FR3046654B1 - MICROPOROUS INSULATION PANELS WITH LOW DENSITY FOR DOUBLE ENVELOPE PIPE - Google Patents

Abstract

The invention relates to microporous insulation panels for double-walled pipe intended to be wound around an inner tube. These panels have under a reduced pressure a powder density of less than 180 kg / m 3 and a thermal conductivity of 3 mW / (mK) at 8 mW / (mK) for a temperature of between 50 and 300 ° C. and more particularly a density of powder between 150 and 180 kg / m3. The reduced pressure is a pressure for example between 0.5 and 100 mbar.

Description

The technical sector of the present invention is that of double-jacketed pipes between which a thermal insulator is interposed.

In the petroleum sector have been used for several decades of pipe or double jacketed pipes to ensure the thermal insulation of the pipe formed by the assembly of these successive pipes by welding, screwing or sleeving.

In configurations well known in this sector, the thermal insulation is provided by a high vacuum level between the inner tube and the outer tube, or by a high vacuum level coupled to a succession of anti-radiative layer between the inner tube and the outer tube, also by a layer of microporous material under average vacuum between the inner tube and the outer tube.

The disadvantages of the jacketed pipes using a high vacuum are of two types: obtaining this vacuum level, typically of the order of 0.01 millibar (or even 10-5 millibar in the case of a high vacuum without anti-radiative layer succession) and the long-term maintenance of this level of vacuum. However, if the vacuum pressure in the annular between the inner tube and the outer tube increases to a pressure of the order of 0.1 millibar or 10 millibar, the thermal insulation property of the annular will be low with a thermal conductivity of the air layer degraded by a factor of 5 to 0.1 millibar, respectively by a factor of 25 to 10 millibars to obtain a thermal conductivity of the order of 25 mW / (mK).

Some artifacts, such as the use of getters that consist of small capsules containing material that adsorb gas molecules, are sometimes used to delay the increase in pressure. This method is nevertheless difficult to implement and is limited in time (until saturation of the getter). This therefore makes it possible to delay a possible increase in the pressure which may be due to degassing of the material of the tubes for example.

However, when the lifetimes typical of the pipes of an oil field or the tubes of an oil well are of the order of 20 years, this solution does not bring today the necessary guarantees to ensure the performances thermal over this period. The use of medium vacuum microporous insulation has several advantages over the previous ones as described in applicant's EP-0890056, entitled pipe for thermal insulation double jacket type pipes. In this patent, the reduced pressure required is between 0.5 and 100 millibars; there is therefore a factor of at least 50 or 50,000 on the vacuum pressure mentioned above. This vacuum pressure necessary for the microporous insulation is quite standard in many industries (food industry for example) and is not very expensive to implement in a ring of a double jacket tube. The duration of the vacuum level (and thermal performance) is therefore prolonged by the same factor (assuming a constant rate of degassing over time) and is compatible with the typical lifetimes of the pipes of a oil field. The microporous insulator is typically composed mainly of silicic material such as fumed silica and a minor amount of titanium dioxide. In addition to these two components, reinforcing fibers can be added. This mixture is then compressed into an unsealed bag. The insulating panels ready to be applied on a tube are therefore in the form of flat panels with thicknesses between 2 and 30 mm depending on the application or the thermal performance desired for the double-walled pipe. This thermal performance can thus vary from 0.5 W / (m2.K) to 5 W / (m2.K). These performances are obtained by realizing a mean vacuum (of the order of 10 mbar) in the annular between the inner tube and the outer tube. The reduced pressurization of the annular and thus the insulating panels increases the insulation performance of the panels: it is the microporous effect. The thermal conductivity can thus be reduced by a factor of 2 to 10.

The density typically used is 250 kg / m3, which makes it possible to obtain panels having good mechanical strength and in certain cases to avoid the use of spacers between the inner tube and the outer tube of a double-walled pipe. . However, this density has drawbacks: the application of these high density panels (250 kg / m3) is difficult for thicknesses greater than 15 mm and on small diameter tubes, less than 150 mm.

Thus, during their implementation, these flat panels before application to a tube will be deformed to be applied to a round tube. The lower the radius of curvature of the tube and the thickness of the panel, the more difficult it will be to apply these panels. The risk is that the insulation inside the panel cracks and the overall thermal performance of the panel is degraded. Another limitation of these density panels 250 kg / m3 lies in the thermal performance.

