Information about welding on dock levelers

By Pat

Date 01-24-2010 19:32

At work we are having some problems with welds cracking on dock plates that we have repaired.. Most of these repairs are on the hinges where the lip that folds out on to the truck trailer. The hinge is made from high tensile mechanical tubing and is 1 1/2" diameter with about 1/4" wall thickness. Through these hinges there is a 1" diameter hinge pin. Initially the hinge tube welds will break from what I suspect is fatigue. We then grind out the old weld where we can, then weld them with 1/8" 7018. In one repair I went back to it about 3 hours later to wire brush and paint the repaired area. The weld had cracked within this 3 hour period even with no loads going over it.

I am wondering what steel the dock plates (tops) are generally made out of. It must be something other than ordinary A36 mild. Most of the guys will not take the time to pre heat, and I am thinking this may be part, but not all of the problem. Should we be using a different electrode made specifically for dissimilar metals, do a pre and post heat, or am I entirely missing something. We have 48 of these dock plates that are inspected weekly. On the average we find cracked welds on 1 of them about every other week. All advice would be greatly appreciated.

By oklawelder (*)

Date 01-24-2010 20:05

on high tensile steel such as frame rails etc. i use 9018 and pre heat . Where is it cracking at , weld itself , or between weld and steel ?

By Pat

Date 01-24-2010 20:38

oklawelder,

Thanks for responding. For the most part what we are seeing is the welds are breaking at the plate, and the bead on the tube is still intact. I am wondering if the initial cracking at the plate is because the plate may be flexing when a lift truck goes over it. If that is the case I would say we probably need to contact the manufacturer, because it should hold up. All of the trucks used to load trailers are under the maximum weight for these dock levelors...........thanks again.

By oklawelder (*)

Date 01-24-2010 22:56

you stated that had cracked with no loads on it , i would see if i could get a spec, sheet if possible and see what steel it is built from and go from there .

By 803056

Date 01-25-2010 13:36

Send a sample of the loading dock frame to a lab for chemical analysis so you know what you are dealing with. Once you know the chemistry you can make some decisions based on sound engineering information rather than supposition. Using the SWAG method is rarely a satisfying experience.
Here’s what we know:
Material – it rusts, it must be steel
Alloy – I don’t know
Tensile strength – I don’t know
Electrode – E7018
Was the electrode properly stored – In an oven set at 250 deg F – I don’t know
Taken from sealed steel can – I don’t know
What failed – along the toe of the weld against the steel frame
What loads were required to cause the failure – no load other than residual stress
What joint detail was used – Removed existing weld where possible
Thickness of material – I don’t know
Was preheat used – yes
What temperature – I don’t know
Is the loading dock properly leveled and installed per manufacturer's directions - I don't know

So, you can see there are a lot more “I don’t knows” than there are “I knows”, and until we have all the answers all we can say is “I don’t know”.

Best regards – Al

By Joe Davidson (**)

Date 01-26-2010 00:21

Hi Pat, I have worked on dock levers for over 5 years before rigging out and going to the ROW. May I ask who's dock plates are installed there? DLM, Poweramp are better than most due to heavier steel used in construction. Rite-Hite, Kelley, Blue Giant, Serco, Maquire, Pioneer, etc. are in my opinion not built as well. You also need to know that if you are running 3 wheel fork trucks, most levelers won't hold up unless ordered to handle a 3 wheeled truck. I have not seen a hinge tube crack after welding from residual stress. I have had to reinforce hinges to stop cracking. I have been to Poweramp's factory and seen how they build them, and they are regular mild steel. But keep this in mind tool. I have seen levelers ordered with special hinges to withstand corrosion in freezers, salt warehouses, etc. so it is possible the are something different than mild steel. I would get the serial number and call the manufacturer so you know what you have. Good luck. Joe