Abstract: A number of pre-production calibration tightenings are performed at a screw joint identical to a screw joint used in production and using the same impulse wrench as to be used in production tightening. The value of one or more tightening related parameters are registered at the attainment of the desired pre-tension level, and those parameter values are used to statistically form a basis for a reference set-up. The tightening parameter values registered during production tightening are compared to the reference set-up, and an indication is obtained as to discrepancies between the reference set-up and the actually registered parameter values to get an indication as to whether the impulse wrench is malfunctioning and/or the screw joint is faulty.

Abstract: A method and a power tool system are provided for performing screw joint tightening using a pneumatic torque impulse power tool that is controlled by a control unit. A torque magnitude and a torque growth are calculated based on signals delivered by an angle sensor, and pressurized air is supplied to the power tool via a flow regulating valve which is successively adjustable between zero and full power flow. The flow regulating valve is controlled by the control unit to deliver a reduced power air flow to the power tool before and during a first delivered impulse, and then to deliver full power flow until a certain torque magnitude or a percentage of a target torque level is reached, whereafter the air supply flow is again reduced until the target torque level is reached, and when the target torque level is reached the air flow is shut off.

Abstract: A number of pre-production calibration tightenings are performed at a screw joint identical to a screw joint used in production and using the same impulse wrench as to be used in production tightening. The value of one or more tightening related parameters are registered at the attainment of the desired pre-tension level, and those parameter values are used to statistically form a basis for a reference set-up. The tightening parameter values registered during production tightening are compared to the reference set-up, and an indication is obtained as to discrepancies between the reference set-up and the actually registered parameter values to get an indication as to whether the impulse wrench is malfunctioning and/or the screw joint is faulty.

Abstract: A method and a power tool system for screw joint tightening by means of a pneumatic torque impulse power tool (10) controlled by a stationary programmable control unit (22) and via a torque magnitude and torque growth calculation based on signals delivered by an angle sensing device (16) on the impulse unit (13) of the power tool (10), wherein motive pressure air is supplied to the power tool via a flow regulating valve (26) which is successively adjustable between zero and a full power flow. The flow regulating valve (26) is controlled by the control unit (22) to deliver a reduced power air flow to the power tool (10) before and during the very first delivered impulse, then delivering a full power flow until a certain torque magnitude or a certain percentage of the target torque level is reached, whereafter the air supply flow is again reduced until the target torque level is reached, and when the target torque level is reached the air flow is shut off.