Tuesday, 24 December 2013

An Engineer Imagines: Why I Studied Mechanical Engineering

 This Christmas, instead publish an article about a technical topic, I go to comment a book that does me remember the excitement with I studied mechanical engineering.

Peter Rice, An Engineer Imagines

  The book is An Engineer Imagines, the autobiography of Peter Rice, one of the most imaginative and gifted structural engineers of the 20th Century, published after he died due a brain tumor.

 With his imagination and his deep knowledge of structures and materials, not only steel or concrete but also glass, polycarbonate, stone or fabric; Rice got the recognition and admiration of all the engineers and architects with whom he collaborated, specially of Ove Arup with he worked in the Structures 3 design departement (great name for an engineering department).

  In his book, Rice alternates his memories of youth in Dundalk, Newbridge and Belfast with his great projects; his ideas about engineering and the research of new shapes and materiales, with his relationship with Arup and with Jean Prouvé.




La Maison Tropicale, by Jean Prouvé
 Prouvé is another great engineer, his projects of La Maison Tropicale and La Maison du Sahara that provide smart solutions for houses in extreme climate conditions, while provides solutions to prefabricated homes, one of my research interestes; or his experimentation with new shapes and new materials, as the cylindrical service stations for Total.



Pabellón del Futuro Expo'92 Seville
 Returning to Rice, we can not forget his works in the Sydney Opera House, the Centre Pompidou, the Lloyd's of London building or the Menil Collection Museum, all with impossible structures, some of them results of the Lightweight Structures Laboratory in Ove Arup & Partners. A highlight is his collaboration in the Pabellón del Futuro of the Expo'92 in Seville, it combines a single row of huge stones arches, of a extreme lightness, with a waveform roof suspended over four display halls and a canopy, also suspended, over the central plaza.. Or the engineering solutions of the Full Moon Theatre to light up the nighttime stage only by reflectors.
Fiat VSS, 1981
  But the engineers specialized in machines shouldn't forget his projects, joined Renzo Piano and the I.DE.A Institute, for Fiat that produced the Subsystems Experimental Vehicle (VSS). Its structure was a steel spaceframe and the body (with plastic panels) had no load-bearing capacity, but for the first time this choice was made in order to reduce the vehicle weight and to obtain a high flexibility in terms of external shape, production and assembly. The vehicle was made by nine external panels that had to be produced separately (as complete "subsystems") and then assembled in a final production line.

 I strongly recommend you to read this book, An Engineer Imagines by Peter Rice, or as I name it Why I Studied Engineering.

Thursday, 19 December 2013

Un Ingeniero Imagina: Por qué estudié ingeniería mecánica

 Dada la proximidad de las fiestas navideñas, en lugar de comentar aspectos técnicos voy a comentar un libro que me ha hecho recordar la ilusión con la que estudié ingeniería mecánica.

Peter Rice - Un ingeniero imagina.
 Se trata de Un Ingeniero Imagina, la autobiografía que Peter Rice, uno de los ingenieros de estructuras más importantes del siglo XX, publicado tras fallecer por un tumor cerebral.

 Gracias a su imaginación y a su profundo conocimiento de las estructuras y de los materiales, incluyendo no solo el acero o el hormigón, sino también el vidrio, el policarbonato la piedra o la tela; Rice se ganó el reconocimiento y la admiración de todos los ingenieros y arquitectos con los que trabajó, especialmente de Ove Arup con el que trabajo en el departamento de Estructuras 3 (fantástico nombre para un departamento de ingeniería).

 En el libro, Rice alterna sus recuerdos de juventud en Dundalk, Newbridge y Belfast con sus grandes proyectos; sus reflexiones sobre la ingeniería y la investigación de nuevas formas y materiales, con su relación con el propio Arup y con Jean Prouvé.


La Casa Tropical, de Jean Prouve

Y es que Prouvé es otro de los grandes ingenieros, sus proyectos de Casa Tropical y Casa Sahariana aportan soluciones sencillas e ingeniosas a los problemas de ventilación y climatización, a la vez que a la fabricación en serie de edificios con materiales ligeros, uno de los campos que más me interesan; o su experimentación con nuevos materiales y nuevas formas, como las estaciones de servicio cilíndricas para Total.

