The system was developed by Micon Group US and has been successfully tested at the former US Bureau of Mines Lake Lynn facility, at the request of the Mine Safety and Health Administration (MSHA). In these tests, the 20 psi Micon ERS was also exposed to an explosive force of 35 psi with the core of the seal sustaining little damage and remained intact. Currently in the US mining industry the Micon ERS holds a significant share of the explosion resistant seal market. The Micon ERS can be designed for a wide range of over pressure ratings including 20, 50 and even 120 psi. The system can also be used for water bulkheads due to their high quality and integrity. Today the Micon ERS is recognised as the world’s best practice for explosion resistant and bulkhead seals.
DESIGN AND CONSTRUCTION METHOD
The Micon ERS design consists of two surface-bonded, dry-stacked, concrete block stopping walls spaced depending on the height and rating required. Micon 550 polyurethane (PUR) and gravel fills the void between the stoppings providing a complete seal. To meet fire standard requirements, the seal is coated with a suitable surface coating. This unique seal with its uncomplicated design offers significant advantages over alternative cement based seals.
The Micon ERS incorporates a construction method that features a composite structure comprised of special MICON high-tech polymer material and, sturdy materials of stone and concrete block.
- The polymer core has expansion and cohesive properties not available in other seal materials.
- Faster curing time to become explosion rated.
- Designed around flexural strength not compressive.
- Explosion tested at an internationally recognised facility.
- The seal is not affected by water once constructed.
- Fast installation time.
- Quality controlled construction.
- No cold joint issues if construction is stopped during construction process.
- Atmosphere sampling tubes, drain pipes and water traps may be added as required.
- More cost effective in mines with ground movement, gas and spontaneous combustion & water accumulation issues.
- Demonstrates tolerance to ground convergence without affecting integrity or rating of seal.
- As deformation occurs the core absorbs / flexes and maintains a seal.
- The PUR core is glued to each block.
- Should convergence be predicted to be greater than 10%, timber convergence layers can be included in between layers of blocks in the seal to minimise crushing of the blocks. NOTE: Micon Seals at various mines have accommodated 900mm of convergence without leakage through the core.
- An appropriate secondary support plan should be integrated with the construction of the Micon ERS.
- Quality Assurance –WM is a quality endorsed company to ISO 9001:2015. All aspects of seal construction have been developed within the guidelines of our quality management system.
- Design Rating –Report by an RPEQ registered civil engineer.
- Materials –PUR is blended in Sydney to Micon Inc. specifications.
- Training – Comprehensive training program of WMS operators.
- Installation –The PUR and gravel are a matched system that will ensure correct core density.
- Completion –A unique identification sign is attached to each seal on completion for QA trace ability.
ADVANTAGES COMPARED TO CEMENT SEALS
- Explosion resistant within one hour of completion.
- The elastic polyurethane/gravel core is designed and proven to bewith stand up to 10% roadway convergence without diminishing pressure rating.
- PUR contours to the perimeter of the roadway. PUR has excellent adhesive properties
and forms an excellent air tight seal.
- No hitching or keying required.
- Not affected by water.
- Monolithic expansion ensures the Micon ERS remains stable.
- Not affected by cold jointing. Each PUR layer fuses onto the previous.
- Accurate pumping of Part A:Part B to ensure accurate placing of the core.
Micon bulkhead seals have the following design features compared to a standard Micon:
- FOS 4:1for the static load of required water head
- Internal cable reinforcement
- PUR injection around the roadway perimeter
The Micon HB (high bond) Seal is a new VCD product development. The design consists of PUR glued masonry blocks and a thinner PUR/gravel core thickness compared to the standard Micon ERS. This reduces materials requirements and cost whilst retaining the important features of convergence and water resistance. The initial Micon HB seals were built using crews formed from both NSW and Qld WM operators and staff to meet the Kestrel mine’s planned longwall start-up schedule. Modifications to the HB seal design can be undertaken to provide a bulkhead rating.