INTRODUCTION
Dissertation Outline
Chapter 1 outlines the study's framework, including the background of Evidence-Based Medicine (EBM), the problem statement, research objectives, research questions, methodology, and conclusions Chapter 2 provides a literature review that addresses the research questions and examines the current maintenance strategies employed in EBM.
This article outlines the research methodology, detailing the approach taken to address the research questions It describes the data collection process in Chapter 4, followed by a comprehensive analysis of the data in Chapter 5 Finally, Chapter 6 summarizes the research conclusions, offering recommendations and suggestions for future studies.
Background of Ekurhuleni Base Metals
In 1967, Gold Fields transformed the defunct Vogelstruisbult uranium plant into an electrolytic zinc facility By 1999, the majority of shares were acquired by Iscor, which later restructured, leading Zincor to become part of Kumba Resources' base-metals division In November 2006, Kumba Resources underwent another unbundling, resulting in the formation of Kumba Iron Ore and Exxaro Resources, with Zincor now operating under Exxaro Base Metals However, in 2011, Exxaro closed the refinery plant due to market conditions In early 2012, Ekurhuleni Base Metals (EBM) assumed control of Zincor, initiating a rehabilitation project expected to last approximately 40 years, focusing on recovering deposits of lead, silver, iron residue, and neutral leach from slime dams.
The rehabilitation project at EBM is divided into five categories, namely:
1.2.1 Plant decommissioning and dismantling of plant equipment
EBM is dismantling unused sections of the plant, where the scrap metal is cleaned on-site and sold to scrap companies, while the remaining waste is managed as hazardous waste.
1.2.2 Reprocessing of old Zincor residue
This project consists of three key phases: lead silver, neutral leach, and iron residue Each phase involves re-mining the residues to recover valuable metals such as gold, silver, zinc, and iron The extracted metals, along with gypsum from the neutral leach phase, will be sold to various companies.
The EBM project is extracting groundwater from multiple boreholes situated on the southern side of the operation The contaminated groundwater undergoes treatment at the effluent treatment plant before being discharged into dam 7L4.
This project has not yet commenced After the EBM is done with Zincor residue, this project will re-mine the gold tailings to extract gold.
1.2.5 Removal of miscellaneous waste and clean-up of surrounding areas
This project will remove miscellaneous waste in and around the plant and dispose of it in a hazardous waste landfill site It will then clean up the affected sites.
Environmental Impact
The projects have the following environmental impact:
• Mining consumes a lot of water, which is a scarce natural resource
• Furthermore, the process pollutes clean water
• Groundwater abstraction, although the contaminated groundwater is treated, can lead to groundwater depletion and lowering out of water tables
The dismantling of the plant significantly affects the Struisbult community, leading to aesthetic concerns and environmental issues Air pollution from dust and soil contamination from potentially hazardous substances pose serious risks to the local ecosystem and residents' health.
• Reclamation of gold tailing has the potential to cause acid mine drainage and severe dust.
Applicable Legislation
The following legislation is applicable to the projects:
• Atmospheric Pollution Prevention Act 45 of 1965(APPA)Constitution of the Republic of South Africa, 1996
• National Environmental Management Act 107 of 1998, and Regulations (NEMA)
• National Environmental Management Air Quality Act 39 of 2004 (NEMAQA)
• National Environmental Management Waste Act 59 of 2008, and Regulations (NEMWA)
• National Water Act 36 of 1998,and Regulations (NWA)
• Mineral and Petroleum Resources Development Act28 of 2002 (MPRDA) –only be applicable once EBM starts with gold tailings
• Ekurhuleni Metropolitan Municipality by-laws
Figure 1: 11kW Peristaltic Pump on Site, LPPT 65 (DN65)
Problem Statement
EBM uses positive displacement pumps on underflow thickeners to transfer the solution These pumps must be reliable so that they can pump solution from thickener to the presses
EBM is currently engaged in reactive maintenance, leading to rising maintenance costs and increased downtime Appendix 2 provides a detailed analysis of these escalating costs Additionally, the pumps are failing to meet the flow requirements set by the Original Equipment Manufacturer (OEM), with current output ranging between 13 m³/h and 17 m³/h for the LPPT 65 model.
(DN65) is designed to deliver a flow of 20m 3 /h The figure below explains pump performance
Figure 2: Pump Performance as per OEM [31]
This research investigates the potential of predictive maintenance to enhance the availability of operational positive displacement pumps by reducing downtime and lowering maintenance costs.
Failures are categories as follows:
A> Electrical failures B> Wear and tear on the hose C>Mechanical failures on pipes and Larox pinch valves
1.5.2 Current maintenance strategy at EBM
An effective maintenance strategy is crucial for managing total costs in manufacturing and production plants Choosing the optimal maintenance approach significantly contributes to an organization's overall success.
Reaction maintenance, also known as run to failure, is a strategy where equipment is only repaired after it fails, without any proactive measures to detect or prevent future failures While this approach can lead to high maintenance costs, it is often considered effective in addressing immediate issues.
CBM is applied in critical components of the machinery to predict failure of the machinery Decision is made after gathering data from monitoring systems like ultrasonic and condition monitoring
When selecting the optimal maintenance strategy, organizations must first establish and compare their maintenance goals These goals can be categorized into four key aspects.
• Feasibility Also maintenance has two different aspects:
Tangible goals are quantifiable through metrics such as maintenance costs and reliability, while intangible goals, though not directly measurable, can be estimated using factors like labor and competitiveness enhancement.
