Spool Buckling Length: 2

[MoreAC]

I am trying to lift a spool. Simple straight pipe spool 10"x 1/2" WT of 45 m length.

To avoid excessive bending, I am using 4 slings from the hook located to carry approximately equal loads.

My understanding was, the axial buckling length will be defined as the length between individual adjacent sling.

While looking at an another design report prepared by engineering consultancy, it seems like, the company has taken buckling length as the distance between extreme (outermost) slings, which leads to minimal axial capacity and members to fail.

Can somebody suggest, if my assumption is correct. the Spool is flexible and has no bending stiffness than the stiffness provided by a circular section.

Anurag

 

[BigInch]

Do you mean defining a length for evaluating a lateral buckling effect, which would limit the allowable bending stress of a beam (calculated for bending only, without any axial load)?

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[StephenA]

As the "beam" is a tube the propensity for buckling is the same in all directions.

I would think that the tube is more likely to buckle in the vertical direction for a static case as that is the way that the tube is deflected due to self weight.

For a dynamic lift and swing operation there will be some inertia loads giving some horizontal loading. The intermediate lifting points will not offer any side restraint, so maybe you have two cases to consider.

All of the slings will put axial forces in the spool.

Stephen Argles
Land & Marine

http://www.landandmarine.com

 

[BigInch]

No. Yes its the same in any direction, however the direction of buckling still depends on the least buckling length, which could be in any direction, depending on the means of support. If there is no or little lateral restraint provided at the intermediate sling points, then the critical buckling length will indeed be the span between outside slings. Offhand, and without further details of any spreader bars etc. , I would think that intermediate sling points provide little or no buckling restraint and the entire length (or outside sling length) of the pipe should be considered.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[MoreAC]

Thank you StephenA and BigInch.

I agree with your suggestions. It seems like, the correct way in absence of spreader bar is to consider full length (i.e. distance between extreme slings) as the buckling length.

If properly modeled and matches with the actual configurations, we don't need any skew load factor considering chain blocks are used for adjusting slings to appropriate length.

As we are lifting the spool with straps or choking arrangement, i can neglect the consequence factor while analyzing the spool.

So, overall, we can lift the spool with said methodology is my solution.