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Do You Know How To Create a Preventive Maintenance Plan for Mechanical Equipment?
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Do You Know How To Create a Preventive Maintenance Plan for Mechanical Equipment?

  • Katarina Knafelj Jakovac

    February 23, 2024

Preventive Maintenance encompasses all types of maintenance activities that are regularly performed according to a predefined schedule to reduce the risk of equipment breakdown in company machinery and equipment.

Preventive maintenance is conducted while the machine is in working order to avoid unexpected machine failure and unplanned production downtime.

Every breakdown and need for emergency repair results in financial and time losses as emergency work orders are the most expensive incidental work orders for troubleshooting faults.

In the manufacturing world where the main goal is to gain a competitive advantage above all else, one way to achieve this is through well-designed and implemented preventive maintenance plans.

In this blog, we will introduce the basic steps for creating a preventive maintenance plan and how to create it using practical examples of pipelines and belt transmissions.

How to Establish a Machinery Preventive Maintenance Plan?

In the following steps, you will see how to establish, compile, and implement your own machinery maintenance plan. The image illustrates the process flow and the 5 basic steps needed to create a maintenance plan.

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Step 1 – Start with one machine and avoid unnecessary complications

Start with a maximum of one or two critical machines. This way, you will quickly gather the necessary data and obtain measurable results regarding repair costs, repair time, and machine downtime duration.

Collecting data and analysis is simple and quick when using a computerized maintenance management system (CMMS).

Criteria for analysis and selection of machines to create a preventive maintenance plan are:

a) Which machines are most important for the production process? Which machines are indispensable for the production process?

b) Do these required machines need regular maintenance?

c) Are the costs of repairing or replacing the machine high compared to others? Have repair costs for these machines in previous years accounted for more than 15%-20% of the annual maintenance budget?

For example, in dairy production, pumps for milk transfer from tanks and milk separators before pasteurization and sterilization are essential.

In this case, pumps in the initial stage of the process would be ideal candidates for a preventive maintenance plan.

The costs of emergency repairs, general services, and/or complete machine replacements are quite high and increase further if pump failure leads to the deterioration of fresh milk, which cannot be processed into products.

Machines that are too outdated or destined for disposal do not need to be considered.

Step 2 – Calculate Return on Investment

After selecting the machines for which you will create a preventive maintenance plan, you need to assess the return on investment that will yield annual savings by implementing preventive maintenance.

Maintain cost tracking in an Excel spreadsheet for clarity and simplicity.

The savings calculation is based on:

  • the cost of routine maintenance, which can be estimated based on the machine's user manual and data obtained from the computerized maintenance management system
  • the average cost of past corrective maintenance for each machine in the past year or over the past 3 - 5 years if you have available data. Here, fixed costs are analyzed.

These costs will indicate how much it costs to repair the machine after a breakdown and the amount of preventive maintenance needed to reduce the number of breakdowns over the next 3 to 5 years.

According to research by the American company Reliabilityweb, with a quality preventive maintenance plan, repair costs can be reduced by up to 70% (okay, realistically, achieving such results requires a bit more experience and a lot more effort over several years :) )

Step 3 – Present Analysis Results to Management

Adopting and implementing a preventive maintenance plan requires certain investments. To secure support and funding for the implementation of preventive maintenance, you need to present the results of the analysis from Step 2 and targeted savings.

Explain to management which machines you intend to monitor, the timeframe, the type of preventive activities, and the implementation method, as well as the costs of previous repairs and production losses, and the potential future savings enabled by continuous implementation of preventive maintenance.

Remember that the emphasis in this step is on adopting a preventive maintenance plan that will enable savings and reduce the number of breakdowns in the future.

Step 4 – Gather Data

After successfully presenting the initiative to introduce a preventive maintenance plan and obtaining management approval, it's time to gather data and compile the plan.

In this step, you can form a team to collect data in parallel and thus expedite the entire process if such an option exists within the company's maintenance department.

Get well informed, talk to all stakeholders involved in the production process, fault troubleshooting, and machine operation.

Ask as many questions as possible, determine in advance what input data you need, and ensure that everything is meticulously recorded.

