Design of pressure regulation skid for natural gas distribution stations
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Our station is a natural gas distribution station; the downstream users are chemical plants, and our role is to supply raw gas to these plants. The chemical plants require that the pressure after regulation remain at 3.5 MPa. However, the pressure in our upstream pipelines fluctuates significantly, which often forces our pressure regulation unit to constantly adjust its control valves in order to maintain a stable outlet pressure. My question is: why can’t our pressure regulation unit perform dynamic adjustments? That is, once the outlet pressure is set, it should automatically adjust itself in response to changes in upstream pressure, so as to keep the outlet pressure steady at 3.5 MPa. Our pressure regulation unit consists of a shut-off valve, a PCV valve, and a PV valve; the PCV valve has pressure sensing tubes for both the upstream and downstream pipelines, while the PV valve does not have any logical control mechanisms
To address the issue you raised, namely ensuring that the pressure regulating unit can dynamically adjust itself to maintain an outlet pressure of 3.5 MPa despite fluctuations in upstream pressure, the following improvement measures can be considered: 1. **Add a PID control system**: Install a PID (proportional-integral-differential) controller on the PCV (pressure control valve). By continuously monitoring the downstream pressure and comparing it with the set pressure, the controller can automatically adjust the valve opening to accommodate changes in upstream pressure. 2. **Optimize PV settings**: Although PVs (safety valves) are already available in the system, it is possible to add logical control functions to them so that they can assist in pressure regulation under specific conditions; for example, they can activate automatically when the upstream pressure exceeds a certain limit, thereby helping the PCV to maintain stable downstream pressure. 3. **Install a pressure buffer tank**: Adding a pressure buffer tank to the pressure regulation system can smooth out the shocks caused by fluctuations in upstream pressure, thereby helping to maintain stable pressure downstream. 4. **Enhance monitoring and data feedback**: Improve the pressure monitoring points on-site, including adding pressure sensors upstream and downstream, to collect data in real time and feed it back to the control system, thereby optimizing the adjustment of control strategies. Through these improvements, the pressure regulating skid will be able to respond more flexibly and accurately to changes in upstream pressure, thereby ensuring stable outlet pressure. .