Pabellón del Futuro Expo'92 Sevilla


 Regresando a Rice, no podemos olvidar su trabajo en la Ópera de Sydney, el Centro Georges Pompidou, el edificio Lloyd's de Londres o el Museo de la Colección Menil, todos con estructuras imposibles, algunas de ellas fruto del Laboratorio de Estructuras Ligeras de Ove Arup & Partners. Destaco su colaboración el Pabellón del Futuro de la Expo'92 de Sevilla, que combina una fila de arcos de piedra, de una ligereza extrema, con una cubierta ondulada suspendida y un dosel, también suspendido, sobre la plaza central; o las soluciones de ingeniería de el Teatro de la Luna Llena para iluminar un escenario nocturno únicamente con reflectores.

Fiat VSS, 1981
 Pero los que trabajamos con maquinaria no podemos olvidar sus proyectos, en compañía de Renzo Piano y el Instituto I.DE.A, para Fiat que dieron como resultado el Vehículo Experimental de Subsistemas (VSS). Este vehículo conseguía reducir su peso mediante la utilización de un chasis compuesto por una malla tridimensional de acero cubierta con paneles de plástico sin ninguna responsabilidad estructural, además de aumentar la flexibilidad en las fases de fabricación y montaje, permitiendo conseguir diferentes configuraciones. El vehículo se componía de nueve paneles externos, o subsistemas, fabricados de forma independiente que se montaban al final de la línea de producción.

 Recomiendo a todos leer este libro, Un Ingeniero Imagina, de Peter Rice, o como yo lo llamo Por Qué Estudié Ingeniería.

Sunday, 20 October 2013

Cloud Monitoring: Maintenance on the Cloud

 All of us know the importance of condition monitoring and the need to perform a good inspection plan that allows us to detect the machine problems on time, based in the P-F curve. To define the inspection periods we can use the risk based inspections principles or reliability programs.

 But we can increase our condition monitoring program effectiveness by a continuous monitoring program with send of real time information to the cloud, these programs are named Cloud Monitoring.

 Because the inspection plan is the most critical part of a condition monitoring program, due the uncertainty of the reliability calculus and, mainly, the difficulty of the P-F curve interpretation due the variety of failures of an equipment.

 We must add the difficult to perform right measuring, either ultrasonic, oil analysis, vibrations analysis, termographies or other techniques, and the difficulty to understand the results.

 Cloud Monitoring programs avoid these problems, increasing the condition monitoring program effectiveness, providing real time information, logging the measure results conitnuously and allowing them to be studied and reviewed on-line by specialists.

How can we get it?

 Cloud Monitoring is based in an electronic acquisition data unit that receives information, continuously, through sensors placed in equipments that we want to study.

 There are a wide range of sensors, as the electrical diagnostic (phase angle and current signature) that we can use in electrical motors, accelerometers to detect misalignments and unbalances in mechanical components, ultrasonic to detect micro cracks, surface roughness, lack of lubrication, electric currents or fluids leakages; vibrations to detect wears and turbulences or cavitation formations, temperatures or, even, lubricant condition.

 These sensors provide a continual signal, so to place and adjust them to obtain the maximum effectiveness is easy.

Fractal diagnostic of a bearing performance.
 The acquisition data unit transforms the signals from the sensor, using specific software, and send them to a web site where we can see, real-time, the results of the measurements and the historicla data, we can review them anytime and anywhere, only visiting a web page; these results can be easily processed using any spreadsheet. We can program the system to send the alarm signals, by e-mail or SMS, if it reaches some limits.

 This methodology is suitable to any industry and any location, because it doesn't require a complex instalation and it doesn't need maintenance.

 The main benefits that this system provides are the reducción of unexpected breakdowns, ensure the spare parts, tools and technicians are available to perform the maintenance tasks, increasing the equipment uptime, avoid false alarms, increase availability and allow joining data with the CMMSs.

Wednesday, 9 October 2013

Cloud Monitoring: Mantenimiento en la nube

 Todos conocemos la importancia del mantenimiento predictivo y la necesidad de realizar un buen plan de inspecciones que permita detectar a tiempo los posibles problemas en base a la curva P-F. Para la definición de los periodos de inspección podemos utilizar las bases de las inspecciones basadas en riesgo o programas de fiabilidad.

 Pero podemos aumentar la eficacia de nuestros programas predictivos con la implantación de un programa de monitorización continua, con envió de información en tiempo real a la nube, a estos programas los denominamos Cloud Monitoring.

 Y es que diseñar el plan de inspecciones es la parte crítica de un plan de mantenimiento predictivo, por un lado por la incertidumbre de los cálculos de fiabilidad pero, principalmente, por la dificultad de interpretar la Curva P-F debido a la gran variedad de fallos que puede sufrir un equipo.


