Savings In Maintenance Costs Research Articles

On the use of time-limited and monitoring information for maintenance decision support

Developments of monitoring techniques provide information on the actual conditions. The information level available on the system (failure times, deterioration, load, usage condition, etc.) and the way to integrate them impact directly the performance of maintenance operations that represent a substantial portion of the total life cycle costs of many systems. In this context, we consider a gradually deteriorating system operating under an uncertain environment. The information about the future environment state is only known on a finite rolling horizon. The system is subject to constraints and maintenance actions cannot be planned at any time, but at fixed times called maintenance opportunities and known only on a finite horizon. Based on the considered system, we aim to use the monitoring data and the time-limited information for maintenance decision support in order to reduce its costs. Several maintenance policies are proposed: age-based policy, condition-based policy and two predictive policies based on a cost and a risk criterions. The comparison of the maintenance cost savings of these policies allows concluding the value of different types of information and the best ways to use them in maintenance decision-making.

Detailed Scheduling of Operations in Single-Source Refined Products Pipelines

The short-term scheduling of refined products pipelines is a very complex problem with many operational constraints to be considered. Available nondiscrete planning approaches just provide the input schedule and the set of aggregate product deliveries to be performed from in-transit lots to depots at every batch injection. To determine the sequence of individual cuts on each batch to be accomplished by the pipeline operator, it is still necessary to refine such an aggregate plan. To do so, new computational tools for efficiently generating the detailed schedule of single-source pipelines with multiple distribution terminals are presented. Two types of methodologies are proposed. On one hand, it is developed a continuous-time mixed-integer linear programming (MILP) formulation that seeks to minimize both the total flow restart volume and the number of single-delivery pumping runs over the planning horizon. In this way, substantial savings in energy consumption and pump maintenance costs are achieved. Effective solution strategies for the MILP model are also designed to deal with large pipeline scheduling problems. On the other hand, three different heuristic rules for selecting the receiving terminal are introduced. By applying those rules in combination with a discrete-event simulation model, not only alternative detailed schedules can be generated in a very short CPU time but also some of them are near-optimal solutions. Three instances of a case study aimed at finding the detailed schedule of a real-world single-source pipeline system are solved through the proposed optimization and discrete-event simulation methods. Results are analyzed to assess the quality of the generated solutions and the required computational costs.

Applications of predictive maintenance techniques in industrial systems

Prognostic methods represent a new methodology for system maintenance which offers significant time and cost savings. The paper offers a short overview of the available prognosis techniques and proposes the implementation of one model-based and one data-driven method. As a representative of the model-based methods the autoregressive moving average (ARMA) modeling approach is chosen. The estimated model parameters are further used for implementing the early change detector which is realized as a Neyman-Pearson hypothesis test. On the other hand, hidden Markov model (HMM) based prognosis illustrates the use of data-driven techniques. Using the cross-correlation input-output functions, HMM prognosis algorithm is proposed, as a suitable way of timely detection. Both techniques were implemented to detect performance changes of the water level sensor in a steam separator system in thermal power plants.

Opportunistic preventive maintenance optimization for multi-unit series systems with combing multi-preventive maintenance techniques

This paper proposes a dynamic opportunistic preventive maintenance (PM) optimization policy for multi-unit series systems by integrating multi PM techniques. Two PM techniques, periodic PM and sequential PM, are considered. Whenever one of the units reaches its reliability threshold, a PM action has to be performed on that unit. At that time the whole system has to be stopped and PM opportunities arise for the other units of the system. An optimal PM practice is determined by maximizing the short-term cumulative opportunistic maintenance (OM) cost savings for the whole system. Numerical examples are given to show how this approach works. Finally, a comparison between the proposed PM policy and the other policies is given.

