How to handle pipeline purging instruments?

I’ve dealt with this a few times; let me share my experience. When purging pipelines equipped with instruments, it is crucial to first determine the pressure rating of the instruments and their compatibility with the medium. It is generally recommended to remove the instruments or use isolation valves/blind flanges to isolate them; otherwise, direct purging may damage the diaphragms or clog the pressure transfer tubes. If blown in the reverse direction, if there are check valves in the pipeline or areas where debris tends to accumulate, it is possible for dirt to be pushed into the base of the instrument, which poses a significant risk. The basic principle is roughly: first check the purge conditions specified in the instrument manual ； If it can be removed, do so; if not, add temporary splices or plugs ； Keep the purging pressure within the range allowed by the instruments, and avoid too high a flow rate. Specific to your work section, it’s best to check GB 50235 or the construction specifications for your project, or simply ask the design institute for their opinion – the conditions vary quite significantly.

During pipeline purging, all connected instruments must be removed or isolated with short pipes; it is strictly prohibited for high-speed airflow to directly impact the sensitive components of the instruments； Open the control valve fully, or remove the diaphragm head and add a short section; remove the orifice plate/flow meter and replace it with a short tube. Shut off the valve in front of the pressure gauge or remove it, disconnect the transmitter and seal it off.