Outplane angle in padeyes

[subengr]

Was wondering how common it is to consider the shackle eccentricity when considering the outplane moment on padeyes.

IOW, instead of considering it acting at the pinhole you consider the sling force acting on the shackle tip.

For larger outplane angles this could be significant. Do you think the 2.0 DAF covers this?

 

[Ussuri]

In my experience the load is usually assumed to act at the inside of the shackle bow, so it is applied eccentrically to hole position.

In addition there is usually an offlead force applied to cover an out of plane load.

The DAF is not applied to cover errors in the design process.

 

[MJCronin]

sub....

Instead of talking about an "outplane angle on padeyes" or "shackle eccentricity" consider posting using the terms "lifting lugs" and "eccentric loads".

Word usage makes a big difference on the internet.....

The esteemed seminal US company and leader in the field - Crosby has the best information on out-of-plane loadings...

This was, of course, befor the Chinese copied everything...

My opinion only..

-MJC

 

[subengr]

MJCronin

In the offshore industry, "padeye" is the norm to describe lifting lugs. I dont think I ever heard someone use the term lifting lug.

Crosby talks about out of plane loading but only in context of the shackle, not in designing a padeye.

 

[TheMan008]

I have run calculations for outplane of a shackle, what company are you working for?

All I can tell you is the force applied out of plane to the padeye severly reduces its strength, and as a rule; force should never be applied outplane of the padeye.

 

[EngineerTex]

Crosby states that their shackles can be de-rated to 50% load capacity when loaded at 90 degrees to the normal usage.

As far as the padeye is concerned, if you design your plate and cheekplates (or solid plate) to be 90% of the open width of the jaw, your problem will not be with the padeye. Rather, it will be with the weld that holds the padeye plate to the frame.

As for the original question, it's not unreasonable to apply 5% out-of-plane loading to the padeye, but I believe DNV 2.7-1 states 3 degrees. But you'd have to look it up and verify.

Engineering is not the science behind building. It is the science behind not building.

 

[subengr]

Theman008:

For the application we are working on there is no way to avoid the outplane angle as there are multiple sling angles as the structure is rotated.

 

[dooron]

Its not common practice (at present) to apply an out-of-plane load to padeyes (lifting lugs), but it should be. DNV2.7-1 and DNV2.7-3 both require an out-of_plane resultant load at about 3 deg. This load should be applied (as a minimum)at the bow shackle top (inside radii). It will in many cases control the thickness of the Padeye at its base. The padeye thickness should be no less then 75% of the shackle opening.

 

[TheMan008]

Subengr, what company are you working for/with?

 

[subengr]

Thanks for all the replies

Theman008: I cannot go into that due to policy. Thanks for your feedback though

 

[EngineerTex]

there is no way to avoid the outplane angle as there are multiple sling angles as the structure is rotated

If you are dealing with rotating an object from horizontal to vertical (or vice-versa), you can do so without loading padeyes out of plane. You will put two padeyes parallel to each other, so that the holes are on the same axis. Then, you lift it with a spreader bar that has the two points of lift exactly the same distance apart as the two eyes on the structure. These two padeyes will be completely separate padeyes from your normal four-part lift.

And on this subject, you should also design a tilting/pivot frame in order to prevent the unit from sliding all over the deck when it's being rotated up or down. If you don't have a frame/cradle or whatever you want to call it, there are a lot of platforms that will require you to use two cranes for the rotation operation.

Engineering is not the science behind building. It is the science behind not building.