A dynamic opportunistic preventive maintenance policy for multi-unit series systems with intermediate buffers

Commonly, for a multi-unit series system, whenever one of the units stops to perform a preventive maintenance action, preventive maintenance opportunities arise for the other units because combining the preventive maintenance activities can save the system-dependent cost (i.e. downtime cost). This article proposes an opportunistic preventive maintenance policy for multi-unit series systems based on dynamic programming, with integrating the online information of the intermediate buffers. Whenever one of the units reaches its reliability threshold, a preventive maintenance action has to be performed on that unit. An optimal preventive maintenance practice is determined by maximising the short-term cumulative opportunistic maintenance cost savings for the whole system which is a combination of the maintenance cost saving, the downtime cost saving, the penalty cost for advancing the preventive maintenance action and the penalty cost for work in process. Finally, a numerical example is given throughout to show how this approach works.

Experimental validation of a novel structural damage detection method based on empiricalmode decomposition

Structural health monitoring, as a non-destructive damage detection technique, has beenadopted by many researchers as well as various industries to keep up with the increasingdemand for preventive maintenance routines. Oil and gas is one of the major industries inwhich effective damage detection can ensure reliable transportation of chemicals andprovide tremendous savings in maintenance costs. The present work investigates theintegrity of a novel damage detection method through a set of experiments conducted ona standard steel pipe commonly used in the oil and gas industry. The methodinvolved collection of the vibration signature of the pipe via certain sensors, anddecomposition of the signature (signals) by empirical mode decomposition. This wasfollowed by the use of a damage index defined on the first intrinsic mode functionresulting from the decomposition. The experiment consisted of a cantilever steelpipe equipped with piezoceramic sensors to monitor the free vibration of a pipeimpacted by an impulse hammer. Three damage cases were studied including singlehalf-circumferential, single full-circumferential, and multiple circumferential andhalf-circumferential damages. A MATLAB code was developed to process and todecompose the signals according to the proposed methodology. The results showed that theproposed damage detection methodology could successfully detect the presence andlocation of damage, and could also identify the severity of the damage. A set ofexperiments was also done to examine the effect of support flexibility on thedamage index, and to examine the sensitivity of the method to support conditions.

Physical Model Study of Chicago's New Calumet Influent Pumping Station

A new raw wastewater influent pumping station was designed for the Calumet Water Reclamation Plant in Chicago. The new station could not be designed to be in full compliance with design guidelines of the Hydraulic Institute due to site constraints. Proper operation of the pumping station and optimum operational flexibility are goals for the successful long term performance of the new station. A physical model study was used to identify deficiencies in the original design relative to flow characteristics. The model enabled development of design modifications to address hydraulic flow deficiencies. The optimized design resulted in pump approach flow conditions that provide proper pump performance under a wide range of varying water levels and different combinations of operating pumps and screen channels. Other benefits of the model included improvement in pump efficiency, lack of air entrainment, decreased pump wear, and decreased scour of concrete surfaces. Optimized design also results in operation and maintenance cost savings which, in the long run, will greatly surpass the cost of the physical model study. The required elements to optimize the performance were integrated with the design of the facility, thereby avoiding potentially costly retrofits if the deficiencies had not been mitigated prior to construction.

Opportunistic preventive maintenance scheduling for a multi-unit series system based on dynamic programming

It is understood that for a multi-unit series system, whenever one of the units stops to perform a preventive maintenance (PM) action, the whole series system must be stopped. At that time PM opportunities arise for the other units in the system. This paper proposes an opportunistic PM scheduling algorithm for the multi-unit series system based on dynamic programming with the integration of the imperfect effect into maintenance actions. An optimal maintenance practice is determined by maximizing the short-term cumulative opportunistic maintenance cost savings for the whole system. Matlab is considered for the optimization which is based on numerical simulation. Numerical examples are given throughout to show how this approach works. Finally, a comparison between the proposed PM model and other models is given.

