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Gas Detection 5


lamps light intensity will change or decrease from pollution and intensive use. Pollution can be removed with the help of a special lamp cleaning kit. The only response to wear and tear is replacing the lamp or even the entire sensor unit. Depending on, how dirty or corrosive the atmosphere is in which you want to operate your PID, you have to calculate with maintenance intervals between 3 and 9 months.


Handling


The Compur Statox 501 PID gas detector consists of two components: sensor head, consisting of sensor, interface and housing and a Statox 501 control module. The sensor is located in a stainless steel cylinder, which is flanged to the interface, also located in a stainless steel housing. The interface transforms the sensor signal into a linear, temperature compensated signal, related to the target gas concentration. This signal is transmitted to the Statox 501 control module, which provides the outputs for peripheral instrumentation: 3 relays which can handle up to 2 A and a 4 – 20 mA analogue output.


The sensor head itself, installed in the field, is designed in protection class Ex (ib) em, therefore it can be operated without any additional Zener barrier or repeater. This saves money, installation cost and space in the control room. Operation is very easy: a magnetic pin triggers hall sensors inside the sensor head and thus gives access to a simple menu for calibration and parameter setting.


The sensor can be removed from the interface without tools.


As the sensor is intrinsically safe, there is no need to declassify the area before removing it. In addition, the sensor is mechanically coded, so that it can only be installed in the correct position.


Does the industry need fixed PIDs? Compur Monitors thinks: yes!


PIDs are capable of detecting gases that cannot be detected with ‘classic’ gas sensors. The PID method has been field – proven in hand held instruments, in the recent years. Now sensor technology has advanced to a level, in that it can be used in fixed systems too. This is a more challenging application of PID, as:


a. They are in operation around the clock


b. They cannot move away from high concentrations together with the user, as portable instruments would do


With the Statox 501 PID, the user has an instrument on hand, including measuring programs for 0 – 10,00 – 100, 0 – 1.000 and 0 – 10.000 ppm. (The true measuring range for the target gas is defined by the PIDs specific response factor to it). PID will give an overall reading of gases with an ionisation potential below 10,6 eV and it requires a degree of maintenance.


Provided the application has been well defined beforehand, this sensor technology will reliably monitor substances such as VOCs with high sensitivity. It is easy to use and affordably priced.


The bottom line: a valuable progress in gas detection!


Safety Fast from New Carbon Monoxide Sensor


Gas sensing experts, City Technology (UK), have introduced the 4CM, a new carbon monoxide sensor designed for use in the world’s most challenging environments. Developed to meet the most stringent toxic gas and mining standards, the 4CM not only improves the functionality, reliability and effectiveness of PPE in hostile environments, but also demonstrates outstanding


performance and stability in temperature and humidity extremes.


The 4CM outperforms other sensors on the market by responding 12% faster to CO hazards and recovering in over half the time of the industry average. This is a major benefit to detection instrument manufacturers keen to improve the performance of their products.


Carbon monoxide (CO) is extremely difficult for people to detect. Exposure to concentrations as low as 100 ppm can be dangerous, higher levels of exposure can be life threatening. In industry, the gas is routinely found in mining facilities, oil and gas plants, petrochemical facilities, steel plants and wastewater treatment plants. It is also major potential hazard when personnel are required to enter confined spaces and therefore effective CO detection is vital.


Rob White, Product Marketing Manager, City Technology, said: “As global leader in the design and manufacture of gas sensors for personal life safety equipment, the 4CM continues City’s tradition of developing products that make a positive contribution to the preservation of life in challenging environments. The 4CM is the fastest CO sensor on the market, the most efficient in terms of reducing calibration costs and complements our growing portfolio of high performance sensors that include the recently launched 4OXV. Manufacturing on fully automated lines in the UK provides full characterisation of every sensor, traceability down to the component level and guaranteed uncompromising quality.”


The 4CM offers electrical and mechanical backwards compatibility with previous generations of City CO sensors. It has a typical T90 time of seven seconds and a recovery time to an indicated level of less than 2ppm in less than 100 seconds. During 50-day exposures in 50°C and 11% relative humidity, and 50°C at 95% relative humidity, the 4CM operated to specification. The sensor provides excellent accuracy and stability at high and low gas concentrations, meeting the EN45544 requirements for uncertainty, typically achieving 1ppm for zero concentrations and less than 1% variation at 250, 750 and 1000ppm.


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       


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IET November / December 2011 www.envirotech-online.com


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