Liquid Sampling

Liquid driven eductors are gaining greater acceptance and application as a reliable method of transporting liquid samples to process analyzers.  Whether driven by water or process fluid, designers are realizing their value and increasingly incorporating these ‘pumps’ in sample systems.

Justification includes:

  • Provide the motive force to transport liquid samples that have insufficient pressure
  • Use process fluid to drive the eductor then return all fluid to the process
  • Reduce or eliminate waste
  • Eliminate disposal and satisfy environmental regulations
  • Reduce or eliminate maintenance
  • Significantly reduce capital costs
  • Take advantage of the intrinsically safe property of the eductor

Although a mechanical pump could perform the job, by its nature it necessarily reduces reliability and introduces maintenance costs.  The no-maintenance, reliable alternative to a mechanical pump is to use an eductor.

To effectively draw a liquid sample, pressurized water or process liquid must provide the motive source.  (Do not use air/gas to draw a liquid sample or vice versa.)  When using a pressurized process stream, the analyzed sample is recombined with the bypass thereby returning all fluid to the process.  This eliminates waste and disposal.  To aid in the design of the sample system, performance curves for the Hi-Flow mini-eductor (ASP-520R-S-4), the Motiv-Air-Torr (ASP-520-S-4) and the Teflon eductor (ASP-500T6) are shown below for water.  (Other materials of construction are also offered.)  These eductors offer the performance required in a compact design.

Sample Flow versus Water use

Sample Flow Versus Motive Pressure

Vacuum Vs Water Pressure

Motive Water Usage