In case you missed months’s webinar with Siemens on oxygen measurement in safety critical applications, we’ve put together some of the key points:
What is a safety critical application?
A safety critical application is one in which system failure could result in loss of life, significant property damage, or harm to the environment.
There are a number of critical applications that anyone in the process industry should be aware of:
- Thermal oxidizers are process units for air pollution control in many chemical plants. They work by decomposing hazardous gases at a high temperature and releasing them safely into the atmosphere. When thermal oxidizers are not working properly, they can be explosion hazards.
- A gas flare is a combustion device used in plants for burning off flammable gas released by pressure relief valves during unplanned equipment overpressure. The oxygen level in the flare gas must be set below that of where an explosion could occur.
- Inert blanketing refers to the layer of gas, typically nitrogen, that lays atop contents in a tank, container, or silo to reduce oxygen content in the vapor space, and ultimately reduce the risk of unwanted combustion. If the inert blanketing fails, there is a possibility of explosion.
Why is oxygen measurement important in safety critical applications?
We measure oxygen in critical applications is to protect workers, operations, and facilities from explosions caused by an excess of oxygen. In some cases, we also measure for deficiencies to prevent suffocation due to lack of oxygen.
How do we measure oxygen in safety critical applications?
We use lasers and continuous gas analyzers like the SIEMENS SITRANS SL to measure oxygen in safety critical applications. The SITRANS SL is an in-situ tunable diode laser (TDL) sampling system.
In-situ sampling offers measurement of gas concentrations in process or flue gases within three seconds.
In-situ vs. Extraction Sampling
In-situ sampling is advantageous in applications with reactive components because you can take a sample without having to touch or “grab” it. In an extraction system, you have to pull the sample out of the process. When this happens, the component can change, and could produce an inaccurate reading.
Extraction also limits measurement to the point of extraction; you’re not measuring through the entire duct or vessel. In-situ gives you an average across the stack, so you get a “big picture” reading by calculating an average reading throughout.
Extraction monitors also require more frequent calibration and maintenance than in-situ equipment since there are pumps, filters, coolers, and heated lines that need to be maintained. In-situ monitors require very little maintenance because there are no moving parts that grind, go bad or wear out. Plus, in-situ typically requires minimal calibration. For the Siemens TDL, you don’t have to cal check the unit for a year.
So, how do I choose an analyzer for my application?
- How fast do you need to have an update on your analysis? If you require fast response, in-situ is the way to go. If you can wait a couple of minutes for your results, an extraction system will suffice.
- Consider interference and accuracy. Extraction sample handling systems and analyzers don’t have the same accuracy as the in-situ monitors, considering the TDL’s inherent lack of interference, especially when measuring oxygen.
- How much maintenance can you handle? Is it critical that the instrument is up and running all the time? Can you take it down and maintain it? If you want an uptime that is very high, the in-situ might be best for you. However, if you are not concerned about maximizing uptime and you can handle the maintenance, the extraction system will work fine.
Learn more about oxygen measurement in safety critical applications, how the diode works, where you use it and its advantages:
Learn more about Siemens SITRANS SL Tunable Diode Laser In-Situ Oxygen Analyzer