Boom failure

[Al Smith]

I have made a post in the accident forum,but felt the failure of the boom,that caused the mishap,should be in this forum.Yesterday,a local tree service,experianced failure of the lower boom section of a High Rager bucket truck.This accident,caused the arborist,to sustain a fractured forearm.The cause of the failure,was due to metal fatigue.The previous owners of the truck,had used it for years,without the proper holddown device,for the lower boom,while being transported.The failure point,was under the reinforcement piece,where the boomsets in the cradle,or lower clamp .These trucks,as I recall,originaly had a rubber type material in the clamp halves.This truck,had none.The resulting occilations,caused by transporting a loose boom, caused a wear mark,of about 40 thou,in the boom section.This,of course,was weak link.The resultant ,long term,vibrations,cuased the metal to fail at the point of oscilation.The damage,prior to the mishap,was not noticable.I might add,the present owner of the truck,has made a dilligent effort to properly maintain it ,in a safe working condition.Perhaps,this is a wake up call,it certainly is for me.

 

[Al Smith]

Another picture

Point of failure.

 

[Al Smith]

One more

Poor ole Ernie,had a nasty ride.He says he doesn't want to do that again.So ,call it devine intervention,karma,blind luck,or the hand of Almighty God,he is one fortunate person,to be still amoung us.

 

[Crofter]

Al, had there been a reinforcing piece welded on over the stress riser caused by wear, and thus covering the crack that developed unseen?

 

[MasterBlaster]

Ernie wuz a Lucky Dawg! :angel:

 

[DDM]

This looks like an older Unit . What is the approx Yr of this unit? Is it a 52' or 57'?

 

[Al Smith]

57 ft

I thought it was a 65 ft but was informed by the owner,it was a 57.I guess I had it confused with the contractor, I worked for.He had a 45 ft,and a 65 ft.,in addition,some dang fool{me} to climb poles. Oh,the truck is a 74 F-600,and I think that is the age of the boom also.

 

[Al Smith]

Missed the question

Crofter:As I recall it,the reinforcing plate,came new,from the factory.I used these old High Rangers,when thet weren't old Also ,it was only tacked on one side,and served more as a wear plate,than a reinforcement point.It did,in fact hid the flaw,as did several coats of thick paint.

 

[buckwheat]

Fire service aerials, including snorkels, are required to have periodic non-destructive testing, usually through ultrasonic imaging. similar testing on that boom probably would have discovered the weak point.

 

[Al Smith]

Ernies ok

He was out here,the day after the accident,naturaly a tad sore,but haven't seen him since.That is a real good point,on the boom inspection.Tom and I had discussed methods of inspection,and I came up with dye check,but that would have required to sand blast the area of inspection.Magniflux,was also talked about.Seriously,hindsite,is always 20-20,the main lesson learned,is prevention,in the future.I know,it was a wake up call in this neck of the woods,and most likely all that saw it,on this site.Perhaps,the silver linning to this cloud would be the prevention of a more accidents,not only in this industry,but in all areas where lifting equipment is used.

 

[MasterBlaster]

Magnaflux.

I haven't heard that term in thirty years. It's sthil called that? Cool. When I worked in the aircraft tire shop, that's what was done to the rims every time we rebuilt them. Black lights, closed area, some special powder...

 

[Al Smith]

Re Magniflux

I,myself,had almost forgotten about this type of testing,When I check for casting flaws,in my shop work stuff,I use the dye,which incidentaly,is made by the magniflux company.From what Tom said,it's not too costly.He's on the membership now,maybe he will add more.

 

[MasterBlaster]

Re: Re: Magnaflux.

Originally posted by netree
...so not much has changed for ya, eh?

Another good one, Erik!

 

[glens]

http://www.magnaflux.com/

 

[buckwheat]

"quote:
--------------------------------------------------------------------------------
Originally posted by MasterBlaster
Black lights, closed area, some special powder...
--------------------------------------------------------------------------------



...so not much has changed for ya, eh? "


now who's gonna clean the soda off my computer screen????

 

[MasterBlaster]

Ha!

Don't look at me, bro! :angel:

 

[Dadatwins]

Sent two older Hi rangers to dealer today for inspection, they had not been pinned and one had no padding left at the cradle. No paint left at all where it sits in the cradle. Dealer talked about a Magnaflux test on each unit. They are 1991 & 1993 so not really that old but all agreed they should be checked anyway. Of course no one knows why there was no padding on one boom and where the pins ever went to, thank you city job, but since seeing the picture of collapsed boom some eyes opened. Hope your buddy is recovering well and thanks again for posting this and bringing it some attention. Hopefully someones life will be saved from this.

 

[Pacific]

You don't see many of that antique equipment used in this area the rules are tough on cranes,buckets etc. To get insurance on a crane truck or a bucket truck the boom has to be inspected and certified every 3-4 years. The truck itself needs a inspection every 6 months the boom also gets a general inspection.

A boom should have its welds X rayed and inspected because steel fatiques and finally breaks. If a accident like that happened here the the owner of the truck would be grilled like a steak buy the worker comp board.

The guy in the bucket was ???? lucky that he didn't fall onto some high voltage power lines or he would have been well cooked.

 

[T_Bone]

Hi Al,

Maybe I can shed some light on the subject.

Both dye penterate and mag particle would be a poor choice (waste of money) as they both only check for defects with-in 1/32" of the surface.

X-ray or Ultrasonic would be the best NDT (non destructive testing) with Ultrasonic testing being the most cost effective.

From what I can see in picture No.3 (not much), this section of boom was broke for a long time. If you look at the right side you will see the shear point was started at the lower radius, continued down the radius to the lower horizontal web.

Notice on the left side at the top of the flange of the channel is where the shear started on this side and continued down to the left cornner radius then horizontal.

The point of shear upward on the left side had been broke for quite some time (years ?) as this seam is rusted.

Some time recently the left top radius corner thru too the top horizontal plate and continues thru the right top radius, sheared completely through. I would need to see a better picture of this area to tell exactly what happened.

Below the Top right radius cornner you will see where there was a existing surface crack for quite some time that continued to the lower top of the right hand radius.

I would need to see more of the truck and boom but I really doubt the boom hanger being unlined would have caused the boom to fail.

I personally would be shocked to see anyone certifiy this boom from the lower pivot point to the bucket witout a total boom replacement. Just too much liabiltiy to do other wise even with NDT being used.

AWS CWI (Certified Weld Inspector)
Member of American Society of Heating and Refrigeration Engineers.

 

[Al Smith]

I concur

This was my take of the situation,for the most part.I am not a certified weld inspector, but was, indeed,at one time certified on pressure piping and structural steel.I.ve since not needed the certs.,so they have lapsed.The boom,as of this writing,has been replaced,from the turn table up, with another,that was restrung,but then not used for several years.Tom,left for Indiana about 20 min. ago,to get new cables.It appears to me,that what kept the boom together,prior to the failure,was tension on the large lift cable,in reference to the boom angle.When it went in the over center condition,the flaw went from compression,to tesion,thus the failure.The company Tom is getting the cables from,said they can preform the testing of the boom,once it is restung etc.As I understand it,the old boom was an "fI" unit,the replacement is an "EI" unit.