D/t ratio for pipe

[prabir]

Hi All,
Is there any standard or guideline which indicates or gives procedure to calculate D/t ratio of steel pipe from structural stability point of view.I have a 60" pipe having wall thickness 0.354",pressure is only 10 psig,support span is 100ft.
Thickness is alright for 10 psig pressure.But is this pipe going to be stable when erected on pipe supports at 10 m height over a length of 100 meter.
Thanks

 

[PlantEng]

I think you are asking for the maximum support spacing for a 60" dia pipe. I haven't used the D/t as a design factor before. Normally, you will model the pipe as a beam and calculate the spacing that will give a maximum stress of 2300 psi (std wt CS) and a sag of no more than 0.1". This is the maximum pipe support spacing. The load will be a distributed load consisting of the pipe weight and the weight of the contents.
FOR A SIMPLY SUPPORTED BEAM WITH UNIFORMLY DISTRIBUTED LOAD,

w = total weight
l = length of span
mmax = maximum moment
dmax = maximum deflection
s = stress at max moment
i = moment of inertia about neutral axis
y = distance to neutral axis
E = modulus of elasticity

mmax = w*l^2/8
dmax = 5 w l^4 / (384*E*i)
s = dmax * y / i

see manual of steel construction for more exciting structural info.

For your application, insert your span and pipe dimensions and make sure the stress is not over 2300 and the deflection is not over .1 inch. Guess which will happen first?

 

[hokie96]

prabir,

Don't forget to consider the effects of the concentrated loads at your support points. In large diameter, thin wall pipes, sufficient saddles, stiffening rings or other appropriate reinforcement is usually required to prevent local buckling/deformation. These concentrated loads may limit your maximum span depending on the reinforcement design.

 

[prabir]

Thanks, PlantEng & hokie96.