capability of performing an in-situ repair as the repair methodology is simple and straight forward.
Inventiveness in the present system:
The advanced system of the present invention is thus adapted for repair of corroded pipelines at elevated temperatures of upto 300°C by way of selective involvement of the CNT loaded epoxy resins which demonstrated surprising and unexpected results in the composite repair of corroded pipelines at elevated temperatures as high as upto 300°C. Such unique aspects of the advanced composite system is being made available for the first time and clearly qualify for the composite repair of corroded pipelines at elevated temperatures as a cost effective and user friendly solution of the repair. The currently available polyurethane based prepregs and polyimides based resin systems being used in elevated temperature repair of corroded pipelines despite having low mechanical and thermal properties and are not suitable for very high temperatures over upto 150°C as they cannot sustain very high internal pressures such as more than 100 bars. The present system serves as an economical alternative while having better mechanical and thermal properties.
Also, the present repair methodology employs the use of the custom designed band heater for different pipe diameters making the repair procedure simple and replicable for varied damage scenarios of any dimensions across various diameters of the pipelines.
The advancement thus resides in the heretobefore unknown and unexpected surprising aspects of the nano CNT filler reinforced polymer composite wrap to repair damaged pipeline at elevated temperatures upto 300°C. The raw material used, its composition and modified repair process suit to challenging site requirements especially on the controlled on-site curing of the composites.

The present advancement thus has many advantages over traditional repair system as:
• Low cost solution and an economical alternative.
• Good mechanical strength and thermal properties at elevated temperatures.
• The repair is faster to be performed as the application is simple, easy and straight forward.
• The risk of fire and explosion is eliminated due to the cutting and welding as the present invention employs a cold repair methodology.
• The custom-made design of band heater setup has a simple construction and cost-effective.
• The repair methodology is replicable for various defect dimensions and various pipeline diameters.

We Claim:

1. A system adapted for repair of corroded pipelines at elevated temperatures of
upto 300°C comprising:
on-site wrap able over defective pipe substrate (1) and heat curable polymer
composite composition (3) including selectively,
Epoxy resin selected from modified epoxy resins of low viscosity, with an epoxy
equivalent of 8.00 to 9.09 (Eq/kg), specific gravity of 1.1 to 1.2 and viscosity
12,000 to 18,000 mPas in amounts of 70 to 72 % % by wt;
Nano CNT filler in amounts of upto 1 % by wt;
Hardeners selected from modified polyamine based hardeners with specific
gravity of 0.9 to 1.0 and viscosity of 10 to 30 mPas in amounts of 28 % to 30
% by wt; and
and optionally including accelerators selected from imidazole based compounds
with chemical name 1- Methyimidazole in amounts of 0 to 1 % by wt,
for generating desired cured polymer composite having tensile strength ranging from 260 MPa to 290 MPa even at elevated temperatures of upto 300°C and thermal stability ranging from 335 °C to 345°C.
2. The system as claimed in claim 1, wherein said polymer composite
composition (3) includes
from 0.5-1 % by wt nano CNT filler reinforced polymer which is an on-site curable polymer composite having tensile strength ranging from 260 MPa to 290 MPa at elevated temperatures of upto 300°C, preferably in the range of 200°C to 300°C and thermal stability ranging from 335 °C to 345°C.
3. The system as claimed in claim 1, comprising said polymer composite (3) as a
in-situ selectively curable wrap able repair system for corroded pipelines (1)
operating at temperatures from 100°C to 200°C comprising selectively,

Epoxy resin selected from Bisphenol-A based systems with epoxy equivalent of 5.3 to 5.45 (Eq/kg), specific gravity of 1.15 to 1.2 and viscosity of 10,000 to 12,000 mPas in amounts of 50 % to 52 % by wt;
Hardeners selected from Anhydride systems with specific gravity of 0.95 to 1.05 and viscosity of 175 to 350 mPas in amounts of 47 % to 49% by wt.;
Accelerator selected from imidazole based compounds with chemical name 1-Methyimidazole in amounts of 1% to 1.2% by wt;
and CNT in amounts of 0 to 1 % by wt.
4. The system as claimed in claim 3, comprising said polymer composite
composition (3) including bisphenol-A based epoxy resin, hardener and
accelerator with said CNT which is obtained of selectively cured cure schedules
selected from any one of:
(a) 2 hr 120°C + 2 hr 180°C, (b) 2 hr 120°C + 2 hr 160°C + 2 hr 180°C and (c) 4 hr 80°C + 4 hr 140°C and wherein the thermal stability (°C) from 290°C to 295°C including Glass Transition Temperature (°C) attained in the range of 155°C to 160°C and with Ultimate tensile strength (MPa) in the range of 230 MPa to 260 MPa, Tensile Modulus (GPa) in the range of 13 GPa to 14 GPa and Tensile Strain to failure in the range of 1.3% to 1.6% and wherein preferably said polymer composite having said bisphenol-A based epoxy resin : hardener : accelerator in ratio of 50% to 52%: 47 % to 49%: 1% to 1.2% respectively with select curing schedule of 2 hr 120°C + 2 hr 180°C for repair of pipelines operating at elevated temperature ranging from 100°C to 200°C.
5. The system as claimed in claim 1, comprising polymer composite composition
(3) including modified epoxy resin, hardener with said CNT which is obtained of
selectively cured cure schedules selected from any one of:
(a) 2 hr 80°C + 4 hr 160°C + 4 hr 200°C and (b) 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C and wherein said polymer composite having said resin:

