The Queensland Mines Inspectorate said it was essential effective risk control measures were implemented when PUR was used in underground mining operations for strata consolidation.
A recent QMI investigation considered the application of PUR for strata consolidation as a potential cause of heating of remnant coal.
"Investigations have identified that the use of PUR for strata consolidation has the potential to cause an exothermic reaction that is capable of heating surrounding coal sufficiently to create an ignition source," QMI said.
It said site senior executives should ensure risk control measures were effective for the use and application of PUR in underground coal mines.
"Whenever a risk assessment is conducted or reviewed for the application of PUR … all relevant technical documents and approvals for PUR should be reviewed and referenced by the risk assessment team," QMI said.
"All requirements for the use of PUR specified in any licence or approval must be addressed in the risk assessment and have effective controls recorded and approved by the Underground Mine Manager. The UMM and SSE must ensure that the controls are effectively implemented."
QMI said participants in the risk assessment should include a cross section of coal mine workers with appropriate technical expertise, including PUR technical specialists, geotechnical engineers, PUR specialist applicators, UMMs and other relevant statutory personnel.
"The potential for PUR to artificially raise the temperature of coal can be exacerbated by circumstances, including … PUR concentrating or disproportionately accumulating in and around coal and other rock types with a propensity to self-heat; specific geological conditions that can influence PUR migration behaviour, for example magnitude of fracturing and proximity of cavities; and PUR hole spacing and design, that is the justification of hole and PUR volume concentration must be considered with respect to each application of PUR."
QMI said SSEs should ensure their mine's safety and health management system contained adequate requirements for risk assessment processes to ensure coal with an artificially-raised temperature - as a result of the use of PUR - did not enter the goaf.
"The SSE should ensure that these risk assessment processes are effectively implemented at the mine to ensure the risk is as low as reasonably achievable," it said.
"In particular, risk assessments should be conducted for each application of PUR to ensure specific risks and hazards relevant to individual mines are appropriately assessed and managed."
Turning to ground consolidation plans, QMI recommended all PUR application and consolidation plans be designed and authorised by an experienced Registered Professional Engineer Queensland, or equivalent geotechnical engineer and approved by the UMM for each application.
"The development of strata consolidation plans that require the use of PUR should specify the installation requirements including hole design - spacing, angle and length - product quantity, and verification processes for compliance against the plan, to be approved by the UMM for each separate polymeric application," QMI said.
"Strata consolidation plans should also consider, in an appropriate matrix, the risk of the combination of coal and PUR entering and remaining in the goaf.
"The SSE should ensure that the SHMS for the mine includes an effective system to monitor, control and record volumes of PUR used for each application. The SSE must ensure that the system is effectively implemented to ensure that the risks associated with using product in excess of the prescribed volume is reduced to a level that is as low as reasonably achievable for each application of PUR.
"UMMs should require and approve fire watch inspections and appropriate recording systems for each PUR application. Fire watch inspections should include the use of surface temperature monitoring; temperature monitoring of injection holes; and gas monitoring pre and post the affected coal entering the goaf ventilation readings."
