Advice on welding 10t lifting eye

[olek]

This whole idea of setting the eye into the plate and welding from the back is a disaster.
The whole point is to have reinforced weld metal around the eye to give it strength. A fillet weld is exactly the way to do this for absolute optimum strength.
It’s a proved, tried and tested design and not one we want to be changing over a diy forum. I’ve seen these eyes made exactly as the op is showing lifting 100’s of tonnes such as windtower sections, huge beams for bridges, under ground tanks etc and it’s always a multi pass fillet weld. Although these are designed for a straight up lift you have to assume some side ways forces are going to be applied and there for the reinforcement from a fillet weld design is essential.

Are there bolts passing from underside in the hook part? Would they add some resistance?

 

[Gwil]

This whole idea of setting the eye into the plate and welding from the back is a disaster.
The whole point is to have reinforced weld metal around the eye to give it strength. A fillet weld is exactly the way to do this for absolute optimum strength.
It’s a proved, tried and tested design and not one we want to be changing over a diy forum. I’ve seen these eyes made exactly as the op is showing lifting 100’s of tonnes such as windtower sections, huge beams for bridges, under ground tanks etc and it’s always a multi pass fillet weld. Although these are designed for a straight up lift you have to assume some side ways forces are going to be applied and there for the reinforcement from a fillet weld design is essential.

Why, as a general principle, is 'the whole idea of setting the eye into the plate and welding from the back.. a disaster'? Particularly when wedged this would seem ok? There would be whatever fillet you wished for on top plus the weld from below. I've made large chainplate connections on heavy displacement sailing vessels this way- potential shock loads in excess of the vessel's displacement, say 30 tons+. Working load in heavy weather maybe 10 tons+ on occasion.

Also nothing like the rather bizarre overkill of the OP's prospective job. No failures or cracking using NDT.

By the way, I'd echo not taking responsibility for this one!

 

[Richard.]

Well this the fun of a good debate as we don’t have to agree and I’m afraid I don’t agree with the above. Cutting a large rectangle in the base plate to allow a weld from the back will effect the overall load carrying capacity of that base plate. The plate will be weaker with a big chunk missing out the middle. Yes you can still carry out a fillet joint but imho it will be a weaker eye if calculated by cutting a hole into the plate and pushing the eye through the hole. Remember it’s a downward pulling force. The middle of that plate is going to be taking more load bearing stress than the fillet weld will be. I’d not be replacing it with a backside weld.

 

[Gwil]

Well this the fun of a good debate as we don’t have to agree and I’m afraid I don’t agree with the above. Cutting a large rectangle in the base plate to allow a weld from the back will effect the overall load carrying capacity of that base plate. The plate will be weaker with a big chunk missing out the middle. Yes you can still carry out a fillet joint but imho it will be a weaker eye if calculated by cutting a hole into the plate and pushing the eye through the hole. Remember it’s a downward pulling force. The middle of that plate is going to be taking more load bearing stress than the fillet weld will be. I’d not be replacing it with a backside weld.

I sort of take your point! But re your last point I'd not suggest replacing the fillet weld, just having both. We're also talking in my case heavy ocean cruising boats, not lightweight racers where they make you drill holes in your toothbrush. So plate thickness is inevitably overkill, although not as much as the OP's job.

 

[olek]

Documentation on computation and design of pad eye type lifting lugs :

http://www.maximumreach.com/PEHELP.htm

Here are the programs :

the one used in the help file (about lifting lungs):

http://www.maximumreach.com/UPENDFORCE.asp

home page
http://www.maximumreach.com/Software.htm

Indeed, standard design is only based on 2 fillet welds (not even on the front small largeness) , reinforcing only with gusset eventually

I did not knew those equipment typically are used to move some heavy load from horizontal to vertical position (hence all the computations )

 

[zeppelin builder]

Prep the padeye each side tack the assembly with 4mm gap tack assembly up in pairs ie back to back ..
Root and hot pass then grind or arc air back to clean metal
Care fully weld side for side as not to pull off square cap need not be heavy just above flush with a slight taper out to plate say 5mm
Use 3.25 7018 and maintain preheat when welded wrap in fire blanket to slow cooling rate a load test with mpi should be ok or if realy critical get it ultrasonic tested

 

[Richard.]

