Nowadays, The refining industry is facing significant transformations as existing refineries modernize to stay competitive. To improve energy efficiency, production output, and roduct quality, refineries face various challenges during this transition, including the need to improve energy efficiency, reduce operational and maintenance costs, and ensure safety while adhering to stringent environmental regulations. These challenges are equally present for new refineries, which face the complexities of integrating automation to process cheaper, high-sulfur or heavy crude oil.

In refinery operations, accurate level measurement and control are crucial. With daily production rates reaching up to 100,000 barrels, refineries may have over 1,000 level measurement points. Traditional methods, such as float-based systems, are susceptible to inaccuracies caused by changes in the density and temperature of different crude oils, which affect the reliability of these measurements. These fluctuations can compromise the control process and negatively impact refinery productivity and product quality. As a result, refineries are shifting towards more precise, low-maintenance technologies to ensure accurate measurements and enhance overall process control.

In this article, we will explore five advanced level measurement technologies suitable for the refining industry: Radar, Ultrasonic, Differential Pressure, Magnetostrictive, and Capacitive level sensors. Each technology has unique advantages and limitations, making them suitable for different applications based on performance requirements, operating conditions, and installation constraints.

1. Guided Wave Radar (GWR) Level Transmitters

Principle of Operation:

Guided wave radar level transmitters (GWR), also known as time-domain reflectometry (TDR) or microwave pulse radar (MIR) level transmitters, offer continuous level measurement. The device sends low-power microwave pulses down a probe, which travels at the speed of light. The pulses are reflected back at the liquid-air interface, and the time delay between transmission and reception is used to calculate the distance to the liquid surface.

Advantages:

Precise and reliable: Provides accurate measurements in challenging applications such as measuring liquid-liquid interfaces (e.g., oil-water interface) and through foam.

Unaffected by medium changes: Changes in density, dielectric constant, or conductivity of the liquid do not affect measurement accuracy.

Low maintenance: With no moving parts, GWR devices require minimal maintenance and can be easily integrated into existing systems.

Limitations:

Installation considerations: The choice of probe type and installation height can limit performance, especially in applications with thick or sticky media.

2. Non-contact Radar Level Transmitters

Principle of Operation:

Non-contact radar level transmitters send signals through steam to measure the surface distance. This type is ideal for measuring viscous, sticky, and agitated liquids in tanks with mixers or agitators, as it completely isolates the sensor from the process media.

Advantages:

No physical contact: Suitable for hazardous or corrosive media, as it does not come into contact with the process material.

Minimal maintenance: Since the device does not interact with the liquid, there are no moving parts to wear out, resulting in reduced maintenance costs.

Limitations:

Installation challenges: A clear line of sight to the surface is required for accurate measurement. Rough or turbulent surfaces can reduce accuracy, and surface foam or agitation can lead to signal loss.

3. Ultrasonic Level Transmitters

Principle of Operation:

Ultrasonic level transmitters use sound waves to measure the distance to the liquid surface. A pulse is emitted from the transmitter, and the time it takes for the pulse to reflect back is used to determine the level.

Advantages:

Easy installation and setup: Simple to install and configure, making it suitable for various applications, including tanks and silos.

Non-contact measurement: Eliminates the need for direct contact with the process medium, reducing maintenance.

Limitations:

Temperature sensitivity: Changes in process temperature can affect the speed of sound, requiring temperature compensation for accurate measurement.

Surface conditions: Foam, vapor, or turbulent surfaces can interfere with the ultrasonic waves, reducing measurement accuracy.

4. Pressure Transmitter Level Measurement

Principle of Operation:

Pressure transmitters measure the liquid level indirectly by gauging the pressure exerted by the liquid column. In open containers, the pressure at the bottom of the container corresponds to the height of the liquid column. For pressurized containers, differential pressure transmitters are used to compensate for the internal pressure.

Advantages:

Versatile: Suitable for a wide range of liquid types, including slurries, and works effectively in high-pressure and high-temperature environments.

Cost-effective: One of the most affordable level measurement technologies, ideal for standard applications.

Limitations:

Density variation: Pressure transmitters are affected by changes in the fluid's density, which can impact measurement accuracy.

Not suitable for corrosive or viscous liquids: Special materials or coatings may be required, which can increase the complexity of maintenance.

5. Capacitive Level Transmitters

Principle of Operation:

Capacitive level sensors measure the changes in capacitance caused by the presence of liquid between two conductive electrodes. As the level of the liquid changes, so does the capaci tance, providing an accurate level measurement.

Advantages:

Ideal for small tanks and low-volume applications: Capacitive sensors are highly effective in measuring the level in small or narrow containers where other technologies might not fit.

Non-contact: Suitable for clean liquids that do not have a high level of particulates or foam.

Limitations:

Susceptible to buildup: If the liquid is viscous or sticky, buildup on the sensor can affect accuracy.

Limited to specific media: Best suited for non-corrosive and clean liquids; not ideal for highly turbulent or foam-prone substances