Currently, EBM run pumps until they fail, using a reactive maintenance strategy
Reactive maintenance often leads to high maintenance costs and idle artisans, as it focuses on repairing machinery only after it fails This fire-fighting approach prioritizes temporary fixes to restore operations, delaying permanent repairs While it may seem cost-effective in the short term, reactive maintenance results in unpredictability, fluctuating production capacity, and ultimately higher expenses due to catastrophic machinery failures.
The study of the breakdown of failures revealed the following:
Research Objectives
• This study’s main objective is to increase or maximize the availability of positive displacement pumps The amount of downtime is increasing every year as per Table 1
• This study aims to determine if a predictive maintenance strategy is the best strategy to maximise the availability of positive displacement pumps
• It will answer the following research questions: Is predictive maintenance cost- effective, and will it reduce maintenance costs and downtime?
Research Questions
The following research questions will be answered to determine whether a predictive maintenance strategy can be used to increase the availability of positive displacement pumps:
• Will predictive maintenance increase the availability of positive displacement pumps?
• What parameters must be controlled and monitored in predictive maintenance? [65]
Research Methods
This research used the following methods:
• Quantitative method – This method contains all the information required to answer the research questions
• Descriptive method – The researcher administered questionnaires
Chapter 3 will explain the research methods.
Chapter Summary
This chapter provides an overview of the study, outlining the background of Evidence-Based Medicine (EBM), its existing maintenance practices, and the associated challenges It also details the research objectives, questions, and methodologies employed The next chapter will focus on reviewing the literature relevant to addressing the research questions.
LITERATURE REVIEW
Introduction
Pumps are classified into two groups, namely positive and non-positive displacement pumps
A positive displacement pump provides a consistent volume with each revolution, while a variable positive displacement pump features an adjustable internal displacement volume In contrast, non-positive displacement pumps, such as centrifugal pumps and turbines, utilize centrifugal force generated by a rotating impeller to move liquid through the system without capturing it, resulting in a variable flow rate These pumps can operate without a relief valve, and their flow rates can range from a few liters per minute to 2,500 liters per minute, with pressure levels between 3 MPa and 100 MPa Understanding the relationship between pressure and flow rates is essential when selecting a pump for installation.
Effective maintenance is crucial in manufacturing and process plants, as downtime can lead to significant financial losses In sectors like aerospace, submarine operations, and nuclear power, robust maintenance strategies not only enhance safety but also boost profitability The primary goal of maintenance is to prolong the lifespan of equipment, such as pumps, or to ensure their functionality until the next failure occurs.
Maximizing profits is essential for the cash flow of any organization, enabling top management and engineers to identify the most effective maintenance plan for the system.
Effective asset management aims to enhance machinery performance while reducing failure and repair costs It serves as a strategic tool for managing resources and financial investments, ultimately improving machinery reliability to meet client expectations.
South Africa invests nearly R578 million in imported pumps and R564 million in locally manufactured ones The life cycle costs of a pump are distributed as follows: 5% for capital, 5-25% for maintenance, and 70-79% for power consumption Consequently, the country spends between R500 million and R2.5 billion annually on maintenance alone.
LCC (Life Cycle Cost) is the total cost of a system or equipment during its lifetime This cost includes planning, purchase, operation and maintenance and disposal [10]
The life cycle cost of a pump is comprised of the pump’s performance, efficiency, operation, and reliability costs The life cycle cost of a pump is divided into the following:
• Costs associated when the pump is not in use: 3% [92]
When comparing different types of pumps with identical capacity and material specifications, the differences in Life Cycle Cost (LCC) are often minimal However, when evaluating the LCC of various pumps, it is essential to consider assumptions regarding inflation and interest rates While pump failures can lead to significant production losses, quantifying this impact can be challenging Additionally, factors such as installation, commissioning, decommissioning, and disposal may be excluded from the comparison based on cost availability or prior experience with pump LCC.
Figure 3: The Structure of Pump LCC [91]
Evaluating the costs associated with maintaining machinery is essential for selecting a cost-effective maintenance strategy A widely utilized tool for this purpose is Cost Benefit Analysis, which helps estimate the potential savings from reduced machinery repair expenses.
MTBF (Mean Time Between Failures) is defined as the average time when the system performed its intended function between failures
MTTR (Mean Time To Repair) refers to the average duration required to fix equipment and restore it to operational status Inherent availability is calculated as the ratio of MTBF (Mean Time Between Failures) to the sum of MTBF and MTTR.
In the pump industry, metrics that are used to define reliability are MTBF, MTTR, availability, reliability and time [38]
Large industries implement various maintenance strategies, including Time Based Maintenance (TBM), Predictive Maintenance (PDM), and Reactive Maintenance (RM), to fulfill their maintenance needs PDM involves monitoring machinery through techniques such as vibration analysis, thermal imaging, and bearing shock-pulse measurement In organizations that adopt Reliability Centred Maintenance (RCM), the PDM requirements for critical machinery are typically determined using Failure Mode, Effects, and Criticality Analysis (FMECA) alongside decision-making logic These maintenance philosophies are essential for the upkeep of positive displacement pumps.
Implementing Reliability-Centered Maintenance (RCM) requires thorough documentation of all maintenance tasks This maintenance data encompasses failure history, condition monitoring data, and domain-specific language.
