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How Inventory Tracking Applications Enhance Mechanical Maintenance?
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How Inventory Tracking Applications Enhance Mechanical Maintenance?

  • Katarina Knafelj Jakovac

    February 16, 2024

Inventory management is a crucial aspect of company operations.

According to a report by the American company Grand View Research on the state of warehouse operations worldwide by the end of 2023, an integrated spare parts ordering system opens up the possibility of increasing productivity by up to 23%, saving space by up to 20%, and improving warehouse efficiency by up to 30%.

Warehouse management is an industrial sector in the United States estimated at 4.16billionin2019,withanexpectedincreaseto4.16 billion in 2019, with an expected increase to 7.90 billion by 2027, with a complex compound annual growth rate (CAGR) of 9.2%.

On a global scale, the expected CAGR increase by 2030 is predicted to be 19%, with a projected total value of $11.8 billion.

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Image: Example of a spare parts warehouse (Source)

The global warehouse management system was estimated at $3.4 billion in 2022. The European Union dominates the warehouse industry with a 32.6% market share, leading in the development of regional warehouse centers and increased warehouse management based on cloud computing systems. Asia and North America follow.

Supply chain management (SCM) expects a 19% increase with the implementation of machine learning, automation, and artificial intelligence, along with market expansion by 23.7%.

The same research indicates that currently only 63% of companies use technological solutions to track supply chain efficiency, with 75% of the time using software for optimization, mobile technologies, and radio frequency identification (RFID) tag tracking.

50.1% of surveyed companies stated that they occasionally use AI, while 46% do not use AI at all.

The remaining 3.9% of companies currently do not use AI but plan to start in the near future.

By 2025, computer applications for supply chain tracking are expected to cost an average of $8 per employee. Maintenance of rotating equipment is inconceivable without available and quality spare parts, with advanced companies organizing and managing spare parts inventory operations through computerized maintenance management systems CMMS.

Inventory tracking applications are software solutions within CMMS designed for monitoring inventory status, managing inventory flows, and ordering materials.

In the following, we will introduce the basics of inventory management and indicators of warehouse operation success, learn maintenance recommendations for rotating machinery and equipment, and discover how to specify spare parts with practical examples of maintaining flexible couplings and rings in piston compressors.

Inventory Management in Warehouse Operations

Modern warehouse operations rely on the use of software solutions for managing spare parts and materials.

Integrated Computerized Maintenance Management Systems (CMMS) feature inventory tracking applications.

The standards that define warehouse operations include ISO 9001, the global quality management system, ISO 14001 and ISO 45001, which standardize environmental management as well as health and safety at work.

Inventory management strategies are mostly based on Material Requirements Planning (MRP) parameters for planning material needs.

The term "material" is equally used to describe spare parts, raw materials, semi-finished goods, and finished products across various industrial sectors.

Inventory tracking applications are led by MRP procedures in 85% of cases to determine the logic the system will use for reviewing existing material demands, inventory control, planning, and allocation.

MRP can be material requirements planning, forecast-based planning, time-phased planning, reorder point planning, and master production scheduling.

Based on the MRP procedure and the current stock situation, a procurement proposal is generated.

The MRP procedure is determined by the type of MRP maintained regarding the MRP master record of the material and specifies whether and how the material is planned.

The MRP type also controls which other MRP parameters (fields) can or must be maintained in the material master record.

There are many different types of MRP available in standard maintenance and asset management software that cover all planning processes.

Companies often configure additional types of MRP as needed.

MRP types, as shown in the example of SAP software:

Screenshot 2024-02-15 at 12.13.07.png

It is crucial to understand each type of MRP, its key functionalities, and the results you will achieve by using it.

An application for tracking mechanical maintenance work is much more agile regarding inventory definition.

The application provides information on inventory status in the warehouse by informing users when a predefined critical inventory quantity is reached.

In the application, the user defines inventory categories according to their company's needs, enters critical quantities, and manages inventory needs by expressing them in work orders.