Curva P-F
 A esto hay que añadir la dificultad para realizar las mediciones de forma correcta, ya sean mediante ultrasonidos, análisis de lubricantes, análisis de vibraciones, termografías o cualquier otra técnica, y la dificultad de interpretar los resultados.

 Los programas de Cloud Monitoring evita estos problemas, multiplicando la eficacía del mantenimiento predictivo, al proporcionar una información en tiempo real, registrando los resultados de las mediciones de forma continua y permitiendo que puedan ser interpretados y revisados, on-line, por especialistas.

 ¿Cómo lo consigue?

 El Cloud Monitoring se basa en la utilización de una centralita electrónica que recibe información, de forma continua, a través de los sensores que se colocan en los equipos que queremos estudiar.

 Existe una gran variedad de sensores que podemos utilizar, como por ejemplo de diagnóstico eléctrico (ángulo de fase y señales de corriente) que podemos utilizar en motores eléctricos, acelerómetros para detectar desalienaciones y desequilibrios en componentes mecánicos, de ultrasonidos para detectar microfracturas, rugosidades, mala lubricación, derivaciones eléctricas o fugas de fluidos; de vibraciones que detectan desgastes y formación de turbulencias o cavitaciones, de temperaturas o incluso del estado del lubricante.

 Al proporcionar estos sensores una señal continua, es relativamente sencillo colocarlos y ajustarlos para obtener el máximo rendimiento.


Diagrama fractal del funcionamiento de un rodamiento.
 La centraliza transforma la señal procedente de los sensores de manera que se pueda enviar a un sitio web en el que podemos ver, en tiempo real, los resultados de las mediciones así como un histórico de resultados, que podemos revisar todas las veces que haga falta desde cualquier lugar, solo con conectarse a una página web; estos resultados se pueden tratar fácilmente utilizando cualquier hoja de cálculo. También podemos programar el sistema para que envíe señales de alarma, por e-mail o SMS, en caso de alcanzar unos valores límite.

 Esta metodología es aplicable a cualquier tipo de industria y en cualquier localización, ya que no requiere de una instalación compleja y no necesita mantenimiento.

 Los principales beneficios que aporta son la reducción de paradas inexperadas, asegurar que se dispone de repuestos, herramientas y personal cualificado para realizar las tareas de mantenimiento, aumenta la vida útil de los equipos, previenen las falsas alarmas, aumentan la disponibilidad y permiten integrar los datos con programas de gestión de mantenimiento (GMAO).

Thursday, 19 September 2013

Lean Maintenance

 I had wanted to write about the develop of Lean Maintenance programs to remove all the tasks that give No value to the equipment.

 That's Lean Maintenance means, to provide the right maintenance with minimum wastes, so the equipments do their functions with the minimum cost; sumarizing, to remove process that give no value and simplify the process that give value.

 But, Can we save in maintenance and increase the reliability of our equipments together?

 Yes, Lean Maintenance does it, applying the Toyota Production System (TPS) basics as remove wastes, standarize tasks, schedule just-in-time actions and focus in quality.

 Generally, through the TPS application we will improve maintenance while minimizing inputs as Labor, Management effort, Parts and materials, Contractors and service contractcs, Equipment rental, Raw materials, Energy, Capital...

  A goob way to start a Lean Maintenance program is with a 7 Wastes analysis, these wastes are:

  • Overproduction, too much maintenance tasks.
  • Excessive Inventory, too much spare parts.
  • Waiting, among maintenance tasks.
  • Material and Information Movement.
  • Motion, movements of people or equipments.
  • Defects, reworks from a poorly maintenance process.
  • Unnecessary Procesing, efforts which adds no value and consume resources.

 Once the wastes are identified and removed, we can implant a TPM (Total Productive Maintenance) program based in Autonomous Maintenance, that's maintenance based in operator, with the maintenance department support. This program use tools as 5S, Poka Yoke, JIT (Just-In-Time) or SMED (Single Minute Exchange of Die), and can be completed with RCM (Reliability Centered Maintenance) or RBM (Risk Based Maintenance) analysis.

 The Lean Maintenance full implantation process is difficult because it requires to involve all the people and process, indefinitely, and provide them trainings and expertises.

 The best way to obtain these goals is through Lean games and activities, that help to improve the motivation providing both knowledge and experience in an enjoynable and effective way.

Monday, 9 September 2013

Mantenimiento Lean

 Tenía ganas de escribir sobre la necesidad de plantear planes de mantenimiento Lean, que eliminen todas las tareas que no aportan nada a las máquinas.

