Straits Chemical Storage Case: Radar Level Meter for Turbulent Liquid Tanks Under Filling Impact

A tank is never harder to measure than while it is being filled - and that is exactly when the measurement matters most. This case study covers a vertical storage tank receiving product by top loading from road tankers, where the incoming stream impacts the liquid surface and creates turbulence, waves, splashing and air entrainment. Level measurement in this service is difficult because the surface is not a flat reflector during filling: it moves, breaks up and generates moving false echoes, and the fill stream itself returns a signal. The previous ultrasonic transmitter produced jumping readings during loading, and manual dipping was unsafe while filling was in progress. A non-contact 80 GHz FMCW radar level meter with echo tracking was selected. This article follows one filling cycle and explains what the measurement must do at each phase - selection, configuration, installation and commissioning.

Client Profile: Straits Chemical Storage Pte. Ltd. (Singapore)

Straits Chemical Storage Pte. Ltd. is a chemical storage terminal in Singapore operating top-loaded storage tanks that receive product from road tankers. Because overfill risk exists only while a tank is being filled, the terminal needs level measurement that stays valid during the filling itself - through the turbulence, splash and foam created by the incoming stream.

2. Real Industrial Condition: The Tank That Is Only Difficult While It Is Being Filled

The tank is a vertical, atmospheric storage vessel filled by top loading: product arrives by road tanker and is pumped in through a fill pipe that discharges above the liquid surface. At rest, the surface is flat and the measurement is easy. During filling - which lasts tens of minutes at a flow set by the transfer pump - the incoming stream strikes the surface at velocity, and the surface becomes anything but flat. The duty is unforgiving in one specific way: the overfill risk exists only while the tank is being filled, so the level measurement must be at its most trustworthy during the very period when the surface is at its most disturbed.

3. Measurement Challenge: What the Incoming Stream Does to the Surface

What the incoming stream does to the surface is a list of radar problems. The impact creates a crater and radiating waves, so the surface is tilted and moving. Splash throws droplets into the beam path, and air entrained by the falling stream forms a foam layer that can persist after filling. The falling stream itself is a moving target that returns an echo of its own - an echo that changes position every second. The result is a measurement environment where the true surface echo is surrounded by moving, competing echoes, and where the apparent surface height can differ from the real liquid height. Any instrument that assumes a calm, flat surface fails here; the instrument has to track a surface that is only calm when the tank is not doing what tanks are for.

4. Why the Existing Method Failed: Quiet at Rest, Wrong in Action

The previous ultrasonic transmitter measured well at rest and poorly in action, for physical reasons. Its acoustic pulse was scattered by splash droplets and foam, so the reading jumped between the true surface, the foam top and random droplets; during filling the output was unusable for control or alarm. The turbulence also defeated the alternatives. A guided wave radar or float in a stilling well suffers mechanical stress from the disturbed liquid and can be coated by foaming product, and a stilling well only helps if the well itself stays filled with calm liquid - which is not guaranteed with a violently agitated surface. Manual dipping during filling was ruled out by the site's safety rules, and a dip taken after settling only confirms what already happened. Every old method shared the same flaw: it could measure the tank, but not while the tank was being filled - the only time the measurement was truly needed.

5. Instrument Selection Logic: What the Replacement Had to Do Differently

The replacement had to do one thing the old methods could not: keep a valid measurement while the surface was turbulent. Non-contact radar was the only candidate that could, and the details were chosen for this specific disturbance. An 80 GHz FMCW radar was selected over a 26 GHz pulse radar because the narrower beam reduces pickup of splash and wall reflections, and FMCW processing with a fast update rate can resolve and track the surface echo among moving echoes. Echo tracking - the transmitter's ability to follow the strongest plausible surface echo rather than locking onto the first return - is the feature that makes the difference in this service. The antenna is a small horn or lens type, sized to the nozzle, with a beam that stays clear of the tank wall at the expected range. For extreme splash, a stilling well or wave-stilling arrangement can be added, but the first choice is correct positioning and signal processing, not hardware.

