Bridging the gap between machinery protection and condition monitoring

Different goals, similar instrumentation

A machinery protection system and a condition monitoring system fundamentally fulfill different goals. According to the American Petroleum Institute’s standard for machinery protection systems, API Standard 670, 5th edition (Annex N Condition Monitoring):

  • The goal of a machinery protection system (MPS) is injury prevention, the avoidance of damage to a machine and environmental protection.
  • The goal of a condition monitoring system (CMS) is to help maximize the availability of a machine. It does this by providing an insight into the operating condition of the equipment being monitored, which allows component replacement and/or machine repair to be better predicted, thereby enabling maintenance and turnaround schedules to be optimized.

MPS and CMS systems both operate by continuously monitoring selected machine parameters. Based on years of industrial expertise, API 670 and other international standards serve as guidelines on the essential parameters for machinery protection and/or the recommended parameters for condition monitoring. As such, these important references help to effectively monitor the condition of essential assets.

The parameters required to be monitored for machinery protection and condition monitoring applications are not one-on-one the same. Typically, a MPS will use a few simple but reliable parameters such as overall vibration levels which are used to set up alarm levels and trigger shutdown logic. However, these same sensor signals carry substantially more diagnostic information that could also be used for machine health monitoring and predictive maintenance. A CMS can apply advanced signal processing techniques to extract this data, including waveforms, spectra, harmonic vibration levels (1X, 2X, etc.), shaft centerline or orbits, to name just a few.

It is important to note here that CMS’s can be employed to monitor the health of many different types of asset, not just machinery that is already instrumented with a MPS.

API 670's perspective on combining machinery protection and condition monitoring systems

As mentioned in our recent General API 670 requirements for machinery protection systems blog post, independence and separation of systems, components or parts is an essential API 670 requirement. Given this, does the standard allow the combination of machinery protection and condition monitoring functionality?

The answer is a definite yes, although with the qualification outlined by API 670 in section 4.8 Segregation:

  • A MPS and a CMS can be combined provided there are no impediments to the ability of the MPS to perform its tasks, specifically, the detection of alarms within the required response time and activation of output relays as required.

In practice, this means that when a MPS is combined with other systems such as a CMS or control system, there should be no “common-cause” failure modes that could interfere with the MPS’s goal of protecting the machine.

Bridging the gap

Bridging the gap refers to the sharing of sensors / measurement chains and electronic devices between machinery protection and condition monitoring systems.

Though this idea is not new, traditionally, it is achieved by using the same sensor / measurement chain but otherwise separate MPS and CMS devices/systems for signal processing and monitoring. In this way, the electrical input signals only are shared in a safe manner. Although, with this approach, the separate signal digitization and processing is largely duplication and could be considered redundant.

Over the last few decades, electronic processing capabilities have dramatically improved. This provides opportunities to extend MPS processing with capabilities that used to be found only on CMS’s. However, as we have discussed, the continuous stream of digital data between a MPS and a CMS must respect the API 670 requirements for system segregation.

Moreover, in our increasingly connected world, it is imperative to shield the MPS from any cyberattack using the data stream's communication path. For example, data-diode (firewall) technology can be implemented to securely separate both systems (MPS and CMS) while still ensuring a safe and reliable data flow out of the MPS. In addition, it is important to consider different industries, applications and equipment that can have distinct requirements in terms of safety and security, and the boundary between the MPS and CMS, which often results in different solution architectures.

A combined MPS/CMS improves quality and reduces costs

A combined or integrated MPS/CMS can lower overall system costs significantly. Today, standard off-the-shelf components provide plenty of computing power in small form-factors and at low prices. This enables both MPS and CMS functionality to be implemented on a single device or multiple smaller devices. This also translates into savings in terms of cabinet space and installation requirements. All of which help to drive costs down.

Another important consideration is the fact that separate MPS, and CMS systems come with their own specific configuration software, which often doubles the configuration effort in terms of time and cost (and initial training). Further, keeping both configurations synchronized with one another can be a source of hard-to-find problems.

For safety and security reasons, an integrated MPS/CMS solution must of course ensure that only the MPS side can change the protection configuration. At the same time, it should support read-only access by the CMS side in order to avoid unnecessary duplication, for easier system configuration and synchronization. For the end-user, having to learn just one software/system and the ability to easily share configurations dramatically improves their experience.

Due to financial constraints, it is quite common to find essential (though non-critical) assets that are protected with a MPS but are not equipped with a CMS. For this category of machines, the possibility to record and process signals with high-frequency content from the MPS directly into a parallel CMS historian would cost-effectively allow detailed analysis and diagnostics of a machine's health.

Looking forward

The industry's growing demand for increased availability, productivity and reliability of valuable assets is driving rapid digitalization. To achieve this goal, protection of essential and critical equipment, as well as the optimization of their operation and maintenance will become even more important. Accordingly, this is driving the development of better, smaller and more cost-effective integrated machinery protection and condition monitoring solutions that meet the latest safety and cybersecurity requirements.

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