Going digital

Manish Verma, TMEIC, USA, looks at how digital services can avoid forced outages by turning them into unplanned outages and carve a sustainable path for medium voltage variable frequency drive maintenance.

orced outages are one of industrial process facilities’ most significant pain points. As per a study by Deloitte, unplanned outages cost industrial complexes an estimated US$50 billion/y.1 Over the past several years, there has been much buzz around terms such as Industrial Internet of Things (IIoT), Industrial 4.0, digitalisation, artificial intelligence (AI), machine learning (ML), and predictive analytics as the next big thing in heavy industrial sectors such as oil and gas. The narrative surrounding these buzzwords is the promise that the mentioned technologies can predict when and how a particular piece of equipment will fail. The term ‘predictive’ is often misused and even misunderstood for technologies that do not deliver predictive capabilities. Hence, it becomes very critical to separate truly predictive technologies from non-predictive technologies and look at what is realistically achievable with large industrial equipment. This article discusses digital services as a maintenance component by considering a critical piece of an all-electric LNG complex: the medium voltage (MV) variable frequency drive (VFD).

Turning forced outages into unplanned outages

For any large facility, the compressor, pump, or other rotating equipment is at the heart of the system, moving gas, liquids, or materials from one process to another. Electric motors and VFDs provide a viable path to electrify and decarbonise energy-intensive processes. Figure 1 illustrates an electric motor-driven system on a compressor. The benefits of a VFD and its related energy savings impact have been very well understood, as shown through the discussion held by Verma and Phares at the 2022 IEEE IAS/PCA Cement conference.2 One of the concerns that end users and equipment operators have raised over the years around a VFD-based system is what is the best way to maintain this equipment. Site personnel are seldom familiar with MV VFDs. While following the manufacturer’s instructions and maintenance schedule is a good start, it leads to either over-maintenance or under-maintenance since the required frequency and extent of care depend on the equipment operation and installation environment.

Condition-based monitoring (CBM) combined with human expert-level analysis answers the concerns raised by equipment operators. CBM is a requirement for any proactive-based maintenance. Any monitoring or digital service aims to convert forced/unplanned outages into planned outages. Industry participants have a significant misconception that AI, big data, and digitalisation will predict impending equipment faults and failures and relieve the burden of off-site maintenance. Predicting impending failures in the context of an MV VFD is extremely difficult to detect with a high-confidence level. It is not to say that predicting failure in the future is impossible. The current technologies and the market’s willingness to pay for such a solution are yet to be determined. Hence, it is far more effective to focus on proactively maintaining the VFD and reduce the mean time to repair (MTTR) so that when a failure or fault occurs, the operator or the manufacturer can quickly bring the VFD equipment online. All VFDs need maintenance, and some VFDs will trip when it is least expected. Unexpected downtime is the reality of any piece of heavy equipment. However, digital services can minimise the duration of downtime. The question then becomes what engagement levels are necessary with the VFD when it trips and goes offline. Figure 2 provides an overview of five levels of engagement that a VFD might encounter.

As shown in Figure 2, most VFD issues are fixed by resetting the VFD fault. Resetting VFD after a fault is level 1 engagement. However, there are specific faults that require deeper evaluation on its cause – these are level 2 faults. Experienced site personnel familiar with the VFD equipment can work through the issue and bring the VFD back in service. However, a site that does not have access to in-house experts must depend on the manufacturer. The question now is how soon the fault is resolvable. Figure 3 illustrates how the response plays out in the absence and presence of a digital service engagement.

As shown in Figure 2, under a typical scenario, the VFD would detect a fault and then trip depending on the criticality of the fault. Since a simple reset did not fix the issue, further evaluation of the fault becomes necessary. The operator often has to contact the VFD manufacturer’s 24/7/365 service line to get support. While the manufacturer attempts to help the customer, the reaction time is not guaranteed since the equipment manufacturer has no connectivity, historical data, and rules of remote web engagement with the client and thus the VFD. Hence, the manufacturer and the equipment operator have to get on the phone and guide the customer to get the fault data off the VFD and then e-mail the settings and fault file. A field tech is often sent out to the site to troubleshoot the issue. This could take several hours or even days if a service tech needs to be dispatched.

However, with a digital services package purchased with the VFD; the fault detection, notification, historical context machine-generated data, and the rules of remote engagement are already available and established between the manufacturer and the site. This materially reduces the time it takes to troubleshoot the VFD and get it back in service. There are a multitude of ways in which digital services are packaged with the original equipment. However, in most cases, VFD operators are looking at a yearly subscription service for monitoring, reporting, notification, and human expert service. Here is a deeper look at the significant components of a typical proactive digital service offering:

z Component 1: Getting the data: This is an essential element of a digital service.There must be a way to capture, log, store, and trend machine-generated data over long periods with sufficient resolution. A VFD is a piece of digital native equipment that generates a large amount of data that needs to be captured and analysed for later use. VFD manufacturers typically capture this in their provided software, which can pull in data by the VFD and publish it to a data historian. The captured data provides context surrounding a fault or a warning. The data-capture software is usually installed on a client-provided dedicated computer that can ‘see’ the VFD on the network. A virtual machine is also acceptable for this purpose. It must be noted that depending on the industry, there are strict requirements around data leaving the facility. Hence, a proactive digital service must be able to operate inside the ‘fence-line’ in the absence of an external network connection and allow access only when necessary.