Recommended Qinwei Instruments for This Application

7. Radar Level Meter Configuration: Tracking, Averaging and the Fail-Safe Direction

Configuration starts with the physics of the fill. The measurement update rate is set as fast as the transmitter allows, because the surface changes quickly during filling. Echo tracking is enabled and the tracking window is set around the expected surface position, so the transmitter follows the true level instead of a splash echo. Averaging (damping) is set with a deliberate compromise: long enough to smooth the wave-induced scatter, short enough to respond to a genuine fast rise - the fill rate determines the right value, and it is set during commissioning, not guessed. The 4-20 mA output is scaled over the working range with HART enabled. The fail-safe direction is set to drive the output high on a lost echo, so that if the turbulence defeats the measurement, the alarm state is the safe state - during filling, a false high is far safer than a false low.

8. Installation Method: Keeping the Antenna Out of the Impact Zone

Installation is where most turbulent-tank problems are either solved or created. The antenna is mounted away from the fill inlet, on the opposite side of the tank roof where the layout allows, so the falling stream and its splash are outside the beam. Where the nozzle position is fixed by the tank design, a deflector plate is fitted under the fill discharge point to break the stream and reduce the impact crater. The antenna extends below the nozzle bottom to avoid the nozzle echo. The beam clearance is checked against the tank wall and any internal fittings at the maximum range - a beam that clips the wall turns the wall into a competing reflector. Where splash is so severe that the surface cannot be seen at all, the fallback is a stilling well with the radar mounted above it; this is a design decision made on site, not a default.

9. Commissioning / Parameter Setting: The First Live Filling Is the Real Test

Commissioning follows the filling cycle itself. With the tank empty or at low level, the empty spectrum is recorded and fixed echoes - nozzle, fill pipe, wall fittings - are mapped and suppressed. The fill pipe echo is noted as a moving target, not suppressed, because it changes with the flow. Then the first live filling is observed from the control room with the echo curve on screen: the tracking window is adjusted so the transmitter follows the surface through the turbulence, and the averaging is tuned against the actual fill rate. When the tank settles, the radar reading is compared with a manual dip and the deviation recorded. The high-high alarm is tested at the end of the fill. The commissioning criterion is simple: the reading must be stable during the fill, and accurate when the tank is at rest.

10. Measurement Result: What the First Filling Cycles Showed

Across the first filling cycles, the radar behaved as the selection logic predicted. During filling, the output stayed on the true surface: it moved with the rising level instead of jumping with the splash. The foam that formed during loading did not capture the reading, because the echo tracking followed the liquid surface below it. At rest, the reading agreed with the dip within the expected tolerance for an 80 GHz radar on liquid (approximately +/-5 mm, depending on conditions). No false high-level alarms were triggered by splash during the observation period - the failure that had made the old ultrasonic unusable during loading. Site-specific figures are not provided; the engineering outcome is that the measurement is now valid at the moment of highest risk.

Why Choose Qinwei Instruments

Xi'an Qinwei Instrument Factory (brand QINWEIYB) is a manufacturer established in 2010 that specializes in industrial automation instruments, with 500-800 employees and 50%-60% of output exported worldwide. For turbulent-liquid service, Qinwei radars support fast update rates and echo-tracking signal processing, with Ex-rated options where the tank area is classified. All instruments are factory-calibrated with traceable certificates; MOQ starts from 1 set, delivery is 5-8 working days, and OEM/ODM customization is supported.

12. Engineering Value: Protecting the Tank at the Moment of Highest Risk

The value is concentrated in the filling window. Overfill protection is only meaningful while the tank is being filled, and this is the first measurement that the operators could trust during that window. Loading no longer has to be stopped to check the level, and inventory is known continuously instead of after the surface settles. The maintenance burden of the old ultrasonic - cleaning and re-verification after every disturbed period - disappeared. The causal chain is compact: non-contact measurement removes the parts that turbulence damages; echo tracking follows the true surface through the disturbance; the fail-safe direction keeps the alarm honest when the signal is lost; therefore the tank is protected at the moment when protection is needed.

13. Recommended Applications: Where the Same Logic Applies

The same logic applies to any tank whose surface is disturbed by its own filling: top-loaded storage tanks receiving from road or rail tankers, reactor feed tanks, mixing and agitation vessels, and tanks with submerged filling that creates foam. For each, the engineering sequence is the same - position the antenna out of the impact zone, enable echo tracking, set averaging against the fill rate, and test against a live filling. When requesting a quotation for this service, provide the fill rate and filling method (top or bottom), tank height and nozzle position relative to the fill inlet, whether foam forms, and the required output and alarm interface.