 Eso es lo que significa Mantenimiento Lean, proporcionar el mantenimiento necesario con los mínimos desperdicios, de manera que los equipos hagan sus funciones con el menor coste; es decir consiste en eliminar procesos que no añaden valor y simplificar aquellos que lo añaden.

 Pero ¿Se puede ahorrar en las operaciones de mantenimiento sin comprometer la fiabilidad de las máquinas?

 Sí, el Mantenimiento Lean lo consigue, y lo hace aplicando conceptos del Sistema de Producción Toyota (TPS) como son eliminar desperdicios, normalizar trabajos, programar acciones justo-a-tiempo (just-in-time) y enfocarse en la calidad.

 De modo general se pueden mejorar, mediante la aplicación de TPS, en aspectos como Mano de obra, Tiempos de gestión, Repuestos y componentes, Contratas y servicios externos, Alquiler de equipos, Materiales de desperdicio, Energía, Costes...

  Una buena forma de comenzar un plan de Mantenimiento Lean es realizando un análisis de los 7 desperdicios, o 7 Wastes, que son:

  • Sobreproducción: Exceso de tareas de mantenimiento.
  • Inventario: Exceso de repuestos.
  • Esperas: Tiempos muertos entre tareas de mantenimiento.
  • Movimiento de materiales e información: Que no se encuentran en los lugares en los que se necesita.
  • Desplazamientos innecesarios: De personal para realizar las tareas de mantenimiento.
  • Defectos: Que requieren repetir las tareas.
  • Procesos innecesarios: Tareas innecesarias que consumen recursos.

 Una vez identificados y eliminados estos desperdicios, se implanta un plan de mantenimiento TPM (Total Productive Maintenance) basado en Mantenimiento Autónomo, es decir, en el mantenimiento realizado por el propio operador de la máquina, con el apoyo del departamento de mantenimiento. Esta implantación utiliza herramientas como las 5S, Poka Yoke o SMED (Single Minute Exchange of Die), y puede completarse con un análisis RCM (Reliability Centered Maintenance) o RBM (Risk Based Maintenance).

 La implantación de procesos de Mantenimiento Lean es compleja porque requiere involucrar a todos las personas que trabajan en la planta y a todos los procesos, de forma indefinida, y en proporcionarles formación y experiencia, incluso a las nuevas incorporaciones.

 Una buena forma de conseguir estos objetivos es mediante la organización de actividades y juegos Lean, que ayudan a mejorar la motivación proporcionando los conocimientos y experiencia necesarias de una forma amena y eficaz.

Monday, 22 July 2013

Lubrication Regimes Simulation Software


 Dear sirs, find attached this post by Lorenzo Asín, Mechanical Engineer, about his Undergraduate Project related with develop a Simulation Software of the Lubrication Regimes. You can know more about this project in this web.

Nowadays it is important to have a precise control of the lubrication regimes in order to reduce costs (either reparations or an excessive energy consumption due to the usage of more lubricant than necessary) and to improve useful life of mechanic components.

 This software has been developed with the idea of allowing the designers to obtain a clear and concise idea about the lubricants behavior under the variation of the most important parameters that take part during lubrication.

 In this software, created trough the MATLABTM programming language, the user can choose between a variety of different mechanical elements to simulate the lubrication in. These elements can be bearings (ball, cylindrical and spherical rollers), gears (parallel axis helical, spur, bevel and planetary gears) and cam-follower systems (sliding and roller systems). If the user knows it has also the option to introduce the contact area manually.
 
 A great database of mineral and synthetic lubricants of different trademarks (Repsol, Shell, Cepsa, bp and Exxon Mobil) has been added in order to facilitate the user the selection and comparison of different products. The manual introduction of the lubricant characteristics is also included, in case that the lubricant is not included in the database.
 
 Other data, as the mechanical elements surface roughness, the mechanical elements materials or the speed and loads that these mechanisms suffer will be necessary to do a correct simulation.

 The software will execute a simulation obtaining the lubricant film thickness for the given parameters. Comparing these thicknesses with the surface roughness, the software will be able to determine the kind of lubrication regime that it is taking place (boundary, mixed or elastohydrodynamic) and to inform the user about it.

 The user can also choose between various graphic representations to observe the lubricant film thickness change as a function of the variation of the three main parameters that take part in lubrication: relative speed, load and temperature. The user will be able to use 2D (graphs relating one of the parameter with the thickness) and 3D graphs (relating two of the parameters with the thickness).



