- Capillary Tube (Flexible) is operable at High Pressure at least (100-350psig).
- 5-way direction control (Direct Acting ) Valves with spring return. See images below.
- Associated Tubings (Impulse Lines).
- THE CAPILLARY FLEXIBLE TUBING: This shall come with the temperature system (A thermowell without an electrical connection). Instead, it is fitted with the tube filled with volatile temperature-sensitive gas (vapour tensioned, since it is for gas operations). This system will generate the necessary pressure to control the 5-way direction control valve.
- As per the diagrams above the valve is NORMALLY CLOSE when no pressure is sensed from the Capillary (Note that some modification is required to enable the capillary to drive the valve spool without loss of vapours in the capillary tube).
- Ports A and B control the MAIN FLOW CONTROL VALVE by allowing or blocking flow on Main Valve Actuator. The "PUMP" in the diagram is where the pressure is tapped from (High-Pressure Line) Upstream the Gas Line and reduced to 250psig or depending on the operating pressure of the MAIN CONTROL VALVE.
- THE 5-WAY DIRECTION CONTROL VALVE: This allows upstream fluid tapped through a PRV (Pressure Reducing Valve) from 2500psig to 250psig used to move the Valve Cylinder.
- Now, very importantly, the inlet and outlet of the control pressure are decided by the Thermosystem and Capillary Tubing as aforementioned. But the big deal here is there is no Instrument Air to control the valves. The main Gas lines are used for the control and that is a major concern.
- Hence, the vents are redirected to the Low-Pressure Line Downstream of the Gas Line along the flow to avoid loss of Gas. That is what should be experimented with if no SAFETY ISSUES, then we are good to go.
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