FIELD OF INVENTION
The present invention relates to a product/formulation and system thereof comprising rapid curing epoxy grout and a process of manufacture thereof.

BACKGROUND ART

Pipeline transmission is the most economical mode of transport for oil and gas transport. These pipelines are made of steel and are classified under American Pipeline Institute (API) grades. These pipelines are exposed to various kinds of corrosive environments such as salinity near the sea shores and oils of different chemical composition. This leads to extensive corrosion and if left unattended, eventually leads to reduced wall thickness, or even through hole defects.

In the conventional method of pipeline repair, in case of a leaking defect, the process involves cutting out the damaged portion ofthe pipe and welding a new pipe segment or welding a steel sleeve above the damagedpipe. The repair of non-leaking corrosion defects can be approached by composite overwrap technique. Standards such as ISO 24817 and ASME PCC2 dictates thedesign and requirements of composite overwrap. The repair of non-leakingdefects is quite developed whereas the repair of leaking defects is still in the developmentalphase.

To extend the composite overwrap technology to the repair of leaking defects, the sealing of leak with a polymericadhesive substance is required prior to applying the composite overwrap. Some such adhesives based on two component epoxy systems are commercially available. Once the leak is sealed, the composite overwrap can be applied over the defect region to impart additional strength to the repair.

There are a few literatures that discusses the formulation of epoxy grouts for structural repair applications as below.

Md.Shamsuddoha et al. [Shamsuddoha M, Islam MM, Aravinthan T, Manalo A, Lau KT. Effectiveness of using fiber-reinforced polymer composites for underwater steel pipeline repairs. Composite Structures. 2013 Jun 1;100:40-54]studied the mechanical and thermal properties of epoxy groutswith fine a coarse filler inclusion. They observe that epoxy grouts can be used as properinfill materials between the pipe annulusand the composite sleeve, thereby ensuring asmooth bedfor composite overwrap and proper load transfer. Silica and Calcium based inert fillers wereused. It was seen that the grout with coarse filler has exhibited highestcompressive strengthand modulus compared to other grouts with only fine fillers, eventhough the resin contentwas low. However, the inclusion of coarse fillers increased the brittle nature of the epoxy grout.

N.R.F. Rohem et al [Rohem NR, Pacheco LJ, Budhe S, Banea MD, Sampaio EM, De Barros S. Development and qualification of a new polymeric matrix laminated composite for pipe repair. Composite Structures. 2016 Sep 15;152:737-45.] worked on the qualification of polymer matrix laminated compositematerial for pipe repair through various mechanical and thermal property testing.Glass fiberreinforced polymer composite was used. Hydrostatic tests were conducted ontype A andType B defects (Non-leaking and leaking defects) as per the ISO TS24817 standard.Theyobserved that the performance of the repair system is satisfactory for Type Adefect where the experimental results showed that the repair system sustained the designpressure of thepipe. For Type B defects, the failure pressure was seen to be decreasing with increasingdefect size. However, there was no mention of any sealant material usedto seal the defectprior to wrapping. The epoxy resin used for the study is commerciallyknown as PIPEFIX developed by Novatec and the resin to fiber weight ratio chosen was2:1.

The article titled “Comparative study on the adhesive properties of different epoxy resins"by Silvia G. Prolongoet al. [Prolongo SG, del Rosario G, Ureña A. Comparative study on the adhesive properties of different epoxy resins. International Journal of Adhesion and Adhesives. 2006 Jun 1;26(3):125-32.]presents an extensive study on the adhesive properties of differentepoxy formulations cured using amine addition and homo-polymerization using imidazoleby lap shear strength measurements. The curing of epoxy resins can be achieved bytwo methods, addition polymerization and homo-polymerization by the use of an initiator.The glass transition temperature, and the variation of adhesion strength and Tgwith temperatureand humidity has also been studied. The author used three curing agents namely 2-methylimidazole, which enables curing by homo-polymerization, 4,4'-diaminediphenylsulfone (DDS) which is an aromatic amine and poly(3-aminopropylmethylsilane)(PAMS) which is a silane compound expected to produce a product with low water absorption.It has been observed that the epoxy cured using aromatic amines has the highestadhesive strength and Tg. The curing temperature and the water absorption observed inthis case is high as compared to the other two. The epoxy cured with imidazole showed less water absorption. Epoxy cured with PAMS shown relatively good adhesive strengthand low water absorption.