 For subsequent analysis of the results the user also will be able to save the generated graphs as images and to export the simulation data to an Excel file.
 This is a user-friendly software that allows the obtaining of a great amount of data about lubrication and gives a potential save of money and time for the user.

Wednesday, 17 July 2013

Software Simulación Regímenes Lubricación

 Estimados lectores, a continuación adjunto un post que nos ha enviado Lorenzo Asín, Ingeniero Mecánico, relativo a su Proyecto Fin de Grado sobre el desarrollo de un software de Simulación de Regímenes de Lubricación. Pueden obtener más información sobre este software a través de nuestra web.

 
 En la actualidad, un control preciso de los regímenes de lubricación es importante para reducir costes (ya sea por reparación de piezas o un consumo energético excesivo debido a un uso de más lubricante del necesario ) y alargar la vida útil de los componentes mecánicos.
 Este software se ha desarrollado con la idea de permitir a los diseñadores obtener una idea clara y concisa del comportamiento de los lubricantes ante la variación de los parámetros más importantes que tienen lugar durante la lubricación.

 En este software, creado mediante el lenguaje de programación MATLABTM, se permite al usuario la selección de una variedad de elementos mecánicos sobre los que simular la lubricación, siendo estos rodamientos (de bolas, cilíndricos y semiesféricos), engranajes (de dientes rectos, helicoidales, cónicos y planetarios simples) y mecanismos leva-seguidor (de seguidor plano o de rodillo). El usuario también tiene la opción de introducir manualmente el área de contacto, en el caso de conocerla.

 Se ha incorporado una gran base de datos de lubricantes minerales y sintéticos de diferentes marcas comerciales (Repsol, Shell, Cepsa, bp y Exxon Mobil) con el fin de facilitar al usuario la selección y comparación de diferentes productos. También se permite la introducción manual de las características del lubricante en el caso de que no se incluya en la base de datos.

 Otros datos, tales como la rugosidad superficial de los elementos mecánicos, los materiales de estos, o las velocidades y cargas que soportan los mecanismos, serán necesarios para realizar una correcta simulación.

 El software ejecutará una simulación obteniendo el espesor de la capa de lubricante para los parámetros indicados. Comparando estos espesores con las rugosidades superficiales, el software podrá determinar el tipo de régimen de lubricación que estará teniendo lugar (límite, mixto o elastohidrodinámico) e informar al usuario de ello.
 El usuario también podrá elegir entre varias representaciones gráficas para observar el cambio del espesor en la capa de lubricante en  función de las variaciones de los tres parámetros que más influencia tendrán en la lubricación: La velocidad relativa, la carga soportada y la temperatura. Para ello el usuario podrá utilizar tanto gráficas en 2D (relacionando uno de estos parámetros con el espesor) como gráficas en 3D (relacionando dos de los parámetros con el espesor).
 

 Para un análisis posterior de los resultados el usuario también tendrá la opción de guardar como una imagen las gráficas generadas o exportar los datos de la simulación a un documento Excel.
 Este es un software de uso sencillo que permite la obtención de gran cantidad de datos sobre la lubricación y da un potencial ahorro de tiempo y dinero para el usuario.
 
 

Saturday, 6 July 2013

Risk Based Maintenance: The latest maintenance strategy

 We can consider Risk-Based Maintenance (RBM) as an evolution of RCM (Reliability-Centered Maintenance), RCM is based in the equipment condition and the importance of equipment to system, but it is limited because it doesnt solve the quantification of failures. (1)

 Due this ability to quantify problems join its simplicity to implant, RBM has been successfully applied in Oil & Gas, petrochemical plants, power generation y distribution networks, etc... And it achieves important savings.

 API RP 580 Standard defines risk as the combination of the probability of an event occurring during a time period and the consequences associated with the event. In mathematical terms:

                                       Risk = Probability X Consequence

 We can obtain and economic value (if the consequence is valued) or a classification by a risk matrix.

 API consider the Risk-Based Inspections (RBI) as the next generation of inspection interval settings, focuses attention specifically on the equipment and associated deterioration mechanisms representing the most risk to the facility. It recognizes the ultimate goal of inspection is the safety and reliability of facilities. (2)

 F.I. Khan and M.M. Haddara propose an RBM methodology (3) that is broken down into three modules:

  •  Module I: Risk estimation, including a failure scenario development, a consequence assessment and a probability failure analysis, it can be conducted using Fault Tree Analysis (FTA).
  • Module II: Risk Evaluation, setting up acceptance criteria and applying these criteria to the estimated risk for each unit in the system.
  • Module III: Maintenance planning, optimizing the maintenance plan to reduce the probability of failure, reducing the total risk level of the system.

