What effect does increasing the spring tension on a pressure regulator diaphragm have?

Increasing the spring tension on a pressure regulator diaphragm directly impacts the gas pressure being regulated. When the spring tension is increased, it raises the threshold at which the diaphragm can open and allow gas to flow through. This means that a greater force is required to compress the diaphragm against the spring. As a result, more pressure is needed to maintain the same flow, leading to an increase in the downstream gas pressure.

In a pressure regulator, the diaphragm responds to changes in pressure, and a tighter spring effectively lowers the capacity for the diaphragm to move freely with pressure fluctuations. Therefore, more pressure from the incoming gas is necessary for the regulator to stabilize and keep a constant output pressure, thus resulting in higher gas pressure downstream.

The other options either suggest a decrease in gas pressure, no effect, or complete shutoff, which do not accurately describe the mechanics of how spring tension affects the regulator's operation. Increasing tension does not lower pressure nor does it cause the regulator to completely obstruct flow; rather, it actively increases the pressure levels maintained by the regulator.