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1.6-Hexanediol (HDO) is an intermediate product in the chemical industry and is used primarily in the synthesis of polyesters and polyurethanes. The Industrial-scale production of HDO takes place in a continuous process by the catalytic hydrogenation of organic preliminary products under high temperatures and pressure (up to 250 °C and 300 bar). A portion of the product is constantly recycled via return lines in order to conduct excess heat out of the reactor. This heat transmission must be monitored with flowmeters which are part of a safety instrumented system (SIS).

In the past, flow measuring points on the Hexanediol return lines were conventionally fitted with differential pressure flow meters. However, these meters incurred considerable maintenance costs. Non-invasive flow measurement with FLUXUS proved to be the superior alternative. Since the clamp-on ultrasonic transducers are simply mounted on the outside of the pipeline, the measuring equipment is not subject to any wear and tear by the medium flowing inside and it is not exposed to the high pressure. Due to the high process temperatures, the ultrasonic transducers are mounted on a special high temperature device, the patented WaveInjector.

A particular challenge is posed by the wide temperature range that must be covered accurately and reliably. The measurements are thus carried out with a two channel measurement system in order to ensure that they were working reliably in every possible operating condition. In addition, the signal strength is fed into the process control system as a diagnostic parameter. As part of the safety instrumented system, measurements are regularly checked and their operational reliability is recorded.


  • Accurate and reliable flow measurement ensuring safe plant operation
  • Non-invasive measuring technology: no pressure loss, no wear and tear caused by the medium and high pressure level, no risk of leakage
  • Practically wear-free, long-term stable measurement
  • Sustained increase in plant availability: minimum repair and maintenance costs, plant operation is never interrupted for pipe work thanks to clamp-on measuring equipment