CALIBRATION SERVICES
Torque tools are precision instruments and should be serviced, calibrated and tested on a regular basis to ensure repeatable accuracy and optimum performance.
Xcalibration is a specialist in calibration services with a focus on the highly specialised needs of the torque control industry.
The Australian Mining Review spoke to Greg Hender of Xcalibration about how the company is constantly gathering feedback from customers to continually evolve and adapt to changing market requirements.
Greg explains how their team goes above and beyond to calibrate, service and monitor the condition of equipment to the highest standards.
Torque tools are thoroughly tested to address uncertainties in the entire calibration process.
By providing a snapshot of the health of the tool as well as its output, errors can be detected and addressed before they result in wear or damage to mining equipment worth millions of dollars.
This will prevent downtime but most importantly, it will prevent catastrophic incidents that can result in severe injury or even death.
History
Greg has been involved in the torque calibration industry for more than 20 years and has been operating Xcalibration since 2008.
‘’Onsite calibrations have always formed a big part of our core business and complement our fixed calibration laboratory,’’ Greg said.
Xcalibration started out primarily doing torque calibrations, which also encompasses sales, repairs and adjustments as required, covering torque wrenches, hydraulic wrenches, manual and powered torque multipliers and testing of torque machinery such as track bolting machines.
The company’s torque capabilities extend from one foot-pound (ftlb) up to 25,000 ftlb. Its calibration capabilities have expanded in line with the evolving requirements of the mining industry and now cover testing of pressure gauges, automatic tyre inflators and dimensional testing.
Torque wrenches
Torque wrenches tighten nuts and bolts to a specific torque value.
‘’The brands and types of torque wrenches are many and varied, however we only sell high quality ones so they will keep performing as required,’’ Greg said.
They are also repairable as parts are held in stock.
They are used for many types of bolting jobs but become particularly important when used in critical applications, such as engine rebuilding.
For safety applications such as wheel nut bolting, there are new mechanical/ digital combination wrenches which allow the user to configure software for vehicle types, axle groups, stud settings, and a process which must be followed for job completion.
‘’This gives the process traceability and accountability which can be downloaded from the tool or the Bluetooth software,’’ Greg said.
As a minimum, all torque wrenches should be calibrated yearly or every 5000 uses— whichever comes first.
However, the user should consider the amount of use, the working environment and the critical nature of their bolting application to assess whether these calibration intervals should be reduced.
‘’I have a customer which gets to 5000 uses within three and a half weeks so I recommend the wrench be tested every month, but it is up to the user to determine if a calibration interval is sufficient for them,’’ Greg said.
Truck companies often opt for more regular calibration due to the regular and critical nature of their tyre usage.
When a torque tool comes in for testing, its model and serial number and owner details are recorded.
But more importantly, the team at Xcalibration will form a sound understanding of the who the customer is, which will determine how they treat the tool.
If it is of a critical nature, it will still adjust even the smallest of errors to bring it back
as close as possible to the nominal torque setting, to extend the life of the calibration.
Some of the digital wrenches can achieve outstanding accuracy, within a 0.2% margin of error while mechanical wrenches can achieve 0.5%.
Higher standards
The accuracy of a torque wrench is specified by the manufacturer, but the only way to be sure the tool is consistently providing repeatable and accurate results is to periodically validate its performance.
The old Australian torque wrench standard AS4115:1993 and international standard ISO6789:2003 have both been withdrawn and should no longer be used.
These standards have now been superseded by the new standard ISO6789:2017, part one and part two, to which torque wrenches should be calibrated.
It should be noted that if a customer has ISO9001 quality systems in place, they should consider asking for the new standard covered by part two to ensure they have a valid Certificate of Calibration.
This addresses the uncertainties involved in the entire calibration process as opposed to part 1, which is only a Declaration of Conformance.
Xcalibration carries out all its torque wrench calibrations in accordance with part 2 of the standard.