In an article titled “The Investigation of Underwater Adhesives in the People's Republicof China" byXie Ju-niang et al [Ju-Niang X, Song-Hui Z, Xiao-ping Z, Ru C, Sang-heng L. The Investigation of Underwater Adhesives in the People’s Republic Of China. InAdhesives, Sealants, and Coatings for Space and Harsh Environments 1988 (pp. 73-80). Springer, Boston, MA]studied four polymeric materials that has the potentialto beused as underwater adhesives. They are epoxy resins, polyurethane, ethylenic terminatedpolyurethane and epoxy-acrylate adhesives. The article suggests that the mainrequirement for an underwater adhesive is that it should contain either a water absorbentmaterial or awater repellant material or a water activated curing agent. They observedthat epoxy has good mechanical properties compared to other adhesives. A bisphenol-based epoxy cured with a modified amine has shown better shear strength compared tothe one cured with ordinary amine curing agents. The article also reports one-year shelf life for epoxy hardener system when stored as two components. Polyurethane adhesivesare used in the form of iso-cyanate terminated prepolymers. They react with water to form carbon dioxide and NH2. The NH2 further reacts with other prepolymers to form polymeric chain. The water sensitivity of these adhesives brings down their shelf life.

Reference is further made to international patent documents on pipeline repair and rehabilitation using composites.

US4396754 provides a rapid curing composition made of a polymer liquid containing epoxy and cured with non-nucleophilic acids of group I or group II metal salts. The catalyst composition (curing agents in this case) are prepared by mixing the salts in a solvent, to which other inorganic materials such as fillers, thixotropic agents etc are added. Later the solvent is removed by distillation. The examples depicted in the patent document shows gel time as low as 20 second for some compositions.

US4316003 provides a curing agent that enhances the curing rate and reduces the water sensitivity and toxicity of the epoxy systems. The goal is achieved by reacting an epoxy resin with a monoamine compound to form an epoxy adduct and the resulting condensate is then reacted with a polyfunctional amine to form the final product. This final product is used to cure epoxy resins at a faster rate. The mechanical properties of the cured products are tested and found satisfactory.

US4569956 “Rapid Curing Epoxy Resin Adhesive Composition” discloses a composition containing a polyepoxide, HBF4as a catalyst, an inert filler and polyalkylene ether glycol, which is rapidly curable at room temperature. The fillers used were acidic fillers like carbon black, silica, mica etc.

US8263694B1 “Polyurethane containing grouts” discloses a polyurethane based water borne grout of which the curing rate is controlled using an accelerator. The accelerators used are metal oxides or hydroxides. The main application is joining of tiles on floors and ceilings, as an adhesive to join materials etc. It is said that glass beads as filler material provides excellent compressive strength and for that reason, glass beads are used.

While there are numerous epoxy grouts available in the market all the products have its own inherent disadvantages like poor bonding strength, poor tensile strength etc. which was a hurdle in the art to overcome and hence there was a need to explore for tailor made product/composition and process thereof that would provide for a desired response in addition to rapid curing of desired tensilestrength, compression strength and adhesive bond strength.

OBJECTS OF THE INVENTION

It is thus the primary object of the present invention to provide for a product/ formulation comprising epoxy grouts and process thereof that would be rapid curing and would be suitable for live repair of a leaking defect in pipelines including oil, gas and water pipelines.

It is another object of the present invention to provide for said product/ formulation that would have enhanced bonding with both steel and glass fiber reinforced composite substrates to make said product more suitable for pipeline repair compared to commercially available products.

It is yet another object of the present invention to provide for said product/ formulation with enhanced interfacial bonding strength, that would be cheaper and economical to use, that would repair faster, would enable easy and straight forward application, and would not cause risk of fire and explosion due to the cutting and welding that would be thus completely eliminated.

It is another object of the present invention to provide for said product/ formulation that would provide further advantages over traditional repair systems including that the pipeline for repair need not to be flushed off with nitrogen before working in case of leakage.

It is still another object of the present invention to provide for said product/ formulation and composition thereof involving epoxy grout whose mechanical properties can be further improvised depending on the application even though the primary goal is to use in oil and gas pipeline repair.

SUMMARY OF THE INVENTION

The basis aspect of the present invention is to provide for rapid curing epoxy grout based formulation in at least two parts comprising epoxy-hardener formulation involving epoxy resin and hardener in synergistic combination with accelerator and fillers selected from nano scale and micro scale-based fillers adapted for a rapid curing grout capable of live repair of leaking defect.

