Which of the following is NOT a cause of zero branch line pressure at the pressure regulator?

To understand why the choice of a blocked lubricator outlet port is correct as the option that is NOT a cause of zero branch line pressure at the pressure regulator, it's important to consider the functions and flow paths in a pneumatic system.

The primary function of a lubricator in a pneumatic system is to add lubrication to the compressed air before it reaches the actuator or other downstream components. If the outlet port of the lubricator is blocked, it would restrict the flow of lubricated air to the downstream system. However, this blockage does not directly affect the pressure reading at the pressure regulator. The regulator is responsible for controlling and maintaining the pressure downstream, and while the lack of lubrication could lead to performance issues, it does not inherently cause the branch line pressure to read zero.

In contrast, a blocked inlet port of the regulator would prevent any air from entering the regulator, directly resulting in zero output pressure. Similarly, if a filter element is completely clogged or the outlet port of the filter is blocked, it would impede air flow to the regulator, leading to zero pressure downstream. Each of these last three scenarios directly impacts the air flow to the pressure regulator and is a direct cause of zero branch line pressure. Therefore, the blocked lubricator outlet port does not create