The following is part of a "Case Studies In Innovation" series of blog posts we will be running on the FlowStream Blog in the coming weeks to highlight winners of the 2013 Flow Control Innovation Awards program.
During a field test at a leading metal supplying company, the SITRANS FC430 Coriolis flowmeter demonstrated exceptional stability and reliability in measuring the concentration of tungsten metal.
H.C. Starck, a global supplier of refractory metals and technical ceramics, produces powder chemicals and compounds, including tungsten and tungsten alloys. To produce tungsten powder and products, the company first sources solid tungsten from other industries. This unprocessed metal tends to be extremely brittle and difficult to work with, which is why it must be purified to 99.99 percent pure tungsten. Purification ensures the final product will be malleable enough for use in metalworking, while still retaining its distinctive hardness.
Once the sourced metal is reduced to sodium tungstate in dissolving tanks, it is passed through filter presses before being sent to an intermediate storage tank, where it awaits transfer to a purification header vessel. When one of the header vessels needs to be refilled, a downstream level controller starts a pump and the required quantity of sodium tungstate is transferred from the storage tank to the vessel.
To ensure the purification process is as effective and time-efficient as possible, the purification system must receive real-time updates on the exact concentration (i.e., fraction) of tungsten within the fluid being transferred to the header vessel. For this reason, the metal supplier required the installation of a flowmeter to provide feed-forward process data to the purification system. The chosen meter needed to be capable of highly accurate density measurement despite the fluctuating flow, pressure, and temperature conditions that result from 15 to 20 pump starts per day.
The customer was interested in the SITRANS FC430 for its ability to measure density, volume, and temperature in addition to mass flow, as well as its compact size and accuracy.
To perform the field test, a SITRANS FC430 meter was installed on a discharge line below an intermediate storage tank and adjacent to a transfer pump. The results were highly successful:
Performance remained stable at zero flow, with a total deviation of only +/-1.5 kg/h (3.3 lb/h) over a temperature range of 1.6 C (34.9 F).
Flowrate and density were reported reliably over the entire duration of a 104-minute trace, with no unexplained fluctuations or spikes in flow trend.
Reliability was demonstrated under dynamic conditions, with nearly instant response times to changes in flowrate caused by pump starts and stops.
Density readings were accurate to within 1 kg/tonne (2.2 lb/tonne) as compared to a laboratory reading.
Performance in fluctuating volume flow was excellent, with the flow signal following the dynamics of a reference reading reliably with no visible deviation.
The driver current demonstrated stability of greater than two significant digits at zero flow and deviations of less than two significant digits in conditions where pressure or temperature fluctuated.
The metal supplier was so encouraged by the early performance of the SITRANS FC430 that they upgraded the Coriolis mass flow sensor to a complete system and implemented it as part of the overall tungsten purification process.