In a bulletin, MSHA said the suspension was effective immediately and added that it only approved a 50psi design known under 50-G-03.0.
It urged the coal mining community to increase inspections for the newly constructed seals.
The bulletin, signed by MSHA coal administrator Kevin Stricklin and director of technical support George Fesak, said the suspension was at Minova’s request.
“MSHA has taken this action to reduce risk to underground coal miners from Minova seals that are deficient as determined by in situ testing performed by Minova following their prescribed testing protocol,” officials said, noting that operators with the seals in their ventilation plan had to cease construction immediately.
They said operators could use the 50psi Minova Mainline Tekseal design (50M-02.0), 120psi Minova Gob Tekseal design (120G-05.0) and the 120psi Minova Mainline Tekseal design (120M-02.0), along with other approved seal designs.
Additionally, within a 60-day period, mine operators must also conduct in situ testing as prescribed by Minova's testing protocol on accessible 50psi Minova gob isolation Tekseals that passed the standard quality control tests.
“These in situ test results must be provided to the district manager within seven days after commencement of the,” MSHA instructed.
“Any 50psi Minova gob isolation Seal that does not pass Step 1 of Minova's protocol will be deemed deficient and must be replaced.”
MSHA said the issue was discovered during a seal examination at the Bull Mountain mine in Montana last July.
“Based on Minova's seal design and testing protocol performed on the longwall gob isolation seals at the Bull Mountain mine, these seals were determined to be deficient in cured strength and inadequate to protect underground coal miners' safety,” MSHA said.
“MSHA notified Minova of the problem found with the integrity of the Minova 50psi gob Tekseal design. As a result of these deficient seals and the cause not yet determined, MSHA has concerns with the design methodology used in the approved plan.”
