Meet the Levels of Preventive Maintenance and Key Steps for Improvement
Preventive Maintenance

Meet the Levels of Preventive Maintenance and Key Steps for Improvement

  • Katarina Knafelj Jakovac

    February 3, 2024

Preventive maintenance is defined according to the standard HRN EN 13306 as maintenance performed at predetermined intervals or according to prescribed criteria, with the purpose of reducing the likelihood of failure or degradation of the item's functioning.

Preventive maintenance is a type of planned maintenance focused on strategies to improve the condition of mechanical equipment, optimize management, and increase productivity.

In the first chapter, you will learn about the levels of preventive maintenance for machines and see how this type of maintenance enhances the management of the production process. Examples of preventive and corrective activities at each level are provided for easier understanding and can be planned and scheduled over time.

In the second chapter, we discuss 10 key steps to improve preventive maintenance of machines and equipment, emphasizing team organization, equipment categorization, identification of causes of failures, and optimization through a computer system.

6 levels of corrective and preventive maintenance

Through a thorough understanding of maintenance levels for machines, you will better manage the productivity of the production process.

Plan maintenance based on professional guidelines and optimize the performance of your equipment for maximum productivity.

Examples of preventive and corrective activities at each level are focused on safe and efficient maintenance of machines, technical systems, and production equipment.

The ISO 13374 standard covers guidelines for reliability-centered maintenance, preventive, and predictive maintenance. It focuses on machine diagnostics and equipment condition monitoring.

The ANSI TAPPI TIP 0305-34:2008 standard provides recommendations on how to develop and use checklists for machine and equipment maintenance on a daily, weekly, and monthly basis.

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Tables display examples of preventive and corrective actions for each maintenance level.

Level 1 involves simple and basic maintenance activities that are essential in the day-to-day operation of machines and can be performed in a simple and safe manner.

These types of activities fall under autonomous plant maintenance and are carried out by employees assigned to specific facilities.

Level 1 of preventive maintenanceLevel 1 of corrective maintenance
Daily machine inspectionsReplacement of worn-out light bulbs
Lubrication on a daily basisCleaning the work area around the machine
Manual inspection of machine parts, e.g., checking the tightness of foundation boltsAdding oil or grease to the bearing housing
Recording the number of working hours and dates of oil changesLight tightening of foundation bolts
Testing bulbs on the control panelVisual inspection of the support condition
Checking the differential pressure values on the duplex filter's manometerLight tightening of the manometer

Level 2 includes slightly more complex maintenance activities and procedures. Trained and experienced personnel, familiar with maintenance procedures and working safely, carry out these activities.

Level 2 of preventive maintenanceLevel 2 of corrective maintenance
Checking operating parameters while the machine is running by reading values on measuring instruments, e.g., manometersStandard replacement of flexible hoses, belts, air filters, etc., due to material damage or leakage
Simple belt alignment and clutch checkReplacement and/or tightening of sealing braids
Checking safety and control devices, e.g., sensors, switches, fuses, etc.Step-by-step procedure for detecting minor faults
Checking the condition of external surfaces, e.g., housings, connections, etc.Replacement of worn or damaged parts such as chains, levers, fuses, sliding tracks, etc.
Lubrication of larger power machines according to a predefined weekly or monthly interval and recording the performed taskReplacement of oil cups
Draining tanks, draining housings, checking the condition of drain valvesReplacement of filter inserts and gasket seals that are difficult to access

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Level 3 consists of more complex maintenance procedures. Qualified personnel inspect and maintain machines and equipment at this maintenance level. The qualification or certification of personnel must be renewed depending on the duration of the certificate.

Preventive maintenance procedures can be planned using a computer-supported maintenance management system, available on a computer, mobile phone, or tablet.

Level 3 of preventive maintenanceLevel 3 of corrective maintenance
Checking and calibrating control devicesComprehensive diagnostics
Preventive maintenance of complex machines, e.g., turbo compressorsRepairing leaks in the cooling system
Checking boiler ignition devices and burner control devicesStandard replacement of parts using simple tools (piston dosing pump components, sealing packages, rubber gaskets, belts, etc.)
Planned interventions of preventive maintenanceRepairs using specialized tools and checking the condition after repair using measuring tools (e.g., measuring vibrations after aligning a centrifugal pump)
Collecting data on changes in operating parameters using measuring toolsAligning pump units using a comparator, visual inspection of the clutch condition

Level 4 maintenance involves procedures that require the essential use of specialized tools, technologies, and maintenance techniques. Maintenance at this level is carried out by qualified personnel or a team of trained individuals, such as specialized service technicians, diagnosticians, or reliability engineers.

