Calculating Tightening Torque for Bolt Packing

• gopinathaengg
In summary, the conversation discusses the use of packing's in valves and how to properly calculate the tightening torque when using bolts. The suggested methods include using a torque wrench or measuring the elongation of the bolt. It is also important to consider the type of screws being used and the finish of the stem for optimal packing life and sealing ability. The conversation also touches on the deflection of the gland arrangement while tightening and the need to find the appropriate amount of torque and deflection for proper functioning.
gopinathaengg
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.

Can you elaborate a little? What kind of screws are you using?

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).

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

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.

metric threads used for tightening bolt. for example M6

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.

1. How do I calculate the tightening torque for bolt packing?

Calculating the tightening torque for bolt packing involves several steps. First, determine the bolt size and grade. Then, consult a torque chart or use a torque calculator to find the recommended torque for that bolt. Finally, add any additional factors such as lubrication or thread condition to calculate the final tightening torque.

2. What factors affect the tightening torque for bolt packing?

Several factors can affect the tightening torque for bolt packing, such as bolt size, grade, lubrication, thread condition, and surface finish. Additionally, the type of material being fastened and the type of joint being created can also impact the recommended tightening torque.

3. How can I ensure I am using the correct tightening torque for my bolt packing?

The best way to ensure you are using the correct tightening torque for your bolt packing is to consult a torque chart or use a torque calculator specific to the bolt size and grade you are using. Additionally, following manufacturer recommendations and conducting torque tests on sample bolts can also help ensure accuracy.

4. Is it possible to over-tighten bolt packing?

Yes, it is possible to over-tighten bolt packing. Over-tightening can cause the bolt to stretch or break, leading to joint failure. It can also cause damage to the threads or the material being fastened. It is important to use the recommended tightening torque to avoid over-tightening.

5. How often should I check and adjust the tightening torque for bolt packing?

The recommended tightening torque for bolt packing should be checked and adjusted as needed during the initial installation process. After that, it is important to periodically check the torque to ensure it has not changed due to factors such as vibration or temperature changes. Additionally, re-torqueing may be necessary after a certain amount of time or usage, depending on the specific application and requirements.

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