While catalytic bead sensors have been in use for many years, infrared sensors are gaining popularity due to their increased reliability and longer life. Understanding the differences between these two major technologies is important as you determine how to configure your gas detection system. In the case of methane gas, it’s crucial to have a sensor you can rely on in your specific environment.

What is Methane Gas?

Did you know that natural gas is made up of nearly 87% methane? Like other combustible materials, methane gas is highly flammable and presents a huge risk for those dealing with natural gas. In its organic state, it is odorless, colorless, tasteless, and nontoxic. As a major greenhouse gas, it is produced during the anaerobic decomposition of manure or in the production of chemicals such as acetylene and methanol.

As a component of natural gas, it is known to rise and accumulate in certain areas of enclosed buildings. If a sufficient amount is present, it will replace the oxygen and may create a long term asphyxiation hazard if allowed to accumulate. If the percentage increases beyond five percent by volume, it becomes a very dangerous explosive mixture. 

Unsafe Levels of Methane

Methane gas that has not been odorized can be very difficult to detect without proper combustible gas detection equipment. According to biotechnology scientists, methane gas has not been shown to be toxic but can cause an explosion (the Lower Explosive Limit)  when one volume of methane is mixed with 20 volumes of air (~5% by volume). With that in mind, a gas detection system can be configured to measure the LEL value in real time. Typically, gas detection systems are programmed to generate a warning if the measured value reaches 20% LEL and an alarm if the measured value reaches 40% LEL. 

Catalytic Bead vs. Infrared Sensor

If you regularly work with methane, a byproduct or component, it’s important to understand the two types of sensor technologies used to detect methane gas.

• Catalytic Bead Sensors – Preceding the use of infrared sensors, catalytic bead sensors usually cost less and have the ability to detect other combustible solvent vapors in the environment. Working as a Wheatstone bridge circuit, the active filament wound in a catalytic bead sensor uses a platinum wire with a palladium-based catalyst. Unsafe levels of methane are detected when the resistance ratio between the active and reference bead changes.

• Infrared Sensors – Due to the risk of catalytic bead poisoning in environments involving silicone, lead, sulfur, or halogenated compounds, infrared sensors were introduced as an alternative. Using two wavelengths of infrared energy, infrared technology compares the  outputs of the gas absorption beam and reference beam to determine if gas is present. Because infrared sensors don’t require oxygen to operate, they can be reliably used around a number of applications without issue. Furthermore, typical infrared sensors include a microprocessor that continuously checks the sensor for proper operation. 

Pro Tip: Methane gas is often combined with an odorant that smells like rotten eggs to help you detect leaks. If you smell a peculiar odor, be sure to survey your equipment or call for assistance.

Real-Time Detection

Both catalytic bead and infrared sensors can be configured to detect methane gas, and both have certain advantages. GDS Corp offers gas detectors that utilize both technologies to give you accurate information no matter what environment you’re in.

Connect with our sales team to customize a methane detection system for your particular

Combustible gas sensors can be designed with two different technologies, catalytic bead sensors or infrared sensors. Catalytic bead sensors detect gas by burning gas molecules on a sensor element. Comparatively, infrared sensors absorb hydrocarbon gas through infrared light at specific frequencies. Learn the advantages of either sensor to find out which technology is best for your work applications.

Catalytic Bead Sensor Advantages

Inexpensive to manufacture and highly reliable, catalytic bead sensors have dominated the market until just recently. Designed with sensor elements that heat up when combustible gas is present, catalytic bead sensors respond to any combustible gas or vapor. With capabilities to detect a broad range of combustible gases, catalytic bead sensors remain a quality choice for gas detection systems.

Pro Tip: Combustible gas detectors measure combustible gas in a range of 0-100% of the Lower Explosive Limit (LEL) value. Be sure to know the LEL limits of the gases you work with to maintain accurate gas detection.

