METHOD FOR THE IN-SITU ENCAPSULATION AND/OR INSULATION OF PIPING

Abstract

This disclosure relates to a method for the in-situ encapsulation and/or insulation of piping using silicone-based compositions such as liquid silicone rubber materials and/or silicone foams. The method is useful for encapsulation and/or insulation of underground piping, particularly underground piping carrying high temperature (e.g., >120° C.) fluids, such as steam. The in-situ encapsulation and/or insulation may be done by inserting a hose into a pipe cavity so that a first end of the hose is remotely positioned next to the pipe and a second end of the hose is attached to a pumping system. A silicone composition is pumped through the hose and into the cavity surrounding from the remote first end of the tubing at a first predefined rate, and the hose is gradually withdrawn from the cavity at a second predefined rate. The silicone material is allowed to cure and become rigid, thereby encapsulating and/or insulating the pipe.

Claims

1. A method for in-situ insulation and/or encapsulation of a restricted access pipe by gaining access to a pipe cavity in which a pipe to be insulated is situated, inserting a hose into the cavity so that a first end of the hose is remotely positioned next to the pipe and a second end of the hose is attached to a pumping system wherein a silicone composition is pumped through the hose and into the cavity surrounding from the remote first end of the tubing at a first predefined rate, the hose is gradually withdrawn from the cavity at a second predefined rate and the silicone material is allowed to cure and become rigid, thereby encapsulating and/or insulating the pipe.

2. The method in accordance with claim 1, wherein the first end of the hose is fixed to a carriage for transport along the extent of the pipe to be coated/insulated, enabling the hose to coat the pipe and/or fill the cavity for the whole extent of the pipe to be treated and to be gradually withdrawn from the cavity as the cavity is filled or the pipe coated.

3. The method in accordance with claim 2, wherein the carriage comprises a robotic means and/or a camera to enable an operator to control the robotic means and ensure the pipe is being correctly/fully coated and/or the cavity is being correctly/fully filled.

4. The method in accordance with claim 1, wherein the hose has a length such that the speed of flow of the silicone composition through the hoseis controlled to reach the point of delivery in a mixed form so as to be curable upon application onto the pipe or into the cavity and to avoid blockages within the hose due to premature cure of the silicone composition.

5. The method in accordance with claim 1, wherein the silicone composition is a hydrosilylation curable composition, the silicone composition comprising: (i) an organopolysiloxane having at least two silicon-bonded ethylenically unsaturated groups per molecule; (ii) an organohydrogensiloxane having at least two silicon-bonded hydrogen atoms per molecule; (iii) a hydrosilylation catalyst; (iv) optionally, a physical blowing agent when the silicone composition is to be made into a foam; and (v) optionally, glass microspheres.

6. The method in accordance with claim 5, wherein the silicone composition can be cured to a silicone elastomeric material to form an encapsulating layer around a pipe when no physical blowing agent (iv) is present or can generate a foamed silicone elastomer.

7. The method in accordance with claim 5, wherein the physical blowing agent (iv) is selected from the group consisting of nitrogen gas, carbon dioxide gas, a solid tailored to undergo a phase change at or below the temperature of cure of the silicone composition, a liquid tailored to undergo a phase change at or below the temperature of cure of the silicone composition, and combinations thereof.

8. The method in accordance with claim 5, wherein the physical blowing agent (iv) is selected from one or more of: 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,3,3-pentafluorobutane (HFC-365mfc), 1-fluorobutane, nonafluorocyclopentane, perfluoro-2-methylbutane, 1-fluorohexane, perfluoro-2,3-dimethylbutane, perfluoro-1,2-dimethylcyclobutane, perfluorohexane, perfluoroisohexane, perfluorocyclohexane, perfluoroheptane, perfluoroethylcyclohexane, perfluoro-1,3-dimethyl cyclohexane, perfluorooctane, fluorobenzene, 1,2-difluorobenzene, 1,4-difluorobenzene, 1,3-difluorobenzene, 1,3,5-trifluorobenzene, 1,2,4,5-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,3,4-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and 1-fluro-3-(trifluoromethyl)benzene.

