Machinery Health Measurement Audit using the Plant Wellness Way EAM Plant Health Index

Providing life-cycle long, holistic equipment health is what makes operations world-class. The start point is doing a machinery health measurement audit to set a baseline for where the operation is at currently. It is a simple yet powerful production strategy because the greatest operational success comes when plant and equipment are outstanding reliable. Once your quality management system has the best life-cycle-long quality-controlled processes you guarantee highly reliable plant and equipment.

Senior business management will always go in the direction of most profit; you only have to make it obvious just how much money there is to be made in having high reliability plant and equipment. This is where the Plant Health Index for machinery health measurement will help you to win support to make your production machinery highly reliable.

First developed by Reliability Consultant and Condition Monitoring Specialist, Paul B Price (MSc), the Plant Health Index (HI) allows you to put a value to any point on the life cycle and P-F degradation curve for any asset function, component, equipment, machine, subsystem, system, process and operating risk resulting from an asset’s health.

Superimposed in the illustration below of a ‘Failing Bearing Degradation Curve’ is a component level HI to show you how it works before reading the explanation underneath.

The Health Index is a holistic, fact-based, subjective, machinery health measurement method using the simple linguistic terms good, satisfactory, poor, very poor and failed-in-service and the numbers 1 – 10, where 1= Good health, 2-4=Satisfactory, 5-7=Poor, 8-9=Very Poor, 10=Failed-in-Service. The use of a wide number range allows for the demonstration of progression through the life cycle, for example, 2 is the boundary between Good and Satisfactory, and 4 is the boundary between Satisfactory and Poor. The terms Good, Satisfactory, etc. can also expressed as No possibility (S), probability (P) and certainty (VP), and ‘I told you so’ (FIS).

The Health Index recognizes that there is a dependency hierarchy which extends from the simplest function level, such as dirty oil, to complete and catastrophic total plant loss. This progression to failure enables assessments to be carried out, and dependency links to be made, at and between sub-function, function, component, equipment, machine, subsystem, system, and process and risk levels.

The assessment of HI is done by a competent Condition Monitoring (CM) service provider using the full range of CM tools, e.g. vibration, acoustic emission, oil sampling, thermography, performance monitoring, valve monitoring, Operator Driven Reliability, and even the most common of all monitoring methods – tactile senses and intuition – as information sources. We won’t detail the coaction and analysis process in this article, what we can say is at the end of the process you have made an assessment of the equipment health and have given it a value from 1-9.

This HI assessment figure is then stored in a suitable database, preferably the condition monitoring database, along with any comments, observations, recommendations and notes to record, attached to the data point.

Once saved the new machinery health measurement is displayed in form of a visual system HI model which then allows you to see if there are any new risks or higher level risks as a result of a change in equipment health status. This model is available to all interested parties at all levels of the organization. Among other things it is used to identify and display associated risk using the risk HI which operates in exactly the same way as the equipment HI but with a parameter.

For example, you have 3 pumps with Pump #1 as duty and 2 standbys on a process critical system. Initially, before monitoring the duty Pump #1, it had last been was assessed as 3 good, Pump #2 as 4-satisfactory/poor and #3 as 5-poor/satisfactory. This gave a system assessment of 4-sat/poor and was deemed as manageable with plans to correct the health degradation at the next planned outage. Pump #1 is now assessed as 5-poor/sat, and gives an overall system HI assessment of 6-poor which is outside of the acceptance criteria. As a consequence there is now a need to get the risk HI back to 4 or below. The equipment HI and the associated attachments are then used to determine which fault rectification provides the most efficient and effective way of addressing the fault(s).

Note the appropriate system and process risk HI can be updated at any time from any measurement and observation. For example, a minor leak on a valve stem in a high pressure gas system will immediately result in an increase in the system risk function to poor, with the associated risk of loss of production and risk to personnel also updated to their appropriate values. When the problem is resolved the values will revert to their normal status. Subsequent reports of the event as part of any regulatory reporting and auditing requirements will include the primary fault HI for reference and explanation of why the rectification work was undertaken.

Doing a machinery health measurement using the Plant Health Index assessment method provides you in one complete solution: a condition monitoring, auditing, risk assessment, operational management, and regulatory compliance tool.

Incorporating the Health Index in a Plant and Equipment Wellness Reliability Improvement Program

Using the HI has the potential for moving your operation towards a plant wellness strategy and away from the traditional failure-based maintenance strategy and organization used by the vast majority of companies. We will summaries as follows.

• Instead of the HI numbers being used to describe the health of equipment, or even the health of the component, they are now used to define the health of the function that leads to component failure, e.g. shaft alignment, unbalance, lubrication film, etc. In other words, the HI value indicates the potential of initiating the cause that will eventually create the failure cause.
• An assessment of very ‘poor’ does not mean that the machine was going to fail, just that the function was going to fail. But we don’t tell the maintainers that, because if we did it would allow them to make excuses for not doing something based on their failure management mindset that the equipment is not close to failure and so nothing needs to be done to improve its health.
• There is a complex but predictable hierarchy of function failures and cause and effect processes. An example is misalignment leads to bearing overload, then to lubrication breakdown, then to metallic stress due to bearing wear, followed by bearing failure, and finally to equipment failure. With HI analysis used in the Plant Wellness Way philosophy you would correct the misalignment so there could be no opportunity to overload the bearing.
• By assessing the development of all of the failure modes and reporting the most significant to the life of the machine as the primary indicator it is possible to document the machine life cycle from minor error to catastrophic failure.
• By making this information readily available in the public domain, so all in the organization can see the equipment, plant owners, operators and maintainer could no longer say, “I didn’t know.”
• To avoid the possibility of future embarrassment equipment owners will subconsciously change their maintenance intervention behavior. Precision alignment becomes the norm because the CM engineer will assess the outcome of a maintenance intervention as poor. After a while people started to talk numbers on one installation we worked on, their forward plan specified that the objectives were to clear all items above a HI assessment of 7.
• As reliability increases the maintainers will start to be seen in a new light, because the number of outages falls, the associated costs fall, and most important of all, profitability increases.
• The inclusion of the risk HI function now makes it relatively easy to assess and display the risks associated with plant ownership. This in turn makes the relationship with the regulators or inspectorate more bearable, while providing the organization with a ‘get out of jail card’ in the unlikely event of there being an incident, since you now have records of monitoring your plant and equipment’s health and proactively addressing unacceptable conditions.

How the additional reliability benefits are gained once the Health Index is incorporated into a Plant and Equipment Wellness program is indicated in the image below.