5 key lessons when using Guided Wave Radar
Guided wave radar is a both a popular and an ideal product for measuring level. It’s virtually unaffected by changing process conditions, temperature, pressure, vacuum, vapours and condensation and changes in the measured product properties like conductivity, density and viscosity. Guided Wave works well with solids too, unaffected by dust and uneven surfaces. Temperature ranges are from -196 to 450°C and Pressures up to 400 Bar.
Its also simple to understand, a rod or flexible cable extends down over the range you want to measure, you can even cut to length to suit the application (with exception of coated, polished and some special design probes) then install and set it up. That’s simple too: just program min and max levels in relation to the rod or cable and its ready to go. They can also be used to measure level and interface in the right process conditions and operate in stilling tubes, bridles and bypass cages.
Our service engineers are setting them up every other day and have given us an insight into some of the most basic issues they regularly see.
The right configuration
Installation
Make sure the GWR is mounted directly into the vessel whenever possible, avoid standoffs as they can cause unwanted interference. If using a concentric probe (see fig 1 - where a rod is inside an outer tube with both attached to the probe), they are not influenced as the signal path is contained inside. If in a plastic vessel use a metal plate or flange greater than 100mm diameter, this helps to ‘push’ the microwaves in the right direction. It’s said all the time, but it really is worth a look at the manual, ideally before you buy, it may save you time and further vessel modifications. And, once again a chat and sharing a sketch or drawing with a knowledgeable manufacturer can help you avoid some pitfalls you might not be immediately aware of. Finally be careful of installing rod probes in agitated vessels, even if it is nowhere near, as long-term fatigue from even a small process movement may cause issues with process seals and signals. Make sure cables cant touch the sides or internal objects, always install them on an empty silo if measuring solids.
Figure 1 A concentric tube format device helps with poor installations like nozzles, but can be susceptible to highly viscous products or long term internal deposits and build up.
Guide Length
Build up
Careful of build up in any mounting nozzle, perhaps insulate it if it's a heated product that sublimates on cooling. Be especially careful if using a concentric tube format between rod and outer tube, or twin rods on high viscosity products, these types of systems often have internal spacers, build up on these can also cause measuring errors and reading hang-ups. Use a single rod format whenever you can. Use minimal spacers (ideally just one at the end) if mounting in a stilling tube or bypass. Explore a contactless measurement format if its a high viscosity, contaminated product that is expected.
Figure 2: Guided Wave Radar installed in bypass with a Magnetic Float Level Indicator as a second technology and side mounted tuning fork switch alarm. These narrow tubes need spacers to ensure the rod is central, but be careful about build up on them.
Measuring oils and hydrocarbons
Summary
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