Effect of changes in the taper-hub shape on the strength of high-pressure flanges

Abstract

Taper hub is the name of a ring of triangular cross-section which is integral with the flange and pipe to strengthen their junction. Eleven models, made of pearlitic-ferritic spheroidal graphite or flake case iron were tested by tightening and pressurizing to failure at room temperature.

Models with four different taper-hub lengths and three different fillet radii were tested. Flange fillet, pipe fillet and pipe strains due to increasing (measured) bolt tensions were recorded and converted to non-dimensional stress indices. An approximately linear response was found owing to tightening and pressurization up to the nominal rated pressure of the basic British standard flange. Bolt tightening caused no stresses in the pipe remote from the taper hub. Pressure caused only small changes at the flange fillet. The lengths of the taper hub could be reduced to five pipe wall thicknesses without increasing stresses above those in the standard shape. Doubling the fillet radius increased the nominal hoop stress in the pipe at burst from 67 to 78 per cent of the ultimate tensile strength of the spheroidal graphite cast irons. A reduction in the hub length does not change the failure pressure.

Keywords

flanges pipes pressure vessels strength of spheroidal graphite cast irons

Get full access to this article

View all access options for this article.

References

BS 10: 1962 Specification for Flanges and Bolting for Pipes, Valves and Fittings, UDC 621. 643, 412:621.882, 1962 (British Standards Institution, London).

Fessler

Perry

D. A.

Stresses in high-pressure taper-hub flanges with recesses for nut facings. J. Strain Analysis, 1975, 10, 119–128.

Fessler

Perry

D. A.

The behaviour of a flanged pipe joint under external bending. In Proceedings of the Fourth IMechE International Conference on

Pressure Vessel Technology, 1980, paper C88/80, pp. 209–216 (Mechanical Engineering Publications, London).

Fessler

Perry

D. A.

Leakage characteristics of flanged pipe joints. J. Strain Analysis, 1977, 12, 29–36.

Morita

Kawashima

Design of flanges for heat exchangers. Sumitomo Metals, 1978, 30, 17–26.

Waters

E. O.

Wesstrom

D. B.

Rossheim

D. B.

Williams

F. S. G.

Formulas for stresses in bolted flange connections. Trans. ASME, 1937, 59, 161.

BS 4504: 1969 Specification for Flanges and Bolting for Pipes, Valves and Fittings, Metric Series, UDC 621.643.4, 1969 (British Standards Institution, London).