Accendo Reliability

Your Reliability Engineering Professional Development Site

Home » Blog

by 1 Comment

Kolmgorov-Smirnov Two-Sample Test for Censored Data

Kolmgorov-Smirnov Two-Sample Test for Censored Data

Submitted to ASQC Reliability Review, Nov. 1996

A client wanted to compare the Kaplan-Meier (nonparametric maximum likelihood) estimators of the reliabilities of the old and new products. That is, he wanted me to test reliability functions, Ho: R1(t)=R2(t) for all nonnegative t vs. Ha: R1(t)≠R2(t) for some nonnegative t.

Because I’m lazy and fixed in my ways and because I thought it would be easier to explain, I chose the Kolmgorov-Smirnov (K-S) test [Gnendenko]. It’s convenient, practically every statistics text has the tables, and I can program tables and the test statistic easily. The test uses the maximum absolute difference between the Kaplan-Meier estimates of the two reliability functions. Reject Ho if maximum absolute difference, Dmn=max|R1(t)-R2(t)| exceeds a critical value, where m and n are the two sample sizes.

[Read more…]

by 2 Comments

Inherent Reliability Explained

Inherent Reliability Explained

Why Inherent Reliability is About More Than Just How Long Equipment Lasts 🌟

In this video, filmed at the iconic Kukulcan Temple in Chichen Itza, Mexico, I explore one of the most important concepts in Reliability: Inherent Reliability. Inherent Reliability isn’t just about how long something will last without failing—it’s about how long it will last when we “feed” it with the right proactive maintenance and appropriate default strategies.

Just as the ancient Mayans offered blood sacrifices to feed their gods, we need to feed our equipment with the right maintenance tasks at the right intervals to keep it performing as needed. Reliability Centered Maintenance (RCM) helps us identify the precise tasks and timing to protect our assets, ensuring that we get the Reliability we need.

In this video, you’ll learn:

The true meaning of Inherent Reliability
How Reliability Centered Maintenance (RCM) helps define what failure means to you
The importance of performing the right maintenance tasks at the right intervals

Equip your team with the knowledge to “feed” your assets and achieve the Reliability you’re aiming for. Watch now to learn more!

[Read more…]

by Leave a Comment

Lifetime Evaluation vs. Measurement. Part 5 – Stone Soup

Lifetime Evaluation vs. Measurement. Part 5 – Stone Soup

We are well aware of cases when Accelerated Testing is successfully creating by statisticians, here I would like to propose an engineer’s approach.

We have created a new product, there is (is) an order for it (50 products at a price of $200). Can we start manufacturing and delivery? No, we can’t. We are stopped by significant warranty obligations and lack of confidence in the reliability of the product during the warranty period.

This is a typical task with uncertainty.

[Read more…]

by Leave a Comment

6: Design & Planning – Part 3: Design for Excellence (DfX)

6: Design & Planning – Part 3: Design for Excellence (DfX)

by Mike Freier

Design for Excellence (DfX) is a holistic approach to designing a hardware product that takes into account how the product is made at scale. In addition to understanding your manufacturing plan and target costs, there are six categories to consider: assembly, cost, manufacturing, test, service, and supply chain.

[Read more…]

by Leave a Comment

Sample Size During Feasibility/Prototyping

Sample Size During Feasibility/Prototyping

During the first prototype stage of product development, there is no one-size-fits-all answer for the right sample size. The appropriate sample size depends on various factors, including the objectives of your research, the nature of the prototype, the variability of the measurements, and the constraints of your project such as budget and timeline.

At the prototype stages of product development, especially for electromechanical devices, understanding the safety factor in your design is crucial. The safety factor, often referred to as the Factor of Safety (FoS), is a measure of the load-carrying capacity of a system beyond the expected or actual loads. Essentially, it indicates how much stronger the system is than it usually needs to be under normal conditions. A common approach to validate the safety factor in design, particularly for new and untested devices, is through step-stress accelerated life testing (SSALT). This method involves subjecting the prototype to increasing stress levels until failure occurs, providing insights into the product’s durability and reliability under various conditions. [Read more…]

by Leave a Comment

The Rule of 3 Significant Digits

The Rule of 3 Significant Digits

Two people have shaped how I guess an answer.

Their comments and guidance have tailored how to form a quick estimate, my ability to articulate a hunch and the effectiveness of those guesses.

You probably guess or make a rough estimate regularly. How good is your gut feel? Do you keep track and score yourself?

