Chemical and Petroleum Engineering, Vol. 54, Nos. 1–2, May, 2018 (Russian Original Nos. 1–2, Jan.–Feb., 2018)
0009-2355/18/0102-0026 ©2018 Springer Science+Business Media, LLC
Irkutsk Research and Design Institute of Chemical and Petrochemical Engineering (IrkutskNIIkhimmash), Irkutsk, Russia; e-mail: o.kabanova@
himmash.irk.ru. Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 1, pp. 19–22, January, 2018.
STRENGTH CALCULATIONS AND CALCULATION OF THE
REMAINING LIFE OF AUTOFRETTAGED COMPONENTS
OF TUBULAR EQUIPMENT AND PIPELINES
O. E. Kabanova and D. S. Golodnenko
Formulas for calculating the strength and determining the remaining life of ultra-high-pressure autofrettaged
pipes and bends of tubular equipment and pipelines are presented.
Keywords: autofrettage pressure, creep radius, stress, tube, bend, remaining life.
A high level of stress on the internal surfaces is characteristic of the elements of tubular components and pipelines
(pipes, bends, T-joints) that function under ultra-high pressures (more than 130 MPa).
Autofrettage, or loading of the element with pressure from within, is a method of redistributing stress across the
width of the wall of an element. When the autofrettage pressure is removed, residual compressive stresses arise on the internal
(plastically deformed) layers, while residual tensile stresses appear on the outer (elastically deformed) layers.
The process of calculating the strength of autofrettaged elements consists in determining the intensity of the stresses
and their components, i.e., the principal normal stresses, including the radial σ
, tangential σ
, and axial σ
stresses (Fig. 1),
which are composed of the residual stresses, stresses caused by pressure under working conditions, and stresses caused by the
drop in temperature across the thickness of the wall of the element (where there does, in fact, exist a temperature drop). The
principal normal stresses are calculated for given values of the current radius r (from r
The total radial, tangential, and axial (principal normal) stresses are generated on the basis of the fourth theory of
strength . The intensity of the stresses for given values of the current radius r (from r
) is calculated.
The strength condition is satisﬁ ed if the intensity of the stresses is less than the yield strength multiplied by a coef-
ﬁ cient usually set to 0.9–0.95. Calculation of the principal normal stresses and stress intensity is performed using the fol-
lowing formulas [2–4]:
• with r
≤ r ≤ r