Safety, both offshore and onshore in the pipeline installations is becoming an increased focus which has led to more efficient Fire & Gas detection systems in recent years. Compared to just 20-30 years ago, when catalytic bead and electrochemical point sensors were the standard in fixed gas detection, there has been a steady development into more advanced gas detection technologies such as Enhanced Laser Diode Spectroscopy (ELDS) open path gas detectors, and Ultrasonic Gas Leak Detectors UGLD.
As these new technologies become more accepted, combining them for individual applications is becoming more commonplace. Together these technologies enhance the overall safety performance of a fire & gas detection system.
In outdoor industrial facilities, conventional gas detectors (point detectors or open path gas detectors) have to be installed so the leaking gas will actually reach the detector. In other words, if there is just a small amount of wind, the gas can be carried away from the gas detector. Therefore, a potentially dangerous gas leak can go undetected for a very long time. Another challenge for conventional gas detectors in outdoor installations is fast dilution of the gas cloud from the leak before it actually reaches the gas detector.
This means the gas detector can falsely detect a low concentration of gas which would be evaluated as not dangerous closer to the leak. In reality, the concentration can be much higher and therefore potentially very hazardous. Ultrasonic gas leak detectors do not need to have the gas physically contact the detector; instead it listens for the specific acoustic noise signature at a distance from the pressurized leaking gas and instantly raises an alarm when detected.
Since the ultrasonic gas leak detector reacts instantly when the leak starts, the safety system reduces the escape of dangerous gas dramatically and ensures a very fast response time essential in all safety systems.
Except for UGLDs, all conventional gas detectors rely on gas concentration measurement which is measured in either ppm for toxic gasses, and LEL (Lower Explosive Level) for combustible gasses. In other words, the conventional gas detectors provide a gas concentration value to control the system which is equal to the gas concentration at the physical location of the gas detector.
As described before, this concentration will be dependent on the distance and dilution factor between the gas leak and the detector. In most cases, this is unpredictable. How fast a gas cloud can accumulate into a dangerous level depends on environmental conditions such as wind and the gas leak rate. The leak rate is the gas which escapes from a leak and is measured 1 kilogram per second (kg/sec). If the leak is large and the gas pressure is high, the leak rate will continue to be high and there will be a higher chance to accumulate a dangerous high concentration gas cloud with a high LEL or ppm concentration. On the other hand, if the leak is small and the gas pressure is low, the leak rate will be small and the chance of dangerous gas accumulation will be less.
In an outdoor windy environment, the leak rate will determine if a potential gas leak can accumulate and ultimately be picked up by the conventional gas detectors. The Ultrasonic Gas Leak Detector relies on the acoustic sound level generated by the pressurized gas directly proportional with the leak rate at a fixed distance. By detecting the leak rate from the gas leak, the UGLD will therefore not need to wait for gas to accumulate. It will detect and produce an alarm instantly when the leak hits a pre-defined leak rate.
From studies the following gas leak rate classification has been made based on how much damage a gas leak will cause if ignited:
Minor gas leak: 0 – 0,1 kg/sec
Significant gas leak: 0,1 – 1 kg/sec
Major gas leak: < 1 kg/sec
The ultrasonic gas leak detectors from GM are used to detect minor gas leaks (0,1 kg/sec) to provide very early and fast gas leak detection to help prevent dangerous gas accumulation.
What is the desired minimum leak rate which should be detected?
As explained previously, the detection range for UGLD is directly proportional with the leak rate. Since vendors can claim very impressive detection ranges (40 meters) without mentioning the detection range, a high leak rate over the accepted 0.1 kg/sec is claimed as a small gas leak.
•Always verify with the vendor their gas leak detection range is stated together with a given leak rate, and what dB levels are measured at the longest range.
•Also verify what angle the detector was measured relative to the leak to obtain the 40 m detection range
The detection coverage of a UGLD depends mostly on the sensitivity of the microphone system used in the detector. Today it is possible to make very sensible microphones and input circuits. An extremely sensitive microphone can pick up unwanted acoustic background noise not related to the special sound of a real gas leak. The challenge, therefore, is to make the UGLD microphone as sensitive as possible to the acoustic gas leak noise while keeping it immune to unrelated acoustic noise. When choosing the right UGLD, a low acoustic detection limit is a very important parameter ONLY if the UGLD is able to actually utilize this high sensitivity by sensing gas leaks only.
