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After crushing and milling, the bauxite ore is heated in a pressure vessel along with a sodium hydroxide solution (NaOH) at a temperature of 150 to 200 °C to extract the aluminium as a sodium aluminate solution.

Flow control of the NaOH solution at such elevated temperatures is crucial. Conventional meters such as DP/Orifice, magnetic inductive systems or even coriolis meters tend to corrode under such harsh conditions, leading to measurement drift, the development of leaks through abrasion and their subsequent failure.

FLEXIM's non-invasive ultrasonic flow meters easily overcome such issues as they are mounted outside the pipe wall. No pipe cutting or process shut-downs are needed for installation. The sophisticated  measuring technology FLUXUS offers a highly accurate, reliable and drift-free measurement solution, even at elevated levels of suspended solids by making use of its patented HybridTrek mode of operation.

Engineering with robust stainless steel housings and permanent pipe wall couplings, FLUXUS ensures stable long term durability and virtually maintenance-free operation. Moreover, when employing FLEXIM's PIOX S system, not only can the flow rate can be monitored, but, by measuring the sonic velocity of the medium and correlating it to an internal database, the concentration of the sodium hydroxide solution as well as the density can be displayed.


  • Accurate and reliable flow and concentration monitoring
  • Measuring from outside of the pipe wall - no pipe cutting necessary, virtually maintenance-free operation
  • Long term durability - no measurement drift - not subject to leak failure