Instrument issues causing shutdown and purging of the unit
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The unit is being shut down for purging; how should instrument issues be handled? For example, how does a flow meter handle it? Some flow meters have bypasses, allowing the flow meter to be disconnected. What to do with a flow meter that has no bypass? Are the pressure-induced valves of the primary instruments also need to be closed due to pressure and other factors? Thank you, please discuss among yourselves
Before purging, the measuring element of the flowmeter should be removed, as some of them can affect the purging airflow and others can damage the measuring element.
A flowmeter without a bypass isn’t designed to have one, so of course it can be purged； I don’t think it’s necessary to close the pressure tapping valve for the primary gauge.
The purpose of shutting down the system for purging is to remove flammable, explosive, toxic, and harmful substances from it. At this point, there are no damaged instruments or debris inside the pipes, allowing the instruments to be purged. However, it is important to ensure that the purging time is not too long, in order to prevent prolonged exposure to high temperatures from affecting the mechanical properties and accuracy of the instruments.
If possible, remove the instruments under appropriate conditions
Extra-precise instruments, such as online analyzers, are removed in advance. For those with bypass lines, after purging the main line, the bypass lines are disconnected; pressure tapping pipes and similar components are generally not disconnected. If welding is to be carried out, it is necessary to contact the instrumentation team to purge and empty these pressure tapping pipes of air (failing to do so poses safety risks; we have experienced minor flash explosions in the past)