9. The method in accordance with claim 5, wherein the silicone composition comprises one or more additives selected from surfactants; stabilizers; adhesion promoters; colorants; antioxidants; carrier vehicles; heat stabilizers; flame retardants; thixotropic agents; flow control additives; inhibitors; and fillers.

10. The method in accordance with claim 1, wherein the silicone composition is supplied as a silicone foam and is prepared via a continuous process which comprises the steps of; (a) blending a part A composition comprising components (i) one or more silicone polymers containing at least two alkenyl or alkynyl groups per molecule and (iii) a hydrosilylation catalyst and separately blending a part B composition comprising a further amount of component (i) and component (ii) an Si—H containing cross-linker; (b) introducing the part A composition and the Part B composition into respective mixing containers and mixing; (c) transferring resulting part A and part B mixtures of step (b) into respective pumping means; (d) pumping the resulting part A and part B mixtures of steps (b) and (c) into a mixer unit and mixing to form a foam; and (e) dispensing the resulting foam; wherein (f) component (iv) a physical blowing agent is introduced into one or both of the part A composition or the part B composition during step (a) or step (b) and/or is introduced into the mixer unit during step (d).

11. The method in accordance with claim 10, wherein the physical blowing agent (iv) is added: (1) completely into the part A blend during step (a); or (2) completely into the part A composition during step (b); or (3) completely into the part B blend during step (a); or (4) completely into the part B composition during step (b); or (5) partially into the part A blend and partially into the part B blend during step (a); or (6) partially into the part A composition and partially into the part B composition during step (b); or (7) completely directly into the mixer unit of step (d); (8) partially into the part A blend during step (a) and partially directly into the mixer mixing unit of step (d); or (9) partially into the part A composition during step (b) and partially directly into the mixer unit of step (d); or (10) partially into the part B blend during step (a) and partially directly into the mixer mixing unit of step (d); or (11) partially into the part B composition during step (b) and partially directly into the mixer unit of step (d); or (12) partially into the part A blend, partially into the part B blend during step (a) and partially directly into the mixer unit of step (d); or (13) partially into the part A blend and partially into the part B blend during step (a) and partially directly into the mixer unit of step (d); or (14) partially into the part A composition, partially into the part B composition during step (b) and partially directly into the mixer unit of step (d); or (15) partially into the part A composition and partially into the part B composition during step (b), and partially directly into the mixer unit of step (d).

12. The method in accordance with claim 10, wherein component (v) glass microspheres are present in the silicone composition and optionally,are introduced before step (d).

13. The A-method in accordance with claim 1, wherein monitors are provided to monitor one or more of temperature, pressure and/or flow rate and are designed to transmit a signal to a control unit: (i) if a parameter strays outside a predefined range; and/or (ii) to enable the control unit to be able to determine a suitable speed of withdrawal of the hose from the cavity; and/or (iii) to allow the control unit to vary the supply of the silicone composition.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0151] The Figures herein are provided to illustrate the methods utilised herein and not to limit the disclosure and are as follows:

[0152] FIG. 1 is a schematic view of an embodiment of this disclosure providing a continuous process adapted to produce the silicone foams utilising a physical liquid blowing agent suitable to encapsulate and/or insulate hot pipes and/or to fill cavities surrounding hot pipes;

[0153] FIG. 2 is a depiction of the test pipe/cavity unit used for Example 6 described below; and

[0154] FIGS. 3a and 3b are photos of the foam generated during Ex. 6 at 150° C. and at 250° C.

