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Torque in bolt

  1. Dec 24, 2009 #1
    hi, thank u
    we r using packing's in our valve.packing's are tightened by bolt.how to calculate tightening torque,while tightening bolt.
     
  2. jcsd
  3. Dec 28, 2009 #2
    Can you elaborate a little? What kind of screws are you using?
     
  4. Dec 28, 2009 #3

    FredGarvin

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    You do it the same way you would in any other scenario. You either properly lube the bolt and use a torque wrench or measure the elongation of the bolt as it is being torqued (most accurate method).
     
  5. Dec 28, 2009 #4
    If you are talking about the nut that tightens the packing around the stem of the valve, that is another story. The packing must "crush" enough to make a seal at the stem, but can not be tight enough to stop the stem from moving. Too much force, especially with soft packing (teflon) may cause pre-mature packing failure. The stem that rides on the packing needs to be smooth. the finish is directly resopnsible for packing life and ability to seal at pressure.
    If you only calculate the max force needed for the thread size and use this as your baseline, the force may be excessive vs what the product needs.

    dr
     
  6. Dec 28, 2009 #5

    FredGarvin

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    That is true, but I don't think that is what the OP was asking. To me it seemed like they already know the torque they need, they just want to know how they can know when that torque has been reached while tightening.
     
  7. Dec 29, 2009 #6
    metric threads used for tightening bolt. for example M6
     
  8. Dec 29, 2009 #7
    packing is pushed by gland arrangement with help of bolt.so while tightening the bolt the gland will deflected.it will occur the gland arrangement is couch the stem. so gland is jam with stem.now i want to calculate the how much tightening torque and also how much deflection will occur in the gland arrangement. any calculation method is available.
     
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