This involves roughly five times the amount of testing that is carried out to adhere to part 1.
‘’You’ve actually got to test the repeatability and reproducibility so it is a lot more in depth and a lot more work,’’ Greg said.
‘’But the end user gets a much better result as we are able to provide them with a comprehensive report.
‘’This allows them to meet their internal quality standards but also means they cover themselves from a liability point of view.
‘’If you only have a declaration of conformance and a wheel comes off a heavy vehicle and kills someone, you may be legally vulnerable.’’
‘’As best practice we provide uncertainty calculations throughout our other torque processes and include them for hydraulic wrenches as well as manual and powered torque multipliers,’’ Greg said.
Manual and powered torque multipliers
The traditional manual torque multiplier is still well used in the mining industry and should be calibrated to give the user confidence in the torque ratio that the multiplier delivers.
The high-quality ones are generally close to the stated OEM values whereas some of the lesser quality ones can vary wildly from manufacturers claims and should be used with caution.
‘’They might give you a ballpark figure of 10-1 but you might find that it might be no better than 8-1 or even 4-1,’’ Greg said.
Poor machining means that when they are under load, internal friction robs the torque, which does not get applied to the output.
‘’The operator may think they are inputting 100Nm and getting 1000Nm out when in fact they are only getting 400 out and there is no way of testing that on site.’’
The performance of all torque multipliers can change over time due to wear, lubrication and damage, so it is good practice to have them calibrated.
Powered torque multipliers have a large presence in the mining industry due to the nature of equipment that is being regularly serviced and maintained where very high torque values are required.
Commonly referred to as Torque Guns or Nutrunners, these high-powered tools are used for applications such as ball mills, wheel nut bolting, cutting edges, undercarriage work such as tie rod ends, suspension bolts and struts, track plates, and rollers and idler cap bolting—to name a few.
Traditionally these have been air powered with shortcomings related to the air supply, so the informed user needs to be mindful of the air pressure and the supply to the tool while in use.
‘’You have a big multiplication factor there so if you have even just a tiny drop off in the performance of your air motor, that can drastically affect the output of the square
drive end of the tool by a significant factor,’’ Greg said.
‘’Not only that, you may have that hooked up to the airline and you may be using that out in the paddock 50 meters away from the compressor, so you actually get a lot of drag internally in the airline.
‘’And so you'll actually get a big drop off in the pressure, which won't be able to keep up with the demand from the tool, so you won't get the correct torque result.’’
The user needs to be very aware of the size of the airline and whether it needs to be increased to avoid drop offs in torque.
Technological improvements
The trend is now toward battery powered torque multipliers, with advancements in technology and software ‘’coming a long way’’ in the last three to five years.
They are not subject to air supply issues and they are safer and easier to use without the concerns over using airlines, which can be a trip hazard and make it more difficult to work at heights.
They can also come with software that includes configuring batch and sequence processes with the ability to record these achieved values that can be downloaded later.
For example, the software could be programmed so that it prompts the operator to fasten a bolt at a particular time in a predetermined pattern.
For example, a company that manufactures hydraulic cylinders might have to tighten 10 bolts and they may decide to do that in three phases.
The first phase will tighten the bolts up to 50% at 500 Nm, the second phase at 750 Nm and the third at 1000 Nm.
A display screen will prompt the user to begin each phase as soon as the 10 bolts have been completed, and the tool can also be used for angles as well as the torque.
To ensure the pneumatic or battery powered torque multipliers are fit for duty they require regular servicing and calibrations.
Xcalibration monitors the condition of the tools, such as air and battery powered
multipliers, through calibration charts and tables, which covers both SI and imperial units for torque and pressure where required.
This includes the logging of air pressure versus torque output, which enables the torque multiplier to be set at the right pressure.
‘’The charts give you a snapshot of the output of the tool, but it also gives you a snapshot of the health and performance of the tool,’’ Greg said.