 In this module, we can use the measures to control and mitigate risks propossed in the ISO 17776 Standard, as prevention, la detection and control. (4)

 Norsok Standard Z-008 (5) not only does RBM propose to design and update maintenance programs but proposes it to prioritizing maintenance activities and evaluates spare parts quantity and location.

 We find in RBM a more simple methodology than RCM, it also requires an initial reliability study but include an economic risk assessment, so it allows doing financial analysis and makes easier to choose timed based and on-condition tasks as well as complex actions as spare parts quantity and location, re-design of equipment or changes in the process.

  
(1)  Zhao M-X., Su J., Liu S-G. Risk assessment based maintenance management for distribution network. Journal of international council on electrical engineering Vol.2, No 1, pp. 84-89, 2012.
(2)  Risk-based Inspection. API Recommended Practice 580. 1st Edition, May 2002.
(3)  Khan F.I., Haddara M.M. Risk-based maintenance (RBM): A quantitative approach for maintenance/inspection scheduling and planning. Journal of loss prevention in the process industries 16 (2003) 561-573.
(4)  ISO 17776:2000 Petroleum and natural gas industries- Offshore production installations - Guidelines on tools and techniques for hazard identification and risk assessment. 1st Edition 2000-10-15.

(5)  Norsok Standard Z-008 Edition 3, June 2011. Risk based maintenance and consequence classification.

Monday, 1 July 2013

Mantenimiento Basado en Riesgo: La más moderna estrategia de mantenimiento.


  Podemos considerar al Mantenimiento Basado en Riesgo (RBM) como la evolución del RCM (Mantenimiento Basado en la Fiabilidad), RCM está basado en el estado del equipo y en su importancia dentro del sistema, pero está limitado por la dificultad para cuantificar los problemas que el equipo presenta. (1)

 Y es precisamente la capacidad de cuantificar los problemas, además de su mayor sencillez de aplicación, lo que hace que RBM se aplique con éxito en el sector del Oil&Gas, plantas petroquímicas, generación y distribución de energía, etc... consiguiendo ahorros muy importantes.

 La norma API RP 580 define el riesgo como la combinación de la probabilidad de que se produzca un suceso durante un determinado periodo de tiempo y las consecuencias de que ese suceso ocurra. En términos matemáticos lo define como:

                                        Riesgo = Probabilidad X Consecuencia

 Pudiendo obtener un valor económico (si la consecuencia está valorada económicamente) o una clasificación utilizando una matriz de riesgos.
 API considera a las Inspecciones Basadas en Riesgo (RBI) como un método de nueva generación para calcular los periodos entre inspecciones, al fijar la atención en los equipos y los mecanismos de deterioro que tienen mayor riesgo para una instalación. Considerando que el principal objetivo de las inspecciones es la seguridad y la fiabilidad. (2)

 F.I. Khan y M.M. Haddara proponen una metodología para la realización de planes de Mantenimiento Basado en Riesgo (RBM) (3) que se compone de tres fases:

- Fase I: Estimación del riesgo, teniendo en cuenta una estimación de las consecuencias de cada fallo y la probabilidad de que ese fallo se produzca, que incluye la utilización de Análisis de Árbol de Fallos (FTA).

Fase II: Evaluación del riesgo, definiendo un nivel de riesgo aceptable y comparando los riesgos estimados de cada fallo con ese valor.

Fase III: Planificación del mantenimiento, optimizando el plan de mantenimiento para reducir la probabilidad de los fallos que sobrepasan el criterio de aceptación, reduciendo así su riesgo.

 En esta última fase podemos utilizar las propuestas de medidas de reducción de riesgos que propone la norma ISO 17776, entre las que destacan la prevención, la detección y el control. (4)

 La norma Norsok Standard Z-008 (5) no solo propone la utilización de Mantenimiento Basado en Riesgo (RBM) para diseñar y actualizar los programas de mantenimiento, sino que además propone su utilización para priorizar las actividades de mantenimiento y calcular las cantidades de repuestos y su localización.

 Encontramos por lo tanto en RBM una metodología más sencilla que RCM, que requiere también de un estudio previo de fiabilidad pero que incluye una valoración económica del riesgo, lo que permite realizar análisis financieros y facilita la elección de tareas preventivas y predictivas así como la toma de decisiones sobre acciones más complejas, como pueden ser la cantidad de repuestos necesarios, su localización, la realización de cambios en el diseño de los equipos o cambios en los procedimientos de trabajo.   


