Failure of our 15 ton crane

[No_Bivy]

Mark,
What circumstance would you want to remain tied to the crane?

 

[treemann]

I had a storm situation this spring where I had no other trees to tie into or to use to support the fallen tree.

My work pocedure was to sta tied into the crane until the cut was made. Then the operator would lift the load slightly. Once the load was in the clear and the fallen tree did not shift I would lanyard in to the tree and the operator would take the load to the work area. I repeated this procedure on every cut that I thought the tre could shift or fall.

 

[No_Bivy]

Would a second crane have been an option?

 

[treemann]

No there was barely enough room for one crane.

 

[No_Bivy]

Were you tying in to the ball or the boom?

 

[treemann]

above the ball on a clevis with a friction saver on it

 

[Colin]

If the hook has a functioning snap I have no problem cliping into it. So sue me.

 

[Mark Chisholm]

Like Treeman says. Sometimes the safest solution for the climber is to be tied into the crane. If there is no room for a lift or extra crane, then that might be a good reason to tie into the boom and go easy.

 

[RemovalWizzard]

OK here is the picture that i promised..... Brace yourselves it's painfull

 

[RemovalWizzard]

sorry that it's sideways, i'll try to fix

 

[Mahk_Adams]

Thanks Rob.

Is that the piece that you picked in the bottom left hand corner of the photo?

 

[Jamin_Mayer]

[ QUOTE ]
Brace yourselves it's painfull

[/ QUOTE ]

Dang!

 

[Colin]

When you swing that jib, you'd better back off from the weight. Or ELSE.

 

[RemovalWizzard]

i was still 20% inside of my charts... that crane (or boom truck) is really too small for what we needed it for. lesson learned!

 

[arborvor]

Mahk
Show the pic to Phil He'll remember the property. One word "Concrete" He did a removal there the tree was filled with concrete. I think the stump of this tree was also filled.

 

[tod_k]

The only part I do not understand is that at full boom extension and the jib on the machine should tip not brake. The crane training I received fron National made that quite clear. And I think the info is in the operating manuel.

 

[Cameron]

I would think it might have to do with the radius of the pick. Our previous crane operator that we rented crane service from cringled his third section of the boom while trying to pick up a concrete sewer basin. His load moment sensor was not working at the time. The crane allowed him to pick the concrete basin about six inches before hearing a loud "pow" sound. He said it was like a gun shot going off. The crane dropped the load but the boom sat bent in the air and did not fold. He was unable to retract the crane. The crane was disassembled on site. I was told the total repair bill was around $27,000.00. The crane being used was a 23.5 ton terex. Sad thing was the crane was less than 2 years old.

 

[allmark]

Tod are you saying the tip should fail before the last hydraulic section??? This is not true. If the third section had been abused it could be weaker than the jib.if the jib wasnt out during previous picks.

 

[tod_k]

The crane should have tip over.

 

[Mahk_Adams]

This is part of the capacity chart for a 30 ton National crane. It shows limits for a 31 to 105 foot boom with 27 and 48 foot jib, single part line, and full span outriggers.

The shaded areas (in the scan these areas seem to just have some scribbles ging through them) are structurally limited i.e. if the crane lifts more than the amount on the chart at the given radius and angle, then there could be a structural failure.

The non-shaded areas are stability limited i.e. if the crane lifts more than the amount on the chart at the given radius and angle, then the crane could tip over.

The crane shown with the bent boom is a 15 ton so the charts for that crane will be differen. I haven't seen them, but there will probably still be structural limits for some configurations and stability limits for others.