Gas Analysis – Beyond the Measurement – Maximizing Availability

Many industrial processes depend on gas concentration measurements to support their operational excellence objectives. If those measurements become unavailable, the consequences are increased operational costs, decreased operational revenue and increased operational risks. Maximizing availability of gas concentration measurement matters!

How can an unavailable gas analyzer affect excellence objectives? What events reduce the availability of a gas concentration measurement? Which activities help resolve these situations now? Does #digitaltransformation offer a significant opportunity to improve availability? What part can an equipment supplier play?

These are the questions I’ll be exploring in this month’s ‘Beyond the Measurement’ blog. Don’t forget to join the conversation and complete our two-question survey here to help shape the future of our gas analysis.

How can a gas analyzer (offline) impact operational excellence objectives?

Operational costs can increase when a gas analyzer is offline, as the process control system has less information on which to base adjustments, so control degrades. In many cases, a process can continue operating and avoid a shutdown, but it cannot run optimally. The result may be higher energy consumption, increased use of fuel or other resources, potential to impact other assets and of course, additional overheads to remedy the offline analyzer.

A typical application example is the process for the reduction of NOx emissions in combustion power plants (deNOx) using Selective Catalytic Reduction (SCR). In this process ammonia (NH3) is injected into the gas flow from the combustion process; this reacts with NOx in the flue gas, in the presence of a catalyst, to form H2O and N2. A surplus of unreacted NH3, commonly referred to as ammonia slip, is wasteful and costly, and may also lead to harmful deposition effects which impact the catalyst and potentially cause corrosion of air pre-heaters located further downstream.

Operational revenue can also decrease when a gas analyzer is offline. The same degradation in control capability described above can result in off-spec product quality, lower product yield or product scrappage. For example, during semiconductor wafer manufacture where ultra-pure gases are required, the smallest impurities can result in major defects, leading to product scrappage.

Finally, operational risks can also increase when a gas analyzer is offline. In the ammonia slip example above, harmful emissions increase and can have regulatory consequences. Additionally, some processes are dependent on gas analysis to maintain safe operation. One such example is combustion in control fired heaters, integral to many hydrocarbon processes. These heaters are highly dependent on reliable continuous measurement of excess air. Efficient operation of larger, fuel-hungry units, such as those on ethylene crackers, involves a delicate balancing act to remain on the safe side of a tipping point from efficient, low-emission operating conditions to potentially explosive low-oxygen and fuel-rich conditions.

From the examples given, the benefits of gas analysis for operational excellence is evident. Equally clear should be the importance of achieving high availability while balancing cost and risk.

What can reduce availability?

Reduced availability can occur due to events broadly categorized as follows:

  • Installation and commissioning issues
  • Exposure to unforeseen process and operating conditions
  • Inadequate maintenance
  • Maintenance
  • Mis-operation of the analyzer
  • Unexpected component failure

Installation and Commissioning issues impact tightly planned and coordinated construction, upgrades, and shutdowns, and may lead to delayed startup/restart of production. Cost of delay can amount to $100,000s per day due to lost revenue and re-scheduling dependent works. Factors contributing to delays here can include late delivery, defective materials, poor installation and limited field access to information.

Exposure to unforeseen process and operating conditions is often detectable by analyzer diagnostics, but not in all cases. Depending on the exact nature of the conditions, gas measurements may discontinue while the analyzer reports NAMUR NE 107 aligned Fault or Out-of-Spec indications to the plant control system. Examples of conditions in this category include ambient or sample gas temperature/pressure/flow levels or rate of change beyond specification, poor power supply, excessive vibration and EMI.

Additional conditions may also be detectable by specific gas concentration measurement technologies. For example, unexpected background gases and high dust or particulate loading in the process gas stream can compromise spectral shape quality required to obtain measurements using Tunable Diode Laser Spectroscopy (TDLS) measurements. Some conditions can result in damage and require replacement parts.

Inadequate maintenance can lead to degraded performance and ultimately to an unavailable measurement. For example, sampling systems and analyzers themselves often include filters to protect the gas sensors from foreseen contaminants such as particulates and moisture. These may need periodic cleaning or replacement. Optics within analyzers are another example where, even under expected operating conditions, obscuration can build up over time and require cleaning.

Maintenance activities, such as cleaning or replacing filters, cleaning optics or performing periodic validation of measurement accuracy (and if necessary calibration) frequently require analyzers to be taken offline.

Mis-operation of the analyzer – for example, inadvertent adjustment of critical configuration – can cause all sort of effects that effectively render the analyzer offline or untrustworthy. Examples include disabling or changing temperature or pressure compensation configuration, modifying assigned behaviour of outputs or even modifying essential measurement details such as optical path length of an in-situ installation.

Unexpected component failures typically result in diagnostics identifying the faulty part. Impact on the gas measurement and its availability to the control system is dependent on the nature of the faulty part.


What activities help resolve these events now?

There is a common theme to many of the activities currently used to resolve the different types of unavailability event. They are manual, inefficient, error-prone and not always sufficiently data-driven.

They often involve writing notes, taking photographs or capturing limited digital logs at the site, transiting from site to an office, followed by referral to various documents (orders, delivery notes, contracts, manuals, drawing, technical bulletins and the like) to determine next steps, before either transiting back to the site or calling/emailing the distributor/supplier for support.