The applicant has therefore undertaken studies to solve the problem posed by these known panels. These studies have shown that by reducing the density of microporous insulation panels, they could be used with small diameter tubes.

The object of the present invention is therefore to provide new panels of microporous insulation with a reduced density while increasing the thermal insulation performance. The invention therefore relates to microporous insulation panels for double-walled pipe intended to be wound around an inner tube, characterized in that they have under a reduced pressure a powder density of less than 180 kg / m 3 and a thermal conductivity of 3 mW / (mK) to 8 mW / (mK) for a temperature of between 50 and 300 ° C.

According to one characteristic of the invention, the panels have a powder density of between 150 and 180 kg / m 3.

Advantageously, the panels have a powder density of 180 kg / m 3.

According to another characteristic of the invention, the microporous insulation consists of fumed silica and titanium oxide with a small proportion of mineral or organic fibers.

According to yet another characteristic of the invention, the inner tube has a diameter of the order of 150 mm.

According to yet another characteristic of the invention, the inner tube has a diameter greater than 150 mm, spacers being inserted between the inner tube and the outer tube.

Advantageously, the spacers are constituted by microporous insulation panels having a powder density of 50 kg / m 3. The invention also relates to a double-walled pipe comprising panels having a density of 180 kg / m 3 and panels having a density of 250 kg / m 3 away from each other wrapped around the inner tube. The invention finds particular use in the manufacture of jacketed pipes for oil fields, panels wound around the inner tube.

A first advantage of the invention lies in the thermal performance obtained. Indeed, it has surprisingly been found that the thermal conductivity of a panel of microporous insulation compressed to a density of between 150 and 180 kg / m3 is 15% to 20% lower than that of the same insulator with a density 250kg / m3.

Another advantage of the present invention lies in the reduction of the cost of the raw material.

Yet another advantage of the panels according to the invention lies in the absence of cracks in the microporous material regardless of its thickness. Other characteristics, details and advantages will appear more clearly on reading the additional description which will follow given by way of example in connection with the drawing of FIG. 1 illustrating the thermal conductivity of a microporous insulator.

A double jacket pipe consists of an inner tube in which the fluid flows and an outer tube, these two tubes defining an annular. In this ring, microporous insulating panels are arranged around the inner tube in order to reduce heat losses.

In the present invention, the term "reduced pressure" means a pressure lower than atmospheric pressure but greater than the vacuum, for example between 0.5 and 900 mbar and more particularly between 0.5 and 100 mbar.

During the manufacture of the double-walled pipe, the insulating panels are wrapped around the inner tube and then the thus-equipped tube is introduced into the outer tube.

By using the low density panels according to the invention, a reduction in thermal losses, of the order of about 20%, is obtained with that obtained with conventional panels of 250 kg / m 3. Thicknesses of approximately 20% less thickness can also be used to achieve the same thermal performance of the pipe.

In Figure 1, there is shown the curve of the thermal conductivity of a microporous insulation subjected to a vacuum of 10 mbar depending on the density. The thermal conductivity is measured at 50 ° C.

It can be seen in the figure that the thermal conductivity passes under a reduced pressure, for example 10 mbar, of 3.3 mW / (mK) for a density of 150 kg / m3 to 9 mW / (mK) for a density of 400 kg / m3 passing through a value of 4.3 mW / (mK) for a density of 250 kg / m3. Far from being degraded by a reduction in density, the thermal performance of the microporous insulation is increased under reduced pressure, the increase in thermal conductivity resulting in a reduction in thermal performance.

We see the whole point of the invention which allows, on the one hand to isolate double-walled pipes of reduced diameter and, on the other hand to provide a microporous material whose thermal insulation performance is higher. The user can therefore either maintain the same thermal performance as that obtained with panels of 250 kg / m3 and his choice can be carried on a panel having a density of 180 kg / m3 by reducing the thickness of this panel, either prefer a higher thermal performance while maintaining the same thickness but with panels having a density of 180 kg / m3.