Linear patterns indicate no undue wear or serviceability issues while non-linear results indicate a problem, such as a gearbox or motor issue, requiring further investigation.
All of these calibrations include uncertainty calculations as part of the process to ensure the best possible outcome for the user.
Hydraulic wrenches
Hydraulic wrenches have a place in industries when extremely high torque requirements are called for, where it is not unheard of to see these tools being used up to 25,000ftlb capacity.
More commonly they are used throughout the mining industry in the 1000 to 10,000ftlb capacity range.
‘’As they are capable of such high torque values, they need to be used with care and the user must understand how they work before attempting any bolting jobs,’’ Greg said.
‘’Advantages include being able to use them for bolting as well as unbolting where time and wear cause bolts to become difficult to remove.
‘’These are extremely accurate tools when used with a hydraulic pump that has a calibrated gauge fitted to it.’’
These are available in a square drive or cassette style arrangement covering a large torque range.
‘’The advantage of the cassette drives is they can slip it over a nut or bolt where there is limited access whereas a square drive may not have that ability.
‘’As the cassette style of hydraulic wrench is quite common, we have a large range of
square drive adaptors in our calibration lab to cover all sizes from 19-135mm cassettes to be able to perform the calibrations.’’
Calibrations performed on these tools are also presented in chart and tabular format for ease of use and include uncertainty calculations as the standard.
Other testing for the mining industry
Xcalibration has been involved in testing and calibrating some of the Caterpillar and WTC track bolting machines.
This is a process where new earthmoving tracks are assembled and old ones refurbished with new track plates.
The track plates require bolting to the track chains (or links) and are bolted with either a hydraulic or electric bolting gantry over a track bench.
‘’As the bolting process is critical for the long life of the tracks, the bolting machines require periodic calibrations in situ whereby we use strain gauge torque transducers introduced to the bolting machine and track assemblies to check the performance of the track bolting machine.
‘’Testing can also cover the calibration of load cells built into these machines.’’
Pressure gauges
Calibration can ensure hydraulic wrenches are performing within their specified ranges, but the results may be affected if a separate pump with a pressure gauge is attached to it.
As these gauges control the input pressure to these tools, it is therefore critical to ensure that they are also are calibrated to be fit for purpose.
‘’As a result, we expanded our capabilities many years ago to include calibrations of pressure gauges, pressure switches and pressure transducers used throughout the mining industry,’’ Greg said.
‘’This helps to give the user confidence in the complete package being calibrated correctly.’’
Tyre inflators
Xcalibration now offers Automatic Digital Tyre Inflation systems for sale along with full service, support and calibration.
These can be configured in a variety of ways which may include configuring the software for different customer outcomes or incorporating Wireless Temperature Transmitters to sense tyre temperatures and adjust pressures accordingly while inflating.
These allow the user to step outside of the tyre blast zone and control the inflation process from a safe distance.
‘’Tyre inflation is actually a very dangerous occupation—if a tyre blows out, it has the potential to kill anyone within 20 metres in front if it,’’ Greg said.
All pressure calibrations for pressure gauges and tyre inflators are performed to the MSA Test Method 1 and 2 which are superior methods to the outdated Australian Standard AS1349:1986.
Always evolving
Xcalibrations’ capabilities now also include dimensional calibrations due to customer demand, enabling calibration of items such as dial gauges, micrometers and callipers.
‘’As part of our continuous improvement program we strive to deliver the best result possible,’’ Greg said.
‘’So we are always looking for new equipment and processes including industry approved staff training to ensure they are qualified for the roles they undertake.
‘’This will allow us to deliver the best possible outcomes in the field of calibrations for the end user.
‘’Feedback from our customers and auditors is considered important in our efforts to evolve and adapt to changing market requirements.’’
Due to its vast experience in the torque industry, Xcalibration can offer calibrations and repairs for not only its end user customers, but also to others in the calibration industry where this is not their primary area of expertise.