ASTM A193 Grade B8 Fasteners 2

[dik]

Some fasteners don't permit re-use or re-tensioning.

Does anyone know if these fasteners can be re-used once they have been tensioned?

There is a wide range of B8 having a yield and UTS of from 30ksi,75ksi to 100ksi, 125ksi, respectivly.

Dik

 

[CoryPad]

The ASTM standard only covers manufacturing and required properties and testing. End use is governed by customer specifications and codes. You will need to check those to get your answer.

In general, fasteners are reusable, though they can accumulate damage due to fatigue and creep. Coating wear and base metal oxidation can change surface characteristics and torque-tension behavior, which may be important.

 

[dik]

Thanks, Cory...

 

[unclesyd]

As posted above it can and is done everyday.

We have thousands of B8 fasteners up to 2 1/4" in process where they are reused until they fail, mainly from from galling. One of the approaches to reusing them is that the fasteners are made up using Cu based thread lubricant in the chemical area of the plant and a colloidal graphite lubricant in the polymer area. When a bolted connection is taken apart the fasteners are broken down to individual components and normally cleaned and then relubed. There is no effort to match or gauge the fasteners. When a nut sticks a good mechanic will not try to drive the nut further but will try to turn it while tapping the nut. If a fastener galls while driving you generally loose nut and stud. There is no effort recover either.

One of the biggest causes of fastener loss stems from mechanical damage that will aggravate the tendency for it to gall.

We replace around five percent of the in service fasteners per year in areas where make and break is high.

90% of these SS fasteners are tightened by impact wrench with the mechanic using the parallel flange approach.