Difference between instrument air control and main pipeline air source control
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In natural gas pressure-regulated transmission systems, what is the difference between using instrument air and natural gas to control the emergency shut-off valves?
Can the instrument air be supplied stably, or can natural gas be supplied stably? Or which one is more convenient and stable?
Typically, instrument air is purified, dry, and ventable. Natural gas generally contains trace amounts of C3, and over time, this accumulates in the liquid phase ； Some of them do not meet the required level of dryness ； It must not be emptied either (as it poses a safety risk). Therefore, instrument air must be used.
When some pipelines are suddenly damaged (by an explosion), it is necessary to shut them down urgently to prevent backflow at the low-pressure end. At this point, the main pipeline is powerless!
Is it a matter of trade-offs? Natural gas and compressed air have different hazard levels. The resulting safety hazards vary. Emergency shut-off valves are used in emergency situations; the types of emergencies include safety incidents, operational issues, quality problems, and so on. If the material inside the process pipeline equipment is a hazardous material, should natural gas then be used as a power source to cut off the hazard? Reasonable? Generally, high-performance instrument air is used