For example, an employee working with milk transfer pumps from the previous example can tell you how many times they had problems with pump or motor failures, what the most common failures were, what activities they perform daily when checking pump operation, and so on.

Additional sources of information include equipment manufacturer recommendations, employee experiences, reports from authorized service technicians and inspection bodies, discussions with equipment manufacturers, and experiences of other companies using equipment and machinery from the same manufacturer.

Using this data, you will compile a preventive maintenance activity plan.

In the following sections, we will see what practical preventive maintenance plans look like using the example of pipelines and belt transmissions.

Step 5 – Implement the Preventive Maintenance Plan

After selecting one or two machines, gathering all the data, and compiling a preventive maintenance plan, the next step is implementation in practice.

Regardless of the complexity of the facility, paper forms were once used for implementing and monitoring preventive maintenance plans, but now computer systems and maintenance tracking applications are increasingly being introduced, automating much of the process.

Once the preventive maintenance plan is adopted and regularly implemented, you can gradually add other machines and expand monitoring. Gradually, all equipment you have will be covered by preventive maintenance, the number of breakdowns will decrease, and thus repair costs will also decrease.

One of the trends in the maintenance industry in 2024 is the application of AI, so now you have the option of creating preventive plans using artificial intelligence.

Don't forget to analyze the results of implemented preventive maintenance plans and compare them quarterly or semi-annually with maintenance results from times when you didn't have maintenance plans.

This way, you will see if you are on the right track and make corrections or necessary adjustments to maintenance plans on time.

The following diagram illustrates the classic PDCA cycle, which will serve as a reminder during analysis and adjustment of activities.

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How to Create a Pipeline Preventive Maintenance Plan?

Now, let's see how to develop and implement a preventive maintenance plan for oil and gas pipelines. According to a study by World Pipelines magazine, maintenance engineers in the process industry spend up to 52% of their time dealing with pipeline and valve-related failures.

Common causes of pipeline problems include leaks due to cracks, pipe overstressing, improperly connected flanges, broken bolts, corroded bolted joints, mechanical stress, thermally induced expansions, issues with working medium, and unauthorized loading.

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Image: Pipelines at a refinery (Source)

Pipeline failures pose a potential risk of human injury, environmental pollution, production losses, and damage to a company's reputation.

Pipeline preventive maintenance can save up to 18% of corrective maintenance costs according to research by the Pipeline and Gas Journal.

In most cases, current pipeline maintenance practices follow the same rules as for maintaining machinery and equipment throughout the plant and the company.

There's a greater emphasis on maintaining valves and individual sections, whereas instead, preventive maintenance plans should be developed for the pipeline system as a whole.

The most common failures recorded in pipelines used for 10 or more years are:

  • Improper installation of supports, expansion joints, gaskets, overstressing of flange bolt connections

  • Damage to pipes or rigid supports affecting spring hanger leveling, pipe deformations, changes in height and distance from supports, and changes in load on other fittings

  • Failure of spring hangers, where one spring hanger loses its capacity, the remaining hangers automatically take on a higher load, increasing the risk of their failure

  • Deformations of expansion joints occur if the joints are mounted too rigidly and do not allow pipe movement, thereby additionally loading the supports (we say that pipes have no room for movement)

Pipeline preventive maintenance starts with understanding how pipelines and fittings function during plant operation or in shutdown, what forces act on them, their intensity and direction, and numerous other parameters.

A pipeline comprising a mechanical system, e.g., a compressor skid unit functions differently from pipelines connected to process pumps or heat exchangers.

Modern preventive maintenance methods include risk assessment-based inspection according to API 581 standard (RBI - risk-based inspection) or according to API 570 standard.

Preventive maintenance begins with regular inspections of pipelines and fittings, detecting non-compliances, checking mechanical integrity, and stress control during changes such as new equipment installation, reconnecting, and so on.

Using diagnostic methods such as wall thickness measurement, applying experiential knowledge to control critical values when assessing the physical characteristics of pipelines, and any additional work to check the condition of pipelines incur additional costs.

The following diagram illustrates all the steps for developing and implementing preventive maintenance plans for pipeline maintenance:

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The first step in creating a maintenance plan is to determine which pipelines and at which facility need to be inspected and reviewed and how it will be done.

