Dry gas seal

• US 20040232622A1
• Filed: 06/21/2004
• Published: 11/25/2004
• Est. Priority Date: 04/30/2001
• Status: Active Grant

• Current Assignee: Aesseal PLC
• Original Assignee: Aesseal PLC
• Inventors: Gozdawa, Richard Julius
• Granted Patent: US 7,144,016 B2
• Time in Patent Office: Days
• US Class Current: 277/401
• CPC Class Codes: F16J 15/342 with means for feeding fluid directly to the face

Abstract

A gas seal assembly comprises a pair of mutually rotatable sealing members A, B, each of which has a face adjacent a gap between the two members. One of the members B is urged in a direction attempting to close the gap h which constitutes a leakage path through the seal assembly. A gas bleed arrangement 7 allows gas from a high pressure side P₃ of the seal assembly to bleed into the gap at a position radially spaced between an inner diameter of the members and an outer diameter of the members A,B so as to apply a force tending to separate the members, the force decreasing as the size of the gap increases.

Claims

1-25. -25 (cancelled).

26. A gas seal assembly comprising:

a pair of mutually rotatable sealing members, each of which has a front face adjacent to a gap between the members, one of the members being arranged in use to be urged in a direction attempting to close the gap which constitutes a leakage path through a seal assembly; and

a gas bleed arrangement for allowing gas from a high pressure side of a seal to be admitted into the gap at a position radially between inner and outer diameters of the members, a gas pressure in the gap applying a force in a direction to increase the separation of the two members, characterized in that the gas bleed arrangement comprises a channel having an associated flow resistance which is dimensioned such that the gas pressure at a gap end of the channel is reduced relative to the pressure at the high pressure side of the seal assembly and such that the gas pressure in the gap decreases as size of the gap increases.

27. The gas seal assembly of claim 26, wherein the gap is a few micrometers.

28. The gas seal assembly of claim 26, wherein a first one of the members is associated with a rotatable shaft and a second one of the members is associated with a casing.

29. The gas seal assembly of claim 28, wherein the second one of the members is biased by a spring in a direction tending to close the gap.

30. The gas seal assembly of claim 29, further comprising a seal ring for sealing between the second one of the members and the casing.

31. The gas seal assembly of claim 26, wherein one of the members is in the form of a generally annular flange and the gas bleed arrangement comprises one or more channels extending from a rear face of the flange through to a front face of the flange adjacent to the gap.

32. The gas seal assembly of claim 26, wherein the gas bleed arrangement further comprises one or more channels extending generally radially from the high pressure side of the seal assembly and formed in the front face in one of the members.

33. The gas seal assembly of claim 32, wherein the channels co-operate with formations in the front face to distribute a bleed gas over the front face.

34. The gas seal assembly of claim 33, wherein the formations comprise one or more generally arcuate or circumferential grooves provided in the front face.

35. The gas seal assembly of claim 26, wherein at least one front face defining the gap is provided with at least three pressure distribution formations each separately connectable via a respective bleed channel with a high pressure region on one side of the seal assembly so that in the event that each face of the two members becomes non-parallel in use a force will be generated tending to return each face to a parallel condition.

36. The gas seal assembly of claim 35, wherein each of the three pressure distribution formations comprises a generally arcuate groove provided in the front face.

37. The gas seal assembly of claim 36, wherein each of the bleed channels comprises a channel ending generally radially from the high pressure side of the seal assembly, the channel being formed in the front face.

38. The gas seal assembly of claim 36, wherein each of the bleed channels comprises a channel extending from a rear face of one of the sealing members to the front face.

39. The gas seal assembly of claim 36, wherein at least one of the sealing members comprises a front annular member and a rear annular member, a front surface facing the gap being formed on the front member and a rear surface of the front member facing a front surface of the rear member, each bleed channel being formed in one or both of the front surface of the rear member and the rear surface of the front member.

40. The gas seal assembly of claim 36, wherein each pressure distribution formation constitutes a generally radially directed groove provided in the front face, each bleed channel being formed by a radially outer portion of the groove of its respective formation.

41. The gas seal assembly of claim 36, wherein the pressure distribution formations are spaced apart generally and symmetrically about the circumference of at least one member.

42. The gas seal assembly of claim 26, wherein one front face adjacent to the gap is provided with a circumferential undulation which is constructed and arranged, upon mutual rotation of the sealing members, to generate a force tending to separate the members, the magnitude of which force is dependent upon the speed of mutual rotation of the sealing members.

43. The gas seal assembly of claim 42, wherein a plurality of generally radially extending grooves are formed in the front face by the circumferential undulation.

44. The gas seal assembly of claim 42, wherein the circumferential undulation varies continuously around a circumference of the front face.

45. The gas seal assembly of claim 42, wherein the circumferential undulation comprises a plurality of discrete generally radially extending grooves.

46. The gas seal assembly of claim 43, wherein the grooves supply formations in the front face, which formations distribute the gas flow over the front face.

47. The gas seal assembly of claim 43, wherein the formations comprise one or more generally arcuate and/or circumferential grooves provided in a surface defining the gap.

48. The gas seal assembly of claim 46, wherein only some of the generally radially extending grooves extend into the generally arcuate or circumferential grooves.

49. The gas seal assembly of claim 46, further comprising one or more passageways extending from a rear face of the member in whose front face the formations are provided to the front face for the supply of high pressure gas through the channels to the formations.