Patent Description:
Conventional cryogenic vacuum insulation systems for double walled piping systems require a vacuum, typically less than <NUM>. <NUM> Pa (<NUM> micron Hg) at <NUM>° C. The purpose of the vacuum is to reduce gas conduction/convection so as to maintain the fluids contained in concentric conduits or other double walled piping systems at cryogenic temperatures, typically <NUM> Kelvin or below. The vacuum required for conventional vacuum insulation systems for double walled piping systems is expensive to produce, requiring long pump out times at elevated temperatures when assembling the vacuum insulated piping system in the field. This results in a high manufacturing cost for such field built vacuum insulated piping systems.

Current methods of assembling vacuum insulated piping systems generally consists of the following six steps: (a) fabricating spools of piping; (b) leak testing; (c) pipe spool storage and transport; (d) field staging; (e) field assembly, welding and testing; and (f) final vacuum pull-down. During construction of a cryogenic air separation plant, the costs associated with the field work associated with a vacuum insulated piping system or arrangement, namely steps (c) through (f) above, can often run near to or in excess of <NUM>% of the total installed cost of the vacuum insulated piping system. The field-based vacuum pull-down step alone is expensive and very time consuming. In many instances of installing a vacuum insulation piping system for a cryogenic air separation plant, the field vacuum work can take between <NUM> to <NUM> days depending on the overall length and geometries of the vacuum insulated piping system or arrangement which translates to higher installation costs. Moreover, from a quality standpoint, the vacuum pull-down step as well as overall quality of the field assembly of the vacuum insulated piping depends on the ambient atmospheric conditions at the installation site and other site variables. As a result, the vacuum levels for vacuum insulation piping systems where the vacuum is obtained in the field are somewhat inconsistent.

In <CIT> there is disclosed a method of fabricating and assembling a modular piping system comprising the steps of: (i) providing a pipe section which includes an outer casing and an inner pipe concentrically disposed within the outer casing and configured to contain a cryogenic fluid, wherein an insulation space is and defined between an outer surface of the inner pipe and an inner surface of the outer casing, (ii) disposing an aerogel insulation material in the insulation space; (iii) transporting the fabricated and assembled modular pipe section to a construction site where it is coupled to a second fabricated and assembled modular pipe section during installation of a piping run by joining the ends of the inner pipes; (iv) sealing the outer casings at the juncture of the inner pipes: (v) providing one or more valves in fluid communication with the insulation space; (vi) introducing a condensable gas into the insulation space via the one or more valves; and (vii) depressurizing the insulation space via the one or more valves.

What is needed, therefore, is a method for reducing the costs of installing vacuum insulated piping systems while also improving the quality of the vacuum and the corresponding performance of the installed vacuum insulated piping systems.

The present invention is a method of providing a modular vacuum insulated piping system, as defined in claim <NUM>. The method comprises the steps of providing a pipe section which includes an outer conduit; concentrically disposing an inner conduit configured to contain a cryogenic fluid within the outer conduit and defining an insulation space between an outer surface of the inner conduit and an inner surface of the outer conduit, the pipe section further including a coupling arrangement disposed on a first end of the inner conduit and a second end of the inner conduit, the coupling arrangement configured to engage or mate with a corresponding end of another modular vacuum insulated pipe section; disposing an aerogel insulation material in the insulation space; sealing the insulation space from the external atmosphere with a sealing arrangement comprising a first seal member disposed proximate a first end of the outer conduit and a second seal member disposed proximate a second end of the outer conduit; and disposing one or more valves on the outer surface of the outer conduit, the one or more valves configured to be in fluid communication with the insulation space; introducing a condensable gas into the sealed insulation space via the one or more valves; pressurizing and depressurizing the insulation space via the one or more valves. wherein the insulation space is at a pressure within the range of from <NUM> Pa to <NUM> Pa (<NUM> microns Hg to <NUM> microns Hg) after depressurization; wherein the condensable gas in the insulation space is configured to condense at temperatures below about <NUM> Kelvin; and transporting the fabricated and assembled modular vacuum insulated pipe section to a construction site.

The present invention may be preferably used for providing a modular vacuum insulated pipe system comprising a plurality of modular vacuum insulated pipe sections of <NUM> (<NUM> feet) or less in length per modular vacuum insulated pipe section, and wherein in operation, when a cryogenic fluid is traversing the inner conduits of the plurality of coupled modular vacuum insulated pipe sections, the condensable gas condenses and the pressure within the insulation filled insulation space in each of the plurality of modular vacuum insulated pipe sections is reduced to a pressure range of between about <NUM> Pa (<NUM> micron Hg) and <NUM> Pa (<NUM> microns Hg).