[0155] In FIG. 1 there is provided a schematic view of a continuous process for making a silicone foam as described herein for insulating hot pipes. There is provided a receiving means (1) for receiving the ingredients of a part A composition as defined herein and a receiving means (2) for receiving the ingredients of a part B composition as defined herein. There is also provided a stirred tank (4) provided to mix the ingredients of the part A composition and a stirred tank (5) provided to mix the ingredients of the part B composition. There is also provided a pumping means (6) adapted to pump mixed part A composition into a mixing unit ((9a), (9b) and/or (9c)) as well as a pumping means (8) adapted to pump mixed part B composition into said mixing unit ((9a), (9b) and/or (9c)). Mixing unit ((9a), (9b) and/or (9c)) comprises one of mixing block (9a), static mixer (9b) and/or dispensing tip (9c) and is provided to mix the part A composition and part B composition together and to dispense the resulting silicone foam.

[0156] In this disclosure the mixing unit ((9a), (9b) and/or (9c)) may be situated prior to entrance into the hose (not shown) or subsequent to the hose. In the latter case said hose is divided into at least two channels such that the part A composition is transported through the hose to the mixing unit ((9a), (9b) and/or (9c)) and then after mixing with the part B composition to the point of discharge and is finally discharged onto the hot pipe or into the cavity. Similarly, the part B composition is transported through the hose to the mixing unit ((9a), (9b) and/or (9c)) in a separate channel and then after mixing with the part B composition to the point of discharge and is finally discharged onto the hot pipe or into the cavity. In a further alternative, the mixing unit may be partially prior to entrance into the hose and partially after the hose. For example, this might occur when one or both of (9a) and (9b) is/are situated prior to the entrance of the hose between the mixing unit and the hose, and (9c) is situated at the exit of the hose or alternatively when (9a) is prior to the hose and (9b) and/or (9c) are situated after transport through the hose. In each instance the mixing regime will have to be designed to prevent premature mixing during passage through the hose prior to delivery around the pipe or into the cavity into which the pipe is situated.

[0157] As hereinbefore described the foam is generated using a physical liquid blowing agent. A reservoir of said physical liquid blowing agent is contained in container (3). The physical liquid blowing agent may be supplied during the continuous process to any one or more of receiving means (1), receiving means (2), stirred tank (4), stirred tank (5) and/or directly into mixing block (9a) so that it is thoroughly mixed with the other ingredients in order to continuously produce a silicone foam. When supplied directly into mixing block (9a) the physical liquid blowing agent may if desired be transported thereto by way of a pump (7) to aid addition into the mixing block (9c). One or more of receiving means (1), receiving means (2), stirred tank (4), stirred tank (5) and/or mixing unit ((9a) and optionally (9b) and/or (9c)) may be temperature and pressure controlled. Given the nature of the physical liquid blowing agent it may be desired to vary the temperature in regions pre or post addition of the physical liquid blowing agent as a means of controlling when and where the blowing agent changes state from a liquid to a solid. Such temperature control must be able to both heat and cool the respective blend and/or composition so that it can be adapted for use with a variety of physical liquid blowing agents dependent on their boiling points. The foam commences generation immediately after mixing of the part A and part B compositions and continues to be generated during its passage through the mixing unit ((9a), (9b) and/or (9c)) and may even continue to be formed after dispatch therefrom.

[0158] As previously mentioned the glass microspheres, when present, may be added simultaneously with the physical blowing agent or separately to the physical blowing agent but in any of the above routes.

[0159] FIG. 2 and FIGS. 3a and 3b are discussed in more detail in conjunction with Ex. 6 below.

INDUSTRIAL APPLICABILITY

[0160] The silicone compositions, silicone materials including foams, and methods of this disclosure are useful to at least partially cover or encapsulate /pipes utilised to transport hot fluids at temperature which can be > 150° C. e.g. up to or >250° C. and or to fill the cavities surrounding said pipes for thermal insulation purposes. Moreover, silicone compositions, silicone materials including foams, and methods of this disclosure can be used as a fire block. In general, the silicone compositions, silicone materials including foams, and methods of this disclosure can be prepared at room temperature or thereabouts.

[0161] The following examples, illustrating the compositions, foams, and methods, are intended to illustrate and not to limit the invention.

