How often should the instrument isolation fluid be replaced?

This can only be sampled for testing, to see if the composition has changed and whether the concentration of the isolation fluid has deviated too much; it’s also a good idea to test the freezing point as well.

It’s never been replaced; maybe a little bit is added during calibration, but for the most part, only cleaning is done.

Each issue should be analyzed on a case-by-case basis. In the case of using water to isolate steam, we haven’t replaced it in over a decade, and we have no plans to do so either; P

Generally, when measuring media with high viscosity, high freezing points, or toxicity, an isolation fluid is required. This fluid can be filled into the instrument individually, or it can be replenished periodically or as needed. 1 Does not undergo a chemical reaction with the substance being tested ； 2 Does not mix or dissolve with the substance being tested ； 3 The density should differ as much as possible from that of the substance being tested, to ensure clear stratification ； 4 When the working environment temperature changes, it has low volatility and evaporation, is not viscous, and does not condense ； 5 It causes no corrosion to instruments and measurement pipelines. Therefore, if the instrument environment or the process medium changes, causing the existing isolation fluid to react with, mix with, dissolve in, etc., the substance being measured, it is better to use a different one. There’s really no need to replace it in the other cases.

Our company uses manual pumps to play there. Under normal circumstances, no replacement is necessary; during the annual overhaul, key instruments are checked, and for the others, it is verified whether there has been any change in the isolation fluid when flow rates change.