Air Products & Chemicals, Inc. : Patent Issued for Rotary Face Seal with Anti-Crowning Features
Resource from: 4-traders Likes:144
Jan 10,2014
From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors McLean, Christopher R. (Vancouver, CA); LeBlanc, Michel P. (Vancouver, CA); McKerrow, Michael J. (Delta, CA); Keefer, Bowie G. (Vancouver, CA); Lu Kong, Xiang (Calgary, CA); Lebeck, Alan O. (Albuquerque, NM), filed on July 1, 2009, was published online on December 31, 2013.
The patent's assignee for patent number 8616233 is Air Products and Chemicals, Inc. (Allentown, PA).
News editors obtained the following quote from the background information supplied by the inventors: "Rotary face seals typically comprise two contacting rings where one ring rotates with respect to the other. The seal is made between the opposing faces of the two contacting rings. Force is provided in some manner in order to maintain sealing contact between the rings.
"Such rotary face seals are used for numerous commercial purposes. A relatively new application for rotary face seals has been for use in compact and/or rapid cycle pressure swing adsorption (PSA) devices. For instance, U.S. reissue Pat. No. RE38,493, incorporated herein by reference, discloses such devices. Therein, rotary face seals form part of pressure balanced rotary distributor valves that are used to open and close the feed and product ends of the adsorbent beds employed in a PSA device. Various rotary pressure swing adsorption devices also are disclosed in U.S. Provisional Application Nos. 60/886,484 and 60/886,486, both of which are incorporated herein by reference. In addition, PCT application number PCT/CA2008/000148, titled 'Gas Separation Device', filed Jan. 23, 2008, discloses a rapid cycle pressure swing adsorption (RCPSA) device which also employs rotary face seals in rotary valves used at both the feed and product ends of the adsorbent beds therein. In the embodiments disclosed by this PCT application, the force used to maintain contact between the sealing surfaces can be provided by various gases as opposed to being provided by mechanical means (e.g. springs).
"Problems associated with temperature gradients and thermal distortion in rotary face seals have been encountered in the prior art and some solutions have been proposed. For instance, U.S. Pat. No. 4,850,599 discloses a rotary mechanical face seal having a construction which keeps the sealing faces substantially parallel in spite of thermal distortion of the seal face members.
"In many PSA applications (such as in separating hydrogen from refinery waste streams), the temperature variations experienced by the rotary valves in the PSA device can be significant. In addition, significant temperature gradients may also exist across the rotary valve and/or seal components. For these reasons, it is important that the rotary face seals in these devices be sufficiently stable against variations in temperature and against temperature gradients."
As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "In some rotary face seal designs, we have found that undesirable distortion of the rotary face seal components may occur during events involving significant changes in operating temperatures due to thermal expansion when the thermal expansion coefficients of certain seal components differ too much. In particular, in designs that employ a seal ring comprising a seal face bonded to a backing ring, undesirable crowning of the seal face can occur if the thermal expansion coefficient of the seal face is much greater than that of the backing ring. This may be the case when certain polymers are used as the seal face material in combination with metals or metal alloys, such as steel, as the backing ring material. We have discovered that this crowning can be eliminated or reduced substantially and thus the seal can be stabilized against temperature variations by incorporating certain anti-crowning features into the seal ring.
"In one disclosed embodiment, the pertinent rotary face seal comprises an improved seal ring, a sealing surface, and a sealing load to urge the seal ring towards the sealing surface. The seal ring rotates relative to the sealing surface about the seal ring axis, and either the seal ring or the sealing surface may be stationary. The seal ring comprises a seal face bonded to a backing ring. The side of the seal face opposite the backing ring contacts the sealing surface and is essentially flat. When the face seal is used in a rotary valve, the seal ring typically comprises at least one port (and often many) through both the seal face and the backing ring. And, the improved seal ring is characterized in that it comprises one or both of the following anti-crowning features: i) a thickness of an edge of the seal face that is different from the thickness of the middle of the seal face; and/or ii) a relief slot in the seal face.
"In particular, when the seal face has a coefficient of thermal expansion that is greater than that of the backing ring, the thickness of an edge of the seal face is made greater than that of the middle of the seal face. In general, most or all of the seal face edges may be greater in thickness than that of the seal face middle. The backing ring is then made correspondingly thinner adjacent the thicker edge, or edges, of the seal face. Generally, abrupt discontinuities are avoided as the thickness of the seal face varies from the middle to its thicker edge or edges. Thus, in this region, the seal face may be angled or sloped to provide for a smooth, continuous transition in thickness. Material combinations for working embodiments include designs in which the backing ring is steel and the seal face is a carbon filled polytetrafluoroethylene. The thicker seal face edges can comprise both the outer and inner circumferences of the seal face. The thicker seal face edges can also comprise the periphery of any ports in the seal face (if so provided).
"In an alternative situation, the seal face may have a coefficient of thermal expansion that is less than that of the backing ring. In this instance, the thickness of the edge of the seal face is less than that of the middle of the seal face. A disclosed material combination includes a design in which the backing ring is steel and the seal face is made of carbon or expanded graphite.
"The anti-crowning relief slot feature can comprise a blind relief slot in the middle of the seal face such that the slot does not go all the way through the seal face to the backing ring. The seal ring may comprise a plurality of such blind relief slots.
"The improved seal ring provides for an improved rotary face seal that is suitable for use in a rotary valve. In the rotary valve, the seal ring and the sealing surface each comprises at least one port that come into and out of fluid alignment as the seal ring rotates relative to the sealing surface. The rotary face seal can thereby act as a rotary valve, and is particularly suitable for use in a rotary gas separation device.
"As in the aforementioned PCT application number PCT/CA2008/000148, the rotary valve may additionally comprise a seal ring backer in which the seal ring floats with respect to the seal ring backer. This is one possible construction that allows the rotary valve to function as a pressure balanced rotary distributor valve."
(4-traders)
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1.The news above mentioned with detailed source are from internet.We are trying our best to assure they are accurate ,timely and safe so as to let bearing users and sellers read more related info.However, it doesn't mean we agree with any point of view referred in above contents and we are not responsible for the authenticity. If you want to publish the news,please note the source and you will be legally responsible for the news published.
2.All news edited and translated by us are specially noted the source"CBCC".
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