The insulation material of the modular vacuum insulated pipe sections comprises an aerogel-based insulation, preferably silica aerogel while the condensable gas is carbon dioxide. Some embodiments may also include a radiation shield as well as a resin impregnated fiber support disposed between the outer surface of the inner conduit and the inner surface of the outer conduit.

The sealing arrangement of each of the modular vacuum insulated pipe sections preferably comprises: a first sealing flange attached to the outer surface of the inner conduit and the inner surface of the outer conduit proximate the first end of the outer conduit and a second sealing flange sealably attached to the outer surface of the inner conduit and the inner surface of the outer conduit proximate the second end of the outer conduit. The first sealing flange and the second sealing flange are configured for sealing the insulation space from the external atmosphere.

The preferred coupling arrangement of each of the modular vacuum insulated piper sections may comprise a bayonette joint or similar coupling means having a projecting section disposed on the first end of the inner conduit and sealably engaging therewith and a distal end extending axially from the first end of the inner conduit. The bayonette joint or similar coupling means also may include a receiving section disposed on the second end of the inner conduit. The receiving section also may have a distal end extending axially into the inner conduit as well as a proximal end defining an opening that is configured to receive another projecting section of another modular vacuum insulated piper section.

While the present invention concludes with claims distinctly pointing out the subject matter that Applicants regard as their invention, it is believed that the invention will be better understood when taken in connection with the accompanying drawings in which:.

The presently claimed system and methods address the above-identified needs by fabricating individual double walled pipe sections with insulation, preferably aerogel based insulation, and designed to operate a vacuum level of between about <NUM>. <NUM> Pa (<NUM> micron Hg) and <NUM> Pa (<NUM> micron Hg). The individual modular pipe sections are subsequently transported to the construction site where an aerogel-based vacuum insulated piping system is assembled by coupling a plurality of the pre-fabricated vacuum insulated pipe sections.

This pre-fabricated modular pipe section approach ensures the quality of each pipe section is uniform and consistent, including the construction of each pipe section as well as the vacuum system within each pipe section. Since the vacuum pull down of each pipe section occurs in the shop fabrication facility, the amount of time spent in the field installing or assembling the vacuum insulated piping system as well as the associated field installation costs and risks are minimized. Specifically, the costs and risks associated with handling the insulation materials, such as aerogel insulation in the field as well as the time and equipment associated with the vacuum pull-down in the field are eliminated.

Turning now the drawings, and particularly <FIG>, there is shown different views of a modular vacuum insulated pipe system <NUM> and modular vacuum insulated pipe section <NUM>. The modular vacuum insulated pipe section <NUM> includes an outer conduit <NUM> having an outer surface <NUM> and an inner surface <NUM> as well as an inner conduit <NUM> concentrically disposed within the outer conduit <NUM>. The inner conduit <NUM> also has an outer surface <NUM> and an inner surface <NUM>. The concentric arrangement between the inner conduit <NUM> and the outer conduit <NUM> defines an insulation space <NUM> between the outer surface <NUM> of the inner conduit and the inner surface <NUM> of the outer conduit <NUM>. Also disposed along the length of the pipe section <NUM> within the insulation space <NUM> is preferably one or more resin impregnated fiber supports <NUM> configured to provide structural integrity of the pipe section <NUM> and maintain the spacing between the inner conduit <NUM> and outer conduit <NUM>. In some embodiments, an expansion bellows <NUM> or other means to allow thermally induced contraction and/or expansion of the conduits relative to the other conduits.

An insulation material <NUM> aerogel insulation, is also disposed in the insulation space <NUM>. The preferred insulation material <NUM> is a metal oxide based aerogel material, such as a silica aerogel. The aerogel insulation may be supplied in a solid monolithic form or as a composite aerogel blanket which incorporates fibrous batting. Alternatively, it is contemplated to use a combination of aerogel composite blankets and aerogel material. Both aerogel materials and aerogel blankets have highly desirable properties including low density and very low thermal conductivity. The thermal conductivity of the aerogel insulation is preferably equal to or less than <NUM> mW/mK at a pressure greater than about <NUM> Pa (<NUM> microns Hg).

If using aerogel particles as the insulating medium, the aerogel particles preferably have a density between about <NUM>/cm<NUM> to about <NUM>/cm<NUM> and has a surface area preferably of at least about <NUM><NUM>/g. The preferred aerogel particles also have an average diameter of between about <NUM> to about <NUM>. Aerogel blankets also have the desirable properties of low density and very low thermal conductivity. In such aerogel blankets, the aerogel may be incorporated into a blanket form by mixing it with fibers such as polyester, fiberglass, carbon fiber, silica or quartz fibers, depending upon the application. The composite aerogel/fiber blanket is then wrapped tightly around the inner pipe in a series of layers. In this layered configuration it is possible to also provide radiation shielding layer <NUM> by interleaving thin sheets of a low emissivity material, typically a polished metal such as copper or aluminum.