Experimental trials to determine effective fence designs for feral Cat and Fox exclusion

Summary Exclusion fencing is being increasingly used to protect areas of high conservation value or to create ‘islands’ of protected habitat for native fauna. The objective of this study was to test a range of fence designs to assess the optimum physical and/or electrical barrier required to exclude feral Cats (Felis catus) and Red Foxes (Vulpes vulpes). We tested against six fence designs by placing individual animals (18 Cats and 18 Foxes) in 20 × 20 m pens and recording their responses to various fence components. Fence design 1 was 1.8‐m high with one electric wire at 1200 mm and another at 1500 mm offset by 80 mm and a curved overhang 600 mm in diameter. Fence design 2 and 3 had single electric wires placed at 400 mm and 1700 mm, respectively. Fence design 4 had a single electric wire at the end of the overhang. Fence design 5 had no electric wire and fence design 6 was 1.2‐m high with an overhang and no electric wire. Neither feral Cats nor Foxes were able to scale the 1.8‐m fence regardless of the position or absence of electric wires. One Fox and one feral Cat successfully breached the 1.2‐m high fence by jumping onto the overhang and climbing over. Four Foxes excavated holes underneath the fence and one chewed through the mesh. Results from this work indicate that fences designed to exclude feral Cats and Foxes should be 1.8‐m high, have an overhang that is at least 600 mm in circumference that is curved or shaped in such a way that prevents animals climbing over from underneath, and have an apron with a mesh hard enough to prevent Foxes chewing through. Exclusion fences do not require electric wires. The omission of electric wires will provide significant savings in building and maintenance costs for exclusion fencing.

Free bearing isolators offered to end users

Inpro/Seal Co has announced a program that will provide qualified companies with as many as 1000 bearing isolators at no charge. This generous sounding offer, which shows considerable faith in the company products, is to be funded by a share in the savings in maintenance costs achieved by the plant operator.

Value of Pavement Smoothness

Smoothness, the absence of bumps and dips in the riding surface of a pavement, improves the quality of the ride and is believed to prolong the life of the pavement. Research addressed the effect of Virginia's special provision for smoothness on contract prices for hot-mix asphalt. The research also examined the financial value of the resulting product (presumably smoother pavements). The analysis included maintenance cost savings for the owner–agency, as well as any reduction in delay and operating costs for the motoring public. A detailed statistical analysis found no statistically definitive effect on bid price as a result of the use of a special provision for rideability. A similar analysis on a more focused data set, however, did document a lifetime reduction in the international roughness index of almost 9 in./mi. This reduction in roughness (increase in smoothness) implies an increase in pavement service life, which translates into reduced annual maintenance costs. The lifetime decrease in roughness can lead to even more dramatic user cost savings. A case study demonstrated a fuel cost savings (for trucks alone) of $190,000 over a 10-year period for each lane mile of highway resurfaced under the special provision.

Constraints and trade-offs in climate-dependent adaptation: energy budgets and growth in a latitudinal cline

Characteristics of temperature-dependent metabolic adaptation as well as their implications for associated changes in energy budgets are analysed based on comparisons of fish and invertebrates from various latitudinal clines in northern and southern hemispheres and on integrated ecological and physiological approaches. To identify putative “bottlenecks” of adaptation and for a general cause and effect understanding, the temperature sensitivity of growth as a key energy budget component is investigated, considering underlying processes at population, whole animal and cellular levels. Available data support the hypothesis that natural selection favours individuals for energy efficiency and maximised growth, but is subject to constraints of limited energy availability and temperature. According to emerging relationships between energy turnover, temperature variability and thermal tolerance, the notion that selection should favour a certain metabolic rate according to mean temperature is too simplistic. Within the energy budget, savings in maintenance costs set free energy for growth, visible as growth increments at a low standard metabolic rate. Such energy savings are maximised at the permanently low temperature of the Antarctic. However, some variability persists as pelagic lifestyles in the Antarctic are fuelled by higher metabolic rates at the expense of reduced growth. Temperature variability in the cold, as in the Subarctic, causes a rise in maintenance costs at the expense of growth, but in favour of exercise and thus foraging capacity. Such transitions in energy cost between sub-polar and polar areas are not visible in the southern hemisphere, where there is less temperature variability. However, these patterns—as well as many of the underlying mechanisms—still remain incompletely investigated, especially with respect to the suggested hierarchy in energy allocation to energy budget components.