EXAMPLES

[0162] Compositions were generated utilizing different types and amounts of components. These are detailed below. All amounts are in weight % unless indicated otherwise. As discussed above all viscosities are measured at 25° C. using a Brookfield LV DV-E viscometer. The alkenyl and/or alkynyl content of polymers as well as the silicon-bonded hydrogen (Si—H) content of polymers was determined using quantitative infra-red analysis in accordance with ASTM E168.

[0163] A series of samples were prepared to show the suitability of silicone foams using only physical blowing agents. There was one Reference Example (Ref. 1) and five examples supporting the present disclosure (Ex. 1 to Ex. 5). The compositions were based on additions of further ingredients to the following part A and part B compositions, excepting that Ref. 1 had no surfactant present and some examples were initially prepared without surfactant but having surfactant added later in the process to the part A composition. The same part B composition was used with all samples. When mixed together the part A composition and the part B composition were mixed in a 1 : 1 weight ratio.

[0164] In the following Tables: [0165] Polymer 1 is Dimethylvinylsiloxy-terminated dimethyl siloxane, having a viscosity of ~430 mPa.s and ~0.46 wt.% Vi; [0166] Polymer 2 is Dimethylvinylsiloxy-terminated dimethyl siloxane, having a viscosity of ~39,000 mPa.s and ~0.08 wt.% Vi; [0167] Surfactant is Trimethylsiloxy-terminated dimethyl siloxane 407 type resin with 2-(perfluorohexyl) ethyl alcohol, having a viscosity of ~350 mPa.s; [0168] Catalyst is 1,3-Diethenyl-1,1,3,3 -Tetramethyldisiloxane Complexes (Platinum)) in (Dimethyl Siloxane, Dimethylvinylsiloxy-terminated; Dimethyl Siloxane; [0169] Polymer 1/resin blend is a blend of Dimethylvinylsiloxy-terminated dimethyl siloxane, having a viscosity of ~430 mPa.s and ~0.46 wt.% Vi; and a .sup.ViMMQ resin, having a viscosity of ~45,000 mPa.s and ~0.39 wt.% Vi; and [0170] cross-linker is trimethylsiloxy-terminated, methylhydrogen siloxane, trimethylsiloxy-terminated, having a viscosity of ~30 mPa.s and ~1.6 wt.% SiH.

[0171] The liquid physical blowing agent used in the examples was 1,1,1,3,3-pentafluoropropane (HFC-245fa) which has a boiling point of about 15.3° C. The solid physical blowing agent used in the examples was frozen carbon dioxide (dry ice) which boils at -78° C. The gaseous physical blowing agent used in the examples was nitrogen gas.

[0172] A reference material Ref. 1 was utilised to enable the difference between a blown foam and a non-blown silicone material. Ref. 1 material comprised 7.53 g of polymer 1, 2.45 g of polymer 2 and 0.03 g of catalyst in part A and 6.27 g of polymer 1, 3.41 g of Polymer 1/resin blend and 0.32 g of cross-linker in part B.

[0173] Five examples were also prepared. The amounts (g) used in the compositions tested are provided in Tables 1a and 1c and the wt. % of the ingredients in said compositions are provided in tables 1b and 1d.

TABLE-US-00001 Part A composition in (g) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Polymer 1 7.53 7.53 7.53 7.53 7.53 Polymer 2 2.45 2.45 2.45 2.45 2.45 Surfactant 1.2 1.2 0.6 0.6 0.6 Catalyst 0.03 0.03 0.03 0.03 0.03 HFC 245fa 1.6 1.6 Nitrogen Purge Yes Dry ice 2.0 4.0 2.0 Total wt. part A (g) 12.8 11.2 12.6 14.60 14.20