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Another way to manage inventory in a computerized maintenance management system is by tracking Key Performance Indicators (KPIs).

There are numerous KPIs in warehouse operations. Each company defines what constitutes a key performance indicator for them.

In the case of a well-known KPI called Inventory Quality Ratio (IQR), we will see how to improve material management.

The Inventory Quality Ratio (IQR) classifies stocks into strategic categories that aid in focused inventory reduction activities.

IQR is an effective tool for reviewing, assessing, and making decisions about inventory reduction. Simply put, IQR is active inventory divided by total inventory.

It is presented as the ratio of the monetary value of active inventory to total inventory.

This effectively separates quality inventory from non-quality inventory.

Many warehouse management experts consider IQR a better metric for inventory performance measurement than inventory turnover or days of inventory outstanding because it is based on future demand, provides a performance measure for each inventory segment, and shows where you have room to reduce excess or obsolete inventory or where you can release working capital.

This will increase the active capital to run your business, reduce the amount of money tied up in inventory, and enable lower carrying costs.

With this KPI, you categorize your inventory into four quality categories:

• Active inventory: items with future demands and current usage.

• Slow-moving inventory: items with future demands but not used for six months.

• Excessive inventory: materials with no demand and not used for six months.

• Obsolete inventory: items with no demand and not used in the last 12 months.

The six-month period is a recommendation based on best practices; however, each company decides independently which time period to consider; it is essential to have some period.

The next step is to determine the euro amounts for each of the relevant categories.

In a theoretically perfect situation (i.e., a situation without excess, slow-moving, or non-moving inventory), the IQR would be equal to 100%. This means that total inventory equals active inventory.

However, most manufacturing companies start with a ratio ranging from 35-50%.

An example of a simple practical calculation of % IQR is shown in the table:

CategoryValueShare in Total Inventory
Active inventory74,000.00 €16%
Slow-moving inventory120,000.00 €27%
Excessive inventory96,000.00 €21.3%
Obsolete inventory160,000.00 €35.6%
Total inventory450,000.00 €100%
IQR (%)16%

IQR explains how inventory moves or behaves, not just its value.

By measuring the inventory quality ratio, you will separate your good (necessary and fast-moving) inventory from bad (obsolete and slow-moving) inventory.

In financial terms, IQR is like the financial quotient of your inventory management.

IQR has additional benefits: quick identification of good, bad, and excessive inventory, setting goals and tracking over time, rebalancing inventory across different supply chain locations, better financial management, and quick identification of problematic inventory.

Inventory Identification in Warehouse Operations

Every material or spare part in the warehouse has its unique identification number (ID), which is automatically assigned by the tracking application upon entry into the system.

The identification number contains data from the Bill of Material (BOM) list and typically consists of the following information:

Machine technical code:
Purpose:
Spare part:
Quantity needed for installation:
Material of construction:
Drawing code:
Position on the drawing:
Part number:
Manufacturer:
Model:
Serial number:

Data about the machine or equipment can be found on the nameplate, technical documentation, drawings, user manual, and datasheet.

Creating an inventory database is a complex and time-consuming task; however, once done properly, it will greatly facilitate your daily work with inventory.

The database in the inventory tracking application needs to be regularly updated and supplemented to ensure you always have up-to-date information.

An up-to-date database is one of the fundamental pillars of equipment maintenance in the process industry.

6 Recommendations for Maintaining Rotating Equipment

Rotating equipment in the process industry (such as pumps, compressors, turbines, gearboxes, fans, mixers, diesel engines, blowers, conveyor belts, separators, etc.) is an essential part of any processing and manufacturing plant, often serving as the heart of a particular production unit.

Given the criticality of individual machines, few production units are resistant to prolonged downtime caused by the failure of rotating machinery.

Rotating equipment operates continuously, 24 hours a day, 7 days a week, year-round. Any unplanned downtime, no matter how small, results in production losses and decreased profits.

