Ensure safety and save on nitrogen gas with inline oxygen meters

Many chemicals are used in the process industry. It is important that these are stored in a controlled manner. For example, depending on the filling, the oxygen concentration in storage tanks must always remain below a certain level to prevent ignition and explosion hazards. Nitrogen blanketing is also necessary for quality maintenance in food products and edible oils. Elscolab offers various inline analysis techniques to measure oxygen content.

"In the process industry, many flammable or oxygen-sensitive products are stored in storage tanks. It is important to keep the oxygen concentration below a certain level to prevent explosions or ignition. This is done by inerting. An inert gas such as nitrogen is added to a system, reducing the oxygen content below a certain limit or until the oxygen is completely replaced by the inert gas," explains Harry Geeraedts. He is a specialist in inline analysis technology for the process industry at Elscolab.

Concentration of oxygen

"Replacing all oxygen completely with an inert gas is often not necessary," he states. "There are charts available for each substance that indicate the value below which the oxygen content must be to achieve a safe situation. As an example, when methane gas is stored in a tank, it is necessary for the concentration of oxygen to be below 12% (Lowest Oxygen Concentration). If this is the case, nothing will happen. Even should a spark occur or should the temperature change, no fire or explosion will occur. So it is important to stay below that value - preferably with an additional built-in safety margin. That's why measuring oxygen content is so important."

To measure is to know

At the same time, guidelines (NPR-CEN-TR 15281:2022, PGS29:2016) describe the need to measure on a regular basis. "This is necessary to ensure at all times that oxygen levels never exceed the desired level. Only sporadic measurement is not safe.

If you measure permanently, this also offers more advantages: you can be sure that you are always in the safe zone and can also record this - after all, measuring is knowing. You comply with laws and regulations and you can save nitrogen by adding only the necessary amount - including a safety margin. Up to seventy percent savings on nitrogen are possible by using oxygen measurement on inerting."

Different variants

Oxygen meters or GPOs (Gas Phase Oxygen Probes) come in different shapes and sizes, think amperometric sensors, optical sensors or Tunable Diode Laser (TDL) analyzers. "All the sensors in our range are ATEX certified. Depending on the customer's needs and desired investment, a simple electrochemical cell that can be mounted on a tank or a more complex, fully automated system that also meets SIL standards, for example."

Maintenance

A major determining factor in the choice is the maintenance required, Geeraedts says. "All analyzers in the field need maintenance. For electrochemical cells, the electrolyte and membranes will need to be replaced regularly. For optical sensors, an optocap may need replacement. Therefore, both electrochemical and optical sensors require regular maintenance, leading to temporary downtime. If you want to avoid this, then a TDL (Tunable Diode Laser) analyzer is very suitable. These analyzers - also called laser analyzers - are reputed to be the best analysis systems for most applications. The GPro500 series from Mettler Toledo is an example. The analyzer has no moving parts and is SIL-certified, making simple cleaning and annual verification sufficient."

Trend

In recent years, more and more tank storage companies are opting for automated solutions. "Laws and regulations are leading to the issue being higher on the agenda. In addition, regular production downtime, because maintenance is required, is no longer acceptable to many process managers. But whatever option companies choose, we are happy to assist them with advice, we take care of the initial installation and, if required, maintenance through service contracts."