October 22, 2013
When using high performance equipment, be it a racing car or wheel loader, it is often the small maintenance checks that separate the high performers.
Wheel loader manufacturers provide detailed information on the regular preventive maintenance (PM) to keep your loader running as one of these high performers. Often, this can be covered in a simple walk around of the loader at the beginning of each shift.
“If you expect NASCAR-like performance from your wheel loader, then it’s important to treat it like one. If you treat your loader like a demolition derby car, then the results will reflect that,” says Jeff Lovell of Riverton, Utah-based Desert Basin Co., a Loadrite dealer/distributor.
While each manufacturer has its own maintenance inspection list, there are four key checks to be performed:
Grease all pins and bearings.
Inspect the cooling package.
Inspect the lift arms for damage.
Ensure the bucket is clean and clear.
As well as prolonging the life of your wheel loader, these simple checks will also help ensure that the onboard scales remain at the optimal level. These are important steps to remember as accuracy and cost efficiency of onboard weighing in wheel loaders continues to fuel its use among aggregate producers.
In terms of the user interface, it has no moving parts and simple sensors, so it requires very little maintenance. The condition of the wheel loader, however, can affect scale performance.
“Proper preventive maintenance has a definite impact on the performance of the loader scale,” says Stuart Wolper, Loadrite’s technical training manager. “Following these basic PM steps, any operator — from the beginner to the seasoned expert — can experience high accuracy from their scale.”
To elaborate on the common maintenance points, here are some simple wheel loader PM checks and the impact they have on the scale.
1) Grease all pins and bearings.
A simple, yet essential part of any preventive maintenance schedule is ensuring the loaders hydraulic cylinders allow for a smooth and easy lift. Pins and bearings should be inspected; fresh grease should be visibly coming through.
“There’s a difference between your loader getting greased regularly and your loader getting enough grease regularly,” Lovell says. “Often, when operators get busy, they forget to apply sufficient grease.”
If the loader has an auto greaser, it is important to check that the reservoir is filled and the system is working properly.
How can this affect your scale?
Wheel loader scales measure the pressure required to lift the bucket and convert it into weight data. If the loader is experiencing mechanical friction in the lifting cycle (due to lack of grease), this can be misinterpreted as extra weight. Also, if the lift is not smooth, the bucket can bounce. This creates spikes and drops in the pressure measurement and leads to false readings. By having a smooth lift, the scale is able to operate effectively and provide accurate payload weights.
2) Inspect the cooling package.
Much like a car, a wheel loader performs best when at its ideal operating temperature. If the hydraulic fluid is cold, it will be thick, and the loader requires increased force to lift and return. If the hydraulic fluid gets too hot, not only does it become thin, but it can be damaged and require replacement.
Loader cooling systems keep hydraulic fluid at the correct temperature and allow the loader to maintain peak performance. Airborne dust and debris can clog cooling vents, so it is essential that they are well cared for. Visual checks and cleaning help the cooling system. Many loaders are now equipped with reverse fan modes to blow out any excess debris.
How can this affect weighing?
Bucket weights are calculated by changes in hydraulic pressure, so the viscosity of the fluid is essential to weighing. A loader that is operating too hot will require increased fluid in the lift cylinder due to the thinning of hydraulic fluid; conversely a cold loader will require less as the fluid has thickened. Both scenarios will return inaccurate bucket payload weight calculations. By ensuring that your wheel loader is operating at a consistent temperature, the on-board scale will perform at its peak.
3) Inspect lift arms for damage.
Regular inspections of the loader will assist in identifying damage or anything out of the ordinary, such as damage to lift arms from falling debris. Check for damage or loose connections regularly, as this will make it easier in the future to identify any components which may be out of place.
How can this affect weighing?
Damage to a sensor or its connections can affect accurate performance. There is a wide range of position sensors which are used with onboard scales. Look for problems such as damage or cracks in the casing. For example, rotary or continuous position sensors should rotate smoothly without binding and have sufficient spring force against the boom. Check also that the trigger finger (rod or face-mounted arm) has not been bent or damaged.
4) Check the bucket.
Change in the weight of the bucket will also impact your loader. Excess wear or damage to the bucket teeth or cutting edge can negatively affect the weighing and prevent the operator from being able to accurately ‘zero’ the scale.
Loader scales may have settings present that allow for a range of attachment changeout. If you use multiple attachments, check that the correct attachment is selected on your scales and that it has been calibrated on the machine.
Finally, buildup of material (e.g. mud, clay, dirt) will negatively impact your bucket total, so ensure the bucket is clear of any built-up material.
“If the bucket holds 10 tons and it already has 2 tons of product built up in it, the loader is instantly losing 20 percent efficiency as it is running well below capacity,” notes Lovell.
How can this affect weighing?
The onboard scale will report on any weight that is in the bucket, therefore, if the bucket has buildup in it, it will register as weight. By ensuring the bucket is clean and clear, you can increase the accuracy of your scale.
It is also important to ensure that you have the correct attachment selected on your scales. Many loader scales have an option which allows for multiple attachments to be calibrated with the scale.
By ensuring that the basic preventive maintenance is completed on the wheel loader, not only is the life and performance of the machine prolonged, but it also ensures the wheel loader scale is operating as expected.
The four simple steps of greasing all pins and bearings, inspecting the cooling package, inspecting the lift arms for damage, and making sure the bucket is clean and clear will ensure your loader scales will maintain accuracy, often to within 1 percent of payload, improving your productivity and performance.
Article courtesy of Loadrite, a brand of Actronic Technologies – A Trimble Company.
For further information, go to loadritescales.com.