RCM establishes an effective maintenance strategy for equipment, encompassing a comprehensive range of tasks to minimize costs and prevent system failures due to inadequate maintenance, ultimately enhancing equipment reliability.
Total Productive Maintenance (TPM) is widely implemented across industries to adopt a holistic life cycle approach for machinery, aiming to minimize downtime Its primary goal is to enhance machinery availability while preventing deterioration, thereby achieving optimal effectiveness The effectiveness and efficiency of machinery are crucial for assessing organizational performance and overall success.
Reliability growth is quantified by Mean Time Between Failures (MTBF) To achieve this growth, it is essential to minimize the causes of systematic failures, thereby eliminating or significantly reducing their occurrence By addressing and mitigating these systematic failure modes, the overall reliability of a product is enhanced.
Test, analyse and fix (TAAF) is a test approach commonly used in reliability growth testing
Accelerated testing involves subjecting products to failure, followed by repairs and retesting This process evaluates whether the design meets its intended purpose Ultimately, testing reveals design flaws and facilitates improvements before finalizing the product.
To design for reliability, it is essential to understand the operating and environmental conditions of the product throughout its useful life This involves identifying irrelevant stresses and recognizing that the product may generate temperature cycles due to varying load conditions Component failures typically arise from the insights gained in the initial steps of this process Additionally, it is vital to analyze the consequences of failures alongside relevant failure modes and operating conditions For instance, interactions between different stress types, such as mechanical loads leading to cracks in a shaft, must be thoroughly considered This comprehensive approach should be guided by Failure Mode and Effects Analysis (FMEA).
Peristaltic Pumps
A peristaltic pump is a type of positive displacement pump designed for transferring various liquids It finds extensive use across multiple sectors, including medical applications, research and development laboratories, pharmaceutical manufacturing, the food industry, and chemical processing plants.
2.2.1 Basic operation of peristaltic pump
When the pump initiates operation, the inlet tubing seals, and the roller advances, pushing the pump segment toward the manifold This action propels the fluid forward, creating a pressure wave To prevent backflow, the roller closes the tube inlet before the wave reaches the outlet As the first roller exits the outlet, the second roller produces the subsequent pressure wave.
Figure 4: Schematic of Peristaltic Pump Flow [3]
Peristaltic pumps are classified in two types, as follows:
Hose pumps differ from tube pumps primarily due to their reinforced tube, known as the pump segment One significant advantage of hose pumps is their ability to operate at higher pressures, reaching up to 16 bars Additionally, peristaltic pumps are known for their precision, with a pressure gradient of under -13.3 Pa (-100 mmHg), while piston pumps also offer high accuracy.
The primary distinction lies in the propulsion mechanism of the pumps, which feature a central rotor equipped with rollers These rollers compress the lining to facilitate fluid delivery and minimize backflow While they occasionally help prevent reverse flow, their main function is to drive fluid movement effectively.
This pump features a self-priming design, eliminating the need for priming and allowing it to run dry without damaging the tubing or lubricant It can operate in reverse, making it versatile compared to other pump types The tubing is easily replaceable at a low cost, and the pump maintains a good suction height, preventing flow when stopped Additionally, the fluid transportation remains unaffected by the fluid's viscosity, and worn-out tubes can be replaced and recalibrated efficiently.
A peristaltic pump consists of key components including a rotor, tube, shoe, pump housing, and base plate This positive displacement pump operates on the peristaltic effect, where a cylindrical rotor rolls along the hose, allowing for the eccentric movement of the roller mounted on a crankshaft It is self-priming and minimizes leakage when handling slurries, viscous, and aggressive fluids, making it suitable for various applications.
The LPP 65T (DN65) has the following main components:
Figure 5: Main Components of LPP65T (DN65) [31]
A peristaltic pump efficiently moves various fluids by periodically compressing a segment of tubing against the pump housing, which increases pressure and propels the fluid forward.
A peristaltic pump features a manifold as its pump segment and a rotary pump head The rotor, which is part of the pump head, includes two or more rollers that compress the tube against the manifold, creating pressure within the tube.
The crankshaft positive displacement pump features a bearing attached to a pole located at the center of the rear wall of its housing The pump's drive unit is securely connected to this pole via a flange, allowing the motor's power to be transmitted from the gearbox to the crankshaft through a coupling As the drive unit rotates, the crankshaft and rotor move together, compressing the hose at a predetermined distance from the inner surface of the pump housing There are two types of drive units available for this pump.
Figure 6: Types of drive units in a positive displacement pump [31]
The control unit includes the following:
• Reversing switch in the stopping position
• Hose leak, overpressure and revolutions detectors
The electric motor is operated with local speed control (potentiometer), which is connected to the control cabinet (using 4-20mA or 0-10V) and it uses control signal [31].
Critical components of pumps, such as bearings, impellers, and seals, significantly impact pump performance, and their failure can disrupt industrial processes This disruption often results in additional costs associated with repairs and replacements Therefore, implementing a monitoring system is essential for maintaining the operational efficiency of these systems Monitoring systems can be categorized into three types: failure detection, response measurement, and performance gauging.
This study will focus on predictive maintenance method/s that can be used to maximise the availability of a Larox pump (positive displacement pump).
The pump performance curve illustrates the relationship between flow rate, pressure (or head), and power consumption (BHP) It features four interconnected curves displayed on a single graph, highlighting the pump's characteristics.