Preferably a rapid curing epoxy grout based formulation is provided wherein said epoxy-hardener formulation has epoxy resin and hardener in curing stoichiometric ratio and provides for semi solid consistency prior to curing with enhanced hardening reaction rate of said epoxy resin in the presence of said fillers thereby providing for said rapid curing epoxy grout capable of sealing through thickness defects in oil and gas and water pipelines curing/sealing within 20-40 minutes.

According to a preferred aspect of the present invention there is provided a rapid curing epoxy grout based formulation comprising
said epoxy resin in the range of 80 to 83 wt% including preferably bisphenol-A based epoxy resin,
said hardener preferably Aradur HY951, an amine based hardener with an amine equivalent of 20.6 eq/g and viscosity in the range of 10-20 centipoise, is in the range of 14 to 15 wt.%;
said accelerators preferably imidazoles is in the range of 2 to 8 wt.%, and, said accelerator preferably 960-1, being teritary amine-based with a viscosity of 150 to 300 centipoise, is in the range of 15 to 16 wt.%;
said fillers selected from nano scale and micro scale based fillers comprising nano scale fumed Silica 10- 20 nm in the range of 12-16wt.% and micro scale Silicon Nitride of about 80 microns being in the range of 10-20wt.%.

Preferably a rapid curing epoxy grout-based formulation is provided comprising
said hardener preferably Aradur 450, Aradur 450 is also an amine based hardener with an amine equivalent 6 times lesser than Aradur HY951 and viscosity in the range of 1000 to 2000 centipoise, in the range of 59 to 60 wt. %,
said accelerators preferably imidazoles is in the range of 2 to 8 wt.%, and, said accelerator preferably 960-1 is in the range of 15 to 16 wt.%;
said nano scale fumed Silica in the range of 20-23 wt.%;
said micro scale Silicon Nitride in the range of 10-25 wt.%;
rest being said epoxy resin.

According to yet another preferred aspect of the present invention there is provided rapid curing epoxy grout based formulation wherein said hardener when is Aradur HY951 is 15 wt.% of said epoxy resin, and, when said hardener is Aradur 450 is 60 wt% of said epoxy resin;

said accelerator when is imidazole is 5 wt.% of said epoxy resin, and, said accelerator when is 960-1 is 16 wt% of said epoxy resin;

said fillers selected from nano scale and micro scale based fillers comprises nano scale fumed Silica in the levels of 12wt.% and micro scale Silicon Nitride in the levels of 10wt.% when said hardener is Aradur HY951, and, said nano and micro fillers being 23 wt. % and 20 wt.% respectively when said hardener is Aradur 450;

thereby providing for curing/ sealing time of less than 20 mins in case of Aradur HY951 hardener and less than 40 mins in case of Aradur 450 hardener.

Preferably rapid curing epoxy grout based formulation is provided comprising defoaming, dispersing and anti-settling additives adapted to decrease foaming of the formulation, preventing settling of fillers to thereby enabling effective dispersion of said fillers.

More preferably, a rapid curing epoxy grout based formulation is provided wherein said formulation provides for enhanced bonding with both steel and glass fiber reinforced composite substrates suitable for rapid live pipeline repair of leaking defect vis-à-vis commercially available products which post curing also enables composite overwrap repair to rehabilitate the pipeline.

According to yet another preferred aspect of the present invention a rapid curing epoxy grout based formulation is provided that has the capacity to withstand an internal pressure of 100 kg/cm2 when epoxy resin part employed is 70 grams and when applied in an elliptical manner with major axis along the axis of repair surface preferably of pipe and when the defect is a circular hole of preferably 10 mm diameter.

According to another aspect of the present invention there is provided a process for the manufacture of rapid curing epoxy grout based formulation comprising providing said at least two component epoxy hardener formulation involving providing epoxy resin to synergistically combine with hardener, accelerator together with fillers selected from nano scale and micro scale based fillers adapted for a rapid curing grout capable of live repair of leaking defect.

Preferably a process for the manufacture of rapid curing epoxy grout based formulation is provided comprising the steps of
(i) Premixing the accelerator with hardener;
(ii) Mixing said epoxy resin;
wherein said epoxy resin having mixed therein fillers preferably fumed Silica and micro scale fillers preferably Silicon Nitride and optional additives, said hardener having mixed therein selectively nano scale silica filler, thus provides therefrom a formulation with semi solid consistency that rapidly cures/seals preferably within 20-40 mins.

According to another aspect of the present invention there is provided a rapid curing epoxy grout based system comprising
(A) said rapid curing epoxy grout based formulation
(B) preform involving glass fiber reinforced plastic (GFRP).

