Bubik
Structural
- Mar 15, 2016
- 103
Hi everyone!!
I have a question regarding tightening of bolts. We use galvanised M27 10.9 bolts for connections of belt conveyor truss in a cement factory.
The required torque for adequate fastening is to be 1650Nm according to the bolt's manufacture without any lubricant (slightly oiled) or 1250Nm with Molykote lubricant. The guys on site tightened the bolts to 1250Nm without any lubricant as it is too hard for them to achieve 1650Nm ( bad equipment they have).Now, they bought the Molykote lubricant (after multiple fights with the contractor) and want to take the bolts out ,lubricate them, re use them and achieve 1250 torque (as required with lubricated bolts). I know that preloaded bolts cannot be reused when plastic region is reached. as the bolt is 10.9 I did simple calculation from BS EN 1090-2 to check when the maximum elastic region in relation to torque tightening is,this would be about 1483Nm.I used 90% of 1000N/m^2,coefficient 0.2 (it is our requirment)and diemeter of bolt(27mm) and I got 1483Nm for maximum elastic treshhold. The equation is :Required torque = F x d x k. Can the bolts be reused then???
THANKs everyone!!
I have a question regarding tightening of bolts. We use galvanised M27 10.9 bolts for connections of belt conveyor truss in a cement factory.
The required torque for adequate fastening is to be 1650Nm according to the bolt's manufacture without any lubricant (slightly oiled) or 1250Nm with Molykote lubricant. The guys on site tightened the bolts to 1250Nm without any lubricant as it is too hard for them to achieve 1650Nm ( bad equipment they have).Now, they bought the Molykote lubricant (after multiple fights with the contractor) and want to take the bolts out ,lubricate them, re use them and achieve 1250 torque (as required with lubricated bolts). I know that preloaded bolts cannot be reused when plastic region is reached. as the bolt is 10.9 I did simple calculation from BS EN 1090-2 to check when the maximum elastic region in relation to torque tightening is,this would be about 1483Nm.I used 90% of 1000N/m^2,coefficient 0.2 (it is our requirment)and diemeter of bolt(27mm) and I got 1483Nm for maximum elastic treshhold. The equation is :Required torque = F x d x k. Can the bolts be reused then???
THANKs everyone!!