• Total head on the pump
• Energy curve (BHP – brake horsepower)
• Pump minimum required curve (NPSH– Net Positive Suction Head)
The LPPT-65 pumps installed on site are currently operating below the required pressure of 10 bar, delivering only between 6 to 7 bar This discrepancy in performance may be attributed to various factors.
Condition Monitoring (CM) is a proactive maintenance strategy that tracks parameters such as vibration, overheating, and overcurrent to identify early signs of failure and predict maintenance needs before catastrophic breakdowns occur This can be accomplished through visual inspections or advanced intelligent diagnostic systems One key method in CM for rotating equipment is vibration measurement, which helps detect bearing faults and pump imbalances The Root Mean Square (RMS) value of vibration velocity serves as a critical indicator of vibration severity.
Temperature measurements are effective for identifying bearing faults and are particularly useful for monitoring pump performance This method leverages the principle that pump efficiency generates heat, with an increase in the temperature of the pumped fluid serving as an indirect indicator of efficiency.
Monitoring the condition of bearings in positive displacement pump units, such as electric motors, can be achieved through various methods These methods include vibration monitoring, temperature monitoring, chemical analysis, acoustic emission monitoring, sound pressure monitoring, laser monitoring, and current monitoring.
2.2.3 Factors that influence pump availability
Availability deals with uptime duration of a pump during operation It measures how long the system is available for the operation Availability is defined as: Uptime / (Uptime +
Downtime) In most cases, availability includes breakdown maintenance and preventive maintenance In this case, supply and administrative delays are not included.
Operational availability is defined as MTBM/ (MTBM+MDT) [65].
The bathtub curve is a very well-known concept that represents the behaviour of various products
Conclusion
The literature discussed in this chapter will help us to answer the research questions
Implementing predictive maintenance effectively enhances plant availability and boosts organizational profits while reducing maintenance costs through early fault detection Additionally, predictive maintenance is associated with Reliability-Centered Maintenance (RCM) The next chapter will explore methods to assess the potential of predictive maintenance in improving the availability of Larox pumps.
RESEARCH METHOD
Introduction
This chapter outlines strategies to enhance the availability of positive displacement pumps by applying predictive maintenance theories from the previous chapter The research employs quantitative and descriptive methodologies to address the research question effectively.
Research Method
A research method involves the systematic collection, analysis, and interpretation of data to comprehend a phenomenon The three primary research approaches are qualitative, quantitative, and mixed methods This study employed a descriptive research survey, which seeks to provide an accurate and valid representation of the factors pertinent to addressing the research question.
Survey
Surveys are a systematic approach to data collection, involving methods such as face-to-face interviews, telephone interviews, and email questionnaires They serve as a descriptive tool for gathering information from a specific population or group, making them essential for research purposes.
Questionnaire design
Questionnaires serve as an effective tool for data collection, enabling researchers to gather essential information to assess specific variables They can be administered in various ways, including in-person, by mail, or through email, depending on the context.
• Make data comparable and amenable to that it is easy to analyse
• Minimise bias in asking questions
This study utilized questionnaires to gather information from EBM maintenance staff, mechanical and electrical artisans, the procurement department, and the maintenance superintendent The questionnaires were administered on-site, allowing participants to select the appropriate answers.
People involved Data collection method Number of questionnaires
EBM Maintenance Personnel (Electrical and Mechanical Artisans)
Documentary Sources
Secondary data sources, including documents, were utilized to validate the information obtained from survey participants These documentary sources also offered valuable guidelines to support the researcher throughout the interview process.
Justification of Research Method
In applying predictive diagnosis to a pump system, the researcher identified five problems in pump operation, as follows:
• Wear causes and increases the total failure of a pump
• Vibration can be caused by high air content in lube oil or the suction condition of a pump
• A change in the viscosity of the hydraulic medium can lead to change in operation condition, which will eventually reduce the pump’s efficiency and power
• Agglomeration of particles in the hydraulic medium, which is caused by wear in the hydraulic circuit, can lead to total seal failure
Pump failures can lead to significant idleness costs for organizations Implementing predictive diagnosis allows companies to schedule maintenance based on the pump's operational state, minimizing downtime and enhancing efficiency.
In a pump system, monitoring is used for systematic data collection concerning the state of pump characteristics like flow, pressure, temperature, torque, current, voltage, current gradient, viscosity and velocity gradient [11].
Condition monitoring techniques, including oil analysis, thermography, and vibration analysis, were implemented at the Strategic Petroleum Reserve (SPR) to enhance the reliability and availability of rotating machinery while reducing maintenance costs SPR collected data to establish maintenance cycles, adhering to a policy of rebuilding pumps every 10,000 hours and electric motors every 16,000 hours, or within a five-year timeframe, whichever occurs first Vibration analysis was utilized to gather data, which was then downloaded to a computer using commercial software, allowing for a comparison of the current pump state and the formulation of an appropriate maintenance strategy.
Vibration tests on a gearbox are conducted to identify its fault characteristics using nine piezoelectric acceleration sensors placed at various locations The collected vibration signals undergo testing, amplification, and filtering of the analog signal before being sent for further processing Additionally, a noise signal is incorporated into the testing signal Wavelet analysis is employed to distinguish fault signals from the tested signals, effectively removing all disturbing signals This process enables accurate diagnosis of gearbox faults.