Infrared Sensor Advantages

With increasing popularity in the last two decades, smart infrared (IR) sensors have the advantage of longer calibration and a unique self-test capability. Infrared sensors work by allowing gas to pass between a source of infrared light and a specially designed receiver. When hydrocarbon molecules pass in front of the IR source, they block some of the infrared energy. As a result, the receiver’s output drops and the microprocessor (inside the sensor) generates an output proportional to the amount of absorption.  

Choosing the Right Sensor

Depending on your application, each sensor has its own disadvantages. Infrared sensors can’t detect non-hydrocarbon gases such as hydrogen. In the same way, catalytic bead sensors are sensitive to contaminants and so risk having the atmosphere endanger their sensing elements. Due to the constant danger of explosion, it’s important to have a combustible gas detection system that is reliable, simple to operate, and easy to calibrate.

GDS Corp offers gas monitors that are equipped to support both catalytic bead and infrared sensors:

• GASMAX II
• GASMAX CX

Unlike other detection systems, our design configurations give users the ability to easily switch between the different technologies. Designed specifically for combustible gases, both monitors feature interchangeable catalytic bead and SmartIR infrared sensors. That being said, you can rely on accurate detection, regardless of application, environment, or target gas.

Protect Your Business Facility

Like any hazardous gas in your environment, having an accurate and reliable gas detection system is crucial for protecting your workers. GDS Corp is proud to offer a number of customized solutions for your facility. Whether you’re offshore or in an industrial environment, our detection systems will quickly and reliably alert you of dangerous situations.

Is your gas detection system armed with combustible gas sensors? Connect with our sales team to find a solution that meets your needs.

Economical and Reliable

Because these sensors have a long life and cost very little to replace, they are considered some of the most reliable pieces of equipment any facility can have on its premises. Known for providing very accurate readings even in high temperatures, they are able to be calibrated to detect gases which cannot be detected by infrared sensors.

Harsh Environment Performance

In many situations, a catalyst detector will need to perform well in a very harsh work environment. By not being sensitive to optics, a catalytic bead sensor can thus perform quite well in environments where dust is a primary concern. Along with being resistant to dust, these sensors also perform well in areas where high temperatures and high humidity levels are present.

Degraded Performance

While it’s true a catalyst monitor is for the most part extremely economical and reliable, there are situations where their performance can be degraded. For example, if exposed to concentrated hydrocarbons for long periods of time, these sensors can become damaged. When this occurs, the result is a sensor that shows a very low signal or no signal at all.

Ease of Contamination

Along with the possibility of degraded performance, sensors in this class can also be very prone to contamination. Since the only way to test these sensors is to expose them to known quantities of certain gases, they can become inactive due to contamination. This can happen through exposure to chemicals which contain silicone and chlorine compounds, as well as those which contain sulfuric and corrosive elements.

Proper Positioning

To take full advantage of the monitoring capabilities of these sensors, one of the keys to success involves properly positioning the sensors within your facility. Along with being installed in places where exposure to dust is likely, it’s also imperative to have these sensors in places where they will experience a minimal amount of shocks and vibrations. In addition to possibly damaging sensitive circuitry within the sensor, this could also lead to false readings.

While there are a variety of pros and cons associated with sensors in this class, it’s clear this group of sensors uses technology that has been proven to be very effective in numerous work environments. Whether they are installed on offshore drilling platforms or within manufacturing plants, there’s no doubt that lives can be saved by using these sensors.

How do catalyst sensors work

Catalyst sensors have two basic elements: a detector which contains a catalytic material sensitive to flammable gases, and a compensator element which is inert. Combustible gases will burn in the presence of oxygen only on the detector, causing a rise in temperature and a corresponding rise in electrical resistance. The temperature and resistance of the inert compensator remains the same.

A circuit is formed including both elements, and a variable resistor is adjusted to maintain balance in clean air. When combustible gases raise the temperature of the detector and a rise in its resistance, it causes an imbalance in the circuit and produces an output voltage signal. The relative strength of this signal can determine the concentration of flammable gases.