(1)  Zhao M-X., Su J., Liu S-G. Risk assessment based maintenance management for distribution network. Journal of international council on electrical engineering Vol.2, No 1, pp. 84-89, 2012.

(2)  Risk-based Inspection. API Recommended Practice 580. 1st Edition, May 2002.

(3)  Khan F.I., Haddara M.M. Risk-based maintenance (RBM): A quantitative approach for maintenance/inspection scheduling and planning. Journal of loss prevention in the process industries 16 (2003) 561-573.

(4) ISO 17776:2000 Petroleum and natural gas industries- Offshore production installations - Guidelines on tools and techniques for hazard identification and risk assessment. 1st Edition 2000-10-15.

(5)  Norsok Standard Z-008 Edition 3, June 2011. Risk based maintenance and consequence classification.

Monday, 3 June 2013

Technical Concepts of High Speed Oil Flushing. Differences with Filtration

 Dear sirs, find attached this post by Ing. Cristián Schimd, Electromechanical Engineer UTN Facultad Regional Mendoza and Development Manager of Grupo Sicelub Lubritech. you can know more about his company in www.sicelub.com


TECHNICAL CONCEPTS OF HIGH SPEED OIL FLUSHING. DIFFERENCES WITH FILTRATION

INTRODUCTION
 When one talks about the term Contamination Control in Industry, it is frequent to hear the word Flushing as one of the necessary measures to reduce the particle content in a lubrication or hydraulic system.
 In this paper, we intend to correctly define this term and to clarify the main differences with the term Filtration.
 It is vital that all the parts involved use the same terminology to work properly and professionally in the field of lubrication engineering and its practical uses in the industry.
Key words: Flushing, Reynold, Filtration.

DEVELOPMENT
 There are various ways to define a Flushing procedure; here we’ll quote the one that appears in ASTM D-6439-05 Standard [1]. It reads: circulation of liquid through the lubrication system or a component, when the turbine is not operating, to remove contaminant.
 It is important to highlight that the procedure is pointed out as the right one to remove contaminants from the mechanical equipment, its lubrication system or components. It is not focused on cleaning or filtering the oil, rather it is focused on cleaning the system, the mechanical components and pipes.   
 Several aspects have to be considered to achieve a successful Flushing procedure, that is, a procedure that removes the greatest amount of dirt from the system and in the shortest time possible. The most important ones are:
1- It has to be performed before the first start-up of the equipment (Commissioning), or in scheduled shutdowns (major outages).
2- Achieve a turbulent flow regime. Regularly, the Reynolds number should be greater than 4,000 to ensure that the different fluid layers inside the pipe have a better action over the internal walls of the pipe.

3- Use of the high efficiency filter media. Filter media with a βx factor higher than 200 must be used to ensure that the particles removed are extracted from the system.
4- Use of in-situ oil analyzers. It’s very important to have analysis equipment of ISO 4406 code (Particle Content) to perform a follow-up of the procedure and determine when the cleaning has ended.
 The above mentioned will give Reliability and Availability to the System, allowing to obtain a start-up without shocks and the optimization during the times of start-up and scheduled shutdowns, concepts which are more and more demanded to increase the Annual Production.
 To achieve a turbulent regime, it is necessary to know the diameters of the tube which will be intervened, and to make the following equation:
                                   Re = 21.200.Q / (V.d)  Q [lts/min]
                                   V [Cts], at the operating temperature
                                   d [mm]
 In practice, to increase the Re, one can choose to use external high-flow pumping equipment, a fluid of lower viscosity for the work, or simply to hit it up to reduce its viscosity. Generally, one chooses a combination of all the previous options. 
 Thus, for example, to perform a Flushing in an 8” pipe (203.2 mm), using ISO VG 32 oil, and taking into account an operating temperature of 40°C, the minimal necessary flow to fulfill the requirements of the Standard would be 1,230 lts/min.  
 In relation to high efficiency filters, it is essential to use a set of external filter media with a βx > 200 factor, remembering that this βx factor indicates how efficient the filter media is in the removal of particles. In this case βx > 200 means that the efficiency of removal will be higher than 99.5% in particles greater than x microns.
 These filters should be mounted in the complete flow of circulation. This is why, frequently, large surfaces are required since we are working with high flows.
 Going back to the main point of our paper, we will indicate now the differences between the procedure we have just defined and the one which tends to be wrongfully used in the industry under the name of Flushing.
 When the word Flushing is mentioned, one is many times simply referring to an external kidney loop filtration of the oil tank or the system reservoir. Even if we use high efficiency filter media, the reader will easily understand that the reach of this procedure is much more limited than that of the Flushing defined by the Standard. In this case, we simply intend to filter the oil, take it into the right ISO Code and not perform a cleaning in the system, which is the main goal of the concept Flushing previously defined.
 This filtration procedure may be carried out with the system in operation using much lower flows, since the use of higher flows here would generate turbulences inside the reservoir which may affect the normal operation of the lubrication or control system. 
 It is normally advised to perform Flushing at the moment of the first start-up of the equipment and at every scheduled shutdown to maintain the system clean during the life span of the machine, thus, preventing the lube oil contamination. During the operation of the machine, and according to the results of the daily oil analysis, it may be necessary to connect an external filtration equipment to reduce the amount of particles present in the system.
 Combining, and not confusing, the Flushing and Filtration procedures during the life span of the equipment, one can achieve a longer duration of the mechanical components, and, therefore, a greater reliability of the equipment. Through the bearing life span calculation, or life extension tables for bearings, hydraulic systems, engines, gears and other mechanical elements, it is proven that the lower the contamination level, the longer the life span of these elements. [2]
 The following table summarizes the main aspects of both terms and their differences:

