During the operation of a packing gland, what is primarily adjusted to control leakage?

In the operation of a packing gland, the primary adjustment made to control leakage is the gland nuts. These nuts are responsible for compressing the packing material against the shaft and the housing. When adjusted correctly, they create a tight seal that minimizes or eliminates leakage of the fluid being contained.

Over-tightening can lead to excessive wear on the shaft and packing, while too little tightening can result in leakage. Therefore, the careful adjustment of the gland nuts is crucial as it directly affects the sealing capability and efficiency of the packing gland. This is why properly managing the tension in these nuts is essential for optimal performance in preventing leaks.

The other options, while they may have some effect on the overall system performance or safety, do not directly control leakage in the context of a packing gland as effectively as the gland nuts.