Intelligent Management of Helicopter Health and Usage Management Systems Data

Helicopter health and usage management systems (HUMS) generate large amounts of data, which are downloaded to ground-based systems. The data are automatically examined on download for damage indications, which provide the immediate go/no-go response required by the aircraft operations management. This level of reactive fault detection and diagnosis is reasonably well understood and has been demonstrated to improve aircraft availability and airworthiness. To achieve further benefit and maintenance cost savings from HUMS, another level of analysis is required, leading to prognostics and predictive maintenance through intelligent management (IM) of the accumulated HUMS records. In collaboration with the Civil Aviation Authority (CAA), Smiths has developed a suite of IM methods and has successfully applied them to gearbox seeded fault data. Working closely with the UK Ministry of Defence (UK MOD), Smiths has tested these methods on Chinook HUMS data, including an in-flight transmission bearing failure incident described in this article. The result is a high degree of early anomaly detection and a clear view of the deterioration to failure. The objective of the MOD programme has been to apply IM tools to the enormous quantity of HUMS data being gathered, thereby enabling improved analysis capability, increased levels of automation, and more intelligent use of resources. The article presents the results of the work carried out under both the CAA and the MOD programmes.

Interstitial Space Design in Modern Laboratories

Modern laboratory design and construction is becoming increasingly complex with advancements in mechanical, electrical, plumbing, and specialty system technologies. Laboratory projects often have critical schedules and rigorous maintenance and operations requirements. The use of interstitial spaces that create additional floors for mechanical systems is a design strategy that can facilitate both the construction and operation of laboratories. By providing additional space and easier access to mechanical systems, interstitial designs facilitate maintenance and reconfiguration of laboratories, thus reducing life cycle costs. Despite these and other advantages, the use of interstitial space is often eliminated as a laboratory design option due to perceptions of high first costs. This paper presents an analysis of the advantages and disadvantages of interstitial space design as an alternative to traditional plenum construction. The opinions of experienced operators, designers and builders of interstitial building spaces are presented. Survey results of design and construction professionals are presented illustrating current perceptions (and misconceptions) of interstitial spaces as a design alternative for laboratories. Finally, a detailed interdisciplinary case study redesign is used to illustrate the comprehensive effects of introducing an interstitial space design in an actual modern laboratory in which a 1.6-year payback was achieved on the investment in an interstitial design alternative. The research concludes increased first costs can potentially be offset by savings in construction time, and that valuable savings in maintenance and operation costs help to justify the use of interstitial space design solutions.

Benefits of Information Integration in Budget Planning for Pavement Management

The budget-allocation process in pavement management occurs at several levels of decision making. In normal practice, the central level is concerned with the allocation of the budget to regional agencies to improve the health of the overall road network, while the regions are responsible for the programming and scheduling of road maintenance in their respective networks. The information processed at different management levels differs, and information at one level may not be readily available to the other. As a result, the maintenance funds allocated by central management to regional highway agencies may not be best used. A budgetallocation procedure based on artificial-intelligence agents is presented; it takes into account information integration between the central and regional management levels by using multiagent systems. Agents are used to facilitate the interaction between decision makers at the two management levels and thus provide a means for vertical information integration. A hypothetical problem containing a two-level funds-allocation structure consisting of a central-level management and three regional highway agencies is investigated. Each regional agency has different road network profiles with different local-level objectives. A genetic algorithm is used as the optimization tool in the decision-making process carried out by each agent. The results are compared with conventional allocation approaches and a two-stage optimization approach. It is shown that, with better integration of information at the different management levels, the resulting budget-allocation strategy produces greater maintenance-cost savings for a given target level of pavement performance.

