Mining Contract: Strengthening an Existing 20-PSI Mine Seal with PPG's Polyurea Coated Retrofit
PPG Industries was awarded a NIOSH contract to develop a spray applied polyurea coating system that would upgrade existing 20-psi approved mine seals to withstand blast pressures greater than 60 psi. The research program coupled modeling predictions from Penn State's Applied Research Laboratory (ARL) and synthesis and formulation expertise from PPG. The research program had three main elements:
Contract Status & Impact
This contract is completed. To receive a copy of the final report, send a request to OMSHR@cdc.gov.
The program goal was to increase the mine seal blast pressure sustainability of a baseline 20-psi seal to greater than 60 psi. Analysis and testing were completed for using a polyurea coating to improve blast effectiveness of a mine seal:
- The MICON 550 seal was selected for analysis and testing for the polyurea coated specification. The baseline seal used two walls of dry stacked solid concrete blocks separated by a 16"-thick polyurethane core. This unmodified seal was an approved 20-psi mine seal. A coated retrofit design was developed for the MICON 550 seal which includes a secondary 8"-thick polyurethane core, secondary block wall, 0.125"-thick polyurea coating, and a flame-retardant latex coating. The retrofit configuration was installed and tested at the Lake Lynn Experimental Mine, and survived two separate blast tests with peak blast pressures of 78.5 and 84.4 psi.
- An alternative seal design was also analyzed with and without polyurea coating. A solid concrete block seal was selected for analysis. The uncoated seal was rated at 50 psi, and was predicted by models to fail at 70-psi peak blast pressure. The coated seal was predicted to survive a minimum 90-psi blast using conservative predictions of potential coating failure.
The completed analyses and testing showed that the PPG polyurea coating can improve the blast protection of mine seal structures.