The acoustic frequency range of an ultrasonic gas leak detector is indicated as a range from 20 kHz to 75 kHz. This range indicates the sound frequency range at which the detectors are “listening” for the acoustic sound. Acoustic noise from a gas leak is normally in the range from 10 kHz to 60-70 kHz. Unwanted acoustic background noise can generate high level frequencies in the range of 100Hz - 20 kHz. The first generations of ultrasonic gas leak detectors had electronic filters which cut away all noise below 20 kHz preventing the UGLD from a state of constant alarm. Since most real gas leak noise is generated in the frequency range of 10 kHz to 60 kHz, the higher frequency range will not add any value to the UGLD. Therefore, there is no difference between a frequency range up to 60 kHz and one up to 75 kHz or more. If the electronic high pass filter in the detector is lowered below 20 kHz, more sound from the gas leak can be picked up by the detector. Most vendors have chosen to cut off the acoustic sound at 20 kHz to ensure all unwanted background noise is filtered out.
An essential performance parameter for an ultrasonic gas leak detector is to ensure high acoustic sensitivity to real gas leaks while at the same time minimizing the influence from background noise not related to gas leaks. To ensure this very important feature, the OBSERVER-i is the first ultrasonic gas leak detector on the market to use Artificial Neural Network (ANN) algorithms in the detectors advanced acoustic sound processing design.
An Artificial Neural Network is a mathematical algorithm which searches for familiarity in a large complex data system. A Neural Network is similar to how the human brain works processing information received through our eyes, ears, smell, and taste. For example, when we have seen the face of a young person and heard their voice we are often able to recognize this same person years later even though they have aged. Our Neural Network in the brain is “trained” to recognize the person’s face from our earlier meetings.
Although our brain is not “programmed” to search for an exact match or pattern, we recognize familiar similarities which the brain is trained to compare and decide upon. If the human brain did not look for familiarity when we met another person but instead looked only for an exact match as we remembered them, we would only recognize a person if they had not changed.
An ultrasonic gas leak detector does not have to recognize people at different ages, but similarly needs to effectively recognize the sound signature from a gas leak while also rejecting sound signatures from acoustic background noise not related to the gas leak. The OBSERVER-i uses advanced Artificial Neural Network (ANN) algorithms to enhance and optimize the detectors ability to distinguish between background noise not related to leaking gas and real gas leaks.
Like the human brain, the Artificial Neural Network in the OBSERVER-i has been pre-trained to reject a series of different sound recordings from various high noise plant locations such as compressor housings and other neural network background noise sources. The Artificial Neural Network in the OBSERVER-i is also trained to positively recognize the unique sound patterns from a number of pre-recorded gas leak recordings and to activate an alarm when such leak noise occurs.
This pre-training of the detector was programed in a factory, so when the detector is installed in an actual plant installation it is ready to perform the high level real-time background noise discrimination as well as the unique sound of real gas leaks.
The Artificial Neural Network (ANN) makes it possible to analyze the incoming acoustic sound based on the frequency domain instead of sound level domain (dB levels). Therefore the OBSERVER-i will detect the sound from gas leaks occurring at a much lower sound level than the background noise. Additionally, the Artificial Neural Network (ANN) will be extremely immune to false alarms from unwanted background noise sources while being extremely sensitive to small and large gas leaks.
Compared to other technologies where “onsite detector training”, “background noise profiling” and “finger print technology” are used to suppress unwanted background noise, the Artificial Neural Network (ANN) comes “pre- trained” which significantly reduces the installation procedure and minimizes the need for specialized acoustic knowledge personnel.
Due to the neural network technology, the OBSERVER-i comes with “pre-trained” neural network algorithms from the factory. Therefore, the detector does not need complicated onsite “training procedures” to adapt to specific acoustic onshore/offshore plant conditions. Instead it will perform optimally in all kinds of acoustical environments right after installation.
It is important to understand that not only one technology, such as ultrasonic gas leak detection, will be the solution in future gas detection systems; conventional LEL and ppm based gas detectors will still be necessary.
In the meantime, by implementing ultrasonic gas leak detection technology as an equal part of the gas detector mix in the system design, a much faster response time can be obtained from the plant fire & gas detection system.
MSA offers a new open path gas monitoring technology that can be used for a wide range of toxic and flammable gases.
The Senscient ELDS uses 'SimuGas' self-testing to eliminate employees entering hazardous areas for gas checks. Nuisance false alarms are virtually eliminated with its breakthrough Harmonic Fingerprint processing.
This new approach of gas monitoring provides a maximum level of protection with the highest service uptime availability and virtually no maintenance.
