Pipe joints or couplings – Packed – Flanged pipe
Patent
1991-09-13
1993-07-27
Nicholson, Eric K.
Pipe joints or couplings
Packed
Flanged pipe
285405, 285412, 285368, F16L 23032
Patent
active
052305406
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to fluid-tight bolted joints between axially consecutive component parts of hollow fabrications such as turbomachine casings or lengths of ducting.
It is a frequent industrial requirement that consecutive component sections of generally cylindrical fabrications such as casings, ducts, or pipes be joined together in a fluid-tight manner; for example, in the construction of turbomachines such as gas turbine engines, in which structural casings are required to surround the rotating parts and provide a boundary for the fluid-flow passages. One of the most widely used means of obtaining a joint between axially consecutive component sections of pipes, etc., is to provide their ends with flange rings which are bolted together face-to-face to define a suitably sealed joint. The flange rings usually project outwards from the body of the fabrication.
General industrial practice for ensuring that bolted flanged joints are fluid-tight is to utilise separate sealing elements between the confronting flange faces of the joints, such as gaskets, `O`-rings or jointing compounds. However, such measures are not utilised in connection with the casings of gas turbine aero-engines because of various factors, such as sealing element material life, or adverse effects on assembly tolerances and maintainability.
Consequently, general aero engine practice for joining together successive sections of casing has been to provide metal-to-metal joints between flanges whose joint faces are machined square to the longitudinal axis of the casing. However, such joints can be difficult to render fluid-tight.
A design stratagem used for such bolted flanged joints in pressure vessel walls, as opposed to aero engines, is to provide the joint faces of abutting flange rings with small annular sealing lands at their inner diameters. In this way better sealing against fluid egress is achieved because the bolt closure loads in the joints are concentrated on the small areas of the sealing lands instead of over the whole extent of the flange faces. Whilst this is satisfactory if the flanges are thick, and hence very stiff, it is unsatisfactory for the less robust lightweight flanges used for aero engine casings because it introduces bending stresses in the bolts due to distortion of the flanges when the bolts are fully tightened.
A specific object of the present invention is to provide improved metal-to-metal sealing of lightweight bolted flanged joints for casings of aeroengines and other turbomachines.
A more general object is to provide flanged joints which do not require separate sealing elements to render the joints fluid-tight.
A further object is to provide lightweight bolted flanged joints in which the bolt closure loads can be concentrated on relatively small sealing areas of the joint faces whilst avoiding excessive bending stresses in the bolts.
Accordingly, the present invention provides a flange ring for a fluid-tight annular joint between axially consecutive component parts of a hollow fabrication, the flange ring having: of the hollow fabrication, the hub portion having a wall thickness which reduces from a maximum adjacent the flange rear face to a minimum which is substantially equal to the wall thickness of the component part; and of fastening means whereby the flange joint face can be drawn into sealing engagement with a confronting complementary joint face to form the fluid-tight annular joint; has a relatively narrow radially disposed sealing flat, the remainder of the flange joint face comprising a frustoconical surface inclined at an angle of c.degree. to the radial direction and meeting the sealing flat at a corner with an included angle of 180.degree.-c.degree., the width and position of the sealing flat on the flange joint face being such that manufacturing tolerances of the fabrication do not prevent sealing engagement with the complementary joint face and that axial loads in the joint do not cause unacceptable bending or buckling in the assembled fabrication, the flange rear face being parallel
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Fessler Heinrich
Hyde Thomas H.
Lewis Leo V.
Marsden Barry J.
Nicholson Eric K.
Rolls-Royce plc
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