|TRANSIT TIME FLOW METER CASE STUDY
FM500, Sonic-Pro transit time flow meter solves build-up challenge.
In a groundwater remediation process at a large oil company located in southern California, the ground water is
contaminated by some unknown bacterial/chemical agent. During the remediation process, the water is pumped
through PVC and HDPE pipes, through a series of filters and into a processing chamber where enzymes are injected
before being returned to the ground. To be effective, the enzymes must be accurately injected into the water
at a rate which is proportional to the water flow rate.
Accurate measurements of the water flow rate and total flow is critical to the application. Initially,
paddlewheel type flow meters were installed but a black deposit built up on the paddles, which required cleaning
every 2-3 days. The paddle wheel flow meters were replaced with insertion magnetic flow meters which failed
after one day, as the coating proved to be non-conductive. A turbine flow meter was tried and failed after
only a few hours of operation. A Doppler type ultrasonic flow meter was tested next but it failed to give any
measurement at all.
A sample of the water was sent to a test lab for analysis. The analysis indicated that there were no particles
present that could reflect the sound waves making Doppler measurements impossible. However, Transit-Time test
measurements were successful using the FM500, Sonic-Pro hybrid transit time flow meter which can function using either
the Doppler or Transit Time measurement methods. The Sonic-Pro transit time flow meter was also able to measure
and display the sound speed of the fluid which, due to the contaminants, was significantly different from plain water. Knowledge
of the actual fluid sound speed is necessary to properly install and calibrate the transit time flow meter.
Besides its tendency to coat the inside wall of the pipe, which over time could possibly block the sound waves, the
contaminants also caused a marked reduction of the sound wave intensity in the groundwater, when compared with clean
water. However, the Sonic-Pro's automatic gain function enabled the transit time flow meter to function properly
over time by increasing and decreasing the sound wave intensity as needed.
Clamp-on FM500, Sonic-Pro transit time flow meters were successfully
installed at the site on 2 inch diameter PVC and 4 inch diameter HDPE pipes at multiple measurement points.
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