Digitally enhanced reciprocating compressor performance
With instant access to compressor data, improved productivity, and expert support, digital technologies are revolutionising maintenance processes.
James Litchfield and Philipp Wolschner
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As the technology for connecting machinery and gathering important data continues to improve, more companies are seeing how they can reduce costs and improve sustainability by adopting digital solutions. One area where this is particularly prevalent is the performance and maintenance of rotating equipment operating in challenging locations.
The ability to assess reliability and schedule maintenance tasks for optimum convenience can ensure minimal downtime to realise the full potential of important equipment. There are several options when considering rotating equipment maintenance. From the most basic ‘run it until it breaks’ theory to continuous monitoring and predictive maintenance supported by advanced algorithms and analytics. Depending on the equipment in question, different approaches may be applied.
The simplest method is to run a machine until it stops due to a failure. This somewhat short-sighted option has very low initial maintenance costs; however, there is a significant potential for very high costs to repair the machine, including those associated with any lost production.
Clearly, a more effective process would consider the wear mechanisms within the equipment and identify more frequent maintenance procedures. Worn parts should be replaced before their lifetime is reached (preventive maintenance) to maximise the use of their wear potential while preventing component failures (see Figure 1).
However, the lifetime of components for reciprocating compressors, such as valves and bearings, is not subject to linear wear, making it difficult to decide on the best time to replace a component based on operating hours. Maintenance decisions on components experiencing non-linear wear are challenging and cannot be made by relying solely on a time-based strategy.
This process requires continuous monitoring of certain parameters that allow judgment of the components’ condition and an estimation of the best time for a replacement. This is known as predictive maintenance.
Focus on reciprocating compressors
Reciprocating compressors have been used in many applications since the 1880s, but in the past, they may not have received the level of monitoring they deserved. Higher priority has been given to centrifugal and axial machines for a number of reasons. Firstly, the larger population of centrifugal equipment meant the focus was usually on the more prevalent machines than the reciprocating variety. Secondly, operators did not encounter significant issues due to the lower kinetic energy of these relatively slow-running machines. As a result, more recently, as the original population has aged, more focus has been required to maintain their reliability.
However, reciprocating compressors are among the most critical assets in the plant. These machines can provide higher compression ratios than similar axial or centrifugal compressors. They play an essential role in many industries, such as oil and gas production, refining, enhanced oil recovery, corrosive gas production, low temperature and cryogenic applications, as well as hydrogen production and petrochemical processes.
In natural gas applications, they are generally part of the upstream/midstream business for wellhead gas gathering, vapour recovery, gas re-injection, gas lift, pipeline gas transmission, gas storage, fuel gas boosting, and boil-off gas compression. However, in the downstream segment, there is greater commercial benefit to implementing condition-monitoring solutions. In these processes, profit links directly to the availability of the reciprocating compressor and, as such, plants often categorise reciprocating compressors as critical machines.
From the outset, original equipment manufacturers (OEMs) have followed their own design specifications alongside those standards developed for the industry, which were effective at the time of construction and, to a large extent, are still valid today.
However, upon studying the age of the reciprocating compressor population, it can be seen that, in many cases, these large, critical machines have never been replaced and have been in operation since their initial start-up date many decades ago. This is testament to their original build quality and the standards that were in place then.
From the first edition of API 670, published in 1976, to the fourth edition in 2000, the focus was on the technical requirements of centrifugal and axial compressors. In November 2014, the 5th edition was released with special guidelines around the monitoring and protection of reciprocating compressors. The aim is to increase the availability, detectability, and monitoring of these compressors.
Traditionally, these tasks have been carried out by expert technicians deployed or trained by the OEM. However, with a global shortage of skilled technicians and the advent of digital technologies, remote support tools have been developed to minimise downtime and expedite repairs (see Figure 2). The use of digital services in the maintenance of reciprocating compressors has revolutionised how maintenance tasks are carried out. This is especially true for marine applications, where vessels can be at sea for extended periods, making any repairs much more challenging.
Remote support technology has enabled OEMs to provide virtual hands-on expertise to their customers, reducing the need for skilled personnel to be on-site. The technology allows a specialist to guide a maintenance technician on-site and provide precise instructions, improving the speed and efficiency of the repair process. This is particularly valuable in remote locations, where expert support may be difficult to obtain, or in market segments where the required expertise is scarce.
The advantages of remote support have been highlighted by the global pandemic, which imposed stringent travel restrictions, posing a significant challenge for on-site support. In addition, digital technologies are having a very positive impact on sustainability, reducing CO2 emissions through reduced travel, especially flights.
Digitalisation and Industry 4.0 have paved the way for improved diagnostics and communication, leading to the more efficient identification and resolution of problems. Companies have developed specialised digital solutions, such as machine monitoring, which can help to reduce both direct and indirect GHG emissions. They also include remote support software, predictive maintenance tools, and systems to calculate optimised servicing intervals, to deliver improved compressor availability and efficiency.
Finally, the use of advanced analytics can also help to improve the accuracy of predicting service life between major overhauls. By analysing large amounts of data and learning from past maintenance events, advanced analytics can help maintenance teams to more accurately predict when an overhaul is needed, reducing the risk of unplanned downtime and improving overall efficiency.
One of the most common concerns of large industrial companies looking to adopt predictive maintenance strategies is the security of their data and their wider process control systems. The use of cloud environments and connecting data historians to the internet can lead to some apprehension about adopting advanced analytics solutions.
From the outset, the priority of OEMs and those developing these solutions is the absolute security of any digital connection and the integrity of the operator’s data. While specific machine data will be used to identify any potential issues with that equipment, it will be anonymised before being used in any wider analysis.
It is important to understand that firewalls remain in place, and only secure connections are made between the machine and the cloud. The involvement of IT specialists both from the OEM and the operator is essential to allay any concerns about cyber security. Technology and software developed and certified according to the international cyber security standard IEC62443 help to set a common benchmark for cyber-secure devices widely accepted across industry.
For its part, Burckhardt Compression has ensured that digital security was a primary focus in the development of its latest digital products, including UP! Remote Support, which offers immediate technical assistance wherever it is required. Using an ATEX-certified tablet and headset enables the technician on-site to communicate and receive instructions from engineering experts via a secure network connection.
The use of live images and instant feedback cuts maintenance time to an absolute minimum, reducing costs and ensuring technical support is always available. The technology also enables training to be delivered as well as supporting pre-inspections and monitoring of maintenance work without the required expert having to attend in person
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