Test & measurement
can react with the carbon dioxide or hydrogen sulfide to form an acid that might collect in a low spot and cause internal corrosion. This leaves natural gas producers, pipeline companies, and users understandably concerned about water content, both liquid and vapor, in the gas flow since a pipeline leak or break caused by unchecked corrosion can cause enormous damage. Knowing the specific moisture content of the gas flow in real-time is thus critical.
CORRECT AND CONSISTENT MEASUREMENT OF THE WATER CONTENT There is a small selection of measurement technologies capable of determining the amount of water in a gas pipeline. All typically involve extracting a sample for individual testing, rather than inserting a sensor for a continuous real- time reading. A common drawback to all these electrochemical and electromechanical approaches is the high potential for contamination. Some contaminants, such as compressor oil, methanol, and amine, can cause inaccurate readings. Other contaminants can poison the sensor and require its replacement. A tunable diode laser absorption spectroscopy (TDLAS) analyser is the most reliable mechanism to measure water content in natural gas. They use an infrared wavelength laser to isolate the very distinct peaks in the wavelength absorption spectrum, indicating water and other components in the stream. This means the analyser can provide a water content measurement unaffected by glycol, methanol, amine, or hydrogen sulfide.
REAL-TIME MONITORING TDLAS analysers enable fewer outages, lower operating costs, and offer increased reliability, all of which provides users a long-term competitive advantage. The J22 TDLAS gas analyser from Endress+Hauser, which includes the diagnostic, monitoring and verification functions of the Endress+Hauser Heartbeat technology, offers comprehensive process monitoring. Alarms for critical measurement values can prevent process outages.
If the water mixes with contaminants in the natural gas, corrosive acids can form that attack the inside of carbon steel piping.
The J22 gas analyser includes web server functions that provide access to the data from any Internet-capable device, such as a laptop, smartphone or tablet. This is especially important if the instrument is installed in locations that are difficult for technicians and users to access.
SIMPLE MAINTENANCE Analysers require specialised enclosures to protect their delicate mechanisms from the harsh surrounding environment. Thanks to the J22 gas analyser’s robust enclosure, combined with improved isolation and enclosure heating, it can be deployed even in wet and cold climate zones. Whenever maintenance is required, analysers can be highly complex or difficult to take apart, so that extensive adjustments are needed
during reassembly. Some analysers require matched component sets, which forces users to purchase costly spare parts kits or send the analyser back to the factory. This can impact the availability of measurements at critical transfer points. The J22’s modular design and easy-to-remove gas sample cells enable simple maintenance without long downtimes, even if the instrument is difficult to access.
Robust internal components protected by a solid enclosure make it unnecessary to install the TDLAS analyser in a protected space.
SUMMARY Ensuring the reliable and safe operation of natural gas pipelines and other petrochemical systems requires the prevention of internal corrosion largely caused by condensation in conjunction with other contaminants. In cases where the water content is critical, to date operators have had to rely on electrochemical methods, but the results are often inadequate. In contrast, TDLAS analysers enable a high degree of accuracy and offer user-friendly interfaces, plus they deliver measurement values on a continuous basis in intervals of just a few seconds. That means users can determine at any time if the gas quality specification is being fulfilled or if corrective measures must be initiated. Users can furthermore continuously monitor the instrument by means of the diagnostic data. The result is quick detection of gas contaminants and rapid implementation of the measures required to rectify the problem. Thanks to the improved connectivity, users can access the analyser from virtually anywhere.
Endress+Hauser
www.endress.com
66
April 2022 Instrumentation Monthly
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