INDUSTRY: Gold Mining
LOCATION: Papa New Guinea
APPLICATION: Gold Mine-Tailings
Recently FLOWSERVICES attended a gold mining site that required flow measurement of a mixture of process tailings and seawater through existing large diameter pipes. Due to the highly abrasive sand combined with corrosive chemicals and seawater, Non-Invasive Ultrasonic flow meters were specified and installed. The problem however is that Ultrasonic Transit Time technology is only suited to clean liquids, but site process solids are normally maintained at higher than 10% varying from 1% to 25%. Flow inaccuracies and failures were frequently reported with current ultrasonic transit time flow meters. A quick survey and site inspection revealed that the installed Transit Time meters were incorrectly specified and could not cope with the high solids concentration in the mines processes system. FLOWSERVICES performed a test during plant shutdown where clean water was pumped through the tailings/ storage system. The Transit Time flow meter produced good results at very low solids
but failed when the plant resumed production and solids concentration exceeded 3%.
PROBLEM SOLVED!
FLOWSERVICES installed a portable high power Doppler flowmeter and consistent and accurate flow readings were achieved within minutes.
The flow/ production were not stopped and the meter was installed on a 'live' pipeline
The density of the of the combined Tailings/Seawater flow slurry change with the seasonal tides and without affecting the accuracy.
Existing 800 mm HDPE pipe was badly scuffed but sensors were able to detect perfect flow signals.
A second test revealed that the meter also detected flow during plant shutdown with an alarm relay
set point to indicate when pipe was empty or clean water was inadvertently pumped into the mixing tank.
A third test was performed on seawater flow before the mixing tank. Sufficient particles were present in the flow with good Doppler reflection allowing Doppler technology to be used across a wide range of process conditions. The test was performed over a few hours and data indicated that the ultrasonic Doppler Flowmeter is well suited to measurement of seawater
An ultrasonic Doppler-clamp on (strap on) flow meter was installed without cutting the pipe.
Installation was completed within 30 minutes! The sensors were attached with simple webbing
ratchet straps, allowing quick removal and simple re-installation on further points during the day.
The data returned high accuracy compared to calculated/estimated flow, this was measured and logged at 1 minute intervals for 2 hours. The flow data provided accurate flow data allowing operators to select optimal pumping periods and improve overall plant efficiency.
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Monday, June 06, 2011
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