Do I need to remove the level gauge for purging?

This post was last edited by ylb913 on 2018-9-21 at 19:53. It has a shut-off valve that can be used to close the flow, or it can remain open; thanks to a relatively long blind section, the diaphragm is not easily damaged. For those without shut-off valves, especially the plug-in type which must be removed and sealed with a flange cover; otherwise the diaphragm will get damaged, and the zero point of the double flange design will be affected.

Even for pressure measurement, the gauge has to be removed. There’s no need to remove the gauge; when cleaning is started, welding slag and scoria fly around everywhere. Besides, who knows where there is slag in the pipes first and where there isn’t? . . Once the slag is blown onto the diaphragm, disaster strikes immediately. In my opinion, it’s better to remove the stop valves on the pressure introduction pipelines as well; otherwise, small debris will get onto the rubber seals of those valves, and that will cause problems down the road. . .

This issue stems from the purging process; generally, purging refers to cleaning newly installed pipes in order to remove residual slag, dust, and other contaminants inside them. If equipment is included in the purging process, its inlet pipes are cleaned first before the equipment itself is introduced; otherwise, the equipment will end up functioning like a trash bin. Furthermore, purging can be carried out either by continuous purging or by burst purging; in either case, the flow rate within the equipment is the lowest, so it is difficult for slag to fly around. In pressure-transmitting tube level gauges, since the gas in the pressure-transmitting tube is sealed, it is already filled with purge gas during the purging and pressurization process; there is no gas flow during this phase, so generally no foreign objects can enter. As a precaution, it is possible to close the root valve ； For flat diaphragm types, the root valve can be closed; for plug-in types, if it has been confirmed that the equipment has been purged, it can remain installed or removed to prevent accidents. Personal opinion, for reference only.

The plug-in type must be removed； It’s fine to use other type of root valves; there’s no major problem if no root valve is used. Ordinary level gauges work just fine, and purging inside the equipment isn’t very effective – it can’t achieve much in terms of cleaning.

The root valve can be closed during purging; it is strictly prohibited for dirt to get in and damage the flange surface, as this could cause damage.

During purging, it is best to close the root valve to prevent debris in the pipeline from damaging the diaphragm box. When using steam for purging, extremely high temperatures, as well as improper handling, can also cause damage to the diaphragm (we have encountered such situations in our work). Therefore, it is recommended to close the root valve; if there is no root valve in the design, it is advisable to remove the double flanges and install blind flanges before proceeding with purging.