TABLE-US-00002 Part A composition in wt. % of total composition when mixed Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Polymer 1 33.01 35.50 29.87 25.78 28.08 Polymer 2 10.73 11.54 9.71 8.38 9.13 Catalyst 0.12 0.13 0.11 0.09 0.01 Surfactant 5.26 5.66 2.38 2.05 2.24 HFC 245fa 7.02 5.97 Nitrogen Purge Yes Dry ice 7.94 13.7 7.46 Total wt.% of combined pts A and B 56.14 52.83 50 50

TABLE-US-00003 Part B composition in (g) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Polymer 1 6.27 6.27 6.27 6.27 6.27 Polymer 1/resin blend 3.41 3.41 3.41 3.41 3.41 Cross-linker 0.32 0.32 0.32 0.32 0.32 Surfactant 0.6 0.6 0.6 Dry ice 2 4 2 Total wt. part B in g 10 10 12.6 14.6 12.6 Total wt. part A + part B in g 22.8 21.2 25.2 29.2 26.8

TABLE-US-00004 Part B composition in wt. % of total composition when mixed Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Polymer 1 27.5 29.57 24.88 21.47 23.39 Polymer 1/resin blend 14.96 16.09 13.54 11.68 12.73 Cross-linker 1.4 1.51 1.27 1.10 1.19 Surfactant 2.38 2.05 2.24 Dry ice 7.94 13.7 7.46 Total wt. part B in g Total % wt. part A + part B 100 100 100 100 100

[0174] Notes regarding the Ex. 1 to 5:

[0175] Ex. 1: A liquid physical blowing agent, 1,1,1,3,3-pentafluoropropane (HFC-245fa) was added to the part A composition.

[0176] Ex. 2: A gaseous physical blowing agent was utilised in Ex. 2, The part A and part B compositions were separately were purged for 12 hours with gaseous nitrogen. The increase in weight by this process was not determined;

[0177] Ex. 3 The part A composition was prepared in a suitable container using the “without surfactant” composition depicted in Table 1a above and part B composition was prepared in a suitable container using the composition depicted in Table 1b above. Dry ice (frozen carbon dioxide) was then added to the part A composition and the part B composition and the respective containers were closed with a lid, but each lid had a pinhole therein to avoid too great a pressure build up. After the carbon dioxide had stopped boiling, surfactant was added to both Part A and Part B equally prior to the final mixing and foaming etc.

[0178] Ex. 4: This example was analogous to Ex. 3 with the exception that double the amount of dry ice was utilised as the solid physical blowing agent.

[0179] Ex. 5: In this example both a liquid physical blowing agent (HFC 245fa) and a solid physical blowing agent (dry ice) were utilised to blow the foam. The foam was allowed to rise and cure in the plastic container itself.

[0180] When the physical blowing agent is a solid, (e.g. solid carbon dioxide otherwise known as dry ice (boiling pt. -78° C.) or is a gas, e.g. nitrogen, the physical blowing agent is introduced into both the part A and part B compositions prior to their mixing together. When a liquid physical blowing agent is used it is designed to boil at around the temperature of cure of the composition herein e.g. 1,1,1,3,3-pentafluoropropane (HFC-245fa) the blowing agent was added into the part A composition such as Physical blowing agent(s) is added to Part A of the formulation shown above.

[0181] The ingredients of the part A and part B compositions, (excluding surfactant and blowing agent) are first prepared and mixed separately in Speedmixer at 3000 rpm for 20 s. The ingredients of the part A composition, (excluding surfactant and blowing agent) are first mixed using a Speedmixer at 3000 rpm for 20 s. Likewise, the ingredients of the part B composition, (excluding surfactant and blowing agent) are first mixed using a Speedmixer at 3000 rpm for 20 s. The desired amount of surfactant and blowing agent are then added into the part A composition or in these examples partly in the part A composition and partly in the part B composition. Subsequently the part B composition was then added to part A composition and the two parts are mixed thoroughly together, e.g. in a laboratory environment with a spatula for 30 s.

[0182] The resulting compositions were cured after mixing. Foaming was left to take place in the containers in which the part A and part B compositions were mixed. The following table provides a number of physical properties identified after analysis.