Study Matrix
This research used quantitative and questionnaire methods to meet the research objectives The parameters used to collect data were as follows:
Data Collection
Data was gathered using on-site questionnaires and condition monitoring of two pumps, which measured their output flow rates Chapter 4 provides an analysis of the collected data.
Data Analysis and Data Interpretation
Data gathered was modelled and helped the researcher to answer the research question, as well as to provide advice on the state of the pumps.
Conclusion
This chapter discussed methods used to answer the research questions The following chapter discusses the results and findings of the research interviews and field data.
RESULTS AND FINDINGS OF THE RESEARCH INTERVIEWS AND
Introduction
This chapter presents the results and findings of the survey questionnaires and collected data
It first discusses the survey questionnaires followed by a presentation of the data gathered in the field.
Response to Questionnaires
All fifteen participants submitted their questionnaires on time, which were subsequently analyzed and discussed by the researcher Interviews were conducted with each participant during working hours, and the questionnaires were returned on the same day Table 4 illustrates the distribution of the responding participants.
Discussion and Graphs
All artisans completed the questionnaire, but one of them did not understand the term
The absence of preventive maintenance suggests that predictive maintenance is not being implemented The artisan mistakenly believed that changing the hose constituted preventive maintenance, when in fact, this action falls under reactive maintenance.
2 How often is predictive maintenance done on positive displacement pumps?
To enhance the availability of positive displacement pumps, management must implement a maintenance strategy focused on predictive maintenance Currently, the maintenance team and most artisans lack familiarity with this concept, highlighting the need for training and education in predictive maintenance practices.
3 Is maintenance history kept after repairs or maintenance?
All breakdowns are documented in a maintenance request and stored in a history file located in the mechanical/electrical workshop However, reports can occasionally be misplaced, and there is currently no established procedure for record-keeping For instance, some artisans have previously left reports in the tearoom.
4 Where is maintenance history kept for reference?
All maintenance and breakdown history are kept in a file situated in the mechanical/electrical
5 How much time is spent on predictive maintenance?
All pumps are currently without maintenance, and many artisans lack an understanding of predictive maintenance Some mistakenly consider hose replacement as preventive maintenance, when in fact, it is a reactive maintenance issue stemming from a breakdown.
6 Do you perform daily maintenance, including inspections and lubrication?
Artisan 4 fails to grasp the issue at hand, as no maintenance or pre-inspection is conducted Artisans are only summoned by control room operators when the pump experiences a breakdown Additionally, the plant is in a dirty state, often requiring artisans to clean the area before commencing their work.
7 What type of communication is being used to report an equipment failure?
Fitter 2 Call out after hours and weekends including public holidays
Breakdowns are documented in a maintenance request book during the day, while after hours, the control room operator contacts the standby artisan Before starting any job, the artisan is required to have a breakdown/maintenance request form However, relying on a maintenance request book can pose serious risks to safety in the event of an incident or accident.
8 What is your response time during the breakdown?
Fitter 4 took 60 minutes to be on site because he is not staying close to the plant Sometimes it takes long, even if it is a small breakdown The company policy says 30 minutes.
9 Is there any fitter or electrician responsible for positive displacement pumps?
Electricians and fitters are tasked with pump maintenance, including after-hours call-outs The mechanical or electrical foreman selects an available fitter or electrician to address breakdowns during the day, while the standby personnel are responsible for any issues that arise after hours.
10 Do you have a storeroom for keeping spares?
Spares are stored in the main inventory, but occasional shortages can create pressure on the maintenance team The store-man manages the spare parts using a filing system for accurate record-keeping However, if spares are available in the workshop after hours, they often go unrecorded.
11 Is the supplier situated locally or internationally?
The spares supplier is locally situated in Benoni in Gauteng Province, South Africa.
12 How long do spares take to reach your premises?
Flowrox, the spares supplier, is 45km away from EBM The driver takes +/- 45 minutes depending on traffic Flowrox’s service is excellent The company has standby personnel 24
13 Do you experience a high volume of breakdowns?
EBM is currently relying solely on reactive maintenance, which is leading to high maintenance costs and missed production targets To address these issues, management must make a prompt decision to implement preventive maintenance strategies.
14 If yes, how many times in a year roughly?
Electricians are experiencing a lot of breakdowns due to electric motor failures The RCFA is not done to prevent the failures from happening
15 What causes the majority of breakdowns of positive displacement pumps?
Clearly Fitter 4 does not understand the question Hose failures are not electrical breakdowns They experience less mechanical breakdowns.
16 Are critical spares kept in stock?
Maintaining optimal stock levels of critical spares is challenging, and relying on a filing system is ineffective An automated stock management system is far superior to the current manual approach, ensuring timely updates and better inventory control.
17 If yes, where are they kept?
1 Who does budget for spares?
The maintenance superintendent and general manager are responsible for the whole maintenance department budget They are always exceeding the budget every year
2 Who controls the maintenance budget for the whole plant?
The maintenance superintendent controls maintenance budget He is one who is deciding on what critical spares to be kept on site
3 In which year were all positive displacement pumps installed?
4 What is the model of these pumps?
5 Are your artisans provided with training to maintain these pumps?
The artisans lacked training in pump maintenance, and a technician from Flowrox only provided a demonstration on-site Consequently, no one has been deemed competent, particularly in changing the hose.
6 How long does these pumps operate?
1 How do you keep record of your spares?
Our department maintains an archive for spare parts records; however, the current filing system is ineffective as not all staff adhere to the established procedures This issue is particularly evident during call-outs and weekends when documentation is often not submitted.