Emails and phone calls provide a limited and imprecise means to convey all the necessary information about an issue. It often takes multiple emails (and trips out to site) to incrementally find and add details before remote support workers gain sufficient contextual awareness to offer insight. In the meantime, offline duration gets longer.

Service team visits don’t happen instantly, potentially extending the impact on revenue further. Travel and subsistence add costs and introduce new workers onto the site, increasing risk. Their expertise and direct access to a team of experts will help resolve the problem, but will one visit be sufficient? Was a diagnosis based on notes, pictures and limited data logs sufficient to bring the right tools and parts to provide a fast and accurate first response?

Why this limitation in data logs? While gas analyzers have been intelligent devices for many years and integrated into control systems, they have been very focused on providing the gas measurement and health indications sufficient to provide situational awareness to process control systems and operators.

They haven’t continuously recorded or exposed all events and data streams to allow a retrospective and contextualized analysis of analyzer and process behavior, as there hasn’t been sufficient processing and storage capacity or connectivity bandwidth.


Another consequence of not recording all events and data streams is that maintenance activities remain scheduled events, regardless of system conditions, contributing to waste and unnecessary risk.

Finally, some issues get resolved through a process of elimination or experience. Inbuilt diagnostics may not explicitly detect a condition, but experts may infer or postulate that a condition exists from other data. Examples include excess vibration, poor power supply and some spectral quality issues.

Does Digital Transformation offer an opportunity to improve these work processes?

We think it does, but it is dependent on increased amounts – and fusion of – real-time and static digital data, with increased access to it. How different could some of these availability issues and activities look if future products and services enabled timely access to the right data for the right people in the right place?

Increased data collection and tracking from order to delivery, throughout our internal processes, could improve transparency and communication of supply issues. While the elimination of supply issues is the goal, problems do sometimes occur, and early situational awareness enables sites to take early action to minimize disruption.

Industrial facilities increasingly build digital twins of their facilities and assets, using Asset Management Systems. These enable #connectedworkers carrying out installation, commissioning or maintenance work to access 2D drawings, 3D models, manuals, technical bulletins and other information at the site via appropriate mobile or wearable devices.   Some systems provide an annotated augmented reality capability, which enhances the workers view with a digital overlay, providing visual guidance for the task.

The “right time, right place” data access removes many of the delays in resolving issues. Can equipment suppliers like Servomex provide data about our products in more appropriate ways or formats to extend these services to gas analysis systems?

Not every facility has advanced asset management in place, but site-wide wi-fi access is increasingly available. So, imagine an always-up-to-date and always-on E-Ink based QR code on gas analysis systems encoding its unique identity, current physical build, firmware details and other vital data. Scanning the QR code with a Servomex app installed on the facilities connected smartphones or tablet allows the app to provide immediate access to correct and searchable versions of 2D and 3D data, manuals, technical bulletins that may help fast local resolution.

The app could also provide direct access to Servomex technical or application support and ensure maximum context about the asset is available to the support operative, minimizing the email and phone call based collection cycle.

Annotated augmented reality technology may be possible here too, enabling our experts to provide the visual guidance and over-the-shoulder support your workforce may need to guide their actions more efficiently.


Mis-operation of the analyzer in the form of ill-considered or inadvertent configuration change is avoidable through additional security controls.  For example, well-established methods such as 2-factor authentication could be employed by analyzers to protect critical configuration.

Service plans provide increased confidence that unplanned downtime can be avoided.  However, preventative maintenance, while nowhere near as costly as reactive maintenance, is still not optimal.  Wouldn’t it reduce operational costs, impact revenue less and lower risks if maintenance were carried out only when conditions require it?  This leads us to predictive condition-based monitoring.

Condition-based monitoring needs significantly more data than required for process control.  Instead of using the NAMUR NE 107 type diagnostic health indicators that gas analyzers currently provide into process control, the data behind those indicators is exposed.  Patterns, trends and correlation analysis can then providing greater insight into how things are changing over time and at what moment those changes may impair performance.

Increasingly capable plant operational Intelligence systems, build on top of or integrated into plant historians, are optimized to ingest and cleanse data this type of data, contextualize it, analyze it and provide dashboards or notifications of critical events to the workforce.

Integrating equipment into these systems using traditional Fieldbus protocols such as Modbus is possible. However, because Modbus maps for all types of device are unique and don’t conform to any standard profile, ingestion would need to be configured, another cost and productivity overhead. Support by gas analyzers for newer connectivity methods, such as Wireless HART or OPC-UA would enable a more plug and play approach.

Additional operational intelligence services and security, in the form of uni-directional gateways, could enable suppliers like Servomex to monitor gas analyzer assets on your behalf under service level agreements, providing new levels of optimized service response.


I’ve briefly highlighted a range of ways in which your operational excellence objectives may be enhanced through the application of digitally transformed capabilities.

Now we’d like to know what you think, so please join the discussion in our comments section. Each blog post also links to a one or two-question survey on our website – let us know your views, as your feedback will help to improve and prioritize not only our future posts but also our future gas analysis solutions.

Contact the author, Tony Dodd, for further information on this digitalization topic.





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