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On the level, sticky situations resolved with RF admittance coating rejection

The coating rejection capability of the Drexelbrook RF Admittance level technology is key to its success in the measurement of highly viscous media. Drexelbrook’s patented, proven Cote-Shield™ technology is able to ignore coating build-up on the probe ensuring accuracy and reliability with the elimination of false trips, regardless of product accumulation on the level transmitter.

This makes Drexelbrook level transmitters ideally suited for level measurement in applications involving adhesives, bitumen (asphalt), cement, tarmac, pitch & resins. Furthermore, other features such as its remote electronics ensure immunity to the high temperatures, pressures and significant vibration that are often associated with these manufacturing processes.

Petroleum Bitumen, normally called ‘Bitumen’ or ‘Asphalt’ is produced by refining crude oil. Used as a binder in road-building products, it is a very viscous black or dark brown material.

At Nynas Bitumen’s Eastham Plant at Ellesmere Port in Cheshire, which is a joint venture with Shell, the journey from crude to highly refined process oil starts in the distillation column. The crude oil is pumped from storage tanks through a heat exchanger system where its temperature is increased to about 200°C – and then further heated in a furnace to around 300°C where it is partly vaporised before entering an Atmospheric Distillation Column (ADC).

In the ADC the physical separation of the components takes place. The lighter components rise to the top and the heaviest components fall to the bottom of the column. The material from the bottom then enters a Vacuum Distillation Column via another heat exchanger. This is where the bitumen is produced. Vacuum distillation helps to maintain the inherently high binding characteristics of crude due to the lower operating temperatures.

As an approved supplier to Nynas, ABLE specified the Drexelbrook IntelliPoint RF Admittance Point Switch for the critical high level alarm duties on the bitumen storage tanks. Spillages from these tanks as a result of overfilling have a high potential for serious injury, as bitumen is stored at high temperatures and has a large thermal capacity. Furthermore, the coating rejection capability of the IntelliPoint is key to the success of the measurement of this highly viscous medium. The subsequent reliable and repeatable performance of the IntelliPoint has allowed Nynas to raise the high alarm level set-point, thereby increasing the storage inventory of the vessels.

Nynas Senior Maintenance & Project Engineer, David Harrison, commented, “We had been having a lot of issues with unreliable high-level probes for some time and after some research and preliminary testing decided to use the Drexelbrook model RMT2 probes from ABLE. Along with the in house designed electrical panels we now have a more reliable probe with indication and controlled stop operations fed to/from the DCS that can be relied upon. We will be purchasing further units for our production vessels and chemical tanks in the near future.”

RF Admittance technology is impervious to changes in density, pressure, or electrical properties, even if they are coincidental, guaranteeing dependable level measurement performance in all kinds of process liquids, slurries, granules, and interfaces.

RF Admittance at a glance:

  • The most versatile level technology for liquids, slurries, interface, and granules measurement
  • Proven Cote-Shield™ technology that ignores coating build-up on the probe
  • No calibration shifts due to changes in temperature or material densities
  • Can be remotely mounted up to 100 feet from the sensing element
  • Available as intrinsically safe systems
  • Output: 4-20 mAdc
  • Immune to tank obstructions such as nozzles, ladders, pipes, and agitators
  • SIL 1 and SIL 2 compliant models

For more information on the Drexelbrook range of RF Admittance Level Gauges, please call 0118 931 1188 or email: or visit us at: and for our ecommerce platform.