2 Do you have a budget for spares?
Yes, every year the maintenance superintendent and general manager allocate a budget for maintenance But the budget is not enough; we are always exceeding the budget
1 What kinds of breakdowns are you experiencing from LPP65 Larox pump?
When the pump is inactive, tanks tend to overflow, and it is not always feasible to check the pump's status regularly.
2 How do you notify the artisans about breakdowns during the day and after hours?
We have a standby list for every week in our control room
3 How do you record breakdowns during your shift?
Every shift report, plant performance is reported in a shift report book, which is checked by the production manager in the morning
4 Do artisans do any maintenance on Larox pumps?
Artisans maintain the pump only during breakdowns
1 Do you always meet your monthly targets?
Not really Our production is always behind due to breakdowns
2 How many shifts do you have per day?
We run the plant for 24 hours, three shifts per day
3 How often is maintenance done on Larox pumps?
None Currently we don’t have maintenance strategy for the pumps
4 How do you communicate with the maintenance superintendent when there are breakdowns in the plant?
We communicate through meeting on daily basis where we discuss plant performance for the previous 24 hours.
1 Where do you get spares?
We locally manufacture spare parts such as tubes, thrust bearings, and electric motors For customers requiring a brand new pump, we import it directly to our head office in Lappeenranta, Finland.
2 How do you update your stock level?
We are using SAP system to update and order stock
3 How do you deliver spares to customers to customers after hours?
Our standby is 24 hours a day, and customers can get after hours
4 How long do you take to deliver spares to customers?
For EBM specifically, it is +/- 45 minutes
5 What is maximum flow rate of the pump you supply to EBM?
EBM is using LPP65, which delivers 20m 3 /h
6 What is the model of the pump you have supplied to EBM?
7 What is the lifespan of the pump you have supplied to EBM?
The pump can last up to 30 years, depending on how you maintain it
8 How do you measure customer satisfaction?
Our sales team do regular visits every month, but if there is a customer complain we attend the customer immediately
9 What is minimum qualification of your salesperson/engineer?
We recruit engineers with extensive experience Our requirement is a minimum ND Mechanical/Electrical Engineering, but BSc Engineering, Mechanical/Electrical is advantageous.
Field Data and Results
This chapter presents the results of the field data where predictive maintenance applied on a positive displacement pump The data was gathered when the pumps were in operation from
2013 to 2015 The researcher chose two pumps on site that were installed at the same time This chapter also discusses the categories of failures and total costs incurred
The results are presented and discussed in tabular form Calculations of costs are also presented Chapter 5 discusses the impact and validity of these results in answering the research questions
Pump Location Year 1 Year 2 Year 3
Classification of Failures
Failures are categorised as follows:
A> Electrical failures B> Wear and tear on the hose C>Mechanical failures on pipes and Larox pinch valves
Each failure has its own downtime Appendix 2 shows the calculations.
Total Downtime and Maintenance
This section explains total maintenance costs and downtime when the plant was on reactive maintenance (breakdown maintenance)
Table 5: Data for classification of failures
Maintenance costs consist of two types: block replacement (Cb) per unit and individual failure replacement cost (Cf) per unit [80]
Appendix 2 shows the calculations of costs for three classes of failure.
Total Downtime Failures
Commonly used parameters, such as MTTF and MTBF, are required for adequate characterisation in most maintenance environments The total downtime for a pump is calculated as follows:
Downtime = Breakdown Period + Maintenance Repair DurationDowntime affects the availability of the pump and the overall production period [46]
Downtime Costs in Rands Downtime in Hours
Failure Classification Year 1 Year 2 Year 3 Year 1 Year 2 Year 3
Table 6: Summary of Total Downtime Costs and Hours
High downtime hours are often caused by pumps being out of service for extended periods, sometimes lasting a day, due to a lack of spare parts The system struggles to maintain sufficient stock levels, particularly for electric motors.
To ensure the production of high-quality products on schedule, it is essential for the organization's machinery and equipment to function efficiently and accurately Inefficient plant operations and excessive overtime costs can significantly hinder the organization's overall operational efficiency.
Predictive Maintenance Implementation
Based on the failure occurrence in positive displacement pumps, a decision was made to concentrate on the high failure rate of electric motors Different techniques are discussed and compared below
4.8.1 Methods used in electric motor condition monitoring
Motor condition monitoring via vibration analysis
Vibration analysis is a widely used and effective method for monitoring motor conditions, as it reveals distinct vibration signatures associated with various bearing faults Commonly employed sensors, such as velocity transducers and accelerometers, are essential for this technique; however, their high cost is a notable drawback Despite this, the ability to easily mount sensors and access the machine is a significant advantage It's important to consider that sensors have a limited lifespan, which may be shorter than the actual lifespan of the bearings they monitor.
Motor condition monitoring via acoustic emission
This method focuses on vibration analysis in noisy environments, where minor deterioration in bearings generates subtle frequencies that can be masked by surrounding noise In such conditions, stress waves exceeding 100 kHz can reveal critical fault information and serve as early indicators of bearing degradation Acoustic emission transducers are employed to detect these emissions, offering a significant advantage of a higher signal-to-noise ratio However, a notable drawback is the high cost of the sensors required for accurate measurements.