Filtration
Flushing
Goal / Target
Clean Oil
Clean System
When?
Machine Operation
Start-up or Scheduled Shutdown
Flows
Low
High (Re)
Filtration Efficiency
High
High
 In the following graphic, we can observe how the use of high efficiency filter media, instead of the filter media of the equipment, ensure a shorter duration in the flushing process. 
 On the other hand, the table below shows the main differences between a conventional flushing and one carried out under the most demanding premises of ASTM D-6439 Standard. It summarizes the main points where advantages in reliability and service performance time can be achieved.






CONCLUSIONS
 To achieve a commissioning or a start-up after a scheduled shutdown, it is essential to carry out a flushing procedure according to the standards, thus ensuring the removal of all the dirt from the system and in the shortest time possible to improve the production time of the intervened system.
 Likewise, during the operation of the equipment, special attention must be paid to the presence of contaminants in the system with the aim of removing them, and, in this way, guarantee the longest useful life of the mechanical elements. In this case, the external filtration resource must always be taken into account.
 It is extremely important to be acquainted with both procedures and apply them in the appropriate times and ways to obtain the best results from a technical and economical point of view.  

REFERENCES
[1] ASTM D-6439-05 “Standard Guide for Cleaning, Flushing, and Purification of Steam, Gas and Hydroelectric Turbine Lubrication System”
[2] Lubricación por Niebla de Aceite y su impacto positivo sobre la vida de los rodamientos [Oil mist lubrication and its positive impact on the lifespan of the bearings]. Work presented in the I Taller Argentino de Tribología [I Argentinean Workshop in Tribology], May 2012, Bahía Blanca.


Sunday, 19 May 2013

RCA: Maintenance isn't just repair.


 Some months ago I did a Maintenance assessment in a facility, the Maintenance team was very efficient, with strong skill, and they repaired quickly any breakdown.

 One day an auxiliary water pump failed, due the maintenance team had the training and instructions needed and the tools and spare parts were in the warehouse, the breakdown was repaired in less than two hours. An excellent job, they said.
  
 But I didn’t agree with them because I thought the job was uncompleted; to repair the pump as soon as possible is important but, Will the pump become fail again?

 Not only must the maintenance team repair the machines, but it has to look into the breakdown causes to avoid the failure happens again.

 So, I recommended them to implant a RCA (Root Cause Analysis) and train the maintenance team to performance it.

 RCA is a logical sequence of steps that allows isolating the facts surrounding an event of failure and determines the best course of action that will resolve the event and ensure that it isn’t repeated.


 A RCA can be as simple as a 5 Why’s process, or can be a more complex one to include questions as What happened?, Where?, When?, What changed?, Who was involved?, Why did it happen? and, mainly, What is the impact? The process must go with some photos of the breakdown, the broken parts and samples of lubricants and coolants.

 This process will spend only some minutes of the maintenance time, so it won’t loss its efficiency, but will allow to make a small investigation to find answers to the two main questions: Will it happen again? and How can recurrence be prevented?  

 Including the answer to this last question in our maintenance program we will avoid downtimes in the future.