Failure of forestry crane

[Brushcutter]

I will load some photos which will show the manufacturer should have picked it up. But first could someone tell me how to get photos on here.

 

Click the little paper clip and it will let you upload them.

[john burgess]

Hopefully you can see from the pictures where the flaw is in the casting

[elfinwood saws]

looks like it,s got worms!

[Brushcutter]

Poor. What do the manufacters have to say for themselves?

[Breezeblock]

from what i can see it looksthat there is enough material thickness in that area and the casting has a small flaw in it but i would say its down to overloading

[john burgess]

from what i can see it looksthat there is enough material thickness in that area and the casting has a small flaw in it but i would say its down to overloading

 

picture one shows a small blowhole at the top on the right-hand side you will see slag in the middle of the casting whets failed and this extends approximately 3 to 4 inches. As to overloading from what I understand it will be impossible to overload on pickup because of pressure relief valve in the valve block which prevention from picking up too much load. Once you exceed the safe working load the valve opens and it bypasses. Which prevention overloading the crane having said that the crane is only used to pick up horse **** so I don't think it was overloaded.

[Breezeblock]

picture one shows a small blowhole at the top on the right-hand side you will see slag in the middle of the casting whets failed and this extends approximately 3 to 4 inches. As to overloading from what I understand it will be impossible to overload on pickup because of pressure relief valve in the valve block which prevention from picking up too much load. Once you exceed the safe working load the valve opens and it bypasses. Which prevention overloading the crane having said that the crane is only used to pick up horse **** so I don't think it was overloaded.

 

relief valves only limit hyd pressure not an overload i presume this has an extending arm on it try next time pick up a heavy log and then extend out there you go you have overloaded it. continually picking up 100% of its lift capacity will shorten its life span where as if you picked up 75% of its capacity it may last 4 times of which it has

[Chris Sheppard]

relief valves only limit hyd pressure not an overload i presume this has an extending arm on it try next time pick up a heavy log and then extend out there you go you have overloaded it. continually picking up 100% of its lift capacity will shorten its life span where as if you picked up 75% of its capacity it may last 4 times of which it has

 

Every crane I've used, if you picked up a big log and extended, the relief valve would start to go and the boom would start to creep down.

 

Surely if it can pick somethign up then it is within it's safe working limit other wise it wouldn't be able to pick it up in the first place

[robbo 110]

relief valves only limit hyd pressure not an overload i presume this has an extending arm on it try next time pick up a heavy log and then extend out there you go you have overloaded it. continually picking up 100% of its lift capacity will shorten its life span where as if you picked up 75% of its capacity it may last 4 times of which it has

 

the idea of a relief valve is to prevent an overload, i disagree with the above comment!!!!

[b101uk]

Well you can definitely see an inclusion and that the crack over time has propagated from the inclusion then the last bit mainly at ~170deg to the inclusion has failed last.

 

However the critical bit will be if the PRV in the valve block was set at the correct pressure as not to cause overload, if you haven’t cleaned up the valve block DONT as the manufacture will more than likely want to test the valve block to check output pressure.

 

It is known that some people adjust the PRV to lift more which in turn overloads the crane, even some people who fit crane tweak the PRV a little to much, so only if it can be proven the PRV in the valve block was set correctly will there be comeback on the manufacture and any comeback on the dealer will depend if they still have the pressure test info or tested lifting weight from the PDI befor it was sent out to you.

 

Overload of a crane even when the PRV is set correctly can happen if upward/downward bounce is induced during lifting of a near maximum weight load.

 

Has the crane ever undergone a SWL test as sometimes they are require to increase the pressure above normal and may have forgot to lower it back to the proper pressure after the test.