the sensing diaphragm 26 are equal when the vpc 20 achieves this equilibrium the supply loading valve 40 and exhaust loading valve 42 will remain closed maintaining a constant output pressure to the process control valve 14 the vpc 20 will exhibit zero emissions at this state during operation the equilibrium or steady state static is preferred so the system operates to return to this state whenever an upset occurs as noted two possible scenarios can occur from the balance state the sensing pressure can rise above the set point or fall below the set point if the sensing pressure rises above the vpc set point the net force on the vpc power module is downward the exhaust loading valve will close or stay closed the supply loading valve opens increasing the flow of supply gas to the output port the combination of these actions creates a rise in output pressure if the sensing pressure falls below the vpc set point the net force on the vpc power module is upward now the supply loading valve will close or stay closed and the exhaust loading valve opens increasing the flow of gas to the exhaust port the combination of these actions decreases the output pressure in order to control how much gas passes through the.