Turning now to <FIG>, <FIG>, <FIG> and <FIG> the modular vacuum insulated pipe section <NUM> also includes a coupling arrangement <NUM> at each end of the inner conduit <NUM>. The illustrated coupling arrangement <NUM> shown in <FIG> includes a first protruding end <NUM> of the inner conduit <NUM> and a corresponding protruding end <NUM> disposed on the other end of the inner conduit <NUM>. End caps <NUM> are attached to each end of the outer conduit <NUM> as well as to the outer surface of the inner conduit proximate such end to seal the insulation space <NUM> with the protruding ends <NUM>, <NUM> of the inner conduits <NUM> extending past the end caps <NUM>. An alternate embodiment of the coupling arrangement <NUM> is generally shown in <FIG> and <FIG> as an example of a bayonette joint that includes a projecting section <NUM> disposed on the first end of the inner conduit <NUM> and a corresponding receiving section <NUM> disposed on the second or other end of the inner conduit <NUM>. At the juncture <NUM> of two adjacent modular vacuum insulated pipe sections <NUM> where there are gaps between the annular spaces of the connected pipe sections, it may be preferably to use external insulation, such as a permanent or removeable solid insulation cover <NUM> or intermediate vacuum can to surround and further insulate the coupled pipe sections <NUM>, as generally depicted in <FIG>.

In the alternate coupling arrangement <NUM> depicted in <FIG> and <FIG>, the projecting section <NUM> has a proximal end <NUM> that is configured to sealably engage the inner conduit <NUM> and a distal end <NUM> extending axially from the first end of the inner conduit <NUM>. The projecting section <NUM> also has a sealing flange <NUM> configured for sealing one end of the insulation space <NUM> proximate the first end of the inner conduit <NUM>. The receiving section <NUM> is disposed on the second or other end of the inner conduit <NUM>. The receiving section <NUM> also has a proximal end <NUM> and a distal end <NUM> which extends axially into the inner conduit <NUM>. The receiving section <NUM> also includes another sealing flange <NUM> configured for sealing the other end of the insulation space <NUM>, proximate the second end of inner conduit <NUM>.

The projecting section <NUM> also defines a first flow path from the distal end <NUM> of the projecting section <NUM> to the interior of the inner conduit <NUM> whereas the receiving section <NUM> defines a second flow path from its distal end <NUM> to the interior of the inner conduit <NUM>. The proximal end <NUM> of the receiving section <NUM> is configured to receive a projecting section of another modular vacuum insulated pipe section. Likewise, the distal end <NUM> of the projecting section <NUM> is configured to engage a receiving section of another modular vacuum insulated pipe section. Given the first and second flow paths, a cryogenic fluid can freely flow from a first modular vacuum insulated pipe section to an adjacent and mated second modular vacuum insulated pipe section and on to another adjacent and mated third modular vacuum insulated pipe section, and so on.

When the insulation space is sealed and filled with the suitable insulation material <NUM>, such as aerogel insulation, a moderate vacuum is produced within the insulation space <NUM> by vacuum pumping the insulation space <NUM> via a vacuum port <NUM>, preferably to a pressure of under <NUM> Pa (<NUM> microns Hg), more preferably to a pressure of under <NUM> Pa (<NUM> microns Hg), and most preferably to a pressure of about <NUM> Pa (<NUM> microns Hg). When the modular vacuum insulated pipe section <NUM> is not being vacuum pumped, a plug <NUM> with O-ring seals <NUM> is sealably disposed into the vacuum port <NUM>. The vacuum port <NUM> may optionally include an isolation valve <NUM> and vacuum pressure gauge <NUM> as depicted in <FIG>. When the modular vacuum insulated pipe section <NUM> is being vacuum pumped, a vacuum connector <NUM> is engaged with the vacuum port <NUM>. A vacuum pump <NUM> together with a vacuum gauge <NUM> and particulate filter <NUM> are connected to the vacuum port <NUM> of the modular vacuum insulated pipe section <NUM> via the vacuum connector <NUM>.