hardener in the ratio of 70% to 72% : 28% to 30% have the thermal stability (°C) 335°C to 345°C including Glass Transition Temperature (°C) attained in the range of 225°C to 235°C and with Ultimate tensile strength (MPa) in the range of 260 MPa to 280 MPa, Tensile Modulus (GPa) in the range from 13 GPa to 14 GPa and Tensile Strain to failure in the range of 1.4 % to 1.6 % and wherein preferably said polymer composite preferably included loading of 1% CNT with cure cycle of 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C, for significant improvement of 42% of the tensile strength with respect to polymer composite free of CNT suitable for composite repair of pipelines at elevated temperature range of 200° to 300°C.
6. The system as claimed in anyone of claims 1 to 5, wherein said on-site wrap able over defective pipe substrate (1) and heat curable polymer composite composition (3) is operatively connected to custom operable band heater system (5) for desired on-site heat curing of the polymer composite overwrap (3) as per desired cure schedule.
7. The system as claimed in claim 6, wherein said custom operable band heater system (5) includes
two half units capable of getting mounted with resepct to any pipe substrate (1) involving hinging the two halves by means of a locking mechanism and said units adapted to be oriented concentrically over the pipe substrate (1), two rigid heaters having respective heating elements (4) mounted on both half units ; a cooperative power unit supplying power to said heating elements (4) via contactors (6) and a PID temperature controller means (7) adapted to protect over current damages and thermocouple means (8) for measuring temperature operatively connected to said PID controller (7).
8. The system as claimed in anyone of claims 6 or 7, comprising whole set up
insulation including glass fabric and Teflon based insulation jacket insulating said
repair and band heater set up.

9. The system as claimed in anyone of claims 6 to 8, wherein said custom
operable band heater system setup (5) is customizable to different diameters of
pipe (1) as high as 48 inches.
10. A method for repair of corroded pipelines at elevated temperatures of upto
300°C involving the system as claimed in anyone of claims 1 to 9, comprising the
steps of,
(i) providing on the defected location of the pipeline substrates (1) interface adhesive (2);
(ii) reinforcing the defected portion with said polymer composite wrap (3);
(iii) setting up the custom operable band heater system (5) with said two half units mounted with respect to any pipe substrate (1) and locking for desired heat curing;
(iv) subjecting the polymer composite wrap (3) to controlled heat curing by operation of the custom operable band heater system (5) such as to achieve desired curing schedule based developing of controlled on-site curing of the composites (3); and finally
(v) removing the custom operable band heater system (5).
11. The method as claimed in claim 10, wherein the polymer composite used includes nano CNT filler reinforced polymer which is an on-site curable polymer composite (3) having tensile strength ranging from 260 MPa to 290 MPa at elevated temperatures of upto 300°C, preferably in the range of 200° to 300°C and thermal stability ranging from 335°C to 345°C.
12. The method as claimed in anyone of claims 10 or 11, wherein said polymer composite composition (3) used includes bisphenol-A based epoxy resin,

hardener and accelerator with said CNT, which is obtained of selectively cured cure schedules selected from any one of:
(a) 2 hr 120°C + 2 hr 180°C, (b) 2 hr 120°C + 2 hr 160°C + 2 hr 180°C and (c) 4 hr 80°C + 4 hr 140°C and wherein the thermal stability (°C) from 290°C to 295°C, including Glass Transition Temperature (°C) attained in the range of 155°C to 160°C and with Ultimate tensile strength (MPa) in the range of 230 MPa to 260 MPa, Tensile Modulus (GPa) in the range of 13 GPa to 16 GPa and, Tensile Strain to failure in the range of 1.3% to 1.4 % and wherein preferably said polymer composite having said bisphenol-A based epoxy resin : hardener : accelerator in ratio of 50% to 52% : 47% to 49% : 1% to 1.2% respectively with select curing schedule of 2 hr 120°C + 2 hr 180°C for repair of pipelines (1) operating at elevated temperature ranging from 100°C to 200°C.
13. The method as claimed in anyone of claims 10 or 11, wherein said polymer composite composition (3) used includes modified epoxy resin, hardener with said CNT which is obtained of selectively cured cure schedules selected from any one of:
(a) 2 hr 80°C + 4 hr 160°C + 4 hr 200°C and (b) 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C and wherein said polymer composite (3) having said resin : hardener in the ratio of 70% to 72% : 28% to 30% have the thermal stability (°C) from 335°C to 345°C, including Glass Transition Temperature (°C) attained in the range of 225°C to 230°C and with Ultimate tensile strength (MPa) in the range of 260 MPa to 290 MPa, Tensile Modulus (GPa) in the range from 13 GPa to 16 GPa and Tensile Strain to failure in the range of 1.3 % to 1.4 % and wherein preferably said polymer composite preferably included loading of 1% CNT with cure cycle of 2 hr 80°C + 4 hr 120°C + 2 hr 160°C + 4 hr 200°C for significant improvement of 42% of the tensile strength with respect to polymer composite free of CNT suitable for composite repair of pipelines (1) at elevated temperature range of 200° to 300°C.

14. The method as claimed in anyone of claims 10 to 13, comprising involving
said thermocouple means (8) for measuring temperature of the polymer
composite (3) for curing and controlling the curing process involving the
operatively connected PID controller (7).