Patent Application
20100032051
Not applicable.
The invention relates generally to the construction of low-temperature or cryogenic storage tanks used, for example, to store large quantities (for example, ½ million barrels or more) of volatile materials such as natural gas. In particular, the invention relates to ways to efficiently insulate parts of such tanks.
Conventionally, low-temperature or cryogenic tanks have an outer shell around an inner tank. Process piping extends between the outer shell and the inner tank, and a thermal distance piece (TDP) is used to insulate that process piping. The TDP creates as an enclosed internal space or void that can be insulated using a fiberglass blanket, field-cut fiberglass disks, Perlite fill, or other granular insulating material. Conventionally, Perlite fill has been pneumatically blown into the void within the TDP through a face plate. This process has been viewed as satisfactory.
The applicants have found a way to fill the void within a TDP more efficiently, with less waste and with less environmental impact.
Unlike the previous method of using a blower or jet pump to provide positive pressure to blow the insulation into the void, the new process uses a vacuum source to draw insulation into the TDP.
To use this method, the applicants have developed a new suction wand that can be easily fabricated from PVC pipe. The wand has inner and outer cylinders. The inner cylinder extends through the outer cylinder and projects outwardly from a proximal end of the outer cylinder. A proximal cap connects the proximal end of the outer cylinder to the inner cylinder. A distal cap connects the distal ends of the inner and outer cylinders. Air vents are provided on the proximal cap and on the inner cylinder near the distal cap.
Portions of the TDP can be sealed by wrapping them with low-density polyethylene (LDPE) sheeting or other suitable material prior to drawing a vacuum.
To use the new method, two or more openings to the void are provided. The openings are spaced remotely from each other, and can be provided, for example, by removing a plug from a pipe coupling or threadolet. A strainer is temporarily provided in one of the openings.
The distal end of the suction wand is inserted into a container of insulation or comparable material, such as a bag of Perlite insulation. The proximal end of the suction wand is connected to the opening on the TDP that does not have the strainer. A vacuum is then drawn through the opening with the strainer, causing the material to be drawn by the vacuum through the suction wand and into the void.
The invention may be understood better by referring to the accompanying drawings, in which:
The size and arrangement of a TDP 10 may vary. Generally, a TDP has a cylindrical outer wall 22 that surrounds the nozzle 20 that extends between the inner and outer tank shells. The TDP outer wall is typically 8-12 inches wider than the nozzle, which can range from 3-40″ in (outside) diameter. Thus, the outer wall can be from 11-52″ in diameter or greater. TDP's of this size are typically from 5′8″ to 6′ long.
As seen in
The proximal cap 34, here made of PVC, connects the proximal end of the outer cylinder 32 to the inner cylinder 30. The inner cylinder 30 extends through a 1 and ¼″ diameter central opening 40 in the cap. Proximal air vents 42 are provided on the proximal cap. In this example, the proximal air vents take the form of a series of twelve 5/16″ diameter holes drilled around the central opening in the cap. A distal cap 44 connects a portion of the inner cylinder to a distal end 46 of the outer cylinder 32. Distal air vents 48 are provided on the inner cylinder near the distal cap. In this example, the distal air vents take the form of four ⅛″ diameter holes drilled approximately ¾″ from the distal end of the inner cylinder.
To ensure good delivery of insulation to the void within a “bird-feeder” type retainer TDP such as the one illustrated in the figures, portions of the TDP can be sealed prior to applying the vacuum. This can be done, for example, with plastic sheeting 50 and duct tape.
In the illustrated arrangement, two openings 60 and 62 in the TDP 10 (see
In the illustrated arrangement, suction is provided through one of the openings 60. Although other arrangements are possible, in this case suction is providing using a Penberthy GH1 jet pump 70 or equal, as seen in
The vacuum provided by the jet pump 70 draws insulation through the opposite opening 62. To do this, the distal end of the suction wand 14 (the end with the distal cap 44) is here inserted into the container 12 of insulation, as seen in
As the insulation is drawn from the container 12 into the TDP 10, the proximal air vents 42 on the proximal end of the wand 14 should be kept above the level of insulation in the container.
During fill, the hose 80 may clog. If it does, repeatedly “throttling” the jet pump 70 off for several seconds and then back on may enable more insulation to be added.
After the initial fill, the TDP 10 can be vibrated to settle the insulation in the void. The vibration process is well known among those skilled in the field. After vibration, the fill process is repeated. The strainer 72 and the hose 80 are then removed, and the openings 60 and 62 are re-sealed.
The illustrated TDP 10 can be sealed, filled, vibrated, and “topped off” with a final fill in less than one hour. In contrast, the conventional process of blowing insulation into the illustrated TDP would take more than several hours, and would result in more insulation being lost to the environment during the fill process.
This description of various embodiments of the invention has been provided for illustrative purposes. Revisions or modifications may be apparent to those of ordinary skill in the art without departing from the invention. The full scope of the invention is set forth in the following claims.
