Solving Level Measurement Challenges in Tough Process Conditions in the Chemical Industry

by | Jun 1, 2021 | Chemical, Level

Varshneya Sridharan

Product Manager for Emerson Asia-Pacific Marketing

According to OSHA, the chemical industry has one of the most stringent safety regulations. Regular inspections, servicing, and maintenance work are required due to the intense stress that is often placed on the equipment due to exposure to very aggressive substances and extremely high temperatures and pressures. Depending on the size and type of plants and operations concerned, maintenance often involves a complete shutdown, however, maintenance and servicing operations in localized production area are common.

More and more frequently, chemical plants are adapting new recommendations and incorporating newer processes to meet the highest safety guidelines prescribed across industries. Faced with many harsh conditions at a typical site, companies are turning to automation and upgrading their activities to simplify manual operations with more sophisticated equipment, driving greater production efficiency and safety management practices.

A pharmaceutical company in Nantong, Jiangsu, China, is an example of one such chemical plant. The company is an end-to-end Active Pharmaceutical Ingredient (API) company, engaged in research and development, production, and the sale of pesticides, pharmaceutical APIs, and other intermediates.

The factory holds more than 400 reactors and storage tanks on site and many operators are required to manually control the processes. However, many of these reactors have extreme process conditions including high operating temperature, vacuum conditions or low-pressure environments, agitation or mixing, and the presence of foam. These conditions pose significant challenges in liquid process control where the liquid level needs to be measured accurately and reliably. Normal operation can easily be interrupted if the level measurement signals are unstable with inaccurate measurement or soft echo which signify a weak signal strength. Inaccurate measurement can be detrimental to the production parameters and the product qualification process. The operations team is also generally concerned with safety of the personnel, automation of the processes and the reduction of number of onsite operator tasks through remote operations. With remote operations, overall safety on the production floor improves, in line with both industry and national guidelines, while aligning operational safety with corporate initiatives.

Challenge 1: Low pressure, Near Vacuum Conditions, and Agitator

  • The process condition of the reactor tank is at negative pressure, sometimes close to full vacuum
  • The reactor contains varying agitator designs including paddle blades, ribbon blades, and multiple impeller blades

Figure 1 (left): Rosemount 5408 Level Transmitter installed on a process reactor
Figure 2 (right): A view of the process reactor with a multiple-impeller blade

Solution

The Rosemount 5408 Level Transmitter with the cone antenna can be used at extremely low-pressure close to vacuum conditions. Rosemount 5408 has excellent software processing capabilities shielding interference caused by the stirring of the multiple impeller blade. By using the world’s leading Frequency Modulated Continuous Wave (FCMW) technology, process noise is filtered out, enabling the level transmitter to automatically track the “clean” echo of the actual liquid level. This results in higher measurement accuracy, stability, and reliability of radar level measurement.

Challenge 2: Corrosive Liquids, High Temperatures, and Stirring Action

  • The reactor tanks contain mainly liquid media types that are highly corrosive
  • The temperatures inside tanks may rise to 410°F (210°C)
  • Turbulence caused by agitation can impact the signal return

Figure 3 (left): Rosemount 5408 Level Transmitter installed on a process tank.
Figure 4 (right): A Rosemount 5408 Level Transmitter with a Process Seal Antenna

Solution

The Rosemount 5408 Level Transmitter is available with a process seal antenna made of PTFE material with good corrosion resistance and is specifically designed for installation in corrosive environments. The tank was coupled with a cooling device to ensure the PTFE material is not affected by high process temperatures outside of the operating specification. Emerson specialists were able to mitigate the high on-site temperature conditions with a custom-engineered level measurement solution.

Challenge 3: Corrosion, Stirring, and Foaming

  • Highly corrosive media stored inside another vessel
  • A single agitator stirring action within the vessel
  • Foam generated by the mechanical agitator action on the process media inside the vessel
  • Foam and Agitator action when the tank levels are close to full can potentially cause overfill incidents if not monitored carefully

Figure 5: A Chemical Tank at the customer’s site with agitator blades showing presence of foam
Figure 6: Rosemount 5408: SIS Level Transmitter is installed in Safety Instrumented Systems for best in class safety and overfill prevention

Solution

The Rosemount 5408 Level Transmitter with process seal antenna made of PTFE material was installed on several tanks. The PTFE material provides good corrosion resistance and is suitable for corrosive environments. Rosemount 5408 is equipped with unique signal functionality and best-in-class software algorithms that can provide strong signal strength, necessary to overcome the influence of foamy or turbulent conditions caused by agitation or the chemical action inside the process tank during normal production.

Challenge 4: Irregular Tank Shapes, Difficult Installations, and Nozzle Considerations

  • Tanks of various shapes and sizes are present inside the chemical plant
  • The nozzles on the tank are tall with irregular shape
  • Nozzles and installation ports can add to interference on the radar signal and affect the quality of the return echo

Figure 7: A Chemical tank at the manufacturer’s site – single tank view
Figure 8: A Chemical tank at the manufacturer’s site – multi tank view

Solution

The Rosemount 5408 Level Transmitter comes with a process seal that is suitable for use in corrosive applications or installation inside tall nozzles. Tall and irregularly shaped nozzles may sometimes pose a problem for level devices, but the Rosemount 5408 Level Transmitter functions perfectly well in this installation design. The Rosemount 5408 level transmitter is equipped with a unique signal quality functionality which mask off interference from internal structures within vessels and the irregularly shaped nozzles often used at chemical plants.

Rosemount 5408 and Rosemount 5408: SIS are two-wire transmitters for continuous level measurement of a broad range of liquids, slurries and solids and the measurement principle utilizes fast-sweep Frequency Modulated Continuous Wave (FMCW) technology. Rosemount 5408 is particularly well-suited for the most challenging applications, including reactors where there may be agitation, foaming and condensation present, as well as high temperatures and pressures. OSHA states the importance of raising the bar on safety regulations inside chemical plants and Rosemount 5408 Level Transmitter serves the purpose to help plants reach the most stringent global chemical safety standards.

Visit the Rosemount 5408 Level Transmitter section on Emerson.com to learn more about how these non-contacting radar level measurement instruments with FMCW technology can deliver high precision measurements for your tough applications. You can also connect and interact with other level measurement experts in the Measurement Instrumentation group in the Emerson Exchange 365 community.

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The opinions expressed here are the personal opinions of the authors. Content published here is not read or approved by Emerson before it is posted and does not necessarily represent the views and opinions of Emerson.