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Oxygen Deficiency Monitor for Your Application

When selecting an oxygen analyzer for your critical process application, consider factors like sensor type, maintenance, and calibration needs. Different oxygen sensors are suited for specific applications, so choose one based on the requirements of your process.

Oxygen Sensor Types:

  • Ambient Temperature Electrochemical Sensors: Known for accuracy in both trace and percent oxygen measurements, these sensors have extended life but are vulnerable to damage from acid gases and over-pressurization.
  • Paramagnetic Sensors: Offering precise measurements across 1%-100% oxygen, these sensors work by detecting the magnetic properties of oxygen. However, they are delicate, sensitive to vibration, and not suitable for trace oxygen measurements.
  • Polarographic Sensors: Ideal for dissolved oxygen in liquids, these sensors are suited for percent oxygen measurements in gases. They have low maintenance requirements but are prone to frequent sensor replacements.
  • Zirconium Oxide Sensors: Operating at high temperatures (650°C), these sensors are ideal for combustion control applications. They can measure a wide range of oxygen concentrations but are unsuitable for trace oxygen measurements when reducing gases are present.

Each sensor type has its strengths and limitations, so assess your process needs carefully before choosing the right oxygen analyzer.

Compare Oxygen Deficiency Monitors

Not all oxygen deficiency monitors are the same. Like automobiles or cell phones, they vary in quality and performance.

Many monitors use “fuel cell” oxygen sensors, which typically need replacement every 10-14 months. However, as these sensors age, their electrical output decreases, mimicking a low oxygen signal. This can lead to false alarms, which, when ignored, can create dangerous situations. Personnel may dismiss alarms as false, potentially missing real low-oxygen events. This frustration may even lead to disabling alarms, increasing risk.

Zirconium oxide-based monitors often claim to be calibration-free for over 10 years, but these claims are misleading. One major supplier of zirconium oxide sensors makes no such claims. Closer inspection of the user manuals reveals that these sensors require periodic adjustments and calibration. Experts agree that gas monitors need occasional checks to ensure accurate readings and protect personnel. The stakes are high, and cutting corners can be dangerous.

CAPABILITIES

Series 1300 Oxygen
Deficiency Monitor
Fuel Cell Oxygen Monitor
High Temperature (450 °C) Zirconium Oxide Oxygen Monitor
Three-year warranty on both the electronics and      sensor

YES

NO – Typically one year

NO – Typically two years

Accepts up to 3 oxygen sensors with one set of electronics drastically reducing the per point monitoring costs

 

YES

NO

NO

Built-In data logger standard

YES

NO

Limited Availability

Easy field replacement of the oxygen sensor

YES

YES

NO – Both sensor and mating electronics need replacement – an expensive repair

Built in alarm relay contacts

YES (4 Standard)

Some at extra charge

Often an extra charge

Can be affected by changes in ambient air now caused by HVAC / air handling systems

NO

NO

YES – Changes in airflow may sufficiently cool the high temperature sensor producing erroneous oxygen readings.

Can be used in the presence of combustible gases, refrigerant gases, other reducing gases

YES

YES

NO

Long-life oxygen sensor

YES

NO

Can fail prematurely from heat fatigue

The Importance of Oxygen Deficiency Monitors in the Workplace

The Importance of Oxygen Deficiency Monitors in the Workplace

If someone were to ask you what the major cause of gas related injuries in the workplace is, would your answer be carbon monoxide poisoning?