Visual inspection may include inspecting pipeline sections for leaks and corrosion traces beneath which traces of process media on the ground, increased gas odor, or color differences on the outer surface of the pipeline or nearby fittings have been noticed, and installing temporary clamps at leakage points.

Since all pipeline works can only be carried out when the plant is not in production or is under maintenance, it is necessary to plan far in advance the necessary resources and materials for troubleshooting. All encountered changes and executed works should be documented.

In the second step, create a preventive maintenance schedule with a list of equipment to be inspected daily, weekly, monthly, semi-annually, and annually for employees.

You can create digital checklists for larger plants or paper checklists for smaller plants and a document storage system.

Example tasks over a certain period may include various types of tasks such as:

Daily tasks: check for cracks or signs of corrosion on the pipeline where traces of process media have been noticed on the ground, increased gas odor, or color differences on the outer surface of the pipeline or nearby fittings, and installing temporary clamps at leakage points.

Weekly tasks: cleaning pipelines or dosing corrosion inhibitors, testing control valves.

Monthly tasks: servicing malfunctioning valves, replacing faulty instrumentation.

Annual tasks: replacing pipeline parts, upgrades, reconstructions, replacing entire worn-out fittings.

The third step is to perform preventive maintenance works after we have previously defined the schedule, works, required materials, and resources.

The fourth step is monitoring preventive works, which is done for many plants using a CMMS system and analyzed according to business needs, no less than once quarterly.

The analysis of completed preventive works, material consumed, and financial results provides a picture of the success or failure of the preventive maintenance plan.

In the fifth step, after a certain period, the preventive maintenance plan needs to be adjusted and updated in accordance with legal obligations, standards, and plant requirements.

Also, new pipeline sections for preventive maintenance should gradually be introduced.

On the other hand, when we encounter more severe breakdowns such as pipe shifting or pipe section movement due to thermal expansion, damaged supports, or inappropriate expansion joints, the only correct solution is to reinstall the entire pipeline according to the original technical specifications when the plant was built to eliminate problems with overload, overstress, bending of supports, and improper fitting positions.

In such cases, preventive plans are put on hold, and repairs are made directly based on incident or corrective work orders.

The challenge is to set supports and flexible supports so that the pipe stress is less than the maximum allowable, reduce flow turbulence through the pipeline system, and ensure long-term stable operation.

However, this solution is technically, financially, and time demanding and is less frequently practiced (only in cases of significant operational problems causing major production losses).

What are the possibilities for correcting pipelines and addressing these issues?

Firstly, when dealing with problematic pipelines in both cold and hot conditions, inspections of the entire line should be conducted to determine the range, locations, and distribution of displacements.

Next, check the operation of spring supports and expansion joints, how many of them have failed, and their positioning.

If it's found during inspection that the expansion joints are inadequate, they should be replaced. Damaged supports or support components should be repaired, adjusted, or replaced depending on the extent of the damage.

Evaluate changes in the elevation of the entire line resulting from pipe deformation or damaged supports, and check when the last stress analysis of the pipeline was performed.

Often, new equipment is installed, leading to the reconstruction of pipeline sections for connection purposes. However, rarely does anyone remember to conduct a new stress analysis of the pipeline due to changed conditions.

It's also necessary to consult with designers, specialists in pipeline work, and maintenance engineers and contractors.

Compile all identified deficiencies into one list, compare the equipment layout with documentation (pipeline routes, isometrics), and plan welding work for repair, order necessary materials, and start addressing issues during the next plant shutdown or overhaul.

The described method of pipeline correction requires a high level of expertise from all involved participants and falls under corrective maintenance.

Regular preventive maintenance of the pipeline system helps mitigate or prevent issues with fittings, excessive pipe stresses, and leaks due to pipe ruptures, saving on expensive repairs and financial losses due to plant shutdowns to repair damage.

How to create a preventive maintenance plan for a belt drive system?

The belt drive system is the most common type of mechanical transmission in the process industry.

This is due to a range of advantages such as simple construction, low cost of spare parts, elasticity and flexibility of transmission, smooth operation without significant noise, suitability for larger distances between the axes of two shafts, and lower maintenance costs compared to other types of transmissions.

