Gas line control system and modular variable pressure controller

A method for controlling a fluid supply through a delivery line having a process control valve therein to maintain a supply side pressure and a delivery side pressure, and a pneumatic actuator having a first pressure chamber and a second pressure chamber and used to operate the process control valve, the method comprising the steps of:

• setting a delivery side target pressure range for the fluid supply;
• sensing the delivery side pressure;
• operating the pneumatic actuator in one of the following ways:
• maintaining the actuator in a static state when the delivery side pressure is within the target range;
• moving the actuator to open the process control valve when the delivery side pressure is below the target range;
• moving the actuator to close the process control valve when the delivery side pressure is above the target range;
• and
• applying 0.001″ hardcoat anodizing to create a barrier between aluminum and stainless steel screws to eliminate electrolysis and aluminum corrosion;
• wherein, the first and second pressure chambers of the actuator are responsive to a first loading valve fluidly coupled to the first pressure chamber and a second loading valve fluidly coupled to the second pressure chamber, and the first loading valve and the second loading valve open and close in response to the delivery side pressure to change a position of the actuator and thereby operate the process control valve.