COAL

Problem Solving

Coal

The following examples illustrate some of our contributions to this business sector:

• Five roof plates and four washers that failed in service, and three plates that were not used, were examined. Touchstone concluded that cracking at the bolt hole resulted from circumferential tensile stresses that built up from distortion of the plates as a result of the force from the bolt and washer assembly at the circumference of the washers.
• An investigation of a cracking failure in a linepan floor plate. Cracking in longwall pan floor plate was examined and found to be the result of substandard plate used in fabrication. The cracks developed longitudinally in several of the individual longwall machine segments. Elemental analysis and charpy tests demonstrated that the plate did not meet mechanical property requirements and developed cracks under the impact of falling coal and rock.
• Touchstone was contacted concerning a failure in use of the drive shaft of an electric induction motor. Touchstone was asked to determine the cause of the failure and suggest a solution to the problem. Analysis showed that little or no radius was provided at the location of a change in shaft diameter where a ball bearing fit onto the shaft. The resulting stress concentration caused the shaft to fail catastrophically after only a short service life.
• Degrading performance of celtite epoxy used to secure mine roof bolts was brought to the attention of Touchstone engineers. Eight celtite cartridges, 4 labelled new formula and 4 labelled old formula, were delivered to Touchstone for evaluation. A GCMS analysis was performed on the samples. No difference was detected between the new and old formula celtite resin cartridges, indicating that some other cause for the poor performance was in effect.
• Touchstone engineers examined a Contactor Enclosure and an Operator Control Station Enclosure which had been recovered from the site of an underground coal mine explosion. It was requested that Touchstone determine if an explosion or fire had occurred within either of these enclosures. Based on Touchstone’s experience with such failures and testing of evidence, it was concluded that no recent fires or explosions had occurred within either of these two enclosures.
• Touchstone evaluated a mine equipment methane sensor which was suspected of failure. The question of lead wire breakage on the internal sensor bead was resolved by SEM examination of the broken wire end. The presence of fatigue striations on the broken end showed that vibration had probably caused the unit to fail. The equipment design, however, still allowed the equipment to operate regardless of local atmospheric conditions. The system was redesigned to provide “fail-safe” operation where the previous design could allow sensor failure yet allow equipment to operate.
• Touchstone is involved in the development of coal-based pitch products. The laboratory has been equipped to produce carbon-based foam material that has strategic mechanical properties including: thermal stability, low density, structural integrity, and the ability to be bonded using polymer based and pitch based adhesives.

The above examples are only a sample of our work in this area. We would be pleased to provide any additional information you may require. We also invite you to review examples on our website of work that we have performed in support of other business sectors.