The sky’s the limit for ceiling tile factory

A new regenerative turbine pump installed at a ceiling tile manufacturing plant, owned and operated by US Gypsum (USG), in Minnesota, USA, has ensured reliable dissolved air generation on a wastewater process stream, leading to significant savings in maintenance, energy and disposal costs at the factory.

Start Cast Breakouts Preventative Prediction Using Multi-Way PCA Technology

Breakouts during continuous caster start-up operations are of major concern in the steel-making industry, because they can lead to severe damage to equipment, significant process downtime, and potential safety consequences. As a multivariate statistical (MVS) analysis tool, Multi-way PCA (MPCA) is applied for monitoring the start-up operation of a continuous caster in order to predict potential start cast breakouts so the caster can be automatically stopped to avoid the catastrophic event. It is shown to provide good prediction of start cast breakouts resulting in significant savings in operating and maintenance costs. An on-line start cast monitoring system has been successfully implemented at Dofasco's #2 continuous caster.

Server consolidation using performance modeling

Server consolidation is crucial to improving a corporation's bottom line by providing savings in hardware, software, maintenance, facility, and labor costs. In today's cost-cutting environment, consolidation efforts can provide significant savings in IT expenditures. Overall potential consolidation benefits include: lower total cost of ownership, improved service levels and availability, and reduced business risks, resulting from consistent business management and resiliency. To fully realize consolidation benefits, businesses must focus on the performance and service levels provided to users in addition to reducing unused capacity. We present a new way to analyze consolidation alternatives using performance modeling and stepwise refinement, a methodology for efficient and effective modeling.

Application of the principles of ILS to the development of cost effective maintenance strategies for existing building stock

Total spending on building maintenance in the UK has increased by 66% in the last 10 years (BMI, 1996). Total expenditure on maintenance in 1997 was £39.8 billion (BMI, 1998). Any significant reduction in building maintenance costs will therefore have a real impact on the national economy. This paper reports the results of a research project supported by the EPSRC at the University of Dundee, which sought to quantify the benefits of applying integrated logistics support (ILS) to the development of cost-effective maintenance strategies for existing building stock. ILS is a managerial and technical approach that ensures that the client/user will receive a building that will meet performance requirements (durability, reliability, maintainability, performance, etc.) at the lowest whole life cost. The principles of ILS are described and a systematic framework for selecting the most appropriate and cost-effective maintenance task for each individual element in a building is developed. The decision logic processes for identifying each failure consequence and for selecting the most applicable and cost-effective maintenance task are derived. The maintenance cost savings arising from the application of two ILS techniques - failure modes and effects analysis, and reliability centred maintenance - to a sample of 18 properties were calculated to be 18.5%.

Analysis of service operations cost for TDM and packet tandem networks

Lucent Technologies has developed operations cost models to compare the trunk operations cost of the present method of operations (PMO) time division multiplexed (TDM) tandem networks and the future method of operations (FMO) packet-based networks. These models take into account three factors: network and service architectures, operations processes, and operations support system (OSS) efficiency. The models consist of parameters whose values can be adjusted to reflect customer-specific network architecture, operations environment, and cost benchmarks. By applying the models to some realistic customer PMO and FMO tandem network applications, we found that substantial operations cost savings can be realized in voice trunk provisioning and maintenance. The FMO per-trunk provisioning cost savings range from about 35 to 62% of the PMO cost, depending on the extent to which the voice gateway (VG) function is distributed in the packet tandem network. The corresponding FMO trunk maintenance cost savings range from about 20 to 40% of the PMO cost. In this paper, we demonstrate that combining asynchronous transfer mode (ATM) switched virtual channel (SVC) technology with a distributed VG network architecture is the biggest contributor to FMO cost savings.