In this section, we will consider general recommendations for reliable operation of rotating equipment. Specific recommendations depend on the type of machinery, its purpose, and the type of industry. For example, maintenance practices for pumps and separators in a pharmaceutical factory differ from those in petrochemicals or food manufacturing.

  1. Oil Cleanliness for Lubrication: All rotating machinery requires lubrication. The greatest enemy of lubrication is particles that contaminate the lubricant and ultimately lead to bearing damage.

Additionally, lubricants must be properly stored and used.

  1. Selecting the Right Machinery: The average age of rotary equipment in Croatia varies between 20 to 40 years, depending on the industry.

Machinery that used to operate smoothly may now be facing difficulties or may have stopped working altogether due to various reasons.

Changes in the working medium, alterations in the production process, discontinuation of spare parts production by the manufacturer leading to unavailability of repairs, acquisition of the manufacturer by a competitor resulting in the production of customized spare parts that do not fit your machinery, frequent repairs and upgrades, incomplete or insufficient technical documentation — these are some of the factors contributing to operational challenges.

It's crucial to remain flexible and timely procure new machinery with equivalent or enhanced operational performance or opt for factory upgrades through the original manufacturer (if available).

  1. Scheduled Maintenance and Servicing Intervals: Every year in January, it's essential to draft an annual maintenance and service plan and pre-order spare parts in advance. Service schedules should be aligned with spare parts delivery timelines, and mandatory spare parts for critical machinery should always be stocked in the warehouse.

A preventive maintenance plan should be established, and lubrication and inspection plans for specific machinery or auxiliary systems should be reviewed and, if necessary, revised by authorized service personnel only.

By doing so, you will proactively reserve authorized service personnel to arrive precisely when needed, as many authorized companies concurrently cover several countries, which could result in delays if they are already booked by neighboring countries.

Based on experience and production conditions, maintenance and servicing plans should be regularly adjusted.

  1. Spare Parts and Materials: It's essential to specify and order all necessary inventory for repairs in advance.

Digital inventory tracking applications streamline this process by allowing quick and easy visibility of spare parts and materials available in the warehouse, those in transit, and those for which orders have been placed.

Practical examples of maintaining elastic flexible couplings and piston compressors will demonstrate how spare parts and materials are specified.

  1. Open Communication and Realistic Assessments: When a machine breaks down, the operator should honestly report the working parameters and observations.

Often, maintenance personnel ask questions about the malfunction to determine its cause and prevent its recurrence, but they may receive distorted or vague responses in return.

Additionally, when maintenance personnel estimate the repair time for a machine as n days (or n hours), that is the only accurate estimate they can provide at that moment.

Finally, in the event of a complete breakdown with (few) spare parts available, rushing compromises mechanics and precision.

  1. Continuous Learning and Informedness: Thanks to the availability of information on the internet, it's possible to learn from the best practices of leading companies in a specific industry.

There is a wealth of scientific papers, technical manuals, knowledge bases, case studies, and countless tutorials available. It's essential to ensure the reliability of your sources.

As you delve deeper into a particular issue, you'll see how the same or similar problems have been solved elsewhere in the world, allowing you to enhance your knowledge.

Example 1: Basics of Maintaining Flexible Elastic Couplings

A coupling is a mechanical component that connects a driving and a driven machine, such as an electric motor and a pump, electric motor and compressor, or turbine and pump.

In rotary equipment, flexible or rigid couplings are most commonly used.

Today, we will see what the basic steps are in maintaining flexible elastic couplings like the ones shown in the image.

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Image: Elastic coupling with rubber insert and intermediate piece

API 671 Standard defines couplings for special purposes, while the API 610 Standards define couplings for general purposes. The ISO 10441 Standard specifies special flexible couplings for critical machines that operate for extended periods without stopping, at high speeds and torque, and have no reserve position in case of failure.

Adhering to standards during the manufacturing, procurement, and use of flexible couplings ensures compliance with quality requirements.

