Getting the measure in harsh operating conditions

Paul Boughton

Ease of maintenance, cost and the ability to survive harsh operating conditions are the key benefits of the latest level measurement technologies. Eugene MacArthy investigates.

Baumer's multi-purpose LBFS level switch is now available in three different ATEX configurations which enable safe level detection in explosive gaseous and dusty atmospheres typically found in the chemical, pharmaceutical and food industries.

No additional Zener barrier is required thanks to ready-for-use isolation module PROFSI3 LS, approval covers all ATEX zones with both gas and dust, while an easy-to-install, compact design boasts high reliability.

Baumer uses a highly specialised protective design for the ATEX versions of the LBFS. Thanks to this, versions Ex ta for dust (zones 20, 21, and 22) and Ex nA for gas (zone 2) can be used without a Zener barrier because the housing itself already provides all the necessary protection.

This is very cost-effective because usually all sensors for hazardous areas require a Zener barrier. The ATEX certifications cover zones 0, 1, and 2 (gas) as well as zones 20, 21, and 22 (dust).[Page Break]

Isolation module

Quick installation and ease of use is also ensured for version Ex ia for gas (zones 0 and 1). For this version, Baumer provides the ready-for-use isolation module PROFSI3 LS which is specially designed for use with Baumer's level switches LBFS and LFFS. This dedicated isolation module saves users the time and effort of selecting and configuring an additional Zener barrier to operate the sensor.

The PROFSI3 LS can operate with DC voltages from 22 VDC to 120 VDC as well as AC voltages from 90 VAC to 253 VAC.

The LBFS is based on frequency-sweep technology, a method particularly suitable for precisely measuring the level of solids and powders.

Explosive dust

As the processing of such materials often creates explosive dust, the new ATEX versions open a wide range of new applications which is particularly valuable for typical LBFS users in the chemical and pharmaceutical industries.

However, industries such as oil and gas, energy production, and milling will also find this new level switch convenient. The ATEX versions of the LBFS level switch can easily be adapted to the needs of very diverse applications thanks to a wide range of available process connections including G1/2", G3/4", G1", G1/2" hygienic, G1/2" for reverse assembly, M18x1, and G3/4 NPT. More connections are available upon request.

For its part Gems, the supplier of liquid level, pressure, and flow sensors, miniature solenoid valves, and fluidic systems, has introduced several new versions of its LS-7 Series of robust point level switches.

These compact, side mount level switches are made from Gems Versaplast engineered plastic for high temperature applications up to 148.9°C.[Page Break]

Challenging fluids

The engineered plastic used on these new level switches is an extremely versatile material compatible with a wide range of challenging fluids such as oils and solvents (Fig.1). The company says that Versaplast enables the new LS-7 Series sensors to provide an affordable solution for handling high temperature applications and corrosive fluids.

The durable Versaplast LS-7 level switches are CE, UL and CUL approved, and are ideal for use within methylene chloride and anti-freeze tanks.

The new versions expand the broad range of small, side mounted level switches from Gems that are available for a wide variety of fluids or applications.

Confined spaces

Additional specifications include pressure capability to 100psi (6.8 bar), and a float arc of just 1.25 inches - beneficial in confined spaces.

Options include internal and externally-installed versions, and metric or US threads. Free samples are available for qualified original equipment manufacturers (OEMs).

"With the development of the enhanced Versaplast LS-7, Gems has continued to expand the broad offering of our side mounted point level product line," says Kevin Castonguay, product marketing manager. "The enhanced Versaplast material offers a robust and reliable solution unique to the market for a wide variety of OEM applications at a cost effective price."[Page Break]

Radar level transmitter

Meanwhile Siemens Industry Automation Division has launched the Sitrans LR250 radar level transmitter with a new threaded polyvinylidene fluoride (PVDF) antenna for liquid and slurry measurement. The antenna opens up new applications in extreme conditions for this non-contacting level transmitter.

The new transmitter is designed for extreme conditions characteristic of acids, alkalis, and other corrosive chemicals.

Some examples include sodium hypochlorite, sodium hydroxide, and sulphuric and hydrochloric acid applications. These applications are not suitable for stainless steel and usually require transmitters be made from exotic and costly materials.

However, the Sitrans LR250 threaded PVDF antenna is able to withstand such environments while remaining a cost-effective solution. It also uses FDA-compliant materials suitable for use in food and beverage, chemical, and water treatment applications

Sitrans LR250 is a compact 25 GHz two-wire transmitter for non-contacting level measurement of liquid or slurry materials for measurement ranges of up to 20 metres. It is available with Hart, Profibus PA, or Foundation Fieldbus protocols.

With the graphical Quick Start Wizard the Sitrans LR250 is operational in minutes and the infrared handheld programmer supports local programming.

Full function diagnostics comply with Namur NE 43 and the Sitrans LR250 has also achieved a SIL 2 functional safety declaration with Safe Failure Fraction (SFF) of 86 per cent, making it suitable for use in Safety Instrumented Systems (SIS). Key fields of application for the Sitrans LR250 include bulk liquid storage tanks, process vessels with agitators, vaporous liquids and low dielectric media.[Page Break]

Stable measurement

Honeywell's new Non-Contact Radar Level Meter FMCW (frequency modulated continuous wave) is for level measurement of liquids and solids and can be used to calculate volume. A key advantage of the SmartLine Non-Contact Radar Level Meter is that it provides a more stable measurement than pulse radar, and is well suited for agitated process conditions and the most demanding applications.

The maximum measuring range of the SmartLine Non-Contact Radar Level Meter is 80 metres.

The Honeywell SmartLine Guided Radar Level Meter is a TDR (Time Delay Reflectometry) level meter for measuring level, distance, interface, level and interface, volume and mass.

This unit is well suited for measuring liquids as well as granular solids. A remote housing can be mounted up to 14.5 metres from the probe.

The SmartLine Guided Radar Level Meter has higher signal dynamics and a sharper pulse than conventional TDR devices and therefore better reproducibility and accuracy.

The maximum measuring range of the SmartLine Guided Radar Level Meter is 35 metres. Among the features and benefits of this technology are:

- The same model can be used for solids and liquids.

- Reducing inventory and lowering costs.

- Two-wire loop powered design saves on wiring.

- Reducing cost; interchangeable and replaceable electronics without the need to recalibrate reduces downtime and lowers maintenance cost.

- Fve different types of probes suitable for a wide range of media.

- Quick to install and easy to operate.

- Chemically resistant to a wide range of processes.

- Accurate level measurements in agitated conditions.

Suited to all process industry sectors, typical applications include: tanks and agitators, process tanks, storage tanks, blending tanks, distillation tanks and separators.

Better process management

Process management is made possible through the use of continuous level measurement. Today's modern facility requires statistical and informational data relating to the consumption, loss prevention, process control or balancing of material used within their operation.

This ever-increasing demand for information adds to the need for continuous level instrumentation.