Preferably, in said rapid curing epoxy grout based system said perform (B) involving glass fiber reinforced plastic has curvature similar to surface of repair and has dimensions to favour sufficient bonding area to withstand internal pressure of repair zone.

BRIEF DESCRIPTION OF THE FIGURES
Figure 1. illustrates representative sample specimens;
Figure 2. illustrates overlaid contour plots for all response variables;
Figure 3: illustrates rapid curing paste cured in pipe surface;
Figure 4. illustrates lap Shear Specimens after failure;
Figure 5: illustrates overlaid contour plot for Aradur 450 formulation;
Figure 6: illustrates burst test specimen after failure;
Figure 7: illustrates area of failure of Cured Rapid Curing Sealant Paste;
Figure 8: illustrates procedure of repair of leaking defects using Rapid Curing Paste;
Figure 9: illustrates line diagram of repaired pipe section;
Figure 10: illustrates cross-sectional view of repaired pipe section;
Figure 11:represents procedure of repair of leaking defects using rapid curing epoxy grout and perform;
Figure 12: illustrates perform;
Figure 13:illustrates pipe spool repaired with preform and rapid curing epoxy grout;
Figure 14: represents line diagram of pipe repaired with rapid curing epoxy grout and preform- Longitudinal cross section;
Figure 15: illustrates line diagram of pipe repaired with rapid curing epoxy grout and preform- circumferential cross section.

DETAILED DESCRIPTION OF THE INVENTION

As discussed hereinbefore the present invention provides for a rapid curing epoxy grout based formulation/product and a system thereof comprising a formulation in at least two parts which involves an epoxy grout formulation herein after called as Part A, and a hardener grout formulation herein after called as Part B comprising of epoxy resin and hardener in synergistic combination with accelerators, preferably imidazoles or teritary amines and fillers selected from nano scale and micro scale based fillers adapted to provide for semi solid consistency of said composition with enhancement in hardening reaction rate of said epoxy resin in the presence of fillers to thus provide for a composition that is particularly suitable for sealing through thickness defects in oil and gas and water pipelines, thus enabling live repair of leaking defect. Being a rapid curing grout, the curing takes place within 20 minutes after which composite overwrap repair can be performed to rehabilitate the pipeline.
Preferably to obtain the formulation made available preferably in two parts (Part A and Part B), Part A being epoxy resin grout is made by mixing fillers and optional additives. Both select micro scale and nano scale fillers are mixed in part A as per the proportion dictated by the present invention.
Part B being the hardener grout consisting of accelerator pre-mixed and nano scale silica filler is added and both A and B are mixed to impart semi solid consistency of the said formulation thus attained.
Leaking defects are scenarios in which there is a through hole defect or a crack is presentin the pipe and the fluid being transmitted is gushing out through the defect. The repairof leaking defects using composite materials is not much discussed in the literatures. However,analytical models available for calculating the wrap thickness for leaking defects inISO TS/24817 and ASME PCC-2, does neither discuss nor provides any clue to conducta live repair of leaking defect. The repair of leaking defect requires an epoxy resin thatcures rapidly in the presence of the fluid that is being transmitted. The fluids of interestin this study are hydrocarbons and water. The epoxy seal is to be used as a plug to sealthe defect. The resin, once fully cured, should have satisfactory bonding and compressionstrength. Moreover, it is important that the epoxy resin has a semi-solid consistency so that it stays in the defect area till it gets cured.

It has been surprisingly found by way of the present invention that when at least two part/two component system comprising epoxy hardener system comprising epoxy resin and hardener is employed together with accelerators preferably imidazoles or teritary amines and fillers selected from nano scale and micro scale based fillers while on one hand provides for semi solid consistency also enhances the hardening reaction rate of said epoxy resin in the presence of the fillers to thus provide for a formulation comprising rapid curing epoxy grout.

The formulation of the present invention is particularly suitable for sealing through thickness defects in oil and gas and water pipelines. Being a rapid curing grout, the curing takes place within 20 minutes after which composite overwrap repair can be performed to rehabilitate the pipeline.

The present invention takes into account the effect of nano scale and micro scale based fillers involving nano silica-based fillers onto viscosity, curing & strength properties of neat epoxy so as to qualify the epoxy grout for repair purposes in oil/gas industries. Advantageously, enhanced bonding with both steel and glass fiber reinforced composite substrates makes the product/ composition of the present invention suitable for pipeline repair compared to commercially available products.