[0183] The “cure time’ results were a measure of the snap time which is determined by applying tongue depressor upon the substrate/foam. The composition /foam was deemed cured when no material is observed to be adhered to the tongue depressor.

[0184] The foams were then allowed to sit for 24 hours before further characterization. The density and cell size of the foams were measured. Density of the foam can be determined via methods understood in the art. For example, density of the foam can be measured via the Archimedes principle, using a balance and density kit, and following standard instructions associated with such balances and kits. An example of a suitable balance is a Mettler-Toledo XS205DU balance with density kit.

[0185] The average pore size (otherwise referred to as cell size) can be determined using a suitable method, as described in ATSM D3576 standard. The following modifications may be used: (1) image a foam using optical or electron microscopy rather than projecting the image on a screen; and (2) scribe a line of known length that spans greater than 15 cells rather than scribing a 30 mm line. The porosity of the foams was determined by calculation based on the result of the density value measured. The porosity of Ex. 1 is determined below as an example: [0186] In Ex. 1 the density was measured as 0.44; [0187] The porosity of a cured elastomer is zero; [0188] The porosity of Ex. 1 is calculated as a % using the following equation:-

TABLE-US-00005 Reference (Ref. 1) and inventive examples (Ex. 1-5) with cure time, density, foam morphology, and average cell size Formulations Properties Ref. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Cure time (min) 3 4 4 3.5 4 4.5 Density (g/cc) 1 0.44 0.78 0.53 0.44 0.33 Porosity (%) 0 56 22 47 56 67 Foam morphology (open or closed) NA, no foam closed closed closed closed closed Average cell size (mm) NA, no foam 0.4 0.3 0.5 0.55 0.50 Compressive strength (kPa) at 10% strain (ASTM D1621-16) NA 18.5 25.5 14.6

[0189] It will be seen that in each of Ex. 1 to 5 the foam morphology was closed cell. A closed cell morphology would suggest the likelihood of water penetrating through the foam is low.

[0190] Of the different examples above it was decided to prepare a larger scale example using the compositions utilised for Ex. 1 above in a suitable continuous process for insulating a cavity around a hot pipe using a continuous dispensing process of the type depicted in FIG. 1 to fill a test unit depicted in FIG. 2 herein.

[0191] In this example, hereafter referred to as Ex. 6, a continuous process as depicted in FIG. 1 was utilised with equal total amounts of part A and part B compositions being produced and mixed in together in the mixing unit. The liquid blowing agent HFC-245fa was introduced into stirred mixers (4) and (5) and the pumping means (6) and (8) were positive displacement ISCO pumps. The mixing unit utilised to mix the part A and part B compositions together in the current example contained each of (9a), (9b) and (9c). The following regime was utilised: [0192] 1. Blend the components of Parts A and B respectively in receivers (1) and (2) [0193] 2. Transfer 1000 grams of each of Parts A and B receivers (1) and (2)into respective stirred tanks (4) and (5) [0194] 3. Load 100 grams HFC-245fa blowing agent into each of stirred tanks (4) and (5) [0195] 4. Fill pistons of the positive displacement ISCO pumps (4) and (5), maintaining sufficient overpressure to prevent boiling the blowing agent. [0196] 5. Discharge the pumps (6) and (8) at a controlled rate, through mixing block (9a), static mixer (9b) and dispense tip (9c) into a collection container.

[0197] In this instance the final mixed composition was introduced into a sample pipe and cavity as depicted in FIG. 2 herein. The sample test piece depicted in FIG. 2 was a rectangular box (20) having the dimensions 10 cm x 10 cm x 15 cm as depicted. The inner pipe (22) had an outer diameter of 1.25 cm and was also 15 cm long. The final mixture of the part A and part B combined mix was introduced into the interior cavity of box (20) through the central “hose” (24) at the top of the box (20). Several of the dimensions are shown in FIG. 2. In example 6 samples were tested with pipe (22) temperature was maintained at 150° C. or 250° C. In each instance, the cavity temperature inside box (20) was approximately 75° C. The Ex. 6 compositions utilised for the testing were introduced into box (20) at approximately 20° C. i.e. slightly above the boiling pt. of the physical blowing agent being used (HFC-245fa). The composition of Ex. 6 was dispensed into box (20) through hose (24) at a rate of 200 ml per minute. Physical property results of the foams prepared using the continuous process and introduced into the cavity in the box at pipe temperatures of 150° C. and 250° C. are provided in Table 3.

