Non-intrusive process metering enabled by Silixa’s iDAS technology

Industrial process flows are often too numerous to meter effectively using conventional technologies.

Silixa’s non-intrusive process metering technology enables flow distribution monitoring throughout an entire plant, mine, or oilfield environment simply by using a single length of fibre optic cable installed on process pipes.

This metering system measures the speed of turbulent eddies and acoustic energy. It can be installed on-the-fly, without disrupting process flow or requiring costly calibration. The system is compatible with liquid, gas, slurry, organic, reagent and multiphase flows.

Applications

  • Mining and mine water
  • Water treatment
  • Process control

Benefits

  • Easy to retrofit, low opex
  • Low capex sensing instrumentation
  • No utility requirements at sensing zones
  • Enable increased process efficiency and reduced energy usage
  • Straightforward monitoring for trends in gas void fraction (GVF) and water in liquid ratio (WLR)

Silixa's non-intrusive process metering, flow distribution, monitoring gas void fraction trends

Silixa’s process metering enables flow distribution monitoring throughout an entire plant, mine, or oilfield environment simply by using a single length of fibre optic cable installed on process pipes.

Product specifications

Zones
10
Flow types Single phase, slurry, multiphase, organic, reagents, tailings
Temperature range 0°C – 60°C
Typical accuracy Better than 5%
Integration CSV to cloud
Pipe material Steel, HDPE, PVC, FRP
Pipe size 2″ – 100″
 * customised variants available

Operating principles

  • Eddy currents are present in turbulent flow, moving close to the average velocity of the flow
    • phase independent
    • no calibration requirement
  • eddy currents impart dynamic radial strain on the pipe wall
  • optical fibre attached to the exterior of the pipe measures the convection of these pipe motions, allowing direct observation of flow speed and sound speed
  • up to 10 individual stations per iDAS, with the same fibre

Non-intrusive flow metering: how it works

Silixa’s non intrusive flow metering system functions by measuring the speed at which turbulent flow vortices move through the pipe.

Previous work has shown that, in constrained, well-developed, fluid flow, the motion of local convective fluid disturbances can introduce dynamic pressure variations which in turn impart dynamic strain on to the boundary walls. In the case of flow within a pipe, this dynamic strain field can be observed using a hoop strain –sensitive sensor mounted on the outer wall of the pipe. Where an array of synchronized strain sensors is spaced with intervals less than the coherence distance for the flow, then the local convection of these vortical entities can be used to monitor the flow speed.  It is in fact possible to use the DAS system to achieve such an array.  By wrapping a continuous length of fibre helically around the exterior pipe, the DAS system can measure the dynamic radial strain exerted along a section of a pipe and measure the convection speeds of eddies. In addition, the speed of sound can be measured both through the wrapped section of the fibre and over the entire length of the cable installation.

Case study: Multizone flow metering at Anglo American’s eMalahleni Water Reclamation Plant (EWRP)

Reference: Finfer, D., P. Newman, N. Rein, M. Amir. Pervasive metering of minewater flows and process water using distributed acoustic sensor technology, SAIMM “Water 2017”, Johannesburg, 10-11 July 2017.

Challenge

To demonstrate metering of water and slurry flows at several measurement zones along a single fibre within an operating minewater treatment plant.

Solution

Using a single optical fibre circuit, a multizone process metering system was installed on several processes on pipes ranging in size from 165 mm to 300mm. Metered flows include reverse osmosis manifold water, clarifier underflow slurry, and minewater slurry feed. Flow data was updated once per minute, and compiled data was transmitted automatically via email from South Africa to the London office every 24 hr. Data compilations were provided to the site over the duration of the 6 week pilot.

Results

Flow rates were monitored successfully in each zone. Flow measurement output from the reverse osmosis process provided process insight along a manifold which would have been burdensome to instrument with conventional means. Over the course of a month period when both iDAS and reference sensors were functioning, the accumulated flow rates for the calibrated minewater and slurry flow rate zones were accurate to 1.5% and 0.5% respectively.

non-intrusive process metering, multizone flow metering, Silixa

Download the case study here.

Watch our distributed acoustic flow meter demonstration here.