What about exposure to ammonia, hydrogen chloride, carbon dioxide, hydrogen sulfide, or chlorine? Even though injuries are reported because of over exposure to these gases, oxygen deficiency continues to pose the largest overall health risk. Often referred to as the “silent killer”, oxygen depleted breathing air is the cause of numerous injuries and/or deaths on an annual basis. Breathing air oxygen can be depleted because of leakage of stored or piped inert gases such as nitrogen, helium, argon, carbon dioxide, sulfur hexafluoride, etc. These gases, as well as others, are often used in laboratories, fertility clinics, heat treating facilities, cryotherapy installations, shipyards, various manufacturing processes, MRI (magnetic resonance imaging) installations, research facilities, dry ice manufacturing facilities, and nuclear magnetic resonance spectroscopy (NMR) installations to mention a few. According to a recent paper released by OSHA (Occupational Safety and Health Administration) “oxygen can even be consumed by rusting metal, stored ripening fruits, drying paint, combustion, or bacterial activities.” so it’s not just leakage of inert gases that can be problematic. Breathing air contains essentially 20.9% oxygen by volume. If oxygen levels drop to 14-16%, individuals exposed to those levels may become disoriented and confused.  When a sustained exposure to oxygen levels of less than 10% takes place, fainting, convulsions, and death may result. The first line of protection to help prevent injury and/or death is the use of an oxygen deficiency monitor(s).

In a January 2016 report by the Center for Disease Control and Prevention (CDC), entitled, “Sudden Deaths Among Oil and Gas Extraction Workers Resulting from Oxygen Deficiency and Inhalation of Hydrocarbon Gases and Vapors — United States, January 2010–March 2015” the article cited the potential dangers associated with exposure of workers to oxygen depleted atmospheres. A study conducted from 2010 to 2015, reported nine deaths attributed to   workers who were attempting to measure and record liquid hydrocarbon levels in storage tanks. Access to the liquid hydrocarbon was through “thief” hatches (closable apertures on atmospheric tanks, used for accessing the contents of the tank). When workers climbed to the tops of the tanks to open the thief hatch, they were often exposed to significantly depleted oxygen levels due to displacement of oxygen by the hydrocarbon vapors.

Another example of a potential low oxygen safety hazard is in MRI (magnetic resonance imaging) facilities where significant volumes of liquid helium are used to cool the MRI’s magnets. If an unexpected magnet quench (liquid helium boils off abruptly) the helium gas released into the MRI room can quickly displace breathing air oxygen levels creating a hazardous, life-threatening condition. For some installations, the volume of stored helium can be as much as 700,000 liters.  Few industries are immune from the risks of oxygen depletion, particularly when inert gases are in use. For this reason, it is prudent to use oxygen deficiency monitors to help protect personnel.

The above examples help to illustrate that the use of inert and/or process gases in the workplace can pose a real and severe threat to the well-being of individuals unless proper precautions are taken. Alpha Omega Instruments has been providing solutions to the safety market for over 26 years offering a comprehensive line of oxygen deficiency monitors and alarms.

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Glove Boxes: Sensors

Selecting an Oxygen Monitor Sensor for a Glove Box Applications

Glove boxes are used to perform manual manufacturing processes where exposure to the components may be harmful to personnel, or exposure to the room atmosphere may be harmful to the product.

Glove boxes, generally, are purged with N2, Ar or CDA to form an inert boundary. They are widely used in the semiconductor/electronic component metalworking, nuclear and crystal manufacturing industries.  Many glove box problems are unique. Gases and residual products can produce aggressive chemicals. In some instances, sensors have required bi-weekly recalibration and a 3–6-month replacement. Most glove box applications, however, are much easier with normal sensor lifetimes expected.

Sensors are normally installed directly into the box. Our preference is to mount the sensor in a sample cell on the discharge point (there is normally a continuous bleed on glove boxes) to minimize the chance of physical damage.  Learn more on oxygen monitor sensors.

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Know the Difference Between Oxygen Monitor Sensors

KNOW THE DIFFERENCE BETWEEN OXYGEN MONITOR SENSORS

Do you know the difference between oxygen monitor sensors?  Oxygen analyzers use one of a several types of oxygen sensors.   As industrial process applications call for improved measurement accuracy and repeatability, users are demanding analyzers that require a minimum of maintenance and calibration.   There is no one universal oxygen sensor type.

