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Here is a quick checklist that can help avoid questionable results due to slippage of the specimens in your tensile tester: · Use the Grips for the purpose they were designed for · Know your fibre type! Its characteristics will affect what grips you need to use, gauge length and pressure that will be required to perform the test. · Make sure the maximum load capacity of the grip is suitable for the specimens to be tested. · Ensure the jaw faces are suitable for the forces that are going to be applied during the test. Note: Rubber faces will degrade quickly at higher loads. · The faces should not be too aggressive for the type of specimen such that it causes premature failure. · Make sure the specimen is centrally mounted and fully inserted into the grip faces. · Correct maintenance of the grips whether they are manual, pneumatic or hydraulic. · If in doubt ask your supplier for advice. General Maintenance · Check all fastenings are secure and in good order no loose or wobbly parts. · Check they are moving freely / lubricated also free of loose fibres and any debris. Manual grips · Do not over tighten them. · Make sure all catches lock securely. Pneumatic Grips · Ensure the compressed air supply is clean and dry; that means regularly emptying the relief valve to drain off any moisture regularly. · Adjusting the pressure to be appropriate in order to prevent jaw breaks but not exceeding the maximum operating pressure. · If you suspect air leaks get them checked/serviced. Hydraulic grips · Check your fluid levels. · Look for any signs of a leak. · Note pressure level required to give a good break and apply this consistently for each specimen. Jaw faces (applicable to all grip types) · Check the faces for wear and tear before you fit them into your grips. · Again you need to use the correct faces for the product you are testing. · Please use the locating pins provided with the grips. · Replace the rubber faces when they show signs of wear; badly worn or uneven faces can lead to slippage, premature failure of specimens and incorrect test results. · Clean off any off any residual lubricants/ finishes’ that may have built up during testing of some specimens. Yarn / cord testing using bollard grips · Check the cord path is not worn or damaged and free of any residual build up from the yarn or cord. · Set up the gauge length from nip point to nip point. · Surfaces of clamp faces can become polished and cause slippage. · Aggressive faces or too much pressure will cause jaw breaks. Nose pieces · Make sure they are tightened correctly but again not over tightened, which may lead to twisting of the load cell and permanent damage of the load cell. · Know the rating of your grips and don’t assume the nose piece size dictates the load capacity. Compression - Puncture Testing · Check probes for damage and/or signs of wear as this will influence the way the probe penetrates the fabric under test and affect your results. · After attaching the probe to the nose piece check for alignment to the lower clamping unit to ensure the probe passes through the aperture freely. · Check the fabric in the lower clamping unit is clamped evenly with sufficient pressure to prevent slippage during testing. |