The belt drive system is used for transferring force and rotational motion between the drive shaft and the driven machine using one or more belts, as shown in the image.

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Image 1. Belt Drive System (Source)

Here, an electric motor is connected to a fan for air circulation using a belt drive.

Of course, no type of mechanical transmission is immune to failures.

The most common causes of failures in belt drive systems are:

  • Inadequate design of the drive part: pulleys are undersized or oversized, incorrect rotational speed of the drive machine, wrong type of belt selected and installed
  • Damage to drive components: damaged pulleys (grooves or teeth), cracked or loose supports, worn-out belts, damaged guards
  • Improper handling and storage of belts: exposure to high temperatures, moisture, long-term storage in warehouses causing rubber aging, exposure to sunlight
  • Environmental impact during operation: dust, dirt particles, moisture, grease, rust, cold, and heat
  • Inadequate maintenance of the drive mechanism: lack of belt tightening over a longer period, loose pulley causing the belt to "dance" on the shaft, damaged pulley not replaced, dirty supports and guards, pulleys and supports not inspected for an extended period, lack of alignment check, pulley corrosion…
  • Improper installation of pulleys, belts, or both: belt slipping or snagging over the pulley, misalignment, incorrect belt tension (too loose or too tight), belt damage due to improper handling (cracks or nicks), incorrect type of pulley and/or belt installed, pulley snagging during rotation

Because of these failures, we need a preventive maintenance plan to ensure the belt drive system operates optimally.

If a belt or pulley looks bad, it's likely in poor condition and may soon result in breakage and machine shutdowns powered by the belt drive.

A quality preventive maintenance plan is specific and prevents unplanned failures and machine downtimes. It includes safe working environment conditions, regular inspection checks of the belt drive system, proper installation of new parts to replace damaged ones, diagnostic checks for malfunctioning, and proper handling and storage of spare parts.

The main guidelines for assembling a preventive maintenance plan for a belt drive system are:

  1. Safe working environment: This includes regular cleaning of the area from dirt and debris because the belt drive system must be protected by a safety screen and have unrestricted access for repairs. Employees responsible for machine monitoring must wear appropriate workwear that won't snag on the machine during operation and lead to injuries.

  2. Regular inspection of the belt drive system at predefined time intervals: First, the electric motor is disconnected from operation and power supply, then the safety screen is removed from the belt drive system.

The condition of the belts is inspected (presence of cracks, cuts, signs of wear), belt tension is checked (whether they are loose or over-tightened), and the pulleys are examined (presence of cracks, wear, broken teeth, or damage to grooves). Pulley alignment is checked, and the pulleys of the driving and driven machines are gently turned by hand to check for shaft binding.

Regular lubrication and monitoring of lubricant levels according to the manufacturer's recommendations are necessary.

  1. Replacement of damaged parts: If damage is detected, such as worn-out belts with cracks, they need to be replaced with new ones, properly mounted on the pulleys, and tensioned to the required level (which is checked with a tension gauge).

  2. Regular checks during operation: During daily inspection and monitoring of the machine in operation, attention should be paid to unusual or increased noise, increased vibrations, noises, increased temperature of the driving or driven machine, presence of dust, leakage of lubricants, loose screws or nuts, etc.

If any unusual situation is detected, the machine should be stopped, and the fault should be identified and rectified, followed by addressing its cause.

  1. Storage and handling of spare parts: The room where spare parts are stored must be clean and tidy, free from moisture and dust, appropriately illuminated, and must not have significant temperature differences.

Spare parts should be kept in their original packaging, clearly labeled, and in the required quantities until installation. When handling spare parts, gloves should be used, and care should be taken to avoid damaging the parts.

In conclusion, implementing preventive maintenance for production equipment can be very frustrating without good foundations.

It is necessary to gradually introduce small steps, after which measurable results of return on investment and savings can be achieved.

This will improve the overall operation of the production facility and reduce costs (and the number of headaches caused by unexpected breakdowns ;) ).

And, what are you waiting for? Have you already started creating preventive maintenance plans for your production machines? 😉

Katarina Knafelj Jakovac
Katarina Knafelj Jakovac social media icon
February 23, 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.