Therefore, this allows in some cases to use an outer tube of smaller size. The overall gain in reducing the size of the outer pipe of a pipe for an offshore application or for an application in an oil well is very important: with an outer tube of smaller diameter, the thickness of this tube can be selected smaller also because, for the same wall thickness, the resistance to buckling by the external pressure is better for a smaller diameter tube. At equal thermal performance, the overall mass of the pipe can be reduced, a mass that can be limiting on offshore pipe laying vessels for projects of development of fields deeper and deeper, beyond 2000 meters depth, as well as only on rigs for drilling rigs and production in an oil well with today's wells drilled more than 3000 meters deep, on land or offshore. The use of a low-density insulation under reduced pressure, and therefore more efficient, can therefore have a significant bearing and reduce the cost of certain projects requiring heat-insulated pipes to make possible the development of field hitherto impossible for economic or technical reasons (thermal performance required or capacity of installation means). The invention results in a reduction in the cost of the raw material consisting of silica and titanium dioxide. Indeed, the material gain between a panel compressed to 250 kg / m3 and a panel of the same volume compressed to 180 kg / m3 is 28% and 40% for a panel compressed to 150 kg / m3. The cost of the panels is partly due to the cost of the material contained in the panel. The application of low-density insulation panels can be done with the same equipment as the traditional panels compressed to 250 kg / m3. For tubes with a diameter greater than 150 mm, use for example equipment to wind the panels with a fabric along the tube 2 by 2 or 3 by 3 depending on the width of the panels. Such equipment is widely used for the manufacture of insulated jacketed pipes for offshore.

For tubes with a diameter of less than 150 mm, it is advantageous to use the conically shaped equipment which allows the insulating panels to be continuously installed on the inner tube. This equipment is described in patent FR2937398. The objective in both cases is that the final density of the panels applied to the inner tube is 180 kg / m3 or 150 kg / m3.

By using the panels according to the invention, lower forces and pressures are used. Indeed, at the end of application by the cone-shaped equipment indicated above, the panels are slightly compressed to ensure a good junction between the two leaves of the panels and thus prevent there being a thickness more weak at the longitudinal junction of a panel see a slight opening which would impact the thermal performance of the assembly. Due to their reduced density, these panels require a lower re-compression than the higher density panels and thus the associated equipment can be selected smaller: winch and traction cable, re-compression cone, ...

If the resistance of these low density panels is too low to take the weight of the outer tube for example, spacers may be placed regularly along the inner tube to take the efforts that could see the insulating panels. These spacers may be parts in half-shells attached to the inner tube and an insulating material so as not to degrade the overall thermal performance of the pipe. Boards with a density of 250kg / m3 or higher can also be used as spacers.

Claims (9)

1. Microporous insulation panels for double-walled pipe consisting of an inner tube inserted into an outer tube, panels intended to be wound around the inner tube, characterized in that they have under a reduced pressure of between 0.5 and 100 mbar a powder density less than or equal to 180 kg / md and a thermal conductivity of 3 mW / (mK) to 8 mW / (mK) for a temperature between 50 and 300 ° C. 2. Panels of microporous insulation according to claim 1, characterized in that they have a powder density of between 150 and 180 kg / m3. 3. microporous insulation panels according to claim 1 or 2, characterized in that they have a powder density of 180 kg / m3. 4. Microporous insulation panels according to claim 1, characterized in that the microporous insulation is constituted by fumed silica and titanium oxide with a small proportion of mineral or organic fibers. 5. Double-walled pipe comprising microporous insulation panels according to one of the preceding claims, characterized in that the inner tube has a diameter of about 150 mm. 6. Double-walled pipe, comprising microporous insulation panels according to one of claims 1 to 4, characterized in that the inner tube has a diameter greater than 150 mm, spacers being inserted between the inner tube and the outer tube . 7. Double-walled pipe comprising microporous insulation panels according to claim 6, characterized in that the spacers are constituted by microporous insulation panels having a powder density of 250 kg / m3. 8. Double-walled pipe comprising microporous insulation panels according to one of claims 1 to 4, characterized in that it comprises panels having a density of 180 kg / m3 and panels having a density of 250 kg / m3 away from each other and wrapped around the inner tube. 9. Use of panels according to any one of claims 1 to 4 for the manufacture of jacketed pipes for oil fields, panels wrapped around the inner tube.