EXAMPLES:

Micro and Nano scale silica-based fillers was found to enhance the bonding strength of epoxy resin while providing it an advantageous semi solid consistency. Commercially available two component epoxyhardener system is used for the development of rapid curing epoxy grout. The Epoxy resin used is preferably bisphenol-A based epoxy resin commercially available under the name AralditeLY-556. Two formulations of Part B are used for curing the epoxy grout depending upon the application. One such formulation uses a hardener by the name Aradur HY951 and another formulation uses a hardener by the name Aradur 450. Aradur 450 has better water compatibility and produces less porosity defects compared to product cured with HY951 formulation, but the amine value of Aradur 450 is 6 times lesser compared to Aradur HY951, which results in more quantity requirement of part B grout.

While imidazole is a known accelerator to enhance the reaction rate of resin hardener systems, for the present invention when imidazole is premixed with hardener before mixing the preferred epoxy resin and hardener together with select fillers of nano scale fumed Silica and micro scale Silicon Nitride, a surprisingly enhanced hardening reaction rate of the resin with semi solid consistency is observed in the presence of select fillers to thus provide for a composition comprising rapid curing epoxy grout. In case of another choice of part B with Aradur 450 hardener, the accelerator suitable was found to be 960-1, a teritary amine-based accelerator.

The composition involving HY951 as part B was fixed from the results of the select experiments. Full factorial experimental design was done based on the input variables involving the percentage of Fumed Silica, Silicon Nitride, Hardener and Imidazole as weight percentage of the quantity of epoxy resin also by taking into consideration the particle sizes of the fillers. The response variables from the experiments conducted were Curing time, the tensilestrength, compression strength and adhesive bond strength of the resulting product bymixing the resin and hardener components together. Since the number of factors in theexperiment are four, a factorial design of experimental trials with two levels of each factor was chosen.

The standards followed for specimen preparation and testing are as follows.
• Tensile Strength – ASTM D638, Type III specimen.
• Compression Strength – ASTM D695
• Lap Shear Strength – ASTM D3163
Experimental data were recorded and regression models of all the four response variables were taken. The select input variables for a satisfactory combination of all the response variables thus attained were recorded.

The data from experimental trials are given in Table 1. The values of the response variables are mean values. +1 and -1 in the input variable columns indicate the high and low levels respectively.
Table 1. Factorial Design of Experiments and results
Specimen Number Fumed Silica Silicon Nitride Hardener Imidazole Curing Time Tensile Strength (MPa) Compression Strength(MPa) Lap Shear Strength(MPa)
1 -1 1 -1 -1 75 10.07 28.21 2.30
2 -1 1 -1 1 62 6.25 22.86 2.37
3 1 1 1 1 15 6.95 13.51 2.46
4 -1 -1 -1 -1 180 11.14 5.41 2.58
5 -1 -1 -1 1 50 6.80 70.76 2.56
6 -1 -1 1 1 18 4.76 105.88 2.50
7 1 1 -1 -1 80 9.93 75.38 2.92
8 1 -1 -1 -1 42 7.91 28.35 3.46
9 1 -1 -1 1 45 8.23 14.22 2.72
10 -1 1 1 -1 15 4.61 16.35 2.66
11 -1 1 1 1 10.5 2.65 15.34 3.08
12 -1 -1 1 -1 15 5.21 17.73 4.05
13 1 -1 1 -1 26 2.55 84.59 2.35
14 1 -1 1 1 10 1.28 79.20 2.35
15 1 1 -1 1 41.5 3.59 106.30 1.92
16 1 1 1 -1 21 3.81 53.82 3.15

The representative sample specimens prepared are given in Figure 1.

Based on the results of the experiments, with the help of statistical regression modelling, a closed form solution for each response variable was formed. The desired results could be obtained, out of the four input factors, two of the input factors, wherein the weight percentage of hardener involving HY951 as part B and imidazole are fixed and the weight percentages of fillers with respect to epoxy are varied. The result is plotted in a contour plot and the plots from all four response variables are overlapped to reach to the select results. The overlaid contour plot and the results based on the requirement is shown in the Figure 2 below.

The recommended composition from graphical method and the corresponding expected values of mechanical properties are given in Table 2 below.
Table 2. Results of region of interest from contour plot
Sl. No Factor Percentage composition of factor Curing Time (min) Tensile Strength (MPa) Compression Strength (MPa) Lap Shear Strength (MPa)
1 Fumed Silica (A) 14-15 17-18 4 30-40 3-3.5
2 Silicon Nitride (B) 16-18
3 Hardener 15
4 Imidazole 5

Several experiments were conducted with other choices of fillers but the fillers selected from nano scale and micro scale based fillers comprising nano scale fumed Silica 10- 20 nm in the range of 12-16wt.% and micro scale Silicon Nitride of about 80 microns gave the best results with regard to the curing time for Aradur HY951. Before going for mechanical characterization, curing time was assessed with those combinations to test the effectiveness of such systems. Some such data is provided in Table 3.

