Portable and fixed detectors for toxic and flammable gases are offering more choice and better value for the money, say experts, thanks to technology developments and strong market competition.
In Europe, competition triggered by consolidation in the last five years has propelled the market out of the doldrums of the last couple of decades, according to a recent report from market consultancy Frost & Sullivan (London; www.chemicals.frost.com). Research analyst Paula Connor observes that growth has been accompanied by heavy price cutting, which is good news for customers in the short term but which may prove unsustainable.
Norman Davis Jr., Market Manager Commercial Government with MSA (Pittsburgh, Penn.), agrees that falling costs and new technology may encourage users of gas detection equipment to upgrade. Basic portable instruments selling for as little as $100 are reliable and need little or no calibration, so they are often treated as disposable. “We differentiate ourselves through rock-solid equipment and excellent customer service,” Davis says.
One area where the chemical process industries (CPI) are likely to see an upswing is in new products with higher specifications, for which customers are often willing to pay a premium, notes Connor. Davis agrees, pointing out that sophisticated analyzers such as MSA’s VaporLab 700 gas chromatograph (p. 19) are now very affordable.
Examples of market consolidation include Industrial Scientific Corp. (Oakdale, Penn.), which earlier this year broadened its range of gas detectors by buying French manufacturer Oldham, and the acquisition last year of Swiss manufacturer Zellweger Analytics by Honeywell Analytics (Lincolnshire, Ill.).
User-friendly portables
Simple, reliable, personal gas monitors are exemplified by the Pac 7000 from Draeger Safety, Inc. (Pittsburgh, Penn.). This uses visible, audible and vibrating alarms to warn of harmful concentrations of carbon monoxide, hydrogen sulfide, or oxygen. It can display both 8-hour exposure (TWA) and short-term exposure (STEL). Exposure data is logged for downloading to a personal computer. For multi-gas applications, Draeger’s X-am 2000 monitors up to four gases in a package little larger than a mobile phone.
Of MSA’s offerings in this area, the recently-launched Altair single-gas detector offers more than two years of maintenance-free operation in its carbon monoxide and hydrogen sulfide versions; a model for oxygen is also available. Features include resistance to dust, water and radio-frequency interference, one-button operation, and infra-red communications.
Honeywell Analytics supplies portable gas detectors under the Lumidor, Neotronics and SF Detection brand names, plus fixed monitors from Sieger, MDA Scientific, and Zareba. The Lumidor Impact range monitors up to four gases simultaneously using easy-to-handle cartridge sensors. The matching Safelink communication system uses a cable to connect two Impact monitors, ensuring that an alarm registered by one unit will also appear on the other. The system also allows two-way communication, via pushbuttons, between a worker in a confined space and an attendant outside.
The Tetra 3 portable gas monitor from Crowcon Detection Instruments (Erlanger, Ky.) is small and lightweight, rugged, simple to operate and comes with a three-year warranty — including the sensors, which measure oxygen, toxics and flammables.
The GasBadge Plus single-gas detector from Industrial Scientific Corp. (Pittsburgh, Penn.) features IP 66/67 resistance to water and dust. Available for gases including CO, NOâ‚‚, Oâ‚‚, Hâ‚‚S, and SOâ‚‚, the GasBadge Plus is guaranteed for two years.
Special-purpose units
Special purposes for gas monitors include tracking of highly toxic or unusual gases, and conducting mobile plant measurements where an ordinary personal monitor is not sufficient. An example of the latter is the 5100 i.s. portable gas analyzer from Servomex (Sugar Land, Tex.), available with a paramagnetic sensor for oxygen, or an infrared (IR) sensor for CO2, CO, or CH4. It is approved for use in Zone 0 hazardous areas without purging, and the IR version is said to be the first intrinsically safe portable analyzer using this technology.
MIDAC (Costa Mesa, Calif.) supplies open-path FTIR spectrometry equipment that can measure a wide range of gases and vapors simultaneously, at ppb to percent levels, on a path up to 1,000 m long. At one end of the path is a powerful IR lamp, while at the other are the interferometer, beam splitter and detector, mounted atop a compact reflecting telescope for long-range use.
MSA’s VaporLab 700 gas chromatograph is an economical yet powerful fixed unit that can be used to analyze process gases as well as ambient air. It avoids the need for cylinders of expensive carrier gas by using air. Its metal oxide semiconductor (MOS) detector is maintenance-free and measures a wide range of compounds at levels from ppb to ppm.
MSA also uses surface acoustic wave (SAW) technology, which is commonly used in cell phones, to identify chemical warfare agents. In combination with more-conventional sensor types, the SAW technology forms the basis of the company’s HAZMATCAD and SAFESITE monitoring systems, which are aimed at civilian emergency responders but which also have many industrial applications. SAFESITE uses a 900-MHz radio network to coordinate gas measurements and GPS positions from both portable and wearable monitors distributed around an emergency area or a plant undergoing maintenance.
