Due to safety reasons and according to BS 4604-1 (Withdrawn):
“If after final tightening a bolt or nut is slackened off for any reason, the bolt, nut and washer shall be discarded and not re-used.”
Under the latest BS EN 14399 standard:
If the assembly has been tightened to the minimum force of 70%, the assembly cannot be re-used.
Andrews Fasteners recommend, once assembly has been preloaded, in any form and needs to be de-assembled, to discard it and replace it with fresh assembly (and relevant components like DTI washers) due to wearing off applied lubrication which may invalidate torque figures supplied for installation (k-Class K1 or K2) or cause difficulty to compress DTI washers at the right level (k-Class K0).
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