z Component 2: Automated notification: The notifications include a high-speed data trace save of variables such as voltage, current, speed, DC bus, speed reference, and others right before and after a fault. This helps in diagnosing what external or internal event might have led to the fault in the first place. Also, during the operation, the VFD generates alarms and is notified via e-mail to a client’s chosen e-mail address. The capability is helpful since it keeps a historical log of all the faults and warnings ever since the digital package was activated and put in service on the VFD.

z Component 3: Expert-level human service: Until the artifical intelligence (AI) algorithms are sophisticated enough, experts with deep domain knowledge are critical. It is usually a service technician or an engineer from the VFD manufacturer itself. The expert usually engages with the VFD remotely for an hour or two monthly to review the fault and alarm notifications that might have occurred during the month and trend critical VFD variables that are leading indicators of VFD failure. This is the only time the end user must provide an outside web connection for the duration of the engagement.

It is not necessary to stop the VFD during this time. The end user is provided with a report at the end of the engagement.

The report outlines what the expert observed, any unusual

trends in the data that might indicate a failure down the road, and an assessment of onsite preventative maintenance service and renewal parts that might be necessary. The monthly report is useful for budgeting maintenance spend for the VFD under observation.

One of the significant benefits of a three-part service offering is that rather than running the equipment till failure, a more proactive-based approach can be taken and frees up the time of the site maintenance person to do other things. Further, should a VFD experience downtime, any trained professional, whether in-house or from the manufacturer, has immediate access to contextual data surrounding the fault. One can log into the digital service that hosts historical data, does an evaluation, and guides the site personnel. In most cases, the VFD is back in

Figure 1. Simple illustration of variable frequency drive electric motor.

Figure 2. Levels of engagement for standard variable frequency drive equipment.

Figure 3. Typical response timeline for variable frequency drive trips under digital and non-digital service scenarios. service in a relatively short time compared to a VFD that does not have digital service components. Hence, a digital service offering from the manufacturer effectively reduces the MTTR. Figure 3 shows the typical network connectivity illustration.

Cyber security

When digital service or remote access type solutions are brought up in internal discussions, the starting position is almost always “it will be difficult to get past the IT department.” The concern is understandable in light of the increased cyber attacks on critical industries. The good news about the implementation of proactive digital services mentioned above is that for the day-to-day data capture, analysis, fault, and warning notifications, there is absolutely no need for remote access to the operational network. Only when the monthly engagement session is initiated is outbound connectivity from the computer hosting the original equipment manufacturer (OEM)-supplied software to an approved client necessary. Further, the time and duration of access are co-ordinated 2 – 3 days before the engagement. The pre-engagement step ensures access is provided only to the authorised service tech and only for the duration necessary to do a monthly VFD health check. Often, end users choose to screen record the actions the VFD manufacturer took for audit and record-keeping purposes.

Conclusions

Industrial facilities are starting to see the value in digital services. As mentioned, most digital services aim to have maximum equipment availability, reduce downtime, and maximise production. The global market sets the price of crude oil or natural gas. Hence, plant efficiency and production uptime can mean the difference between profitability and loss of a petrochemical facility such as a refinery, LNG facility, and others. MV VFDs in the range of a few thousand hp to tens of thousands of hp are used on critical services such as pumps, compressors, fans, extruders, and others. Their availability and reliability are critical to plant operations. Digital services provide a sustainable path to maintaining electrical equipment.

Further, the recent COVID-19 pandemic spotlighted the need for digital services for industrial equipment’s safety, reliability, and maintainability while preserving health. As a large part of the experienced workforce retires, there is increasing pressure on companies around how to replace the decades of equipment and process knowledge. Hence, the operators are increasingly dependent on the OEM to maintain their equipment, provide timely guidance on upcoming maintenance issues, and keep the equipment available. Proactive-based digital services have become accepted where the OEM can look over a plant maintenance personnel’s shoulders and track the equipment’s health and status.

References

Figure 4. Typical network connectivity illustration.

1. COLEMAN, C., DAMODARAN, S., CHANDRAMOULI, M., and DEUEL, E., ‘ Making maintenance smarter’, Deloitte University Press, (2017), www2.deloitte. com/us/en/insights/focus/industry-4-0/usingpredictive-technologies-for-asset-maintenance. html, (Accessed on 30/07/22). 2. VERMA, M., and PHARES, D., ‘Reaching environmental, sustainable & governance (ESG) goals with Medium Voltage (MV) Variable

Frequency Drives (VFD)’, 2022 IEEE IAS/PCA Cement Conference.