Table 3. Curing Time results with different filler combinations.
Sl. No Filler composition Curing Time (minutes)
1 Micro Silica – 23.33%
Silicon Nitride – 20 % 80

2 Nano Silica – 15 %
Alumina Filler – 25% >80

In the above table, a replacement of Nano Silica with Micro Silica of the same size employed and in another case, a replacement of micro Silicon Nitride with much coarse alumina filler were tried. The results of curing time were not qualifying the objective of the invention. The experiments were conducted with part B containing hardener quantity in exact stoichiometric ratio to cure the epoxy quantity in part A.

A hydrostatic burst test was conducted with the above-mentioned formulation in Table 2. Figure 3 shows the result paste applied on a 10 mm circular defect hole in a 6-inch diameter pipe spool. Figure 3 thus shows rapid curing paste cured in pipe surface.

In the above experiment, and subsequent study, it was observed that the formulation has inherent disadvantage of no water compatibility and porosity defects associated with rapid curing.
All the lap shear specimens while testing underwent adhesive failure, de-bonding from the steel substrate indicating requirement of improvement to enhance adhesion to steel substrates. Figure 4 shows a representative Lap Shear Specimen after failure. (The lap shear specimens consist of two strips, one being the GFRP (Glass Fiber Reinforced Plastic) substrate while the other is a steel substrate, which are adhesively bonded. The failed test specimens exhibited adhesive mode of failure. The bonding of the adhesive with GFRP was intact while de-bonding occurred with the substrate. This indicates that the adhesive’s interfacial bonding strength can be improved) Figure 4 shows the lap shear specimens after test.

To describe further HY951 is an amine based hardener with an amine equivalent of 20.6 eq/g and viscosity in the range of 10-20 centipoise.
Aradur 450 is also an amine based hardener with an amine equivalent 6 times lesser than HY951 and viscosity in the range of 1000 to 2000 centipoise.
960-1 is a teritary amine based accelerator with a viscosity of 150 to 300 centipoise.
Nano silica employed for the formulation of epoxy grout is having a particle size of 10 to 20 nm and micro silicon nitride has a particle size of approximately 80 microns. Changing the particle size below and beyond does not provide for the desired results.

The curing agents used in the present system are hardener Aradur HY951 and accelerator imidazole. These curing agents are replaced with hardener Aradur 450 and Accelerator 960-1 respectively which are also compatible with the resin Araldite LY556 to make the system cure even in the presence of moisture. Hardener Aradur HY951 has nearly 6 times the amine value of hardener Aradur 450 i.e., 6 parts of hardener Aradur 450 is taken if 1 part of hardener Aradur HY951 is used to maintain proper stochiometric ratio of the reagents. Similarly, imidazole has nearly 3.2 times the amine value of accelerator 960-1 i.e., 3.2 parts of accelerator 960-1 is taken if 1 part of accelerator imidazole is used. To decrease the intensity of the exothermic process the concentration of factor C i.e., Hardener Aradur HY951 is decreased from 15% to 10% and the concentration of factor D i.e., Accelerator Imidazole is kept fixed at 5%. This means that 60 parts of Aradur 450 and 16 parts of Accelerator 960-1 is used in the modified composition for 100 parts of resin.Defoaming, dispersing and anti-settling Additives are added also to decrease the foaming of the product and to increase dispersion of fillers and to prevent settling of fillers.
A change in percentage concentrations of these additives does not affect the mechanical properties of the product and hence are not considered as a part of the analysis. And to increase the semi solid consistency of the system, the percentage of concentration of fillers A and B under (Table 2 above) needed to be increased. So, to find out the concentration of factors to arrive at the desired solution of response variables considering all the above changes, the graphical superimposition method for simultaneous select characteristic features are employed. The overlaid contour plot and the region of interest is shown in the Figure 5.
The finalized range of composition of the formulation providing for the desired results are shown in Table 4 below.

