Press columns on forging press
The Challenge
Due to the nature of big presses, large diameter columns must be used to distribute the extremely high working loads generated. However, the torque required to prestress these columns is almost impossible to achieve with conventional bolting methods. Traditionally, sledgehammers, overhead cranes, or stud heaters are used. These methods are inaccurate, ineffective, time consuming and are a safety hazard. Sufficient and accurate preload is difficult to achieve on small presses and nearly impossible on larger presses. If the columns are not properly prestressed, fatigue fractures can occur.
The Solution
Superbolt nut-style multi-jackbolt tensioners (MJTs) are designed as direct replacements for the OEM nuts, and are being used by press OEM companies, press repair shops, and end users. Only ordinary hand torque wrenches are required to properly prestress any size press column.
The entire operation can be performed safely by a single man in a fraction of the time it takes to use traditional tightening methods. The Mesta Press shown required less than 6 hours installation time with only 1 man for all 8 nuts vs. the 2-1/2 full days it previously took with additional personnel. Removal is also a simple task. MJTs will not gall the main column thread during removal. Once the preload is relieved by loosening the jackbolts, the tensioner easily spins off!
Before:
Preload = 2,625,000 lbs.
Hex Nut Torque = 695,756 ft•lb.
After:
Preload = 2,625,000 lbs.
Superbolt Jackbolt Torque = 275 ft•lb.