Level 4 of preventive maintenanceLevel 4 of corrective maintenance
Partial or general overhaul of a machine that does not require complete disassembly of the machineReplacement of suction and discharge valves on a reciprocating compressor
Analysis of vibrations of the driving or driven machineReplacement of the entrance of an electrical cable
Laboratory analysis of lubricating oilPump overhaul in a mechanical workshop by disassembling it after a failure
Infrared thermography of mechanical, electrical, and instrumental installations or a combination of all mentionedRepairs using complex tools and equipment (portable systems for calibration, numerical control of regulatory systems, PLC programming, etc.)
Collection of data on operating parameters using special devices (ultrasonic diagnostic device, vibration measurement) and analysis of resultsReplacement of damaged sensors, replacement of mechanical seals, laser alignment of complex systems such as dual lines of turbines-coupling-fan-coupling-electric motor for air intake into the steam boiler furnace

Image: Infrared thermography of an electric motor (Source)

Level 5 maintenance consists of complex procedures for monitoring the condition of machines and machine systems in operation or in standby, requiring a high level of specialized knowledge and the application of expert work techniques or methodologies.

Level 5 maintenance includes maintenance activities such as major overhauls with upgrades and/or complete reconditioning of machines, often performed by equipment manufacturers or narrowly specialized companies authorized by the manufacturer. Upgrades are sometimes carried out by companies with extensive experience in working on the same or very similar machines.

In the EU, there are numerous specialized companies that perform major services or complex upgrades for all types of mechanical, electrical, and instrumental equipment.

Before engaging a selected company, it is essential to thoroughly examine references, collect and analyze engineering service offers, and if possible, inquire about experiences with a particular company from other companies that have used their services.

Corrective maintenance Level 5 is usually contracted and executed on a <u>"turnkey basis."</u>

Level 5 Preventive MaintenanceLevel 5 Corrective Maintenance
General overhaul of a compressor unit with a power greater than 0.5 MWReplacement of damaged parts, e.g., shafts longer than 2m, replacement of rotors with a diameter greater than 400mm, etc.
Dimensional control and testing of the geometry of multi-stage rotor assembliesComplete replacement of the upper or lower housing of the driven machine
Overhaul of pump units at the manufacturer's factoryProduction and installation of reconditioned parts for the machine or machine system

Level 6 is the most complex and covers the broadest area. It has evolved over the past decade.

Level 6 encompasses all steps from previous levels and the application of technology mentioned at Level 5.

However, preventive maintenance is based on data collection using the Internet of Things (IoT) and real-time data integration.

After computer and expert analysis, comprehensive preventive maintenance plans are created for an extended period.

For corrective maintenance activities, the work is planned based on the estimated lifespan of machine parts and the optimal moment to stop the machine and perform service or corrective replacements, such as replacing a thrust bearing or complete replacement of electronic components.

Preventive maintenance plans are then entered into the Computerized Maintenance Management System (CMMS) and auto-generated as work orders according to predefined time intervals.

Maintenance costs increase proportionally with the maintenance level, so Level 1 costs almost nothing as it falls under daily operational activities and is part of the job description of operational staff.

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Simultaneously, Level 6 can reach seven-figure amounts, depending on the size and complexity of the machine or mechanical system.

10 Steps to Improve Preventive Maintenance

Implementing levels of preventive and corrective maintenance can be complex, but once adopted, they bring significant cost savings and increased productivity.

After establishing a preventive maintenance program (PM) over a certain period and looking to improve it, let's now consider 10 steps that will help in the enhancement.

You will simultaneously identify shortcomings such as a lack or excess of preventive activities for certain machines and equipment, along with identifying non-critical machines that receive more attention than necessary (read: leading to unnecessary or unjustified spending of time and money on maintenance).

By analyzing preventive maintenance activities, you will see if there are delays in the schedule of performing preventive activities and gain valuable feedback for optimizing the schedule.

An optimized preventive maintenance program is not and should not be a replacement for reliability-centered maintenance but represents a solution for improving the reliability of machines and equipment in a shorter time interval.

Later, by applying reliability-centered maintenance analysis, you will obtain confirmation of the success or failure of your preventive maintenance program.

1. Organize a team for optimizing the preventive maintenance program

To establish roles, responsibilities, and influence over the implementation of the preventive maintenance program, assemble a team of several employees to lead and oversee the program.

The number of involved employees will depend on the complexity of the facility, the number of pieces of equipment, the age of the facility, the complexity of the technological and production process, and the annual maintenance budget.

Employees should be members of the maintenance department to contribute to the overall improvement of the company's operations through the preventive maintenance program, not just based on key performance indicators of individual departments.

Employees should have a thorough understanding of the equipment and the production process.

2. Categorize the equipment

To determine which machines and equipment to optimize in the preventive maintenance program, create a list of equipment in categories: 1) critical equipment, 2) very important equipment, 3) other equipment.

Categorization of equipment is done based on a risk matrix, where each piece of equipment is assigned a risk level by considering the probability in relation to the severity of consequences.

Risk is the product of the probability of a hazardous or harmful event, in this case, a failure, and the harmfulness of that event, or its consequences.