Motor condition monitoring via shock pulse method
Bearing impacts generate shock pulses that lead to damped oscillations in transducers, offering valuable insights into the bearing's condition Bearing faults create resonance in a high-frequency range, approximately 32 kHz, which can be detected by transducers.
3.Subject to sensor failure Acoustic Emission 1.High signal to noise ration
2.Detects faults at incipient stages
1 Detects fault at incipient stages
3 Factors may cause temperature change
Motor condition monitoring via a temperature sensor
Maintaining the bearing temperature within a specific limit is crucial for machine operation, as elevated temperatures can arise from grease deprivation, increased stator temperature, or higher operating speeds Effective temperature monitoring is essential for assessing the condition of motor bearings; however, a significant drawback is that sensors may not identify the root cause of temperature increases Consequently, this technique has fallen out of favor.
Motor condition monitoring via stator current analysis
The implementation of the stator current technique is straightforward and highly cost-effective, as it eliminates the need for sensors This approach offers significant economic advantages and benefits in terms of implementation Additionally, valuable information regarding motor efficiency, performance, torque, and speed can be derived from the motor current.
Stator Current Analysis
Vibrations in electric motors are primarily linked to issues with bearings, rotors, or stators This research utilized the stator current technique, which effectively differentiates between electrical and mechanical faults Notably, a significant portion of electric motor failures is attributed to bearings (40%), followed by rotors (10%) and stators (12%) The accompanying figures illustrate an example of current measurement and its frequency.
Figure 22: Time plot of a stator current measurement [21] [28]
Figure 23: Frequency spectrum of the stator current measurements [21] [28]
Most failures that are related to stator errors are caused by a stator winding short circuit as a
• Thermal stress due to overload
• Electrical stress caused by partial discharge
• Environmental stress due to dirt or moisture
• Mechanical stress and vibration due to misalignment or sloppy bearing replacement All the above-mentioned effects interact with one another [21][28]
Common failures of bearings result from:
• Poor lubrication leading that leads to abrasion and heating
• Dirt in a bearing (bearing with air, water)
Errors in an induction motor's rotor can arise from electrical or mechanical faults Electrical issues are primarily linked to broken rotor bars, which often result from heavy-duty operations On the other hand, mechanical faults stem from misalignment, imbalance, or torque ripples.
Results of Predictive Maintenance
The trend indicates that the pump experienced problems in the past.
The spectrum is within ISO standards; it indicates slight looseness, but it is acceptable
The waveform is normal and acceptable
The trend shows that the component experienced problems several times in the past
The spectrum is acceptable; it indicates multiples of running speed that of looseness
Predictive maintenance results indicate that both pumps are experiencing failures due to cracked or loose broken bars Prior to implementing predictive maintenance, motors were sent to suppliers for repairs without conducting any failure analysis The Root Cause Failure Analysis has allowed us to identify the underlying causes of these failures It is crucial to highlight that EBM does not engage in preventative maintenance; instead, the pumps are operated until they fail.
Conclusion
The following chapter will discuss the research question and present the predictive maintenance data in response to the research question.
RESEARCH DISCUSSION RESULTS
Introduction
This chapter presents the research results from the survey questionnaires and collected data It discusses and analyses the data and questionnaires.
EBM and Flowrox, the supplier and manufacturer of pumps, completed the questionnaires, revealing that many artisans lack an understanding of predictive maintenance and its significance Consequently, the organization is failing to meet its targets due to frequent breakdowns.
Predictive maintenance significantly outperforms traditional maintenance methods, as indicated by field data Key parameters for assessing pump availability include Mean Time Between Failures (MTBF) and Mean Time To Repair (MTTR) This chapter provides an in-depth analysis of these parameters and explores strategies for their enhancement Additionally, it addresses each research question in the context of the findings and existing literature.
Research Question No 1: Will predictive maintenance increase the availability of
The results of the field data show that pump reliability increased following the implementation of predictive maintenance The table below explains the failure rate of each pump
Table 9: Failure Rate of Each Pump
After predictive maintenance was performed, the results were compared with the manufacturer specifications and recommendations regarding the pumps
Pump failures can result in significant damage, production losses, and customer dissatisfaction To prevent these failures, the maintenance or engineering department plays a crucial role Implementing condition monitoring is the most effective strategy for this purpose, as it allows for the assessment of pump conditions, ultimately reducing both maintenance costs and downtime.
Condition-based maintenance techniques assess equipment conditions through continuous monitoring data The goal is to establish a maintenance plan before potential failures, thereby minimizing costs while enhancing operational safety and preventing catastrophic equipment failures This process involves monitoring, diagnostics, predictions, and subsequent actions.
Condition monitoring is essential for predictive maintenance, involving the assessment of equipment conditions through sensors or manual methods This approach aids in informed decision-making regarding equipment management The primary goal of condition monitoring is to gather data that enables the early detection of potential failures, allowing for the effective planning of preventive maintenance tasks.
Since implementing predictive maintenance, the pumps have consistently operated without failure, ensuring that production targets are achieved Additionally, Root Cause Failure Analysis (RCFA) has been crucial in identifying the underlying issues with the electric motors Chapter 6 offers recommendations to prevent future occurrences of these problems.
Accurate data collection is crucial for any study, as inaccuracies can significantly affect the results It plays a vital role in identifying the root causes of pump failures, serving as the foundation for effective analysis and decision-making.
