Bolts that properly tightened use their elastic properties and must work like springs to work effectively. This behavior is manifested when a load is applied as the bolt stretches and returns to its original length to create a compressive force across the joint members. The more load is applied, the more the elongation increases. The further load application can cause the bolt to fail which is called ultimate tensile strength (UTS). At this point, when more force is applied to the bolt, it will continue to elongate until it breaks. Thus, bolt failure can be prevented by paying attention to the bolt grade, equipment being used, and the operator skill.
The Number of Tensioners Required
The majority of applications can be tensioned with a hydraulic tensioner. But, on applications that involve tensioning several bolts, operators need to use many hydraulic tensioners depending. In fact, it should be one tensioner for every other or for every fourth bolt.
To increase productivity on circular flanges, operators must use at least 4 tensioners. This bolt tensioning method makes sure that the flange is closed evenly and safely. If bolt tensioning is not even, it can lead to bolts being overloaded or loose, crushing of the gasket or less than 100 percent tensioning.
For applications that do not allow simultaneous tensioning devices on bolts, operators can apply at least 2 tensioning pressures. This accounts for a load loss in bolts already tensioned as the next sets are tightened. It is important to begin each tightening procedure by lubricating the nuts and bolts and then hand tightening to make sure they are flushed against the flange.
Benefits Controlled Bolting Techniques
Controlled bolting provides the following advantages:
- Ensures accurate bolt loads. Controlled bolting techniques integrate tooling that has been controlled outputs. Operators need to calculate load bolts correctly to know the required tool settings which ensure ease of use.
- Guarantees bolt loading consistency. This benefit is especially essential on joins with gaskets. An even and consistent compression is necessary to prevent damage and ensure the gasket works effectively.
- Ensures the safety of operations. Controlled bolting equipment is safe to operate which eliminates the unsafe actions of manual uncontrolled tightening. With controlled bolting equipment, specific procedures must be followed by operators.
- Reduces operational time. Using controlled bolting tooling increases productivity by minimizing the tightening time and operator fatigue.
- Offers dependable and repeatable results. By using calibrated, tested equipment, and skilled operators, the expected results are achieved in a consistent way.