“MSHA is taking this action to reduce risk to underground coal miners from Micon seals that are self-generating heat shortly after construction and prior to reaching design strength,” the agency said in a public information bulletin issued Tuesday.

“Mine operators with an approved Micon seal in their ventilation plan must cease construction of these seals immediately until MSHA can determine the cause of the heating and promptly take appropriate measures to resolve the problem.”

The fire occurred with a Micon 120psi seal at Consol’s Buchanan operation on May 22, and an evaluation of the seal showed evidence of what was thought to be extensive heating in its core.

Six days later in an examination by an MSHA inspector, the reviewer found a “large portion” of the seal’s centre to be melted or scorched.

“MSHA removed polyurethane and wood samples from the seal for testing the ignition temperatures,” the agency said in the PIB.

“MSHA will also subject each sample to a temperature of 330 degrees Fahrenheit for a period of 24 hours.”

The agency instructed mines which have begun to erect a set of seals but have not yet completed the project to submit a revised plan with the seal method and type they plan to use to complete the set. That site-specific outline should be submitted to the MSHA district manager overseeing the jurisdiction where the minesite is located.

MSHA pointed out, however, that it recognises some operations will not need to resubmit plans as their ventilation designs include at least two seal manufacturers that are MSHA approved.

For those sets which already have newly placed Micon seals constructed within them, the agency said mine staff must examine each one at least every 24 hours until the seals reach their design strength. This practice should be in place for 30 days from the day of each seal’s completion unless an operator provides to its DM evidence of cooling to an ambient temperature.

“MSHA expects the mine operator to produce quality control samples of the polyurethane or material of the seal along with core-temperature sampling results and provide all sample results to MSHA,” it stressed.

“To more effectively examine seals for heating hazards, mine operators must check for unusual circumstances at the seal and in the atmosphere near the seal, such as increased temperatures, the presence of elevated concentrations of carbon monoxide, and any unusual smells or odours.”

In the meantime, the agency said it will “proceed expeditiously” with its review of the Micon seals heating to find a resolution.

Testing commenced June 4 at its Approval and Certification Center in West Virginia to determine ignition temperatures, and that series of evaluations is expected to be completed June 20.

MSHA also said that it will address any additional seal issues that may arise during the process and will issue further information on its findings once the investigation is complete.

While they currently have been pulled from the agency’s website as approved, the agency’s warning to mines includes the following Micon seals with an MSHA design approval:

120-75.336.1.07.03.0 MICON seal

120-75.336.1.07.03.1 MICON seal with Dowel coupler changes (for entries 5.5ft to 8.5ft and 24ft in width)

120-75.336.1.07.23.0 MICON seal (for entries 9ft to 16ft and 26ft in width)

120-75.336.1.07.26.0 MICON Gob Isolation Seal (for entries 4ft to 16ft and 26ft in width)

120-75.336.1.07.27.1 MICON 120psi District Seal (for entries 4ft to 16ft and up to 28ft in width)

120-75.336.1.07.27.2 MICON 120psi District Seal (for entries 4ft to 16ft and up to 28ft in width) with revision to installation instructions

120-75.336.1.07.30.0 MICON 4ft to 16ft Longwall Gob Isolation Seal

50-75.336.1.08.08.0 MICON Longwall Gob Isolation Seal (for entries from 3ft to 21ft in height up to 28ft in width)

For a complete, printable version of this PIB, visit MSHA’s website.