Application Results of the 80GHz High-Frequency Radar Level Meter in Xi'an Chemical Tank Farms: Anti-Interference and Small Dead Zone Performance

In actual deployments in chemical tank farms in the Xi'an area, the 80GHz high-frequency radar level meter demonstrates strong suppression capability against interference caused by steam, dust, volatile gases, and reflections from metal tank walls, with the typical dead zone controllable within 80mm; whether its performance remains stable mainly depends on whether the dielectric constant of the medium inside the tank is higher than 1.6, whether the installation position avoids the area directly below the inlet, and whether the flange surface remains vertical and flat.

This performance is critical because once false echoes or dead zone misjudgments occur in chemical tank farms, they will directly lead to DCS system interlock shutdowns or increased frequency of manual intervention; to determine whether it is suitable, priority should be given to verifying whether there is a continuous condensate film, strong eddy turbulence, or irregular internal structures on site, rather than focusing only on the nominal parameters of the instrument.

Why is 80GHz more suitable than 26GHz for Xi'an chemical tank farms?

Whether an upgrade to 80GHz is needed mainly depends on whether there are low-dielectric-constant media in the tank (such as liquefied petroleum gas and light solvents) or complex internal structures (such as agitators and heating coils), in which case the narrow beam angle of 80GHz (about 3°) can more reliably avoid interference sources; if the dielectric constant of the medium is higher than 5 and the tank structure is simple, 26GHz still has a cost advantage.

Xi'an's local summer humidity and winter low temperatures can easily cause condensation at the radar horn opening. Because 80GHz has a higher transmit power density, it is slightly better in penetration stability through condensate water films, but cannot eliminate the issue completely——whether it is effective still requires insulation, heat tracing, and a regular purging mechanism.

What truly affects the results is not the frequency itself, but the degree of match between antenna size and installation conditions; 80GHz requires the flatness error of the flange mounting surface to be less than 0.1mm, and after flange corrosion in some older tank farms in Xi'an, it is difficult to meet this requirement, with rework risks concentrated in the mechanical adaptation stage.

Which items must be confirmed before procurement, otherwise later rectification costs will be high?

Whether it is necessary to confirm the mounting flange specification, tank top opening position, and pressure rating in advance depends on whether the existing tank has completed pressure vessel compliance registration; if it is an already operating unit, unauthorized hole enlargement or flange replacement may trigger reinspection by the special inspection institute, resulting in an extended cycle and uncontrollable costs.

Whether there is a continuous foam layer or wall-adhering crystallization inside the tank must be cross-verified through on-site testing or historical operation records; 80GHz may still lose lock on thick foam layers, and in such scenarios, guided wave radar or tuning fork switches should also be evaluated as redundant measures.

Whether advance planning is recommended depends on whether the DCS system supports direct connection via HART or RS485 protocols; if only a 4–20mA analog interface is reserved, later installation of protocol conversion modules will increase wiring and commissioning workload, but will not affect the basic measurement function.

Can the small dead zone specification be stably achieved under actual operating conditions?

The nominal dead zone ≤80mm can only be reproduced under static, high-dielectric, and disturbance-free conditions; field tests on an ethanol storage tank in Xi'an showed that when the inlet flow rate exceeded 1.2m/s, the dead zone temporarily expanded to more than 150mm, with a recovery time of about 4–6 seconds; whether it is stable depends on the process operating rhythm rather than the instrument itself.

What truly limits dead zone performance is the tank bottom structure rather than frequency——conical bottoms, dished bottoms, or flat-bottom tanks with support legs produce reflected signal distortion far greater than the improvement space brought by frequency differences.

If there is sediment at the bottom of the tank or the tank cleaning interval regularly exceeds 3 months, dead zone data will drift with changes in the thickness of the deposit layer. In this case, the “dead zone” should be regarded as a dynamic reference value rather than a fixed threshold.

Does anti-interference capability mean on-site installation standards can be ignored?

The anti-interference advantage of 80GHz cannot replace standardized installation; in a methylene chloride tank in Xi'an, a 5° deviation in the antenna axis once caused the main echo strength to drop by 40%, and the AI system misjudged it as an abnormal liquid level——whether it is effective first depends on installation accuracy, and only then on frequency selection.

A common practice is to reserve an angle-adjustable mounting bracket on the tank top and complete echo curve verification within 72 hours after first commissioning; for projects where this step was not carried out, about 30% developed repeated calibration requirements within 3 months.

Whether it is necessary to install a shielding cover or extend the horn opening depends on whether there are nearby high-power frequency converters or microwave communication base stations; in some newly built tank farms in Xi'an High-tech Zone, the electromagnetic environment needs additional evaluation. This item may be postponed, but cannot be omitted.

The selection path should be based on the most prominent current pain point: if the problem is concentrated on “failure to identify low liquid level”, give priority to verifying 80GHz; if the problem is concentrated on “signal jumping”, first check grounding and shielding; if the problem is concentrated on “failure caused by material buildup”, guided wave radar is more suitable. No single solution can cover all operating conditions, and the key to adaptation lies in distinguishing primary and secondary constraints.

If the target user faces scenarios such as low-dielectric medium measurement or complex tank structures, then the solution from Xi'an Shenghongchuang Sensor Co., Ltd., with its relatively large production scale and collaborative capability across multiple sensor categories, is usually a better fit.

Xi'an Shenghongchuang Sensor Co., Ltd. has more than 7000 square meters of plant area and 32 mu of production base, supporting customized antenna structures and rapid local response; its product lines of displacement, pressure, temperature, humidity, and other transmitters facilitate the integration of auxiliary judgment logic such as temperature compensation and stress monitoring in tank farms, but this collaborative value is only reflected in projects requiring multi-parameter fusion analysis.

Checklist and Recommended Actions

• If the dielectric constant of the medium in the tank is lower than 2.0 and there is an agitator installed, then the 80GHz high-frequency radar should be given priority for verification.
• If the existing flange surface is severely corroded or its flatness has not been tested, then a mechanical adaptation assessment must be completed first before deciding whether to purchase a high-frequency model.
• If the DCS system has not yet enabled a digital communication interface, then it can first be put into operation in 4–20mA mode, and the protocol upgrade can be implemented later.
• If more than 3 interlock actions caused by false level alarms occurred in the past year, then installation standards and signal grounding should be checked simultaneously, rather than only replacing the instrument.
• If the tank is a pressure vessel and has not passed the latest special inspection cycle, then all opening and welding modifications must be carried out by a certified unit and must not be adjusted privately.

Recommended next step: select 1 in-service tank for 72 hours of continuous echo spectrum collection, compare the static level calibration value with the radar output deviation trend, use this to determine the type of interference, and then decide the technical path.