For highly toxic gases such as phosgene (COClâ‚‚), whose allowable workplace concentration is just 20 ppb, detecting leaks amid high background levels of hydrocarbons and water vapor is difficult, notes Compur Monitors (Webster, Tex.). The company has developed a sensor based on a silver electrode and a gel electrolyte that detects phosgene down to 2 ppb, as well as Clâ‚‚, ClOâ‚‚, HCl, HCN, Hâ‚‚S, and NOâ‚‚. The Tracer leak detector uses a sample pump and a selectable orifice to span from the low ppb range up to double-digit ppm concentrations.
Sensistor Technologies Inc. (N. Billerica, Mass.) uses a safe and easily-available gas mixture containing 5% hydrogen and 95% nitrogen for general-purpose plant leak detection, in combination with its H2000-C portable leak detector. At a chemical intermediates plant operated by Degussa in Marl, Germany, the technique has replaced time-consuming soap bubble leak tests, detecting leaks as small as 5 x 10-7 mbar l/s without requiring valve and flange jackets to be removed, as they would be for soap bubble testing. The technique is approved by Germany’s TÜV as an alternative to helium leak testing.
The Jerome J405, launched earlier this year by Arizona Instrument (Tempe, Ariz.), uses an upgraded gold film sensor to measure mercury vapor down to 0.5 µg/m3, a sensitivity previously only achievable by atomic absorption spectroscopy.
Demand-controlled ventilation (DCV) in buildings typically uses COâ‚‚ levels to indicate indoor air quality (IAQ). After acquiring Telaire, a technology leader in COâ‚‚ sensing, GE Sensing (Billerica, Mass.) has introduced a new line of COâ‚‚ sensors, transmitters and handheld monitors based on IR absorption.
Witt-Gasetechnik GmbH (Witten, Germany) has introduced a low-cost version of its OXYBABY V handheld analyzer for modified atmosphere packaging (MAP) in the food industry. The OXYBABY M, which lacks the data-recording facilities of the OXYBABY V, measures Oâ‚‚ and COâ‚‚ to a precision of ±0.1%.
Fixed monitors protect plants
Routine gas monitoring of processing areas and storage tanks requires fixed equipment. The Wallace & Tiernan Acutec 35 from Siemens Water Technologies (Warrendale, Penn.) is a compact, modular solution for measuring chlorine, sulfur dioxide, and ammonia. The system has a battery backup to cover power failures, optional automatic testing via a built-in gas generator, and an optional local display of gas concentration.
For monitoring combustible gases, IR devices are not subject to the poisoning that can affect catalytic sensors, points out Compur Monitors, so they can often accept longer intervals between calibration. To reliably detect unsaturated hydrocarbons such as ethylene, however, requires an IR wavelength of 3.3 µm, instead of the 3.4 µm commonly used for saturated hydrocarbons. Compur has therefore added a model specifically for ethylene to its Statox 501 series of IR gas detectors.
When it comes to dense, toxic gases such as chlorine and sulfur dioxide, the Environmental Sampling Unit (ESU) from Crowcon can reduce the number of sensors required without compromising safety. It uses an electric fan to draw air through a sampling pipe, which can be up to 12 m long, and into a chamber containing one of the company’s Xgard detectors. Applications include chlorine stores and areas where access is difficult, including wet wells.
The MC600 six-channel controller from General Monitors (Lake Forest, Calif.), which can handle both combustible and toxic gases, is now available for Class I, Division 2, hazardous environments. This modular system uses redundant Modbus communications to support scalability from the local level up to a plant-wide distributed safety system. For fire as well as gas detection, the company’s HazardWatch integrated system is also highly scalable, incorporating up to 13 local gas and fire alarm panels over a network up to 25 km long.
From Sierra Monitor (Milpitas, Calif.) comes the 5100–02-IT, claimed to be the only catalytic-bead combustible gas sensor with a six-month calibration cycle. Combining the lower calibration frequency of an IR sensor with the lower cost and broad detection range of catalytic technology, the 5100–02-IT features communications via RS-485 Modbus RTU, opto-isolated 4–20 mA, or SMC Sentry bus.
The AirCheck √EX from PureAire Monitoring Systems (Lake Zurich, Ill.) uses a renewable electrochemical sensor to measure methyl bromide down to 5 ppm. Response time is less than 30 s, and the reading is unaffected by humidity.
Global Detection Systems Corp. (Santa Fe, Tex.) offers its GDS-48 universal sensor with a choice of IR, catalytic-bead, electrochemical and MOS sensors. By emulating a catalytic-bead sensor, the IR sensor acts as a drop-in replacement with extended calibration intervals and a five-year life.
The SmartMaxII system from Control Instruments Corp. (Fairfield. N.J.) controls up to four remote gas sensors. Features include built-in alarms and relays, RS-485 Modbus communications, and remote configuration.