Guided Wave Radar Pros and Cons
Post on 11-Feb-2016
DESCRIPTIONGuided Wave Radar Pros and Cons. By David Land, P.E. ConocoPhillips Field Instrumentation Network Lead. Time. GWR Cons First. - PowerPoint PPT Presentation
Guided Wave RadarPros and ConsBy David Land, P.E.ConocoPhillipsField Instrumentation Network Lead
GWR Cons FirstGWR is a contacting technology the probe is in the process fluid. If the fluid is particularly corrosive or there are material compatibility issues this can become a limiting factor. There are alternate metals available for probes and Teflon coating is an option, but with Teflon coating you run into Temperature issues.The maximum process temperature for most units is around 750 F. Temperatures over this require a different technology.GWR is unpredictable in foaming applications. In light foam the GWR will ignore the foam and reflect back the liquid level. In heavy foam, the signal can be absorbed and reflect back the top of the foam as level and/or weaken the overall signal.
GWR more ConsHighly viscous fluids should be approached with caution. They tend to coat the probe. Single probes work well with coating, but heavy coating will weaken the signal. Dual probes and coax probes can strengthen the signal but can also bridge in coating service meaning the fluid will bridge across the two probes or inside the pipe of a coax and cause the signal to lock on the bridging as the level.Tanks with agitators or extreme turbulence should be approached with caution. If the agitator hits the probe it will cause a false signal. Extreme turbulence can either break a rigid probe or cause a flex probe to hit against the nozzle, causing a false signal. A coax probe or bridle is a good solution for turbulence as long as the process media does not plate out or coat metals.Interface applications where the product dielectrics are not at least 10 apart will not work with GWR, since GWR depends on a difference in dielectric to reflect back the interface level. Oil/Water is the ideal interface application water with a dielectric of 80, oil with a dielectric of approx. 2. They are much more that 10 apart.
GWR more ConsFiberglass or plastic tanks should be approached with caution. The GWR requires a solid ground for the microwave signal on the probe. We have successful installations on Fiberglass, but dual probes or a metal flange at least 2 OD for a mounting surface is recommended.
In interface applications, if the dielectric constant of the upper product varies there can be an error in the measurement. The dielectric of the upper product must be lower than the dielectric of the lower product to have an interface reflection. The upper product cannot have a dielectric greater than 10 for the single probe and 5 for a dual probe. Depending on the probe, the upper product must be at least 4-8 for the radar to distinguish the echoes between the two fluids.
Emulsion layers between two liquids can cause some inaccuracies.Longer probe lengths may require a crane to extract from the vessel.
GWR ProsDirect level measurementNo moving partsHandles changing density, dielectrics, conductivity, temperature, pressure, pH and viscosityHandles small tanks, difficult tank geometry, interfering obstacles Easy swap (small openings) Virtually unaffected by dust, vapor and turbulence
GWR ProsSolids, powders, granulesLevel and Interface Level from one transmitterGuided Wave Radar technology is virtually unaffected by probe coatingRecalibration not necessary Recalibration cost dramatically reducedMeasurement availability improved
GWR ProsReducing CAPEX Cost Low installation costInstallation while tank is in serviceEasy CommissioningPre-configured transmittersNo re-calibration requiredUser-friendly Configuration tools
GWR ProsReducing OPEX Cost Increased AvailabilityNo re-calibrationEntire tank rangeAdvanced Signal ProcessingNo moving parts less down-timeIncreased Safety, Health & EnvironmentDual CompartmentConfiguration adjustments without opening tankOne point entry on top of tank
GWR ProsReducing OPEX Cost Reduced Operations & MaintenanceNo matching partsNo moving parts, less spare parts, less maintenanceRemove electronics while tank is in serviceEasy troubleshootingHigher QualityReliable, accurate level measurementVirtually unaffected by process conditions