Partial Penetration and Full Penetration Joints on Lift Padeyes

[hungrydinosaur]

Hi All,

I am currently working on a offshore structure with beams which have lifting padeyes welded to them. As per DNV requirements all lifting padeyes need to be welded with a full penetration joint. What I have is a padeye 35mm thick and I-beam flange 10mm thick. If we bevel the padeye with a root of 3mm, we are left with a bevel of 16mm on each side. Doing a 16mm bevel weld on a 10mm flange will practically distort the flange.

1. My question is, whether a Complete Joint Penetration is practical here? Otherwise a 10mm bevel on either side of the padeye will be practical to weld on a 10mm flange (base metal).

2. I have done calculations and the 10mm weld are sufficient for the loads. But I want the criteria of DNV to be fulfilled, that is the padeye joint has to be full penetration. Any way out here? Any suggestions?

Thanks in advance.

Regards,

HungryDinosaur

 

[NickClark]

Which DNV code?

2.7-1 doesn't mandate full pen. But its a good idea from an NDT perspective. Can you modify the design to set in the pad eye?

Nick

 

[hungrydinosaur]

Nick,

Its difficult to modify the design. What do you mean "set in the padeye"?

Regards,

HD

 

[ak762]

2.7-1 doesn't mandate full pen

And how to interpret 4.3.1 Welding of padeyes
All main welds between pad eyes and the primary frame structure
shall always be full penetration welds.

 

[NickClark]

Thanks for the correction ak762. I am thinking of 2.7-3 which allows fillet welds in shear if I read correctly. If you can't modify the design but need to meet the dnv then your a bit stuck. I still don't know the code you need to meet or the eye design but I was speculating that you could insert the eye into the flange and prep the flange instead. Its up to you to come up with a solution and it will be difficult to provide more without details

Regards

 

[hungrydinosaur]

Nick,

Yeah looks like I am stuck here. The code is DNV 2.7-1.

Regards,

HD

 

[Ussuri]

Can you use a doubler plate? Would that be acceptable?

 

[hungrydinosaur]

Ussuri,

I never thought about that. But is it normal to do so?

 

[Ussuri]

In accordance with DNV 2.7-1? I don't know. I have never designed to it. It was just a thought so I would guess you would need to investigate.

 

[jbeckhou]

Can you design the pad-eye to be slotted into the I beam? Search for the following TCM153-474863, shows different ways to mount pad-eyes.

Petrotrim Services

http://www.petrotrim.com

 

[PooyaKhodadadi]

Dear Ussuri,

please provide your thoughts on the double plate.


Thank You

 

[desertfox]

Hi

Below is a copy of an extract from the DNV, the last sentence talks about transferring the lifting load through a plate and its thickness must be adequate, how does your 10mm thick plate and your pad eye compare with this statement.
It suggests to me that if your plate isn't thick enough, then using a doubler might be an option. See another extract further down.


The thickness of the pad eye at the hole shall not be less than 75% of the inside width of the joining shackle.

Guidance note:

When the pad eye thickness is below the 75% limit, it can be increased by welding on cheek plates or by inserting a

thick walled pipe or drilled out boss through the pad eye. See Appendix D for strength calculations of such structures.

Pad eyes shall be welded to the frame with full penetration welds. If the lifting force is transferred through the

thickness of a plate (the z-direction), plates with specified through thickness properties must be used.



---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---








The thickness of the pad eye at the hole shall not be less than 75% of the inside width of the joining shackle.

Guidance note:

When the pad eye thickness is below the 75% limit, it can be increased by welding on cheek plates or by inserting a

thick walled pipe or drilled out boss through the pad eye. See Appendix D for strength calculations of such structures.

Pad eyes shall be welded to the frame with full penetration welds. If the lifting force is transferred through the

thickness of a plate (the z-direction), plates with specified through thickness properties must be used.



---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

 

[Ussuri]

A doubler plate is a thicker section of plate welded onto a thinner plate. It acts as an interface between the one structural element and another. Sometimes used when you have to put some high loads into a thin plate. The doubler is thicker and designed to take the loads and then distribute them over a wider area on the thin plate.

 

[TomekZeWschodu]

So, the most reasonable solution for this is to use higher strength steel for padeye (to reduce a thicknes, probably cheek plates shall be provided to ensure mentioned 75% of shackle clearance), or / and (when not requirements are not fullfiled) insert an I-beam with thicked web(s) in region when the padye to be installed.
You can also ask DNV Advisory (DNV GL since few moths) whether another solution is acceptable.

Naval Architect/ Structural Engineer
Poland