Table 4. Finalized formulation and results for Aradur 450 hardener
Sl. No Factor Percentage composition of factor Curing Time (min) Tensile Strength (MPa) Compression Strength (MPa) Lap Shear Strength (MPa)
1 Fumed Silica (A) 18-25 40-60 5-7 100-150 3.5-4.5
2 Silicon Nitride (B) 18-25
3 Hardener (Aradur 450) 60
4 Accelerator 960-1 16

The developed Rapid Curing Sealant paste is applied in an elliptical configuration with its major axis along circumferential direction over the defect with effective interfacial bonding are of 80 times the area of the defect i.e., 6283 mm2. The repair failed at 110 kg/cm2 and the failure was predominantly cohesive failure of the material and it failed normally to the pipe specimen which attributes to the high interfacial bonding strength of the rapid curing sealant paste. The burst test specimen is as shown in Figure 6 and the area of failure is shown in Figure 7.

So, as a result of the study, two formulations are identified, which are to be used based on the situation of application in terms of moisture content on the surface, rapid curing requirement etc. The formulations are as defined in Tables 2 and 4, one with HY951 hardener system and another formulation with Aradur 450 system respectively.

The repair procedure is given in Figure 8 in a flow chart manner.
The procedure of application of Fiber reinforced composite overwrap is explained in patent document 201731007916. The line diagram of repaired pipe section is given in Figure 9 and the Figure 10 showcross sectional view of the repaired pipe respectively.

It was observed through hydrostatic burst tests that the failure of applied rapid curing grout when pressurized internally is predominantly catastrophic in nature. No seepage or cracks were observed prior to failure. The failure is a sudden burst of the cured grout material. As a method to prevent catastrophic failure, a method of applying a preform over the grout prior to curing is adopted. A preform is a cut out piece of glass fiber reinforced composite having the same curvature as that of the pipe surface. The dimensions of preform is chosen such that sufficient bonding area to withstand the internal pressure is obtained.

The methodology of repair is explained in the flowchart given in Figure 11.

Figure 12 shows a typical preform. Figure 13 shows aPipe spool repaired with preform and rapid curing epoxy groutparticularly repair of 6-inch pipe spool with 10 mm circular through hole defect repaired with preform.

The line diagrams of cross sections of pipeline repaired with preform and rapid curing epoxy grout is shown in Figures 14 and 15.

It is thus possible for the present advancement to provide fora formulation and system thereof comprising rapid curing epoxy grout comprising a two component system comprising epoxy hardener system comprising epoxy resin which when employed together with accelerators preferably imidazoles or teritary amine in the presence of fillers selected from nano scale and micro scale based fillers while on one hand provides for semi solid consistency also enhances the hardening reaction rate of said epoxy resin in the presence of the fillers to thus provide for a composition that is particularly suitable for sealing through thickness defects in oil and gas and water pipelines. Being a rapid curing grout, the curing takes place within 20 minutes after which composite overwrap repair can be performed to rehabilitate the pipeline.
The present invention takes into account the effect of nanoand micro scale based fillers being silica based and silicon nitride respectively onto viscosity, curing & strength properties of neat epoxy so as qualify the epoxy grout developed for repair purposes in oil/gas industries.
Advantageously, enhanced bonding with both steel and Glass Fiber reinforced composite substrates makes the product of the present invention suitable for pipeline repair compared to commercially available products.
Further advantages over traditional repair system include: enhanced interfacial bonding strength, cheaper and economical to use, the repair is faster to be performed as the application is easy and straight forward; risk of fire and explosion due to the cutting and welding is completely eliminated; the pipeline for repair need not to be flushed off with nitrogen before working in case of leakage; further the mechanical properties of the epoxy grout can be tweaked depending on the application eventhough the primary goal is to use in oil and gas pipeline repair.

The present invention thus provides for a technically advanced composition comprising rapid curing epoxy grout and a method thereof. While there are numerous epoxy grouts available in the market all the products have its own inherent disadvantages like poor bonding strength, poor tensile strength etc. which could be overcome by the Applicants tailor made product and process thereof to attain desired response based on the selectivity of the components used in respective wt.%. The change in response for change in composition based on input variables is the crux of the present invention.

We Claim:

1. A rapid curing epoxy grout based formulation in at least two parts comprising epoxy-hardener formulation involving epoxy resin and hardener in synergistic combination with accelerator and fillers selected from nano scale and micro scale-based fillers adapted for a rapid curing grout capable of live repair of leaking defect.

2. A rapid curing epoxy grout based formulationas claimed in claim 1 wherein said epoxy-hardener formulation has epoxy resin and hardener in curing stoichiometric ratioand provides for semi solid consistency prior to curing with enhanced hardening reaction rate of said epoxy resin in the presence of said fillers thereby providing for said rapid curing epoxy grout capable of sealing through thickness defects in oil and gas and water pipelines curing/sealing within 20-40 minutes.