The technology behind ELDS open path gas detectors (OPGD) relies on enhanced laser diode spectroscopy (ELDS) to detect specific toxic and flammable gases. In the event of a gas leak, the sensor’s laser technology recognizes and analyzes a gas’s specific harmonic fingerprint.
During normal operation some of the detector’s laser light is reflected continuously through a sample of the target gas contained by a hermetically-sealed reference cell.
This design ensures the laser remains locked on the selected gas wavelength for the specific target gas. False alarms caused by interference gases, which are experienced with other detection technologies, are no longer a problem. The detector’s harmonic fingerprint technology helps ensure precise gas recognition, eliminating the potential for false alarms, even during adverse environmental conditions.
False alarms are a serious problem with many gas detection technologies. They can result in excessive plant down-time, which often requires complex investigations and regulatory reporting. From a safety perspective, frequent false alarms lead to a lack of confidence by employees in the gas detection technology and a culture of apathy that can cause employees to fail to act promptly during an actual emergency event.
Class 1 eye safe lasers designed into ELDS detectors are used to penetrate thick fog, heavy rain and snow beyond the capability of traditional open path infrared (OPIR) detectors. With its automated SimuGasTM safety integrity self-check, there is no need for the typical OPIR sensor gas checks and recalibrations requiring field technician time to address. Unlike electrochemical cells, ELDS sensors are also immune to sensor poisoning and interferent gases, thanks to their gas specific harmonic fingerprint detection method.
The ELDS gas detectors are constructed of high grade corrosion resistant 316 Stainless Steel, which helps ensure long life in rugged industrial plants. They are ideally suited for open and enclosed environments. That includes the cold freezing winter temperatures in northern latitudes or the high temperatures required for service in much of Asia, the Middle East or Africa.
Heated optics provide service over a wide temperature range from -40 to 140°F (-40°C to +60°C). ELDS detectors are also hazardous area approved to CSA/UL, ATEX, IECEx, EAC and INMETRO standards.
With their daily auto-self testing diagnostic feature called SimuGasTM, ELDS detectors offer significant installed and operational cost savings over conventional fixed point toxic gas detectors. Manual intervention and ongoing costs for routine real gas testing are eliminated with SimuGas. Many times the cost of inspecting and maintaining some gas detector technologies can over time exceed the cost of the actual instrument.
While the cost of an open path detector may be higher than traditional point gas detectors, the total installed cost can be similar or less expensive than installing multiple fixed point devices to achieve an equivalent coverage area. For example to achieve a 50 to 60m path length, a plant would require six separate point gas detectors to provide the same monitoring effectiveness as one open path ELDS detector.
ELDS detectors are also virtually maintenance-free in terms of their construction. They have no consumable parts, therefore resulting in zero ongoing costs for replacement of sensing elements and associated service labor costs. With virtually zero drift because of their harmonic fingerprint detection method, there is no re- calibration effort required with the result that the ELDS detectors offer significantly reduced lifecycle costs compared to traditional point gas detectors.
The future of gas detection is there, with the introduction of the MSA ULTIMA® X5000 and General Monitors S5000 gas monitors. For over 40-years, MSA has been the global leader in Fixed Gas and Flame Detection. With the addition of General Monitors in 2010, and our commitment to quality, we have developed the most advanced technologies to provide complete solutions for your gas detection needs.
This platform has integrated cutting-edge technology such as non-intrusive touch button operation, dual sensor capability, extended calibration cycles and Bluetooth® wireless communication offering benefits such as a low total cost of ownership and a completely new user experience making this platform years ahead of its time.
Design elements such as a touch interface, an industry first, as well as a bright OLED (Organic LED) display for an easy visual status indication ensures plant and worker safety. In addition to the enhanced interface, the ULTIMA X5000 offers extreme visibility with two side LED indicators for normal operation, fault and alarm indication.
An easy retrofit of the detector is possible because it shares the exact mounting footprint as the ULTIMA X and S4000 series, making installation simple using the existing conduit and wiring.
Do more with less utilizing the dual sensor capability.
The 5000 series dual sensing technology doubles the sensing power with half of the wiring or conduit of a single gas transmitter. Any sensor combination can be remotely mounted and mixed to suit your gas detection needs. Maximum remote mounting distances have increased as well, making the 5000 series the most flexible transmitters available.
