Articles About failure
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When a power transmission component fails, it can adversely affect the performance of the assembly, often making the machine inoperable. Such failures can not only harm the reputation of the manufacturer, but can lead to litigation, recalls and delays in delivery due to quality concerns. Some failures can even result in bodily injury or death. Understanding why a part failed is critical to preventing similar failures from reoccurring. In the study of a failed part, the analyst must consider a broad range of possibilities for the failure. Although some failures can be attributed to a single primary cause, it is common for multiple secondary factors to contribute. The failure analyst must evaluate all of the evidence available to prepare a hypothesis about the causes of failure.
A bearing service life prediction methodology and tutorial indexed to eight probable causes for bearing failure and removal are presented - including fatigue. Bearing life is probabilistic and not deterministic. Bearing manufacturers' catalogue (L10) bearing life is based on rolling-element fatigue failure, at which time 90% of a population of bearings can be reasonably expected to survive, and 10% to fail by fatigue. However, approximately 95% of all bearings are removed for cause before reaching their L10 life. A bearing failure can be defined as when the bearing is no longer fit for its intended purpose. For a single bearing, you can only predict the probability of a failure occurring at a designated time - but not the actual time to failure.
Iâ™m building a custom gearbox with 7075 T-6 spur gears, and Iâ™m concerned that aluminum flakes will enter the races on the roller bearings (SKF 2307) and cause premature failure. So my question is â” should I place an oil seal on the shaft first to protect the bearing â” or is this an unfounded concern and I should mount the seal in the typical manner outside the bearing? Or both? Or go with a sealed bearing? Iâ™m confused and could use your expertise, please.
Power density is a key factor in gear design. Increasing the power density enables engineers to use smaller gears for their applications which lead to smaller and lighter gear boxes. The benefit for example for the automotive industry is less moving load in the vehicles and therefor a reduction of fuel consumption and subsequently a reduction of CO2 emission. The limiting factor for the increase in power density of gears is the material strength in regard to the critical failure mode.
A critical problem for wind turbine gearboxes is failure of rolling element bearings where axial cracks form on the inner rings. This article presents field experience from operating wind turbines that compares the performance of through-hardened and carburized materials. It reveals that through-hardened bearings develop WEA/WECs and fail with axial cracks, whereas carburized bearings do not. The field experience further shows that a carburized bearing with a core having low carbon content, high nickel content, greater compressive residual stresses, and a higher amount of retained austenite provides higher fracture resistance and makes carburized bearings more durable than through-hardened bearings in the wind turbine environment.
Guy Gendron, certified bearing specialist and technical sales representative at Timken Canada L.P. explains how he used his bearing expertise to increase a customerâ™s productivity.
Dovetails, gears and splines have been widely used in aero engines where fretting is an important failure mode due to loading variation and vibration during extended service. Failure caused by fretting fatigue becomes a prominent issue when service time continues beyond 4,000 hours. In some cases, microslip at the edge of a contact zone can reduce the life by as much as 40â“60 percent.
All major manufacturers of 3-phase AC induction motors offer "inverter-duty" or "inverter-readyâ models, but while these motors have inverter-rated insulation to protect the windings, the bearings--their most vulnerable parts--are too often ignored.
The use of motor current signature analysis (MCSA) for motor fault detection â” such as a broken rotor bar â” is now well established. However, detection of mechanical faults related to the driven system remains a more challenging task. Recently there has been a growing interest for detection of gear faults by MCSA. Advantages and drawbacks of these MCSA-type techniques are presented and discussed on a few industrial cases.
In 1991, Needelman and Zaretsky presented a set of empirically derived equations for bearing fatigue life (adjustment) factors (LFs) as a function of oil filter ratings.
SKF Product Investigation Center Troubleshoots Critical Rotating Equipment Applications with Analysis, Research and Testing Procedures.
Mean Time Between Failures is a very frequent and broadly used reliability measure of components, systems and devices used mainly in conjunction with electrical and electronic equipment.
Michael Odom, certified bearing specialist and customer sales and service at Applied Industrial Technologies, explains how he used his bearing expertise to save a customer both money and downtime.
Until now the estimation of rolling bearing life has been based on engineering models that consider an equivalent stress, originated beneath the contact surface, that is applied to the stressed volume of the rolling contact. Through the years, fatigue surfaceâ“originated failures, resulting from reduced lubrication or contamination, have been incorporated into the estimation of the bearing life by applying a penalty to the overall equivalent stress of the rolling contact. Due to this simplification, the accounting of some specific failure modes originated directly at the surface of the rolling contact can be challenging. In the present article, this issue is addressed by developing a general approach for rolling contact life in which the surfaceoriginated damage is explicitly formulated into the basic fatigue equations of the rolling contact. This is achieved by introducing a function to describe surface-originated failures and coupling it with the traditional, subsurface-originated fatigue risk of the rolling contact. The article presents the fundamental theory of the new model and its general behavior. The ability of the present general method to provide an account for the surfaceâ“subsurface competing fatigue mechanisms taking place in rolling bearings is discussed with reference to endurance testing data.
Th e primary sources of bearing failure are lack of lubrication and contaminant ingress. Industrial sealing devices are the primary protection against bearing failure. When the sealing device fails, bearing failure is imminent. Th erefore, extending the life of sealing devices extends bearing life and in turn improves equipment uptime.
Wind turbine gearboxes are subjected to a wide variety of operating conditions, some of which may push the bearings beyond their limits. Damage may be done to the bearings, resulting in a specific premature failure mode known as white etching cracks (WEC), sometimes called brittle, short-life, early, abnormal or white structured flaking (WSF). Measures to make the bearings more robust in these operating conditions are discussed in this article.