• Assessing the effectiveness of the solution The goal of collecting data is to:
• Determine what happened during the occurrence
The RCFA technique is used to address a problem, in order to determine its root If RCFA is
• Why did the breakdown occur?
• How can future breakdown be eliminated?
For example, future breakdowns could be eliminated by: a) Changing the procedures b) Changing the operation c) Training all personnel d) Changing the design e) Repairing or rebuilding the pump [78]
RCM is essential for analyzing failure modes that impact the entire system, particularly in the context of positive displacement pump maintenance It aids in determining maintenance needs and strategies by confirming failure ranges and conducting FMECA and FTA analyses This process helps identify actual failure modes and their after-effects, ensuring that maintenance decisions align with the specific failure modes of the pumps.
5.3 Research Question No 2: What are the parameters that must be controlled and monitored in predictive maintenance?
The flow rate of a pump is crucial for the proper functioning of specific processes, and it can be measured using a flow meter or assessed via a pump curve Immediate corrective action is necessary if the pump fails to deliver the required flow rate or pressure It's important to note that the flow rate is not static; it can fluctuate throughout the pump's life cycle.
In South Africa, we have time-of-day tariffs, and there is potential to change operational strategies to suit the tariff [92].
Incorporating online flow rate analysis into a PLC network enables efficient and reliable monitoring of pump conditions This system not only provides flow rate output but also includes alarms to alert users of potential pump failures and inconsistencies Automation enhances the efficiency of the monitoring process, while personnel engaged in predictive maintenance play a crucial role in ensuring accurate results Although an online flow rate system offers valuable condition-monitoring data, it is essential to employ additional techniques to identify all potential failures.
In this research, the critical parameter to monitor is the flow rate, as the pump is intended to deliver 20 m³/h but is currently failing to meet this requirement Accurately measuring the flow rate is essential for assessing the pump's condition.
The issue at hand is the pumps' failure to deliver the required flow rate Key factors to consider include whether the artisans are adhering to the correct procedures for changing the hose, if they possess the necessary training and competence for this task, and whether the pumps have been installed according to the manufacturer's specifications.
Artisans are not adhering to proper procedures for hose replacement, as evidenced by a hose failure following the implementation of predictive maintenance It is essential to use at least five liters of glycerine for lubrication Additionally, low pressure discharge in pumps resulted from improper adjustment of the hose tongue.
Below is the manufacturer’s recommended procedure for changing the hose:
1 Open the front cover and release hose compression.
2 Unbolt the connector flanges and take off the splitted sleeve.
3 Pull the hose ends through the pots.
5 Push the hose end through the pots.
6 Connect the hose ends to the port and bolt the connector flanges.
7 Lubricate the hose and drive the rotor to the lowest position.
8 Insert the upper part of the hose and drive the rotor back to up
9 Close the front cover Set the compression, and tightly lock the cover.
10 Add lubrication through the maintenance window.
For optimal performance, the pump should be installed on a robust foundation, ideally secured with fastening bolts or mounted on a stable base plate It is crucial for the user to verify that the foundation can support the weight of the pump along with any additional loads The accompanying tables provide detailed information regarding the minimum free distance (in meters) and the specifications for bolts required for the pump foundation.
Model Front (m) Right (m) Left (m) Behind (m) Flatness requirements
Table 10: Minimum Distance Around the Pump
Table 11: Foundation Bolts and Tightening Torque
We can conclude that the flow rate is the parameter that needs to be controlled in predictive maintenance in order to increase the Larox pump’s availability.
Benefits of Predictive Maintenance
There are two primary approaches to pump maintenance: run to failure and preventive maintenance In the United States, organizations typically employ preventive or predictive maintenance strategies, achieving a reduction in maintenance costs by 33% to 50% Predictive maintenance offers several advantages for organizations, enhancing efficiency and cost-effectiveness.
• It reduces unscheduled downtime of the pump
• It increases utilisation of manpower
• It increases the life time of the pump
To execute predictive maintenance successfully, the following ingredients must be included in the methodology:
• Organised and planned predictive maintenance methods
• Execution and following up of all recommended maintenance actions
Early detection of failures is crucial for preventing critical issues, minimizing downtime, and lowering maintenance costs, ultimately maximizing equipment availability Additionally, it facilitates efficient scheduling, effective spare parts management, and optimized man-hour planning.
Total Productive Maintenance (TPM) is essential for effective quality management systems, focusing on proactive and preventive maintenance It empowers operators and artisans to take charge of machinery upkeep, ensuring optimal performance and reliability.
Total Productive Maintenance (TPM) is essential in lean manufacturing, offering a holistic approach to managing machinery failures and production defects throughout their life cycle It focuses on optimizing production operations to minimize losses caused by breakdowns, defects, or accidents TPM engages all levels of an organization, from top management to production support staff and external suppliers.
FRACAS is a crucial tool designed to identify and rectify system deficiencies, effectively preventing future occurrences It encompasses two primary perspectives: reliability-related information and operational tasks This includes essential data such as field reports, failure documentation, part specifications, and profiles.
To summarise, FRACAS, if implemented correctly, must have the following features:
• Reliability tasks, including their attributes; they need to be clearly defined and standardised
• Functionalities of tasks; handling the need must be provided to support the tasks and control the process [88].
Conclusion
Chapter 6 will discuss recommendations, suggested areas for future research and the research conclusions It is proven that predictive maintenance increases the availability of positive displacement pumps since there were no failures after its implementation The literature