In pharmaceutical plant (where foaming can occur) or in aircraft de-icer systems where foaming is not expected (there is no return flow) online vibrating element density meters are used; for pharmaceutical applications the Emerson Mobrey tube type with Entrained Gas Amplifier to compensate for bubbles).
These measure the density at line temperature and calculate the density at the reference temperature.
The reference temperature density can then be related through simple identity or by using a special algorithm (configure the existing algorithm) to determine volume or mass concentraion of Ethylene glycol in water (or visa versa).
The simple approach is to linearly relate the base density to concentration. This isn't always valid and where significant or where extra sensitivity is required the density/conentration algorithm can be configured.
This type of online measurement is especially valuable in Pharmaceutical plant to ensure that contamination doesn't raise the freezing point such that the lines freeze.
In many cases the coolant is supplied to quench reactions driven by steam heating so the vessel jacket will be flooded with steam then coolant. Change over valve sequencing is important but over time the valves start to leak and condensate dilutes the solution... not so much a problem in the retrn as the temperature is elevated, but a real problem if this is cycled through the refrigeration plant.
The concentration measurement is thus used to prtect the refirgeration plant and allow the solution to be topped up as necessary and it helps detect when valves need servicing.
JMW
