Off-road vehicles are used extensively in the mining industry. The correct maintenance and follow-up of these machines are essential to achieve optimal productivity levels.
One of the allied techniques for the correct inspection and predictive maintenance of this equipment is vibration analysis. However, traditional vibration collection methods in off-road vehicles can pose several risks to employees. Thus, Vale Carajás sought solutions that would bring safety, quality of analysis, and, consequently, increase the reliability and availability of this type of asset.
Despite all the robustness characteristic of this type of equipment, which is designed precisely to work with very heavy loads or with sudden movements, keeping this type of asset in good operating condition can be challenging. Due to the load they are subjected to and the environment they are exposed to, the chances of structural damage, suspension damage, or even damage to their rotating components, are great.
Regarding rotating components, inspections are required with a certain frequency, in order to ensure the health of the asset as a whole and the safety of the people operating them. In terms of operating condition monitoring, vibration analysis is one of the most widespread and effective techniques for detecting potential failures, and it is widely used on this type of asset.
In the context of Vale’s Carajás Mine, located in the state of Pará, when it came to collecting vibrational data from this equipment, some challenges were part of the inspection team’s daily routine:
1) Difficulty of access
The structure of an off-road vehicle, whether it is a truck, an excavator, a drill, or any other type, is usually quite sealed and protected, for the sake of the equipment’s own robustness, not to mention that some inspection points in these machines are located at height. All this makes the manual data collection process more difficult and often leaves inaccessible points for data collection.
2) Exposure to risks
Even because of the issues mentioned in the previous item, besides other factors, such as the transit of large equipment, the inspection activity can expose inspectors to risks.
3) Equipment in operation
Another point is that to perform condition-based monitoring (CBM), through techniques such as vibration analysis, the equipment must be in operation. This need increases the risks and difficulties for the inspectors performing data collection.
Given the situation and the challenges cited, Vale’s Serra Norte Predictive Maintenance Supervision Team invested in technological innovation to improve the inspection process, aiming at greater safety and reliability of the equipment.
Project and implementation
Next, we will discuss the project to implement this modernization in data collection at the Carajás Mine.
I. Wireless sensor installation and collection via App
The first initiative occurred in off-road trucks, with the installation of sensors on several components, with emphasis on the motor wheels. In this component, before the installation, the vibration collection procedure was done manually and offline, involving 5 professionals from different areas.
The vehicle had to stop so that a professional could access the truck and remove the pinion from the wheel. A complex and accident-prone process. After removal of the pinion, it was still necessary to disassemble the motor wheel frame. Only after this procedure would it be possible to attach the accelerometer to the wheel and start data collection.
This process was similarly applied in the measurement of various other components, where inspectors often had to bend down, get close to the desired component, such as motor, pumps, compressors, and then connect the accelerometer to collect the data.
Many of these procedures, besides being unsafe, resulted in the need to stop the vehicle. In the motor wheels’ inspection process, for example, the inspection kept the equipment stopped for about 2 hours or more, generating impacts on production.
Driven by the values “Obsession for safety and risk management”, the Predictive Maintenance team identified improvement opportunities and sought to enhance this collection process. In partnership with Dynamox, the solution found was the use of wireless vibration and temperature sensors, enabling remote data collection.
In the case of the motor wheel, the device is fixed inside the wheel and stores the vibration and temperature data in its internal memory. In addition, with a defined periodicity for each truck, the inspector collects the data that is saved in the device’s internal memory and obtains a vibration spectrum in a stable and known condition.
This known condition is produced by placing the truck at a continuous speed during a short trajectory. At this point, with a tablet, the inspector makes the connection to the sensors installed on the wheels at a safe distance.
Other equipment and sites also had sensors installed, drills, loaders, and excavators among them, in the most diverse components: engines, compressors, pumps, generators, alternators, etc.
Automation of collections
As a next step and aiming to further remove staff from the field and automate data collection, Vale began installing gateways in the vehicles. The installed gateways collect data via Bluetooth and send the data over mobile networks, with a data chip positioned inside each device. Several gateways were then installed and powered on the 24V option available in the devices. As a result, the data now arrives via the Internet directly into Dynamox’s Analysis Platform.
However, another challenge was still present: the repeatability of the data collected for further analysis. Off-road vehicles are subject to several operating conditions (loading, route, unloading, maintenance…) susceptible to uncontrolled variations, such as non-constant RPM, acceleration and deceleration, and vibration arising from the ride.
All these factors make it difficult to obtain more standardized measurements that have a certain repeatability and allow comparisons in the analysis. Considering this, Vale and Dynamox have begun to explore options for collection.
Trigger: Device for optimizing data collection
In this context, the development of the Trigger device was agreed upon, a hardware module used as an accessory to the Gateway, responsible for understanding the machine’s physical signals in order to perform collections at the best possible times. The triggers have digital, analog, and CAN (telemetry network common in off-road vehicles and that carry with them a lot of useful operating information) inputs (in green).
This device is attached to the USB port of each gateway and allows the gateway to define several single or combined logic rules so that it understands the best time to collect data and trigger the spectral timing of the sensors when it recognizes this moment.
The Vale and Dynamox teams, after months of joint development and testing, relying on several modifications and improvements, arrived at this product definition and results as the following example shows:
Monitored machine: Off-road truck CAT 794
Standard collection: spectrum collection
Global vibration and temperature levels every 5 min
By installing the accessory on the gateway, it was possible to configure the combined reading of the following signals: brake-lock activation, equipment rotation, and weighbridge activation.
This success case was awarded at the 25th Mining-Metallurgical Industry Excellence Award at the 14th Opex 2023 Workshop.
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