When City Scrap & Salvage experienced a catastrophic failure of the driveline between the motor and rotor of its automotive shredder, the company called on Voith Turbo for a potential manufacturing solution.
If youâ™re replacing your belts more than once per year, itâ™s time to analyze your drive. From belt crimping damage to high belt installation tension to sprocket misalignment and adverse environmental conditions, this guide walks you through how to identify the reasons behind premature failure and makes recommendations on corrective and preventive measures.
When software goes bad, what do we call it? System failure? Human failure? A virus? A number of words will work. How about this? Glitch. It has that onomatopoeic quality that fairly screams, Downtime! And with good reason -- software-generated miscalculations can have very expensive -- if not perilous -- repercussions.
A Chicago-area bakery was replacing the tray support bearings in its ovens on a reactionary basis. Their weekly inspection cycle was resulting in two mechanics spending an average of 20 labor hours per week to replace failed bearings. The premature bearing failures were caused by a combination of the high heat and humidity in the ovens, resulting in lubrication failure and contamination. When BDI was asked to recommend a solution, the bakery was averaging one month of bearing life in this application.
Experienced operators can often tell if a machine is not working properly, on the basis that it does not â˜sound right.â™ The same principle can be applied â” using modern electronics â” to identify the exact cause of the problem. Sensitive accelerometers can detect and analyze the vibrations from industrial equipment, highlighting problems such as misalignment or bearing imbalance. The technique is known as vibration analysis. It can identify bearing failure in the very early stages, when there is a microscopic defect on the raceway, for example. The problem is that the identifying signal is usually drowned out in all the other noise emanating from the machine.
Health monitoring or condition monitoring has been used for many years on machines and in plants where the cost of an outage is high. It allows failures to be anticipated and maintenance or repairs to be scheduled for the least loss of production, as well as avoiding unnecessary periodic maintenance.
Slow speed operation of fan systems within the air handling industry is generally performed due to two reasons: a coast down operation is required for hot (induced draft) fans to cool down before shutdown (often by using a turning gear), and operational efficiency improvements can be achieved during non-peak periods by slow speed operation using a VFD. In either case, when these fans are supported by hydrodynamic bearings, it is the oil film thickness developed from the bearing-shaft interaction that limits the minimum speed that can be maintained without causing premature wear and bearing failure. This paper will present a brief overview of lubrication theory and critical design parameters to achieve slow speed operation.
When it comes to selecting a connecting element between a drive motor and a pump unit, engineers most often choose an elastomeric coupling because of its failure protection and its vibration damping capabilities. Elastomeric couplings, traditionally manufactured with metallic hubs, feature a rugged and robust design noted for its simplicity.
Modern drivetrains with voltage-source inverters not only offer advantages like, for example, variable speed operation, increased efficiency and higher dynamics, but also an increase in failures caused by induced parasitic currents.
Student research project at Purdue could revolutionize predictive bearing failure.
Now more than ever, manufacturing companies are examining what steps need to be taken to ensure improvements to machine reliability by predicting system failures and minimizing downtime.
The repair-versus-replace decision is quite complicated, depending upon variables such as rewind cost, severity of the failure, replacement motor purchase price and other factors.
In an industrial application, equipment uptime is vital for on-time performance and profitability. The rotating members of industrial machines are subject to the highest degree of wear and are more susceptible to failure than non-moving parts. Bearing surfaces are the most critical and often the most expensive portion of the rotary assembly; it is imperative to protect these components. The primary protector of these components is the industrial seal.
A new preventive maintenance program at a leading New England Ivy League university demonstrates how the push for more sustainable "green" building management has led to a growing awareness of a chronic, widespread problem with HVAC motors—electrical bearing damage and failure.
Even when the critical components of industrial power transmission gear drive systems are properly designed, specified and manufactured consistent with application requirements, performance problems can develop over time and failure may follow.
Energy costs and downtime can be greatly reduced by instituting a motor management plan. Part II of this three-part series specifically addresses the establishment of a motor failure policy and the development of purchasing specifications. Part I addressed the general aspects of a motor management plan, including the first steps of creating a motor inventory and guidelines for motor repair and replacement. Part III will examine motor repair specifications as well as preventive and predictive maintenance.
Reducing losses and increasing profits by instituting a motor management plan is what this series of articles is all about. Here in Part I, we discuss how to create a motor inventory and establish repair-or-replace motor guidelines. Subsequent topics in this three-part series will address (Part II) motor failure policies and purchasing specifications, and (Part III) repair specifications and preventive and predictive maintenance, respectively.
Failure to specify the proper motor for use in a hazardous location can have serious consequences - lost production, extensive property damage, and even loss of human life. Selection of the proper motor requires an understanding of Underwriters Laboratories' (UL) and National Electrical Code (NEC) class, group and division designations and the T code letters.
News Items About failure
1 ATC Diversified Electronics Introduces Single-Channel Seal Failure Alarm Module (November 13, 2014)
ATC Diversified Electronics, a division of Marsh Bellofram Corporation, has introduced the Model SPM 120AAA single-channel shaft sea...
2 Hansford Sensors Publishes White Paper on Early Bearing Failure Detection (January 17, 2017)
Hansford Sensors, a manufacturer of vibration monitoring equipment, has published a new white paper that reveals how to use envelope sign...
3 Napoleon Engineering Services Offers Expedited Bearing Failure Analysis (April 10, 2020)
Global reliance on essential businesses is extremely high during this time of crisis. Companies need to maintain or even increase product...