Bestech Australia speaks with Australian Mining to share expertise on using strain gauges, instrumentation and data acquisition for effective condition monitoring on mining assets.
Every mine site is designed with a system in place to avoid catastrophic structural failures, from minor structural cracks to total roof collapse.
For this purpose, implementing sensor technology for regular and continuous monitoring is imperative to ensure maintenance can be performed before the damage progresses into total structural failures.
Bestech marketing engineer Wirhan Prationo emphasises the need for continuous monitoring of the health of mining infrastructure to allow sites to achieve maximum productivity with minimum downtime.
With time, infrastructure at mine sites wears out and needs regular maintenance, but the costs of repairing it after collapse are far greater than if it had been maintained regularly.
“Strain gauges are one of the most widely used sensors in preventive maintenance to allow the early detection of structural failure,” Prationo tells Australian Mining.
Bestech Australia supplies a wide range of strain gauges, from general foil strain gauges to high temperature strain gauges to ensure reliable measurement under diverse and challenging conditions.
These strain gauges are manufactured in a clean environment and are tested according to the NAS942 and ASTM E251-74 standard. They are low cost and are generally easy to be applied on the surface.
These different strain gauge types include the foil strain gauge, waterproof strain gauge, weldable strain transducer, mould strain gauge, magnetic strain gauge, bolt strain gauge and crack detection gauges.
Depending on the type of applications, Bestech can advise on which strain gauges are the best fit for the measurement, taking various factors into consideration, such as temperature, nearby objects and humidity.
Foil strain gauges can be used on different types of surfaces, thus allowing site engineers to monitor each piece of critical infrastructure.
These surfaces can include metal, plastic, wood and composite materials, or they can be embedded into concrete or mortar.
The gauge will measure strain on the object based on changes in electrical resistance across the Wheatstone bridge, which could occur because of movement, changes in temperature or pressure.
“The gauges are generally installed at the most vulnerable location in the structure. Depending on the trend of the data, engineers can determine whether maintenance needs to be scheduled to preserve the life of the structures,” Prationo says.
“For example, the gauges have been used to monitor the stress distribution of the rock bolts, which are commonly used to provide temporary roof support in underground mines and for tunnels.
“Installing the strain gauges in four vertical grooves enables the measurement of axial and shear stresses. Any sudden increase in these values indicates the instability of the infrastructure.
“The whole measurement system includes strain gauges coupled with a highly advanced data collecting system with a four-groove bolt. The strain measurements are based on the increase or decrease of resistance of the conductor due to compression or tension.”
Other than strain gauges, Bestech also supplies a range of accelerometers and fibre optic FBG (fibre-bragg grating) sensors that can be applied for condition monitoring applications on the mine site.
FBG sensors can measure strain, vibration, angle and displacement for monitoring the health of the infrastructure. FBG strain and temperature sensors, along with interrogators (which process the information), work as data collection units and help to acquire the complete information of the structure.
“They monitor the effect of dynamic mining activity on structural stability by comparing strain variations,” Prationo says.
“The system allows sharing valuable information at remote places by assessing and analysing the collected data. This data can be recalled anytime, anywhere by authorised users.
“Hence, the system aids in substituting the reactive approaches of mine structural monitoring to proactive failure detection and accident prevention strategies.”
As FBG sensors are electromagnetically safe and can also be used in highly explosive atmospheres; they are also ideally used as monitoring tools for maintaining the structural integrity of underground mines, especially as blasting occurs.
Additionally, mining-induced strain in road pavement is another crucial aspect that requires continuous monitoring.
Subsidence of the ground surface is the common outcome of the underground coal extraction process. Thus, an array of FBG sensors is used for the uninterrupted measurement of subsidence-induced strain in the pavement. This measurement helps to ensure safety and on-time maintenance scheduling.
By implementing these discrete monitoring solutions, mine conditions can quickly and easily be processed and transmitted for remote analysis – furthering safe mining practices.
“The monitoring system equipped with optical strain gauges eliminates the exposure of mining professionals to the harsh environmental conditions of underground mines,” Prationo says.
“They boost the efficiency of the mine sites and help to minimise the overall expenses for infrastructure monitoring.
“In addition, by providing critical information in real time, the system helps to predict, plan and optimise maintenance activities across any mine site.”
This article appears in the October issue of Australian Mining.