Looking for some help. Have recently started a new job working in a quarry and part of my job is loading trucks. Now I don't have a problem loading trucks as have been doing this for a few years but, This is only the second time I have had to use scales. It's a load rite express system in a cat 972H. The problem is first up in the morning it loads heavy, eg on 12 tonne truck if the scales say 11.800 the real weight would be somewhere between 12500 and 13 tonne. And yes I have checked that the bucket is empty and have zeroed the scales, and it's not just me. Another operator there used to have the same issue with the cat so he swapped to an older volvo and doesn't have the same issue. Oh here's the kicker, after about 3 hours it all seems to work fine? Any ides
No experience with the Load Rite, but I know the Cat PCS systems we have need to be cycled a few times to warm up things like oil and the grease in the pins. Not 3 hours though! Also if not equipped with auto lube system they recommend that the loader linkage be grease everyday.
I think relative humidity and temperature can affect springs and scales. Especially if the weather changes dramatically over those 3 hours.
Get the implement oil temperature up to normal (85C or higher) before starting to load, on cooler mornings this usually involves stalling out the hydraulics. The implement oil temperature has a major bearing on the accuracy of any PCS system
I agree. With the loadrite you are sensing boom lift pressure to calculate weight. Cold oil has a major effect. Could be that the 972 takes much longer to warm up than the Volvo.
Thanks for the replies. The loader does have auto greasing. It's a strange one to work out. Can not really wait till it warms up as such as trucks are lined up when we start, so just time for a normal prestart and let it warm up a bit. I then do a few warm up lifts and reset the zero. Getting the hang of it a bit , just have to get feedback from the weigh bridge and adjust as I go.
Spend about 2 minutes with the engine at high idle and the tilt lever held in the fully racked forward position. That'll get some heat into the hydraulic system PDQ.
We have trouble with the loadrites on R2900 LHD's too. Now given the environment and the work cycles they work under I would have thought oil temperature could be near ruled out. When a new operator comes on shift the whole machine is still very warm to the touch and the temp gauge is not all that much lower than normal operating range. They just seen possessed, sometimes giving 15 tonne inaccuracies over 3 to 4 buckets. Usually the loadrite weighs heavy, but not always. I can see how it would be very easy to get into trouble if you relied totally on a loadrite. How accurate are they actually meant to be? The shock loading that a loader experiences, especially if ride control is turned off, can't be good for accurate instruments.
I feel that much of the problem with inconsistent weights once the machine is fully warmed up could be traced to operator technique or floor conditions where it is working. As mentioned above all these scales work of hydraulic pressure in cylinders while in the calculating range of the ECM. A jerky operator or rough surface the machine is moving over can cause spikes in the pressures the sensors are seeing. I have done the calibration on a few loaders with the Cat PCS scales and when finished I can sit there and lift the same load several times with at the most a 0.1 ton variation. Then when it goes out to an operator get complaints that they are reading 1 ton high on one truck and then 1 ton low on another. Worse yet is when one operator has to let another use "his" machine for a day. Then when regular operator gets back in the loader next day the substitute operator gets blamed for making all kinds of changes in the calibration. I really wonder what an operator could due to the calibration that would to cause a random error like being high on time then way low on the next truck?
Hydraulic temp, engine speed, and lift speed all factor into how accurate the system is.