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 06-13-2012, 18:54 Post: 183881

Join Date: Jun 2012
Location: belgija
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Posts: 2
 Komatsu PC230-8 problem with hydraulic hammer

I have a problem with one of ours hydraulic excavator Komatsu PC230-8, the problem start when the machine have around 3600 working hours, we install on that machine hydraulic hammer Furukawa F35xp when the machine have around 2500h.

This hidraulic hammer work very well on that machine, komatsu PC230-8 can gave 210l/min with each pump and Furukawa F35xp need 160-180bar and 180-220l/min.

The problem start on last summer when we used hammer. When the hydraulic oil reach 62"C (temperature sensor is under pumps on the oil intake tube) the hammer start to lose blow power and the stroke of the hammer slow down greatly, hammer almost stop.

When the temperature decrease below 62"C the hammer start to work like new.

After that we call technician. That technician suspect that hammer is going to fail very soon but it did not happen because we work with that hammer for a very long time after that diagnose. We try install that hammer on the another komatsu PC230-8 but that machine never exceed temperature of 57"C working with that hammer (the same weather conditions).

So we call another technician and he suspect that the pilot valve beneath the cab that operate the hammer and other attachment is out of order, because he measure the servo pressure on hydro pump and the gauge show 30bar but on the servo valve beneath the cab servo pressure have only 18bar when the hammer start to lose blows power, before temperature reach 62C servo pressure was 30bar on that valve.

We think that we found cause of our problem but after we change the pilot valve the problem was still there, maybe we got few celsius with that so the hammer slows down on 64"C.

I need to mention that one day hammer slows down even on 74"C but I do not way because we did not repair anything on the machine, that day the weather was hot and air was dry.

Ok, we call the third technician and he install all new filter (main hydraulic filter on top of the reservoir, hammer line filter, servo line filter, he even inspect and clean intake filter in the bottom of hydraulic tank), we fill hydraulic oil almost to the max line in the reservoir (oil is SEA 10w). After that the hammer slows down on 67-69"C. It is a little improvement but not much So Sad

One thing is happening when the hammer slows down, if I use command stick for lowering the arm while the hammer slows down the command do not have the force to put some excavator body weight to the hammer.

We install flow meter on the hammer line and measure the flow and pressure and we got around 160bar and 160l/min, before of that technician adjust overflow pressure valve to 160bar (this valve is located on the distributor intersection, I do not know what is the english word for that oil distributor in the middle of the machine )
The gauge in some moment show 160 bar and 95l/min (the throttle is always on max when we tested with flow meter) but when I disconnect the hammer with my foot command and start again the gauge show around 160 bar and 160l/min.

In last test with flow meter we started when the hydraulic oil temperature was on 51"C, we read pressure on 160bar and it show 160l/min, while the oil is getting warmer the pressure/flow fluctuated only 4bar and 4l/m (156bar and 156l/min). In that test I hold hammer command "ON" the whole time until the oil temperature reach 74"C. I was surprised that the pressure/flow did not drop when the oil temperature reach 67"C and more, pressure/flow was in constant state.

Today I used hammer and in one moment the oil pumps start to get loud like the valve is closed and the oil can get out of the pump, in that moment hammer start to slow down when I disconnect foot command for engaging hammer I try to lift boom and it barely move. I stop the machine and the oil pump was boiling hot, maybe 100"C but the oil was only 64"C. After one and a half hour I started the machine and it work ok.

Then we try to disconnect hammer from machine and the oil returns line was pressurised (not much but it was) that never hapened before. I need to mention that technician replaced some pressurised bottle beneath the cab (our was empty and because of that we did not able to lower the boom (arm) when the engine was off.

We check the ball valve on the arm where we connect hammer pipe, they are ok.

And the last thing that I notice is that pressurised line that go out from the two oil pump is hard on touch and like the high pressure is on them even when the engine is off.

Do you know what is wrong?


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