TABLE-US-00006 Ex. 6 dispensed on heated pipe maintained at 150° C. and 250° C. Properties Ex. 6- 150° C. Ex. 6- 250° C. Density (g/cc) 0.35 0.44 Porosity (%) 65 56 Foam morphology (open or closed) closed closed Average cell size (mm) 0.25 (away from the heated pipe) 0.27 (away from the heated pipe)

[0198] FIG. 3a depicts the foam produced in the box at pipe temperatures of 150° C. and FIG. 3b depicts the foam produced in the box at pipe temperatures of 250° C.

[0199] As previously indicated the pipe may be coated with a coating of silicone material which is not a foam. Two examples using alternative coating compositions for the encapsulation and/or insulation of the hot pipes or indeed the filling of the pipe cavity with such compositions are provided below as Examples 7 and 8. Again the compositions are two-part compositions which need to be suitably mixed prior to introduction of the composition into the pipe cavity or as a coating on the pipe itself. The part A compositions for said Ex. 7 and Ex. 8 are provided in Table 4a below and the part B compositions are depicted in Table 4b below.

TABLE-US-00007 Part A hot Pipe coating compositions Ex. 7 Ex. 8 Dimethylvinylsiloxy-terminated Dimethyl Siloxane having a viscosity of about 500 mPa.s 48 61 Silica having an average particle size of 5 .Math.m 44.8 12.7 CAB-O-SIL® MS-75D fumed silica 19.7 1,3-Diethenyl-1,1,3,3 -Tetramethyldisiloxane Complexes (Platinum)) in (Dimethyl Siloxane, Dimethylvinylsiloxy-terminated; Dimethyl Siloxane; 0.3 Cerium hydrate 0.5 Dimethylhydroxy terminated polydimethylsiloxane having a viscosity of about 15 mPa.s 4.7 water 1.1 pigment 7 Pt catalyst 0.2

[0200] CAB-O-SIL® MS-75D fumed silica is a product sold by the Cabot Corporation.

TABLE-US-00008 Part B hot Pipe coating compositions Ex. 7 Ex. 8 Dimethylvinylsiloxy-terminated Dimethyl Siloxane having a viscosity of about 2000 mPa.s 57.3 Dimethylvinylsiloxy-terminated Dimethyl Siloxane having a viscosity of about 500 mPa.s 48.3 Silica having an average particle size of 5 .Math.m 45.6 14 CAB-O-SIL® MS-75D fumed silica 19.1 Trimethylsiloxy-terminated Dimethyl, Methylhydrogen Siloxane, 5.9 2.5 Dimethylhydroxy terminated polydimethylsiloxane having a viscosity of about 15 mPa.s 4.5 cyclic methylvinylsiloxanes 0.2 0.1 water 1.2 Inhibitor masterbatch of 3.5% by weight of ethynyl-1-cyclohexanol (ETCH) in in a silicone rubber base composition. 1.3

[0201] The examples shown in the table above depict two very different liquid silicone rubber materials capable of filling a cavity underground and coating a steam pipe installation. The use of silicones has the added benefit of being a heat stable material capable of resisting the high temperatures experienced on the surface of the steam pipes to be coated.

[0202] Ex. 7 describes a material with a relatively low viscosity and therefore capable of a fast flow in narrow annular areas around a steam pipe in the order of 2 inches (5.08 cm) and a flow rate of 3 cm /s based on a box used for testing having the dimensions approximately 180 cm long by 12.5 cm wide and 12.5 cm high. and a time to cover the base of the box being 60 s.

