Imagine a world in which industries like the software development, aerospace, automotive, chemical, and nuclear energy sectors can foresee and prevent safety incidents by addressing reliability. This proactive strategy is possible because of fault tree analysis (FTA). FTA was created in 1962 at Bell Laboratories by H. Watson and A. Mearns for the Air Force, and it has since been adopted by major corporations like Boeing.

In this blog post, we’ll delve into the world of fault tree analysis and examine its various types, symbols, and methodologies. We’ll also highlight a few beneficial software programs that can help you succeed. But first, let’s understand what FTA is all about and how it can help identify the root causes of system-level failures.

What Is Fault Tree Analysis (FTA)?

Fault tree analysis is a handy tool that helps us delve into the reasons behind system failures. It takes a graphical form and employs Boolean logic to combine various lower-level events. Think of it as a step-by-step approach that allows us to pinpoint the failures at the component level (basic events) that ultimately lead to system-level failures (top events).

When we conduct a fault tree analysis, we work with two main elements: “events” and “logic gates.” These elements are interconnected to help us identify the root cause of the undesired top event.

Compared to another analysis method called failure mode and effects analysis (FMEA), fault tree analysis is generally considered more straightforward. That’s because FTA focuses specifically on all possible system failures related to the undesired top event. In contrast, FMEA explores all potential system failure modes, regardless of their severity.

Which Industries Use FTA?

Generally speaking, fault tree analysis assists in identifying critical areas of concern for new workflows, products, and services as well as failures that need to be prevented in the future. To analyze safety and reduce risks, these industries are currently using FTA:

  1. Defense, aerospace, and aviation operations
  2. Power generation and system security
  3. Cybersecurity System Analysis
  4. Chemicals
  5. Pharmaceuticals and Healthcare
  6. Environmental research and disaster management

Observe a pattern here? If something goes wrong, these industries could have a big effect on people’s lives. A plane going down or a medical device not functioning properly increases the likelihood of fatalities or other tragic events. These sectors rely on FTA to safeguard these high-risk activities.


When to Use Fault Tree Analysis

Fault tree analysis is a useful technique that may be used throughout the system’s design phase or even while it is in use to analyze probable flaws in a system. The major goal of this study is to locate any areas of vulnerability in the subsystems and components that have a high likelihood of failing or causing a serious incident before such occurrences take place.

To improve its efficacy, this study can be carried out either alone or in conjunction with failure mode and effects analysis. We use fault tree analysis in order to proactively foresee probable failures and take preventive measures, hence reducing the risks related to system malfunctions.

How is Fault Tree Analysis Performed?

FTA utilizes a diagram known as a fault tree analysis diagram to visually depict various events or circumstances that could potentially result in an unfavorable outcome, such as the failure of equipment. The FTA process encompasses three steps:

  1. Development of a fault tree diagram.
  2. Identification of failure events, triggering events, and contributing factors based on the diagram.
  3. Evaluation of the relationships between failures and initiating events (or contributing factors).

In fault tree diagrams, the symbols employed are referred to as events, conditions, or states. These entities can occur at any given time during the operation of a system. Connecting lines illustrate the potential progression from one symbol to another, ultimately leading to an undesired event (referred to as a fault) at the end of the line. These faults represent instances of malfunctions or anomalies within the system.

What are Symbols Used in FTA?

In fault tree diagrams, there are two categories of symbols: event symbols and gate symbols.

Event Symbols

  • Top Event (TE): This event is located at the top of the fault tree and initiates the disquisition into the system failure. It has a single input but no relative labors since it represents the starting point of the failure.
  • Intermediate Events (IE): These events are caused by one or further events and have both input and affair. Intermediate events can lead to further failures down the fault tree.
  • Basic Events (BE): These events are the root causes of the top event and are deposited at the bottom of the fault tree.
  • Underdeveloped Events (UE): These events warrant sufficient information and are placed as subtrees.
  • Transfer Events (TE): Transfer events do when a fault tree becomes too large to fit on a single runner. Larger corridors of the tree are hidden using a symbol and expanded in a separate tree. There are two types Transfer- eschewal events have a triangle with an affair on the right, and transfer- events have input on the top of the triangle.
  • Tentative Events (CE): These events act as conditions for a type of gate called an inhibit gate.
  • House Events (HE): House events are used to enable or disable events. However, the event won’t do, but if set to 1, If set to 0. House events allow inflexibility in including or banning the corridor of the fault tree.

Gate Symbols

  1. AND Gate: This gate is connected to affair events. The affair events only do if all the input events to the gate do contemporaneously.
  2. Priority AND Gate: This gate triggers if all the input events be in a specific order.
  3. OR Gate: This gate has one or further inputs, and an affair event occurs if one or further of the input events be.
  4. XOR Gate: This gate generates an affair if only one input event occurs.
  5. k/N or VOTING Gate: This gate visually resembles an OR gate. It has ‘N’ input events and one affair event ‘k.’ The affair event occurs when a specific number of input events do.
  6. INHIBIT Gate: This gate produces an affair event when all input and tentative events do.

