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Big companies are allways right????

Number of messages: 7

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oliveiraport
Santarem, Portugal

Hello
My name is Oliveira I live in Portugal and I have, together with my sons, a small company that deals and provides maintenance to forklifts. I've been an Electromecanic Engineer for the last 34 years but for the last 4 years I'm in the forklift business.
I provide maintenance mostly for a client who have around 80 Crown machines, and for the last 3 months I've been having problems and I'll put my question so that I can have some trully good technical advice for it:
Some of the new forklifts I have in this clients are showing up with the following problem, the forks descend very fast when I stop the machine with the forks up, and I think the problem is something to do with the hidraulic valves. I've exposed the problem with the manufacturer and the dealer in Portugal and they told me that the forks are legally allowed to descend at the rate of 10mm per minute (60cm/hour) and the problem is that I haven't purged (purge=take the air out from a closed sistem) the hidraulic sistem. Notice that from 25 new forklifts only 3 are making this.

    IS THIS RULE TRUE (10mm per minute)???

    IS THE DESCENDING OF THE FORKS CAUSED BY NOT PURGE THE HIDRAULICS???

I really hope that I get your attention and all the information you can provide me will be very helpfull and I will provide everything I know to help you in the future with whatever you might need.

Thanks,
                             Joaquim Oliveira

Posted 22 Apr 2008 04:41 AM

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megatron
Thessaloniki, Greece

thats right, normaly 100mm in 10 minutes or 10mm in 1 minute

Modified 22 Apr 2008 07:04 AM
by poster.

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roadrat
North Carolina, United States

It is a good practice on a new machine, to fully extend the mast 5 or 6 times to purge the lift cylinders of air. Forklifts normally do not have "locking" cylinders like a crane or man lift. A certain amount of "drift" is normal with a forklift when the hydraulic oil is at normal operating temperature. Excessive drift is an indication of a problem. It is advisable to find a service manual for the specific machines you have and see what is acceptable, taking the"word" of someone you do not know is not good and certainly not SAFE. If these machines are new and still under warranty, then the dealer is obligated to check these machines for problems.

Modified 22 Apr 2008 09:53 AM
by poster.

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megatron
Thessaloniki, Greece

look at the section of UVV(European-standards) STILL-Software (8.7), 100mm in 10 minutes is acceptable

Posted 22 Apr 2008 02:36 PM

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edward_t
North Carolina, United States

This will vary with the amount of surface area the lift cylinders internal seals have, really large (full container handlers like Taylor or Kalmar) may even have a faster rate of drift. Usually the rate of drift is calculated at the forks, but should be more accurately calculated at the cylinder, (but the forks rate of drift will be x2 the cylinders rate of drift, unless the chains do some more multiplying of the mechanical advantage than just one up and one down).

Some machines do have a "bleeder" screw near the top of where the oil will be, and the air should be bled out (carefully, not with the forks high in the air, and do not remove the screw completely, just raise the forks and carriage a inch (26mm?) off the ground, (if at all) and loosen the screw enough to allow air to escape, when oil runs from screw, you have bled the air. On a Crown, I would look for a large head common slotted screw about an 3 or 5 inches below the gland nut, in the lift cylinder, usually the stage that lifts first, but possibly in all the stages.

This is one of the reasons we (in the USA) have rules that say when ever you park a forklift, the forks must be all the way down.

In my experience, air in the cylinder usually does not cause drift, as much as "bounce", (is lifting smooth, with no load?) but I can see how drift could happen in a new unit.

And Like roadrat said, if it's under warranty, make the dealer that sold the units fix them, and let the factory pay for it.

If these are order-pickers (man-up trucks) it may just be a defective or not tightened emergency lowering valve.

Big companies do have more chance to test problems than little companies, and do have more eyes to see a possible problem, and create a database of those complaints and what really did cure the complaint.

Modified 22 Apr 2008 08:07 PM
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johngen
NB, Netherlands

its normal en accepte 100mm in 10 min Are the cilinders inside not defect and the sealing good.

Regards

John.

-------------------------
Email harlekein@hotmaildotcom djdotdj@onsmaildotnl

Posted 26 Apr 2008 06:08 PM

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luca_l
SAVONA, Italy

Dear Sir
I dont think so bot of them
Ter is one % wer the fork can lowering wail the machine is inert
but if i remember well is somthing like millimiter per one hour (according to Italian rules )
The presence of bable even big quantiti of air in the jaks can give the incovinient to make the lifting or the lowering elastik with sudenly muviment but only wail the muviment untyl the aire rais to the same pressur of the oil (that is somthing that appen immidiatly) after that the air dosent caus any muviment.
I have some client in portuga ( Acore Island Graziosa & Ponta del gada FACIL COMPANI)
Beast regards
Luca Lodigiani

-------------------------
love yours job and it well be so esy

Posted 1 Aug 2008 07:55 AM

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