Advantages of catalytic sensors
* Easy to install, use, and calibrate
* Economical, with a long life and low replacement cost.
* Very reliable
* Can be calibrated to gases such as hydrogen which can’t be detected by infrared scanners
* Not sensitive to optics and perform more reliable in dusty environments
* More reliable in high temperature
* Less sensitive to humidity and changes in air
* Detects most hydrocarbon gases

Disadvantages
* Catalyst sensors can become inactive through contamination by chemicals containing chlorine and silicone compounds, as well as sulfuric and other corrosive chemicals.
* The only means of testing sensors is to expose them to known quantities of gas and recalibrate them as needed.
* They require oxygen to operate
* Long exposure to concentrated hydrocarbons may degrade performance.
* If subjected to extreme gas concentration, the sensor may become damaged and show low or no signal

Successful use
* Avoid using silicon sprays or materials near the catalyst sensor, as silicon particles could coat the detector and inhibit it from working properly. Do not pack or store the sensor with silica gels.
* Sensor performance may be degraded by the effect of alkalines such as salts and salt water.
* Organic vapors such as alcohol may permeate and ruin the detector element.
* Water on the catalyst sensor can degrade performance, while ice forming on the sensor in cold environments could damage it.
* The catalyst sensor should be positioned where it won’t be subject to shocks and vibrations that can damage it. Vibration could also cause false readings.
* Sensors that have been stored for a long time should be recalibrated when reconnected.
* If the catalyst sensor is to be repaired, hand-solder without resins, as high temperatures or resin fumes could affect the detector.

In the end, however, a catalytic sensor is a tried and proven technology that works reliably, and over a long period of time. If it is properly installed and maintained, it could save lives.

A thorough analysis of the unique field of application is required to ensure safety, optimal performance, reliability and cost-effectiveness. A wrong decision will compromise the performance, safety, and maintenance costs, and will affect the durability of your detector.

Catalytic Sensors

Catalytic sensors represent a big number of gas detection devices being manufactured today. They are used in detecting combustible gases such as hydrocarbons, and they work through catalytic oxidation.

The sensors in the detector are made using wire coils treated with platinum. As the catalytic surface comes into contact with a combustible gas, it is oxidized, and the resistance of the wire changes because of the heat released. A bridge circuit is used as an indicator of the resistance change, which is proportional to the quantity of gas present.

Advantages of Catalytic Sensors

Catalytic sensors have several significant advantages because they are:

• Easy to operate
• Simple to install, calibrate and use
• Sturdy
• Durable with a low cost of maintenance
• Proven technology that is reliable and predictable
• Easy to calibrate to individual gases

Disadvantages of Catalytic Sensors

Catalytic sensors also have some disadvantages because:

• Catalysts become contaminated, thus deterring their functionality
• The only method of identifying the loss of detector sensitivity due to catalytic poisons is to use the appropriate gas on a regular basis, and this requires calibration
• They require oxygen for detection
• Prolonged exposure to high concentrations of combustible gas may impair the sensor performance

Infrared Sensors

IR sensors work through a system of transmitters and receivers in detecting combustible gases. Usually, the transmitters are the sources of light, and the receivers are the light detectors. The presence of gas in the optical path interferes with the strength of transmission between the transmitter and the receiver. A change in the state of light will determine the presence and the type of gas present.

Advantages of Infrared Sensors

IR sensors have several advantages because they:

• Need less regular calibration
• Are immune to contamination and poisoning
• Can operate in the presence or absence of oxygen
• Can detect at levels above 100 LEL
• Can work in a continuous presence of gases

Disadvantages of Infrared Sensors

The disadvantages of IR sensors are:

• The Gas being measured must be infrared active
• Optimal temperature for detection is 70ºC
• It requires a considerably large volume of gas for response testing
• To replace the IR source, the system must be returned to the manufacturer
• It doesn’t work well for multiple gas applications

Conclusion

There is an evident need for both catalytic and IR detectors in the industries. To make an informed choice, consider the application field environment and the sensor design variables. This requires you to be keen in analyzing the detectors, and your field experience will help you to choose the best detector to suit your needs.