Rotation speed and torque are the primary factors for determining the model of a flexible coupling, while the remaining elements include balancing method, assembly, mounting method, and labeling.

Preventive maintenance of elastic couplings involves manually rotating the coupling when the machine is stationary to check its free movement.

Next, it is necessary to check the condition of the screws and their tightness, as well as visually inspect the condition of the insert or discs.

Another good practice of preventive maintenance is periodically inspecting the coupling for signs of wear, initial corrosion, damage, or material fatigue.

When even the smallest crack is noticed, it is mandatory to replace the insert or discs.

The same procedure should be applied during periodic checks of alignment when the coupling is disassembled.

Failures of elastic couplings are mostly due to breakage caused by excessive torsional overload or misalignment, as well as cracking of the discs or rubber insert.

When a specific type of failure recurs, the first step is to check whether the chosen coupling is properly selected and mounted depending on the power of the driving machine and operating speed.

After frequent occurrences of repeated breakage of the intermediate piece or inserts, a delayed check is made, revealing that a more powerful electric motor has been installed, rendering the existing coupling inadequate.

Corrective maintenance of elastic couplings involves replacing damaged rubber inserts or discs. It begins with inspecting the parts in the warehouse for damage to the inserts or discs, threads and bores, and hubs if the entire coupling is being replaced.

If the coupling is not immediately installed, it should be stored in its original packaging, horizontally, in a dry place, and at ambient temperature until installation.

Along with the coupling, documentation from the manufacturer usually comes, which should be kept for future use together with the documentation of the machine it is being installed on.

When planning to replace the coupling, it is necessary to measure the dimensions of the existing coupling, especially the bores of the hubs, concentricity, and parallelism with the face of the flanges.

During assembly, it is often necessary to heat the hubs, but heating to a temperature greater than 175°C is not recommended, as it will cause material dilation.

It is also necessary to check the shaft drawings on which the hubs are mounted because the dimensions of the bores and sleeves may differ. If there are differences in dimensions, the shaft is turned to the required measure before balancing.

The distance between the shaft ends (DBSE) is measured from the face of one hub to the face of the other hub, as shown in the image.

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Image: Measuring DBSE distance

A bad practice example includes measuring the distance from the end of the driving shaft to the end of the driven shaft.

Then, the rotation of both shafts with mounted hubs is checked by hand, followed by mounting inserts or discs and an intermediate piece, rechecking alignment, and manually rotating the mounted coupling 4 to 5 times for control of unhindered rotation clockwise and counterclockwise.

Care should also be taken regarding the tolerances of allowable deviations for movements in the vertical and horizontal directions.

Each coupling manufacturer provides permissible tolerance values in the documentation; however, these values should be taken with caution because the coupling itself is not centered but rather the shafts of the driving and driven machines. Finally, a protective mesh or cover is mounted.

When replacing a driving machine with a more powerful one, care should be taken to ensure whether the existing coupling meets the new conditions, and if not, both the machine and the coupling should be replaced simultaneously.

In the warehouse, there should be available rubber inserts, discs, and even complete couplings in some connections. Spare parts in the inventory tracking application are specified as follows:

Machine technology code: 123-K-001A
Purpose: connecting the compressor for supplying gas mixtures and electric motor
Spare part: Rubber insert for flexible elastic coupling
Quantity required for installation: 2 pieces
Material of construction: Polyurethane elastomer
Drawing number: 123456789
Position on the drawing: 8
Spare part code number: ELUM654
Coupling model: A251
Machine serial number: 084678WYX
Manufacturer: Company Ltd.

One example of poor practice is replacing only broken discs, while the remaining existing discs are retained and reinstalled.

When replacing discs, all discs should be replaced with new ones, even if visually not damaged, as they have already been compressed during previous tightening, resulting in bending and metal deformation, making them unusable.

When replacing rubber inserts, all damaged rubber inserts should be replaced with new ones.