3. A rapid curing epoxy grout based formulationas claimed in claims 1 or 2 comprising
said epoxy resin in the range of 80 to 83 wt% including preferably bisphenol-A based epoxy resin,
said hardener preferably Aradur HY951, an amine based hardener with an amine equivalent of 20.6 eq/g and viscosity in the range of 10-20 centipoise, is in the range of 14 to 15 wt.%;
said accelerators preferably imidazoles is in the range of 2 to 8 wt.%, and, said accelerator preferably 960-1, being teritary amine-based with a viscosity of 150 to 300 centipoise, is in the range of 15 to 16 wt.%;
said fillers selected from nano scale and micro scale based fillers comprising nano scale fumed Silica 10- 20 nm in the range of 12-16wt.% and micro scale Silicon Nitride of about 80 microns being in the range of 10-20wt.%.

4. A rapid curing epoxy grout-based formulation as claimed in claims 1-3 comprising
said hardener preferably Aradur 450, Aradur 450 is also an amine based hardener with an amine equivalent 6 times lesser than Aradur HY951 and viscosity in the range of 1000 to 2000 centipoise, in the range of 59 to 60 wt. %,
said accelerators preferably imidazoles is in the range of 2 to 8 wt.%, and, said accelerator preferably 960-1 is in the range of 15 to 16 wt.%;
said nano scale fumed Silica in the range of 20-23 wt.%;
said micro scale Silicon Nitride in the range of 10-25 wt.%;
rest being said epoxy resin.

5. A rapid curing epoxy grout based formulation as claimed in claims 1-4 wherein
said hardener when is Aradur HY951 is 15 wt.% of said epoxy resin, and, when said hardener is Aradur 450 is 60 wt% of said epoxy resin;

said accelerator when is imidazole is 5 wt.% of said epoxy resin, and, said accelerator when is 960-1 is 16 wt% of said epoxy resin;

said fillers selected from nano scale and micro scale based fillers comprises nano scale fumed Silica in the levels of 12wt.% and micro scale Silicon Nitride in the levels of 10wt.% when said hardener is Aradur HY951, and, said nano and micro fillers being 23 wt. % and 20 wt.% respectively when said hardener is Aradur 450;

thereby providing for curing/ sealing time of less than 20 mins in case of Aradur HY951 hardener and less than 40 mins in case of Aradur 450 hardener.

6. A rapid curing epoxy grout based formulation as claimed in claims 1-5 comprising defoaming, dispersing and anti-settling additives adapted to decrease foaming of the formulation, preventing settling of fillersto thereby enabling effective dispersion of said fillers.

7. A rapid curing epoxy grout based formulation as claimed in claims 1-6 wherein said formulation provides for enhanced bonding with both steel and glass fiber reinforced composite substrates suitable for rapid live pipeline repair of leaking defect vis-à-vis commercially available products which post curing also enables composite overwrap repair to rehabilitate the pipeline.

8. A rapid curing epoxy grout based formulation as claimed in claims 1-7 has the capacity to withstand an internal pressure of 100 kg/cm2 when epoxy resin part employed is 70 grams and when applied in an elliptical manner with major axis along the axis of repair surface preferably of pipe and when the defect is a circular hole of preferably 10 mm diameter.

9. A process for the manufacture of rapid curing epoxy grout based formulation as claimed in claims 1-8 comprising providing said at least two component epoxy hardener formulation involving providing epoxy resin to synergistically combine with hardener, accelerator together with fillers selected from nano scale and micro scale based fillers adapted for a rapid curing grout capable of live repair of leaking defect.

10. A process for the manufacture of rapid curing epoxy grout based formulation as claimed in claim 9 comprising the steps of
(i) Premixing the accelerator with hardener;
(ii) Mixing said epoxy resin;
wherein said epoxy resin having mixed therein fillers preferably fumed Silica and micro scale fillers preferably Silicon Nitride and optional additives, said hardener having mixed therein selectively nano scale silica filler, thus provides therefrom a formulation with semi solid consistency that rapidly cures/seals preferably within 20-40 mins.

11. A rapid curing epoxy grout based system comprising
(A) rapid curing epoxy grout based formulation as claimed in claims 1-10
(B) preform involving glass fiber reinforced plastic (GFRP).

12. A rapid curing epoxy grout based system as claimed in claim 11 wherein said perform (B) involving glass fiber reinforced plastic has curvature similar to surface of repair and has dimensions to favour sufficient bonding area to withstand internal pressure of repair zone.