Successfully do a plant and machinery health measurement audit using a Health Index (HI) to monitor, trend, and deliver high reliability equipment
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.
Example of How the Plant Health Index from Machinery Health Measurement is Used to Maximize Your Plant Uptime and Lower Your Maintenance Costs
This story from Paul B Price provides a case study of the great value gained from use of HI assessments.
“By coincidence one weekend I was traveling from Scotland to England and decided to stop near a quarry at which I provided CM training and support 7 years earlier. In a chance encounter I made contact with the engineer I had worked with back then and invited him out for drinks. Over drinks he told me that he was still using the health index as a way of explaining problems to his managers, and most importantly, as he explained, as a means of giving his engineers, craftsmen and apprentices a degree of autonomy and responsibility.
“The conversation went like this. Everyone in the department had their own day-to-day tasks to do and he kept his interference of the daily routine to a minimum. He managed his people by telling them that their objective was to proactively care for the plant and equipment by recording the day-to-day HI assessment and keeping the condition as near as possible at 3. If they assessed HI at 5 they were to let him know the details at their next daily meeting and also advise him what they were doing, or had done, to get the item back to 3. If the HI was assessed at 6 or 7 they were to let him know as soon as possible, and if necessary he would help them to sort out the cause of the high value. If HI was assessed as 8 or 9 he was to be told immediately, as he would take on the problem and the craftsman would work with him to sort it urgently. When an item did fail in service, and if they had been following the guidelines above, they were not to worry, since a HI-10 event can happen even with the best of intentions.
“When the question was asked of him, “What is a 3, 4, 5, etc.?” The answer he gave was, “It’s your equipment (or system, or process), these are the guidelines used to address the PF Curve, you decide how bad the condition is that a HI value represents.” The outcome of this methodology, he explained, was a well-motivated team not afraid to make day-to-day decisions, who wanted to learn and grow and were not afraid to talk to the manager about solving reliability problems.”
This is What Happens When You Focus on Plant Wellness and Stop Using Equipment Failure Based Maintenance Strategy
Understanding how machinery health measurement via a HI assessment is used in the Plant Wellness Way to monitor health function condition gives you a simple, sensible, and worthwhile way to bring companies outstanding plant and equipment reliability.
When the full set of health functions for an equipment item are well managed there will be no degradation curve and reliability is guaranteed—hence why the methodology is called Plant Wellness. If companies want to get the most outstanding reliability, maximum uptime and the least maintenance costs possible, they need to be managing their plant and equipment’s ‘wellness’.
Once you adopt Plant and Equipment Wellness as your asset management and maintenance strategy you will cause the equipment in your operation to behave like in the diagram below. It will become highly reliable, you will create world class uptime, and you will get the lowest maintenance costs.
What you now have through the HI assessment concept is a practical and achievable strategy for getting plant wellness performance in your operations. Starting with a machinery health measurement, HI becomes your ‘vehicle’ to turn the world class operating performance vision you want to achieve in your company into reality. With the combination of Condition Monitoring and the Plant Health Index you create a Plant Wellness Way EAM System-of-Reliability to get outstanding reliability from your machinery and equipment.