Example 2: What Are the Rings on a Reciprocating Compressor for?

Each piston on a reciprocating compressor has a certain number of guide piston rings and oil scraper rings, designed to remove various particles often found on the inner surface of the compressor cylinder.

In everyday language, we refer to them as scraper rings. The image shows an example of a piston with 2 guide rings and 6 scraper rings.

Each manufacturer of reciprocating compressors calculates the piston construction and the number of required piston rings.

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Image: Piston with 6 scraper rings and 2 guide rings (Source)

The number of rings varies from one compressor type to another; indeed, different compressor models produced by the same manufacturer may have different numbers of rings.

What they usually have in common is the material from which the rings are made and their diameters.

This simplifies the manufacturing process for piston rings and reduces production costs.

Today, there are companies on the market producing replacement piston rings (designed through reverse engineering), directly competing with the original compressor manufacturer for their share of the market.

When a company is introduced to you for potential collaboration and supply of spare parts for your compressors, which is not the original equipment manufacturer (OEM), do not hesitate to ask them questions: how they produce spare parts, how they guarantee the identity of replacement parts, and what the mean time between failures (MTBF) is for machines where their spare parts are installed.

You have every right to request concrete figures.

Another position where oil rings are commonly used is the oil seal ring, marked in yellow in the following image and mounted on the piston rod.

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Image: Reciprocating compressor with marked oil rings on the oil seal ring (Source)

The oil seal rings shown in the image contribute to the reliable operation of the reciprocating compressor by collecting excess oil for lubrication when the piston rod moves linearly, evenly distributing it along the piston rod, and preventing leakage towards the high-pressure part of the compressor.

The number of rings also varies from manufacturer to manufacturer, defined by the oil seal ring's design.

To be effective, oil rings must remove excess oil from the edge along the entire length of the piston rod during its movement and have a structural profile that allows oil to drain freely from them.

Properly installed oil seal rings reduce excessive oil consumption, thereby reducing oil costs, and prevent leakage into the surroundings.

Certain types of oil rings also have an additional sealing role in case of gas leakage.

In the cross-section on the right side of the following image, we see radial grooves for more uniform oil distribution and bores for draining excess oil.

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Image: Oil seal rings (Source)

The rings are made of metal and non-metal materials.

Non-metallic materials include PTFE composites, which provide flexibility to the rings during operation to continuously adhere to the piston rod's inner diameter and maintain proper oil distribution without leakage.

This prevents wear on the piston rod. According to research, rings made of composite materials remove up to 11% more oil from the piston rod and last 64% longer compared to bronze rings.

Properly installed rings made of suitable materials contribute to maintaining optimal compressor performance and increasing reliability.

It is good practice to have piston rings and oil seal rings available in the warehouse. Spare parts for reciprocating compressors are specified in the inventory tracking application as follows:

Machine technology code: 123-K-001A
Purpose: compressor for supplying gas mixtures
Spare part: Piston ring
Quantity required for installation: 2 pieces
Material of construction: PTFE
Drawing number: 397589
Position on the drawing: 2
Spare part code number: PIST008
Coupling model: ABCD-333
Machine serial number: 084678WYX
Manufacturer: Company Ltd.

Conclusion

Every spare parts warehouse represents a complex and fluid inventory system.

Warehousing operations have tremendous potential for utilizing inventory tracking applications, improving and reducing costs, monitoring and managing inventory, during orders, deliveries, and material shipments.

A Marketwatch study from 2023 predicts the highest CAGR growth of 21.0% in the inventory tracking application segment by 2030, through the implementation of cloud-based software solutions for small and medium-sized companies.

Companies that have already implemented computerized maintenance management systems (CMMS) will benefit most from timely specification of materials in inventory tracking applications, regular application of recommendations for proper maintenance of machinery and equipment, and active monitoring of key performance indicators.

Katarina Knafelj Jakovac
Katarina Knafelj Jakovac social media icon
February 16, 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.