During the manufacture of the modular vacuum insulated pipe section, the aerogel containing insulation space is purged and cooled. During the purge process, a vacuum pump arrangement (shown as vacuum connector, <NUM>, vacuum pump <NUM> with vacuum gauge <NUM> and particulate filter <NUM>) is used initially to evacuate the insulation space to a pressure below about <NUM> Pa (<NUM> microns Hg) and more preferably between <NUM> Pa (<NUM> microns Hg) and <NUM> Pa (<NUM> microns Hg) in order to remove any moisture or heavy hydrocarbons in the aerogel material. The aerogel containing insulation space then undergoes at least one purge cycle that includes a pressurization step and a depressurization step. The pressurization step preferably comprises introducing a condensable gas such as carbon dioxide gas to the sealed and aerogel containing insulation space via another port equipped with another isolation valve <NUM> and vacuum pressure gauge <NUM>. Other condensable gases which may be used during the pressurization step include nitrous oxide, nitrogen, oxygen and argon. The pressurization step may be to pressures as high as the pressure rating of the outer wall. The depressurization step reduces the pressure to a range of about <NUM> Pa (<NUM> microns Hg) to <NUM> Pa (<NUM> microns Hg).

Preferably the aerogel containing insulation space undergoes at least two such pressurization and depressurization cycles and may undergo up to ten such cycles. Preferably, the final pressure of the aerogel containing insulation space following the last depressurization cycle is in the range of about <NUM> Pa (<NUM> microns Hg) to <NUM> Pa (<NUM> microns Hg). Optionally, the modular vacuum insulated pipe section may also be heated during such cycles using an external heat source (not shown) to accelerate the outgassing and desorption of the condensable gases.

In operation, the outer surface of the inner conduit is cooled to a temperature less than about <NUM> Kelvin as a result of a cryogenic liquid flowing through the inner conduit. Suitable cryogen liquids include liquid nitrogen, liquid oxygen, liquid argon, and liquefied natural gas, or other cryogenic liquids. As the outer surface of the inner conduit is cooled to a temperature at or below the freezing point of the condensable gas at the prevailing pressure, the condensable gas, e.g. carbon dioxide, will migrate to the cooled surface and freeze, further reducing the pressure in the insulation space. In this manner, the vacuum pressure of the modular vacuum insulated pipe section during operation falls to a pressure of less than <NUM> Pa (<NUM> microns Hg) and preferably to a final operating vacuum pressure between <NUM>. <NUM> Pa (<NUM> micron Hg) and <NUM> Pa (<NUM> microns Hg).

The preferred length of modular vacuum insulated pipe section is less than about <NUM> (<NUM> feet) long to facilitate easy storage and subsequent transport to the construction site for assembly of the vacuum insulated pipe system or arrangement that comprises a plurality of the above-described modular vacuum insulated pipe sections.

Claim 1:
A method of providing a modular vacuum insulated piping system, comprising the steps of:
fabricating a plurality of modular insulated pipe sections (<NUM>);
wherein each pipe section (<NUM>) is fabricated by:
providing a pipe section (<NUM>) which includes an outer conduit (<NUM>);
concentrically disposing an inner conduit (<NUM>) configured to contain a cryogenic fluid within the outer conduit (<NUM>) and defining an insulation space (<NUM>) between an outer surface (<NUM>) of the inner conduit (<NUM>) and an inner surface (<NUM>) of the outer conduit (<NUM>), the pipe section (<NUM>) further including a coupling arrangement (<NUM>) disposed on a first end of the inner conduit (<NUM>) and a second end of the inner conduit, the coupling arrangement (<NUM>) configured to engage or mate with a corresponding end of another modular vacuum insulated pipe section (<NUM>);
disposing an aerogel insulation material (<NUM>) in the insulation space (<NUM>);
sealing the insulation space (<NUM>) from the external atmosphere with a sealing arrangement comprising a first seal member disposed proximate a first end of the outer conduit (<NUM>) and a second seal member disposed proximate a second end of the outer conduit (<NUM>); and
disposing one or more valves (<NUM>, <NUM>) on the outer surface (<NUM>) of the outer conduit (<NUM>), the one or more valves configured to be in fluid communication with the insulation space,
introducing a condensable gas into the sealed insulation space via the one or more valves (<NUM>, <NUM>);
pressurizing and depressurizing the insulation space via the one or more valves.
wherein the insulation filled insulation space is at a pressure within the range of from <NUM> Pa to <NUM> Pa (<NUM> microns Hg to <NUM> microns Hg) after depressurization;
wherein the condensable gas in the insulation space is configured to condense at temperatures below about <NUM> Kelvin; and
subsequently transporting the fabricated modular vacuum insulated pipe sections (<NUM>) to a construction site where the vacuum insulated piping system is assembled by coupling the plurality of fabricated modular vacuum insulated pipe sections (<NUM>).