Making an estimate should be second nature for you. It’s not something to do in public, too often. The practice can aid you in numerous ways. [Read more…]

by Leave a Comment

How to Design Operational Excellence into Your Company the Plant Wellness Way

How to Design Operational Excellence into Your Company the Plant Wellness Way

ENSURING YOUR MANAGEMENT DESIGN-IN OPERATIONAL EXCELLENCE TO GUARANTEE THE LASTING SURVIVAL OF YOUR COMPANY IS WHY QUALITY GURU W. EDWARDS DEMING ASKED HIS FAMOUS “WHAT?” AND “HOW?” QUESTIONS.

—

Deming would expect that managers had a solid answer to the question: “If you want your company to reach Operational Excellence in the next five years, then explain to us all, EXACTLY HOW will you do it?”

[Read more…]

by Leave a Comment

Project Management Dashboards: Data, Decisions, & Horsesh*t

Project Management Dashboards: Data, Decisions, & Horsesh*t

Guest Post by Malcolm Peart (first posted on CERM ® RISK INSIGHTS – reposted here with permission)

A project controls colleague of mine recently wrote:

“Really, I never had to deal with delivery directors / managers who did not understand or appreciate the effort which goes behind a digital data fed dashboard”

Sarcasm, according to Oscar Wilde, may be the lowest from of wit but it’s the highest form of intelligence.  While being humorous at the expense of those who demand dashboards it’s a sad truth that most demanders have no idea as to the effort required in producing a dashboard.  For them dashboards can be instantly tailored to any whims or fancies at the flick of a switch or the stroke of a key on a keyboard. 

[Read more…]

by Leave a Comment

Reliability Growth: Crow AMSAA Model with Application Case Study

Reliability Growth: Crow AMSAA Model with Application Case Study

Dear All, we are happy to release our 76th video on Crow AMSAA Model for Reliability Growth. We recommend viewers to watch the following videos before watching this video for better experience:

(1) Homogeneous Poisson Process (HPP) and Nonhomogeneous Poisson Process (NHPP)

(2) Reliability Growth Concepts and Duane Model with Illustration

We welcome your feedback!

[Read more…]

by Leave a Comment

5 Key RCM Concepts

5 Key RCM Concepts

Why RCM is a Must for Every Reliability Professional 🛠️

In this video, I’m taking you to the foundation of our new metal building to show why learning Reliability Centered Maintenance (RCM) should be a must for every reliability professional—even if you never formally implement it. RCM creates the foundation for an effective Reliability Culture by teaching five core concepts that are essential for any team.

Here’s what you’ll learn:

Core Concept 1: How defining Functions establishes the reliability you need.
Core Concept 2: Why identifying Failure Modes correctly is crucial for managing failures.
Core Concept 3: How to choose proactive maintenance tasks that are technically feasible and worth doing.
Core Concept 4: Understanding the role of Protective Devices and Failure Finding tasks.
Core Concept 5: The power of multidisciplinary teams in RCM and why collaboration leads to stronger, more reliable outcomes.

Whether you fully implement RCM or simply learn its core concepts, understanding these fundamentals makes you a more effective reliability professional. So, are you ready to build your foundation?

[Read more…]

by 4 Comments

A Couple of Questions for You Concerning MTBF

A Couple of Questions for You Concerning MTBF

Do make compromises around gathering and analyzing data since you only need to report MTBF?

Do you use MTBF (exponential distribution) based test planning when you know the product has a non-constant hazard rate?

These questions came up this week via email looking for advice when directed to ignore the actual situation and just do what the customer wants.

I’m traveling this week, rather jet-lagged today, so going to keep this one short.

How would you answer these questions? What advice would you give someone using exponential based reporting, test planning, or data analysis approaches knowing the customer expects that process yet the data and your experience suggest you should use another method  (Weibull or MCF, for example)?

Please add you comments below and let’s prepare a list of what one should say or use to respond to such actions.

 

by Leave a Comment

Wear Out Prediction Model

Wear Out Prediction Model

In the realm of mechanical engineering the reliability and longevity of pumps are critical for numerous industrial applications. Predicting wear out of pumps can significantly enhance maintenance strategies, reduce downtime, and optimize operational efficiency. One effective approach to predicting wear out is by monitoring the revolutions per minute RPM of pumps over a large population in extended time periods.

This video delves into the methodology of creating a wear out prediction model.

[Read more…]

by Leave a Comment

Don’t Waste Your Time and Money with Condition Monitoring 

Don’t Waste Your Time and Money with Condition Monitoring 

Predictive Maintenance applies condition monitoring techniques to discover potential failures. While finding a problem before it becomes a failure is good, companies can end up with so much work that maintenance backlog skyrockets, maintenance costs blow-out and people burn-out. Understanding when a predictive maintenance strategy can cause uneconomic maintenance, or why condition monitoring can produce unending failures, is vital if you want reliable equipment with low maintenance cost.

[Read more…]