BOLT LOAD STRETCH - FINALLY an EXPLANATION!!

[muthaffreddy]

how do you determine the pre load? is there a formula for a specific size of bolt?

[WWWNIBTORQUECOM]

NO there is not a formula. The pre-load is the tension created in a threaded fastener when the nut is first tightened. Pre-load is often used interchangeable, but incorrectly with WORKING LOAD or bolt force, or bolt tension. What you probally meant to ask is "CLAMP FORCE". Clamp force is the force which a threaded fastener exerts on the joint members it is holding or clamping together.

[WWWNIBTORQUECOM]

The CLAMP FORCE is determined by the manufacture of a bolted connection. We only provide tools to create clamp force. We follow the instructions of the manufacture of the bolted connections. We can guide you, and recommend torque if we have all the specs..meaning, bolt material, gasket material, how many pounds of force needed, lubrication used, soft or hard joints, K factor.. You have to remember that torque is only an estimate clamp load applied because there are too many variables.

[WWWNIBTORQUECOM]

Us as well as some of our competitors have released Torque Guides. My competition (before 2006-2007) has always recommended 70% so sell a bigger tool. That is incorrect for 95% of all bolted flanges. We have a competitor who does not train or educate their salespeople, and this causes all kinds of prolbems we have to clean up afterwards! We have 2 salespersonel from this certain competitor and had to retrain them on proper bolting education.

[gjy2001]

I agree, there is a lot of misinformation out there and that is a problem. My original comment was primarily aimed toward people who may erroneously believe that 50% of yield is a one-value-fits-all number.

[WWWNIBTORQUECOM]

You must be a Rocket Scientist. Your Correct, if your bolted connection has a gasket! Not every bolted connection has concentrate flow. Some bolted connections are holding machinery together. We have a competitor who knows nothing about providing solutions to customers, they are only concerned about selling the biggest tools. Or Raising the salepersons tool count. What they are doing is causing more accidents around the world.

[JohnsZX2]

Really good explanation.

[mxmang]

rip