The 5000 series provides the data granularity that you need, where you need it. Optional Bluetooth wireless communication allows you to securely access detailed gas, sensor health, and fault information on your mobile device, while maintaining the simplicity of the analogue signal for each sensor. Both HART and Modbus protocols come standard on the 5000 series, making it the most dynamic offering of communication protocols compared to any current industry transmitter. Check status and get alerts up to 23 m away, initiate calibration and view progress. Reduce setup time by at least 50%.
Let us cut your maintenance cost and time in half with the ability to go up to 1.5 years between calibrations using our revolutionary TruCal technology. The new advanced sensor platform will allow for longer sensor life, longer warranties, better stability, extended calibration cycles and multiple sensor status checks per day to ensure operation. Challenge your expectations with a three year sensor warranty and a five year expected life cycle on toxic and combustible digital sensors.
Today, best practice for the Oil and Gas industry is to calibrate gas detection devices with electrochemical cells every 90 days, depending on region and local regulation. However, the devices currently on the market are only able to communicate a cell’s end of life during calibration. Therefore, the 89 days between calibrations represents an unknown for the end user as the cell could have failed at any time.
TruCal technology reduces this unknown period to 6 hours with self-checks four times per day.
Other manufacturers today claim to have similar functionality in their sensors, but look closely. Their check of the sensor is nothing more than a continuity test. The problem is electrochemical cells rarely fail in a manner that disrupts the circuit. Instead they lose sensitivity to a point where they are no longer able to respond to gas; a condition only discovered during a full calibration.
Think of your car battery. One day you get in your car and it will not start. It still holds some voltage and turns the radio on, but that is little consolation when you are trying to get to where you have to be. Wouldn’t it have been nice for your car to tell you two weeks ago that your battery was about to fail? Competitive sensor checks are similar to knowing that your car’s battery is dead and can no longer start your car. TruCal gives you advance warning to replace your battery before you end up stranded.
TruCal technology is enabled through MSA’s patented XCell® sensors. The pulse check within the sensor provides a reliable sensor interrogation method that identifies and corrects for changes in output sensitivity. The pulse check uses MSA’s patented technology to calculate gas response by applying an electronic pulse to the sensor and analysing the response curve. Through proprietary algorithms, MSA can quantify gains and losses in output sensitivity that result in real-time accuracy adjustments during the pulse check. Users not only save time, but can also more easily comply with industry best practice of testing detector functions daily. Users can also rest assured of accurate indication of sensor functionality.
The pulse check calculates the change in sensor output
response electronically. A pulse is applied to the sensor where the response is analysed and used to indicate the sensor’s output sensitivity, and verify that internal sensor components are functioning properly. Sensor output sensitivity is comprised of quantifiable aspects of internal sensor components. Sensitivity can be measured without the use of gas. The pulse check analysis determines output sensitivity changes using measurements associated with the sensor’s electrode catalytic loading and increases or decreases in ionic conductivity. Calculated sensitivity is based upon a regression model that uses initial sensitivity levels from the most recent calibration, and measured changes in sensor response function to subsequent electronic checks. Calculated sensitivity is compared to stored sensitivity from the last gas calibration and the previous pulse check to determine sensor accuracy. Output from regression is used to determine whether sensors require recalibration or if they are within acceptable variation from the previous calibration’s sensitivity level.
The pulse check occurs four times per day. If a difference is measured in sensor response within an acceptable range, a correction is applied to the measured output to adjust sensor response for accuracy without the use of calibration gas. This is referred to as Adaptive Environmental Compensation (AEC). This compares the stimulated responses to the last calibration and makes appropriate adjustments. Such adjustment is possible due to MSA's application-specific integrated circuit (ASIC) used in MSA’s XCell sensors.
In short, MSA’s TruCal technology ensures that a sensor is present and operating within its predetermined sensitivity limits and is corrected to account for drift or change since the last calibration or pulse check event.
If the output signal has drifted outside of the acceptable range, the instrument will notify the user that gas calibration is necessary.
Six actions that TruCal enables:
1. Validates that the sensor is operating normally.
2. Compensates for sensitivity drift due to changing environmental conditions.
3. Recommends when a full calibration should be performed.
4. Warns when a sensor needs to be replaced in the near future.
5. Reports the life and health status as “Good” or “Fair.”
6. Alerts the end user that the device is no longer able to monitor the area. A fault will initiate.
TruCal sets a new standard for reliability. Since 1914, MSA has been innovating and creating revolutionary gas detection products. We’re called The Safety Company for a reason.
Our goal, every day, is to provide workers with dependable, high-quality products, instruments and service to help ensure a safe return home when the work is done.