Image: Example of a simple risk matrix (Source)

In the equipment categorization, colleagues from production facilities and maintenance departments should participate in determining objective reasons why a particular machine should be in a specific category.

Objective reasons include arguments such as: machine age, availability of spare parts, past maintenance costs, whether there is a redundant position, etc.

3. Define critical equipment

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The whole team should focus on improving the preventive maintenance program for the chosen pump. Later, you can simultaneously improve preventive maintenance for the entire group of similar machines, such as all centrifugal pumps with a power range of 50 kW to 100 kW in the first stage of preparation and raw material supply.

Make sure to record all improvements introduced into the computerized maintenance management system (CMMS) to create a database of machine maintenance history for later review and monitoring of preventive maintenance progress.

Regularly storing reports on a weekly and monthly basis allows for efficient monitoring of the success of applied preventive maintenance activities.

4. Identify the causes of failures

To successfully modify existing shortcomings in the preventive maintenance program and introduce improvements, we must understand the patterns of failures for each machine.

To start, a rough division of failures into a) failures related to the machine's lifecycle and b) failures related to process causes and operating conditions is sufficient.

5. Determine preventive maintenance levels

By reviewing and analyzing reports collected in step 3 over a longer period, you can make an evaluation of different types of preventive maintenance activities applied to a specific machine.

You should divide activities into the 6 levels described in the previous chapter, depending on the complexity, e.g., equipment inspections, hidden failure inspections, general services, preventive part replacements, etc.

Then, determine if the activity is related to a specific cause of failure.

All activities must be entered into the computerized maintenance management software.

6. Review preventive maintenance activities in the computer system

When using a computerized maintenance management system (CMMS), the program management team must check whether each activity is adequately defined in the computer system.

Activities must include guidelines for mechanical technicians conducting preventive maintenance and checklists. You must customize and update activities as needed.

7. Review the frequency of preventive maintenance

The frequency of preventive maintenance indicates whether specific activities are performed according to the schedule, more or less often for individual machines, or if there is a delay in activities and the duration of the delay.

Did any failures occur between 2 intervals of preventive maintenance?

What influenced the occurrence of failures despite preventive maintenance?

How can the causes of such failures be eliminated, and has the approach to their elimination been initiated?

How was the troubleshooting approached?

All data collected from steps 3, 5, and 6 provide answers to such questions.

8. Check the condition of other equipment

Other (non-critical) equipment should also be checked by applying steps 4-7 at specific time intervals.

The frequency of checking should be a maximum of 2 times per year. More than that leads to unnecessary waste of time and resources.

Discover the causes of failures, preventive maintenance methods, review activity lists in the CMMS system, and the frequency of preventive maintenance, ensuring simultaneous updating of activities.

9. Set goals

Setting goals directs you towards executing preventive maintenance within deadlines and better understanding the equipment's condition.

Goals can be on a monthly, quarterly, semi-annual, or annual basis with accompanying reporting.

Reviewing preventive activities for critical machines on a weekly or monthly basis with report generation contributes to a thorough understanding of the individual machine's condition and better prediction of potential failures.

An additional advantage is achieving more accurate planning of preventive repairs while preventing production losses due to unexpected breakdowns and production process downtime.

10. Align the preventive maintenance program

You must ensure that all planned preventive maintenance activities that have been reviewed and optimized are completed on time.

Plan ahead to take advantage of periods of slower production for performing preventive maintenance.

Check that the activities have contributed to improving the condition of individual pieces of equipment by analyzing the number of failures in a specific quarter compared to the number of failures in the previous and pre-previous year.

One of the tools for monitoring equipment condition and executing preventive maintenance activities is checklists. By introducing and regularly using digital checklists, you will quickly gather information about the quantity of completed preventive activities and the equipment's condition afterward.

Time-planned activities should be scheduled according to the frequency and needs of each machine. Check to what extent your current schedule is adapted to preventive maintenance activities and adjust as needed.

The following scheme simplifies the previously described steps for improving the preventive maintenance program.

The scheme can serve as a reminder when conducting an analysis and improvement of existing preventive maintenance activities in your facilities or as a tool to familiarize all involved employees with all steps in the improvement process.

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Source: Created by the author

Proactively manage maintenance for better performance and reduced production losses. Thorough knowledge of preventive and corrective maintenance levels and the steps to optimize existing processes will undoubtedly help you in achieving this.

Katarina Knafelj Jakovac
Katarina Knafelj Jakovac social media icon
February 3, 2024

Katarina Knafelj Jakovac holds Master degree in Mechanical engineering with long term work experience in Oil industry. She is Certified Reliability Leader specialized for mechanical equipment and operational excellence. Author of blog Strojarska Radionica (Mechanical Workshop) where she shares professional knowledge and personal experience in maintaining various rotating machines, machine systems and process equipment. Adores mechanics, thermal engineering and internal combustion engines. She is dedicated to the continuous improvement of machine maintenance and quality management of physical assets.