AMBIENT TEMPERATURE ELECTROCHEMICAL SENSOR

  • Often referred to as a galvanic sensor, is typically a small, partially sealed, cylindrical device (1-1/4” diameter by 0.75” height) that contains two dissimilar electrodes immersed in an aqueous electrolyte, commonly potassium hydroxide.
  • Refinements in electrode materials, and enhanced electrolyte formulations, the galvanic oxygen sensor provides extended life over earlier versions and are recognized for their accuracy in both the percent and traces oxygen ranges.
  • Response times have also been improved.
  • They are easy to damage when used with samples containing acid gas species such as hydrogen sulfide, hydrogen chloride, sulfur dioxide, etc.

PARAMAGNETIC OXYGEN SENSORS

  • This is the magnetodynamic or `dumbbell’ type of design and is the predominate sensor type.
  • The paramagnetic oxygen sensor consists of a cylindrical shaped container inside of which is placed a small glass dumbbell.  The dumbbell is filled with an inert gas such as nitrogen and suspended on a taut platinum wire within a non-uniform magnetic field.
  • A precision optical system consisting of a light source, photodiode, and amplifier circuit is used to measure the degree of rotation of the dumbbell.
  • Some paramagnetic oxygen sensor designs, have an opposing current is applied to restore the dumbbell to its normal position.
  • In general, paramagnetic oxygen sensors offer very good response time characteristics and use no consumable parts, making sensor life, under normal conditions, quite good.
  • Offers excellent precision over a range of 1% to 100% oxygen.
  • They are quite delicate and sensitive to vibration and/or position.
  • Due to the loss in measurement sensitivity, in general, the paramagnetic oxygen sensor is not recommended for trace oxygen measurements.

POLAROGRAPHIC OXYGEN SENSORS

  • Often referred to as a Clark Cell [J. L. Clark (1822- 1898)].
  • This sensor, both the anode (typically silver) and cathode (typically gold) are immersed in an aqueous electrolyte of potassium chloride.
  • The electrodes are separated from the sample by a semi-permeable membrane that provides the mechanism to diffuse oxygen into the sensor.
  • The current output generated from the sensor is measured and amplified electronically to provide a percent oxygen measurement.
  • An advantage of the polarographic oxygen sensor is that while inoperative, there is no consumption of the electrode (anode).
  • Storage times are almost indefinite. Similar to the galvanic oxygen sensor, they are not position sensitive.
  • One major advantage of this sensor type is its ability to measure parts per billion levels of oxygen.
  • The sensors are position sensitive and replacement costs are quite expensive, in some cases, paralleling that of an entire analyzer of another sensor type.
  • Not recommended for applications where oxygen concentrations exceed 25%.

ZIRCONIUM OXIDE OXYGEN SENSORS

  • This sensor is referred to as the “high temperature” electrochemical sensor and is based on the Nernst principle [W. H. Nernst (1864-1941)].
  • Zirconium oxide sensors use a solid-state electrolyte typically fabricated from zirconium oxide stabilized with yttrium oxide. The zirconium oxide probe is plated on opposing sides with platinum which serves as the sensor electrodes.
  • The zirconium oxide oxygen sensor has excellent response time characteristics.
  • The same sensor can be used to measure 100% oxygen, as well as parts per billion concentrations.
  • Due to the high temperatures of operation, the life of the sensor can be shortened by on/off operation.
  • A major limitation is their unsuitability for trace oxygen measurements when reducing gases (hydrocarbons of any species, hydrogen, and carbon monoxide) are present in the sample gas. At operating temperatures of 650 degrees Centigrade, the reducing gases will react with the oxygen, consuming it prior to measurement thus producing a lower than actual oxygen reading.
  • The magnitude of the error is proportional to the concentration of reducing gas.
  • Zirconium oxide oxygen sensors are the “defacto standard” for in-situ combustion control applications.

Explore our range of oxygen safety and deficiency monitors.

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