Superbolt tensioners secure slurry pump cover
Two sets of hydraulic wrenches were used previously, with one used to achieve 21,000 lb•ft (28,470 Nm) on the 16 perimeter bolts and another used to achieve the 35,000 lb•ft (47,450 Nm) for the cut water bolt. The larger hydraulic wrench could not be used for all of the nuts because it would not fit.
Four millwrights were needed for the installation. The hydraulic tools weighed 51.5 lbs (70 N) and 96.5 lbs (130 N), with the smaller tool needing to be passed from worker to worker. The customer had trouble correctly placing the reaction arm, and safety was a concern.
Additionally, scaffolding was put into place in order to perform the task, requiring additional time and effort. Total time to complete the torque sequence was 2.5 hours.
Superbolt multi-jackbolt tensioners (MJTs) were purchased and directly compared to the previous hydraulic wrenches method. For the initial passes, electric impact wrenches were used. This speeds up installation. To obtain the final target torque value of 80 lb•ft (108 Nm), two 1/2” torque wrenches were used.
Because only hand tools were needed, the safety and weight concerns associated with the hydraulic wrenches were eliminated, and only two millwrights were needed instead of four when using the previous method. Also, no scaffolding was needed for the installation. In the end, the customer experienced a substantial time savings. The total time to complete the torque sequence using MJTs was only 1 hour!
The millwrights involved in both installations were experienced with the hydraulic tools, but this was their first experience with Superbolt tensioners. The satisfied customers had nothing but positive things to say about the MJTs, with one noting: “Definitely the way to go.”