Sampling Systems

Sampling systems 

Online particle size measurement is only as good as the sample being analysed. For this reason, Xoptix does not simply supply a particle size analyser, but delivers complete integrated sampling and measurement systems. The objective is to ensure that the sample reaching the IntelliSizer remains fully representative of the process stream under all operating conditions. Accurate PSD measurement depends not only on the analyser itself, but equally on the ability of the sampling system to consistently extract and transport a representative sample.

A significant portion of the know-how behind successful online particle size measurement lies in system integration and sample handling. Process conditions such as material loading, particle velocity, pressure, temperature, humidity, and process flow can vary continuously during operation. A properly designed sampling system must ensure that these changing conditions do not influence the measured particle size distribution. The PSD reported by the analyser must reflect actual process changes rather than changes introduced by the sampling system itself.

To address these challenges, Xoptix has developed a comprehensive portfolio of sampling solutions covering a wide range of materials, process conditions, and installation requirements. Each sampler is designed for a specific application while maintaining the same objective: obtaining a representative sample that accurately reflects the process stream being monitored.

For continuous dry process applications, Xoptix offers three primary sampling technologies: cone samplers, auger samplers, and sampling probes. These systems operate in continuous mode, meaning that the sample is collected without interruption while measurement is ongoing. In practice, a small bypass flow is continuously extracted from the main process stream and transported to the analyser, providing real-time PSD information with minimal delay.

The cone sampler is primarily used on large cement ducts and other high-capacity conveying systems. Its design ensures that the material is properly conditioned and reaches an appropriate conveying density before sampling takes place. Because the sampler itself contains no moving parts inside the process stream, it offers exceptional reliability in harsh industrial environments. Multiple configuration options allow the cone sampler to maintain representative sampling across a wide range of operating conditions.

The auger sampler is the most versatile solution within the Xoptix portfolio and is suitable for a very broad range of materials and process conditions. The sampling screw continuously extracts a controlled quantity of material from the process and delivers it to the analyser. Numerous design parameters can be selected to optimise performance, including screw diameter, pitch, rotational speed, material selection, wear protection, and sampling rate. This flexibility allows the auger sampler to be adapted to many different industrial applications.

Unlike many traditional online sampling systems, Xoptix auger samplers are specifically designed to match the sample throughput capacity of the particle sizer itself. As a result, the entire sample extracted by the auger is measured directly by the analyser, eliminating the need for additional sub-sampling stages. This approach reduces complexity, avoids potential sampling bias, and improves overall measurement representativeness. In contrast, some competing systems use much larger augers that extract significantly more material than the analyser can handle, requiring a secondary sub-sampling step before measurement. Each additional sampling stage introduces another opportunity for segregation and loss of representativeness, making the Xoptix approach inherently simpler and more reliable.

Sampling probes extend the portfolio into applications where traditional mechanical samplers are less suitable. Sticky, cohesive, hygienic, explosive, or contamination-sensitive materials are often best handled using probe-based systems. Since the sample is extracted directly without mechanical conveying elements, probe samplers can provide extremely fast response times. This rapid feedback loop is particularly valuable when process control requires the shortest possible measurement delay.

For probe-based sampling systems, achieving isokinetic sampling conditions is often critical to maintaining sample representativeness. The velocity of material entering the probe should closely match the velocity of material in the process stream. If the sampling velocity is too high or too low, particle segregation can occur, causing either fine or coarse particles to be preferentially collected. Xoptix carefully designs probe geometry, extraction rates, and operating conditions to achieve the best possible isokinetic performance, ensuring that the measured PSD accurately reflects the true particle size distribution within the process.

In addition to continuous sampling systems, Xoptix also offers a range of batch sampling solutions. In batch mode, material is collected over a predefined period before being transferred to the analyser. The accumulation period can range from a few seconds to several minutes or even hours, depending on process requirements. Once collected, the material is fed continuously through the analyser using a controlled feeding system, typically based on a dosing screw.

The primary advantage of batch sampling is its versatility. It allows representative samples to be obtained from process locations where continuous sampling would be difficult or impractical. Examples include dilute phase pneumatic conveying systems, airslides, and other installations where segregation effects or process conditions make direct continuous sampling challenging. Batch sampling often provides the most practical route to obtaining reliable PSD information from difficult process locations.

Another important benefit of batch sampling systems is their independence from one another. Each sampler operates as a self-contained unit, allowing samples to be collected from process lines with completely different operating conditions. This makes batch sampling particularly attractive for multi-line and multi-spot installations, where a single analyser may be required to monitor several process streams distributed throughout a plant.

The spoon gravity sampler is designed for applications where material is moving under gravity or low-velocity conveying conditions. The sampler periodically collects a representative portion of material and transfers it into the measurement system. Operation is fully automated through the Xoptix control system using pneumatic actuators and programmable sampling sequences.

The pneumatic sampler is designed specifically for high-speed dilute phase conveying lines. These installations often involve elevated pressures, high material velocities, and demanding operating conditions. The pneumatic sampler is engineered to withstand such environments while maintaining representative sampling performance and reliable operation over extended periods.

The airslide sampler has been developed specifically for airslide applications, where maintaining sample representativeness can be particularly challenging. The sampler design ensures that material is extracted without introducing bias caused by segregation effects or flow disturbances, allowing the measured PSD to accurately reflect the actual process material.

Wet process applications present many of the same sampling challenges as dry systems. Obtaining a representative sample remains essential if reliable PSD data is to be achieved. For straightforward applications, Xoptix can provide bypass sampling systems that continuously extract representative slurry samples directly from the process stream. For more complex primary sampling requirements, Xoptix collaborates with leading specialist partners to design and implement sampling solutions that ensure representative sample collection under even the most demanding operating conditions.