I know you meant both mate. Inc the fillet as well. What I meant was I wouldn’t give up the solid plate for a plate with a hole and a weld. I just wouldn’t

 

[dannyp]

when we've got big stuff very stuck and been using the TUG in anger Lots of things get broken and you do get quite a good feel for what things will actualy take.

if you put a lug over a hole and weld it from behind then weld around it allways rips it off, i allways go the feeling that the plug must have cracked around and then due to the hole in it the plate flexes more and the lug just gets peeled off.

usally once we've riped the lugs that were on it off, the corners get lobbed off a 40 or 50mm road plate with the gas and some holes burnt in it. tack it on give the lot a quick sortch with the gas an weld if the vantage is about it's flux core wire time if it's not it's a lot of 7018 rods, but even done like that we've never had issue with a fillet weld, you can if really giveing them some stick stretch them so the hole becomes oval or untill it tears out but the base lug will still be sat there welded on.

tho on a safety note the TUG has a lot of driver protetion in the form of thick steel plate , it was never a question of if it would get hit by flying lugs and shakels but how often. and lugs stuck on things for recovery allways get gassed or air arced off once were done with them

 

[rory1]

Just out of interest.... do you have any pictures of your TUG. I can't really work out what it is!

 

[dannyp]

i'll have to to have a rummage migth have some of the build, never get chance to take any when it's working as its allways panic stations if it needs to come out.

to give you an idea of what it is, its basicly the bottom including running gear from heavy russian tank, the engine from that was dead so got tossed, and we stuffed an old deltic locomotive engine in there ( it's a bit of an odd thing not really right for the job ether but it was cheep and it was the cheepest way to get a lot of HP by a long way at the time ) with a big drum winch perched on top.

it was a proper billy bob redneck build not proud of the asthetics ether, was never meant to have the winch on it orignaly we thought lots of HP and tracks would do all the pulling we needed. but a boggy potato field put pay to that idea so on went the biggest winch we chould get out gruby mits on

 

[KaneH]

25mm fillet weld?! I think they must have missed a digit off of the load rating there. As an example you'll get approx. 1.15kN per mm run of a 6mm fillet weld. Even assuming a 2xSWL load test you'd still have plenty of meat left using a 6mm fillet weld all round on a mild steel plate of that size.

 

[olek]

The program provided above allows to compute the size of the weld leg ; Despite the detailed informations I could not do it, but the explanations are complete I think (to compute a "worst case scenario" as the LUG is supposed to lift a vessel - in that case that have orientation from horizontal to vertical (I think) so the effort on the lug need to be computed for all angles .

I am surprised to see how strong simple fillet welds could be. I was not aware that they have to resist in different orientations, and was persuaded that some bolts reinforcement was installed from below the plate.

(nice programs BTW, to compute crane operations and different efforts)

 

[steve t]

danny we got to see it now!!

 

[olek]

BTW I find the program to compute eye lung

http://www.maximumreach.com/PadEye.asp

Or that one let you choose between 2,3 or 4 welds

http://www.maximumreach.com/PlateLug.asp

 

[olek]

I will take a moment and compute a 10T lug, it surprise me that only 2 fillet weld will assume such heavy loads, (plus 60xx électrodes or 70xx envisaged) , but... Could not compute because of imperial measurements.

Once welded, 2steel pièces are considered as one? (metal continuity)?
When the OP say 10T is it kg tons?

 

[Pete.]

A Ton and a Tonne are only something like 16kg difference so it doesn't matter much.

 

[olek]

Thanks, I will use à correspondence table and try to compute.

Do you have a rough idea of the size of the lug pictured?

I seem to read they say the weld may be 0,7 of the thickness of the base plate.. If I am not confusing vertical eyed lug and the ones with a plate square to the eye part.

Also I am surprised that shackles are in metrics, this is a standard (Crosby shackles)
The shackle is only the part that goes on a chain or on the lug?! If they are in metrics the lugs should too, no?

 

[8ob]

This is being overthought and over engineered, that lug on the OP is massively over engineered for a ten ton lifting eye. There are lifting lugs on some heavy plant that we move about that have a fraction of the strength/material for a similar lift. I always think of the words of a sage fabricator I worked with yonks ago that would "engineer" this type of thing using his experience without drawings or calculations, he would remind me of the strength of a small bolt and in this case one half inch grade 8 on a straight lift would come close to ten ton. http://www.rdfasteners.com/pdf/boltstrength.pdf

Bob

 

[mike os]

With the info you have... run away.

Paul is spot on , you need a full spec

 

[olek]

I am just curious, also the fact that the piece is not intended for straight pull only make le understand computation may be useful. Anyway this site propose computing for different cranes lifts. I have seen enough cranes went in down because they where overwhelmed (youtube have a fair amount of these) to understand basic computation have their merit.

Of course not being in the trade, or an engineer this is really curiosity.
But I noticed the input data is not that difficult to obtain, and it is probably cool to know if the parts the welds are correctly dimensionned , the software tells you if you are wrong and where.