[0203] Ex. 8 on the other hand displays a more thixotropic effect due to the much higher viscosity of the polymers used. Such a composition can be of use in areas where the annular space around the pipe can be in the order of 6 - 12 inches (15.24 - 30.48 cm) with a flow rate of 0.3 cm/s allowing the material to remain where applied rather than flowing away.

[0204] The compositions described as Ex. 7 and Ex. 8 in Tables 4a and 4b were used in turn to evaluate their potential and usability for the process of filling a large cavity housing to experimentally simulate the process of applying the materials in a large volume to coat and fill any cavity around steam pipes.

[0205] As previously indicated the test pieces used to provide a test cavity were boxes having the dimensions approximately 180 cm long by 12.5 cm wide and 12.5 cm high. Ex. 7 and 8 were tested in turn. The part A and part B compositions were brought together in the required ratio (1:1) using a high-pressure meter, mix, dispense, equipment (HFR) from Graco fitted with a static mixer attached to one end of the box.

[0206] The part A and B of each material was maintained at room temperature throughout the injection as the mixed material was pumped into the box filling the cavity over time. Once filled, the combined composition left to cure in the box.

[0207] Given the much higher viscosity and greater thixotropic nature of the composition used in Ex. 8 the flow behavior of the material is one where layers of subsequent material injected build on the previous and could tend to block the annular space around the pipe. Should a blockage occur in the field this would require a new excavation site to be created leading to significantly extended coating times which are unsatisfactory due to the often, public location of the steam lines and the significant disruption caused.

[0208] Therefore, the use of a retractable hose offers an advantage in both these systems as well as for other silicone materials considered whereby the hose can be withdrawn at a rate where flow and / or thixotropy of the material (hence any layering effect) can be adequately controlled. Ultimately leading to a more efficient filling of the annular space and a reduced application time.

[0209] A follow up experiment was undertaken using the same formulation as was used in Ex. 8 (see Tables 4a and 4b). This is referred to in Table 5 below as Ex. 9.

[0210] In Ex. 9 an alternative process was evaluated, i.e. the filling of a large cavity housing to experimentally simulate the process of applying the materials in a large volume to coat and fill any cavity around steam pipes underground. The same test pieces were used as in Ex. 7 and 8 above. The part A and B parts of the composition were mixed together in a 1 : 1 ratio using a high-pressure meter, mix, dispense, equipment (HFR) from Graco fitted with a static mixer attached to one end of the box. The parts A and B compositions were maintained at room temperature throughout the Ex. 9 process.

[0211] The part A and B were brought together in a static mixer (½″ (1.27 cm) 30 elements) where a 12 feet (3.66 m) long hose (⅜″ (0.95 cm) Polyester based “Parker parflex S10C/6”, rated to 2250 psi (155.13 MPa) was attached to the end of the static mixer. Prior to filling the box enough material was allowed through the static mixer to completely fill the hose. The hose was then fully extended to the end of the box and slowly retracted as the material was injected at a rate of 30 g/s and the box filled. After a period of approximately 20 mins the box was completely filled. The material was then allowed to cure in the box.

TABLE-US-00009 Ex. 7 Ex. 8 Ex. 9 Viscosity mPa.s (0.1 s.sup.-1) 5100 713000 713000 Viscosity mPa.s (10 s.sup.-1) 2700 55000 55000 Specific gravity 1.38 1.21 1.21 Time to cover base of box (s) @ 48 g/s 140 660 Time to cover base of box (s) @ 150 g/s 60 -* Time to fill box (s) @ 30 g/s - - 1200 Time to fill box (s) @ 48 g/s 680 780 - Time to fill box (s) @ 150 g/s 218 -* - *= Pressure too high for injection

[0212] It was found that using this retractable hose method enabled the material to be less flow dependent which can be a challenge underground due to obstructions and annular space available around the pipe and therefore allow the material to be applied where specifically required.