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Durability and reliability in level measurement

1st November 2013


Accurate, often continuous level measurement is a crucial part of materials management and a wide range of solutions are available to ensure that it occurs. Eugene McCarthy reports.

The new CAP-300 Series from Gems Sensors & Controls is a durable and reliable point level sensor designed to perform over long periods of time under the most rugged coolant applications.

"With the launch of the CAP-300, Gems is excited to offer the best-in-class solution," states Kevin Castonguay, integrated marketing programmes manager. "After spending over two years consulting with industry leading customers and conducting rigorous testing, we are confident that this is the most reliable point level sensor on the market. The CAP-300 is unique in that it operates in a frequency range which minimises the effects of the conductivity of the media to ensure long-term performance and the sealed design prevents any fluid intrusion," he added.

The CAP-300 requires nearly zero maintenance, is small in size (2-in in length), tolerates coating and will remain reliable even in the standby mode. In addition, it is compatible with temperatures up to 125°C, comes with variety of mounting types and electrical connections, and is easy to install and maintain.

Gems has also launched the XM/XT-300 and XM/XT-700 level sensors designed for where space is at a premium or tighter resolution is important.

"These new products are essentially the blending of two level stalwarts for Gems, the LS-300/700 point level switch and XM-800 continuous level transmitter," said Tim Kelley, product sales manager.

"By taking the best of both worlds, we now can offer our customers a compact sized, continuous level transmitter option."

The XM/XT 700 series combines the durability of metal with a compact design for restricted spaces. These compact units feature the rugged durability of stainless steel or brass construction in a lightweight package - making it ideal for broad range of applications where shallow tanks and reservoirs are used in the process.

For Baumer, the correct level measurement solution depends on the job in hand, so when looking for the right measuring technology and the right product the company says three questions must be answered: is it continuous measurement, or knowing when a limit is reached? Is it measuring solids or liquids? Is it contact-free measurement or in contact with the product?

The company also investigates user conditions such as the geometric surroundings and other aspects such as foaming or turbulence, as well as the chemical/physical properties of the substance to be measured. Cleaning standards are an important consideration, too, as is the degree of precision needed in the process.

Based on this information, the company will make its recommendation. For example, an ultrasound solution is often ideal for applications in pharmaceuticals, food and beverage processing, wastewater treatment, and gravel works. Depending on the size of the sensors the reception range varies from a few centimetres to several metres. Substances measured in this way include liquids, creams, pastes and granular materials such as cereals, sands and gravels. As ultrasound sensors work contact-free, the sensor is protected from wear and tear and aggressive fluids, and the material being measured is protected from contamination. Ultrasound metres are also very tolerant to dirt such as dust, smoke, steam and fluff.

Baumer describes capacitive sensors as the true all-rounders of level measurement technology. "They are robust and suitable for many different uses because they can be used for detection of practically any medium," notes the company. In a robust all-metal housing they are also suitable for use in aggressive media with direct contact. If the medium does not allow direct contact, they can also see through (non-conductive) container walls. They are not troubled by adhesions or dirt, nor can the medium be contaminated by the sensor.

From Siemens, SITRANS LU10 is an ultrasonic long-range level monitor for liquids and solids, offering 10-point monitoring in a single unit.

It can be used in a wide range of applications to scan liquids, solids or a combination of both contained in vessels of differing size, shape and configuration up to 60metres.

SITRANS LU10 uses ultrasonic technology to measure level, space, distance, volume or average/differential. Transducers can be mounted up to 365metres from the monitor. It features patented Sonic Intelligence echo processing software for superior reliability, while readings are displayed in user-selectable linear engineering units on the LCD.

The monitor will connect to a DCS or PLC using Siemens SmartLinx interface modules, giving users remote two-way communication and full parameter access. Modules for popular industrial buses such as PROFIBUS DP and DeviceNet can be factory installed or added later to meet changing needs. No external gateway is required, reducing hardware and cabling costs.

Key applications include chemical storage, liquid storage and bulk solids storage such as sugar, flour bins, grains and cereals, and plastic pellets.

For its part, Honeywell's SmartLine non-contact radar level meter measures distance, level, volume and mass. Based on frequency modulated continuous wave (FMCW) technology, it provides a more stable measurement than pulse radar and is well suited for agitated process conditions and the most demanding applications.

SmartLine can measure the level of a wide range of liquid or granular products on a large variety of installations, including LPG and LNG. The level meter does not require calibration or commissioning when installed and can be applied in agitated process conditions and agitated vessels. The product is available in two versions; the RM70 has its electronics designed specifically for liquids, while the RM60 is meant for powders or granulates.It offers: +/-3mm/+/-0.04-in standard accuracy; operability up to a flange temperature of 200°C and 40barg; measuring range of up to 80metres; and reliable measurement in difficult and agitated process conditions.

Based on an FMCW radar signal, the level meter transmits a high frequency signal which increases linearly during the measurement phase. The signal is emitted, reflected on the measuring surface and received with a time delay, t (t=2d/c, where d is the distance to the product surface and c is the speed of light in the gas above the product).

For further signal processing, the difference is calculated from the actual transmission frequency and the received frequency and is directly proportional to the distance.

Finally, new from Pepperl + Fuchs is the UC 0GM-IO series. With these it is possible to adapt the basic parameters without using external tools. The switching distance can be adjusted at the press of a button. The projection cone as well as the function of the switching output can be adapted in further steps.

The IO-Link interface and the PACTware parameterisation software together enable optimum adaptation of the sensor to the application. IO-Link also provides an easy way of integrating the sensor into a control system (Fig.1).

Guided radar sensor win innovation award

VEGA has won one of the innovation awards at this year's Powtech mechanical processing technologies and instrumentation exhibition in Nuremberg, Germany. The company's VEGAFLEX 82 guided radar sensor won in the category for innovation in process and control technology/automation.

According to VEGA, the decisive factor for the jury's decision was the instrument's ease of use in combination with many new features. First of these is the automatic probe end tracking function that switches on automatically if, for example, the product signal becomes too unreliable. The instrument then outputs the probe end signal, which is stable and exactly proportional to the product level.

A second key feature is the automatic false signal suppression, which dynamically adapts the signal processing to changing process conditions such as the formation of heavy build-up on the probe.

Thirdly, the sensor was commended for the improvements made to existing features, for example the new quick start function and the memory that stores up to 100,000 readings, 500 events and 10 echo curves indelibly with real-time stamps.

The VEGAFLEX 82 sensor is specifically tailored to the needs of the bulk solids industry. Applications range from large-volume bins to 75 metre-high silos, and from light, fine powders to heavy, coarse gravel. New intelligent algorithms, such as probe end tracking and automatic false signal suppression, increase measurement certainty in these applications. In addition to reliable measured values, the most important demand made of the new sensor is simple setup and commissioning, notes VEGA.







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