Sigra - Extensometer | Doughnut

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Applications for this product

• It is ideally suited for use in coal mine roof installations where it can detect delamination of the strata.

Features of this product

• The extensometer consists of a hollow plastic ring with a port on the side which is connected to a clear plastic tube
• The ring contains a fluorescent grease which is squeezed out into the clear plastic tube when the ring is compressed
• The extent of grease movement within the plastic tube is easily visible with the aid of a small amount of light, due its fluorescence
• To use the doughnut extensometer, a hole is drilled to the desired measuring depth then a rock bolt is inserted into the hole and locked in place using a point anchor
• The anchor can be mechanical or made by trimming off a resin cartridge to a short length
• If the resin cartridge is used, the bolt must be spun for a set time instead of waiting for the normal bolter torque to be reached
• The bolt drive nut is removed and a sandwich of an inner washer, doughnut extensometer and outer washer are slipped on to the bolt and loosely retained by a nut
• The clear plastic tube is then aligned with one of the roof mesh wires and tied to it with cable ties
• The nut is advanced to squeeze some fluorescent grease out into the tube, usually to the location of the first mesh grid crossing
• The lock nut is then screwed on and tightened against the nut to secure the setting

Specifications of this product

• Ratio of movement: approximately 1:100

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To contact Sigra about Sigra Extensometer | Doughnut use Get a quote.