Oilers/Plant Tenders (HHC) Civil Service Practice Exam

When installing three new packing rings in a stuffing box, the joints of the packing should be placed at what angle?

1. 90°

2. 180°

3. 120°

4. 150°

The correct answer is: 120°

In the installation of packing rings within a stuffing box, the orientation of the joints plays a crucial role in ensuring effective sealing and prolonging the life of the packing. When the joints of the packing are spaced appropriately, it helps to distribute the wear evenly and reduce the risk of leakage. Placing the joints at a 120° angle is optimal because it provides a balance that prevents any single joint from bearing the entire pressure or stress. This spacing allows each joint to work in conjunction without compromising the integrity of the packing or the sealing effectiveness. Moreover, the 120° configuration minimizes the chances of continuous leakage paths forming, as the packing material can better conform to the shaft and sides of the stuffing box. In contrast, other angles such as 90°, 180°, or 150° do not offer the same benefits. For instance, a 90° angle would result in joints placed too closely together, increasing the likelihood of pressure points and potential leaks. A 180° configuration would create an alignment directly opposite each other, which can lead to uneven wear. Likewise, 150° could be too close to preventing effective sealing and would not distribute the pressure adequately. Therefore, the 120° angle is the most effective configuration for joint placement in