Determination of maximum span between pipes supports using maximum bending stress theory Suspended natural gas pipelines are supported throughout the length of pipeline on different forms of supports at more or less regular spans
Determination of maximum span between pipes supports using maximum bending stress theory
Suspended natural gas pipelines are supported throughout the length of pipeline on different forms of supports at more or less regular spans. If the distance between supports is minimized the number of supports required, which in turn reduce the total cost of
erecting these pipe supports. ASME has suggested the standards for support span, but the bending stress considered in its calculation is very low (15.9 Mpa). There are other references also who have listed the maximum support span. Here the equations for calculating the
maximum span using maximum bending stress are given.
Supports for piping must be spaced with respect to three considerations:
a) Ability to place a support at some desired location.
b) Keeping sag in the line within limits that will permit drainage.
c) Avoiding excessive bending stresses from the uniform and concentrated loads between
2.6 Need of Pipe Support
The layout and design of piping and its supporting elements
shall be directed toward preventing the following:
(a) Piping stresses.
(b) Leakage at joints.
c) Excessive thrusts and moments on connected equipment (such as pumps and turbines).
(d) Excessive stresses in the supporting (or restraining) elements.
(e) Resonance with imposed or fluid-induced vibrations.
(f) Excessive interference with thermal expansion and
contraction in piping which is otherwise adequately flexible.
(g) Unintentional disengagement of piping from its supports.
(h) Excessive piping sag in piping requiring drainage slope.
2.7 Procedure for Calculation of maximum span length:
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Design formulas for calculating bending stress and deflection between supports are derived from the usual beam formulas, which depend upon the method of support and the type of loading.
Maximum Bending stress
Where, w = uniformly distributed weight of pipeline in N/m
w c = concentrated weight on pipeline in N
L = Span length in m
D = Outside diameter of pipe in m
d = Inside diameter of pipe in m
E = Modulus of elasticity of pipe in N/m2
I = Moment of Inertia of pipe in m4
Calculation of total weight
Total weight = weight of pipe (wp) + weight of fluid (wf)
Weight of pipe
Thickness of pipe can be calculated as :
Where, P = Pressure of the fluid in pipe in N/m2
S a = Allowable stress in pipe in N/m2
E = Quality Factor from ASME B 31.3
Y = Coefficient of material from ASME B 31.3