By utilizing these symbols and following the steps of FTA, analysts can gain insights into the causes of system failures, leading to effective risk mitigation and system improvements.

Types of Fault Tree Analysis

The only method for examining system failures is not the traditional fault tree analysis. FTA has been extended in several ways to address the needs of various sectors and use cases. With the help of these extensions, features that are difficult to visualize using conventional fault trees can now be represented. Several notable instances include:

  1. Dynamic FTA: Dynamic fault trees (DFTs) incorporate complex behaviors and interactions of system components, going beyond conventional fault trees.
  2. Repairable Fault Trees (RFT): RFTs improve the FTA model by enabling the description of complex, interdependent system component repairs.
  3. Extended FTA: This extension allows for a more thorough analysis by taking into account random probabilities and multi-state components.
  4. Fuzzy FTA: Fuzzy Fault Tree Analysis incorporates the consideration of uncertain and hard-to-predict factors, such as weather conditions, using a sophisticated mathematical concept known as fuzzy set theory.
  5. State-event FTA: State-event Fault Tree Analysis (SEFT) is utilized to examine dynamic behaviors that cannot be effectively modelled by traditional fault trees.

Benefits of Fault Tree Analysis

  1. Visual Representation: Fault tree analysis presents a clear and logical visualization of the event’s causes, enabling teams to identify and address failures systematically.
  2. Identification of Critical Components: By examining the fault tree, one can easily pinpoint the key components associated with system failure, allowing for focused attention and preventive measures.
  3. Efficient Analysis: FTA offers an effective approach to evaluating complex systems, streamlining the process, and facilitating a comprehensive understanding of potential failure paths.
  4. Inclusion of Human Errors: Unlike some alternative analysis methods, fault tree analysis takes into account human errors, recognizing their role in system failures and helping to devise strategies for improvement.
  5. Action Prioritization: Fault tree analysis aids in prioritizing action items required to resolve the problem, enabling teams to allocate resources effectively and tackle critical issues promptly.
  6. Qualitative and Quantitative Analysis: Fault tree analysis provides both qualitative and quantitative insights, allowing for a comprehensive assessment of the system’s failure probabilities and potential impact.

Disadvantages of Fault Tree Analysis

  1. Complexity of Analysis: When working with big systems, fault tree analysis can be difficult since there are so many gates and events to take into account. The analysis process may be less effective as a result of this complexity.
  2. Single Top Event Focus: Its exclusive focus on analyzing only one top event is one of the main downsides. This limited viewpoint could miss connected failures or neglect future problems that might simultaneously develop from several sources.
  3. Hidden Common Cause Failures: Using fault tree analysis to detect common cause failures, where several components or events are impacted by a single underlying cause, can be difficult. These errors might not always be visible or simple to spot, which could result in insufficient analysis and the possible omission of important aspects.
  4. Limited Time and Delay Considerations: It might be challenging to include time-related considerations and delays in fault tree analyses. This restriction can make it difficult to accurately mimic real-world situations, particularly when examining systems where timing and delays are key factors in the occurrence or spread of problems.
  5. Expertise Dependency: To conduct accurate evaluations, one must have a solid grasp of the logical gates employed in fault tree analysis. Because it prevents broad adoption and raises the expense of applying this analysis approach, the reliance on knowledgeable, experienced persons could be a possible drawback.

Fault Tree Analysis vs FMEA

These procedures might appear to be very similar at first glance. Both of them consider failure. They offer various approaches to risk reduction and prevention. What is the difference between FTA and FMEA?

FTA starts with a failure event and works its way down, whereas an FMEA starts with all possible failure modes and works its way up.

You can think of FMEA and FTA as two methods that complement each other, approaching the same event from different perspectives and using different processes. Interestingly, these methods actually work well together and can be seen as a cooperative pair. When a more comprehensive analysis is needed, using them together can yield significant benefits. However, if you must choose only one of these methods, it’s important to carefully evaluate your company’s needs and existing problem-solving structures before making a decision.

Fault Tree Analysis vs Event Tree Analysis

Event tree analysis approaches a problem or subject completely differently than FMEA. An event tree analysis focuses on providing logical, clear solutions to specific concerns. Even though they both use “tree” thinking structures, the fault tree and event tree are extremely distinct from one another.

The most notable distinction between the two is that a fault tree may be applied across a wide range of businesses, whereas event tree analysis is often employed in finance, banking, and other specialized industries.

Use a CMMS with FTA

Organizations can cope with system and asset failures using fault tree analysis since it is simple, scalable, and long-lasting. It’s a potent tool that, when properly applied, can aid a company in minimizing its maintenance expenditures. However, in order for FTA to work well, it’s important for the organization to gather precise data and make informed predictions about the potential causes of failures. Achieving this goal requires the organization to allocate enough resources towards implementing FTA. Using a user-friendly computerized maintenance management system (CMMS) can greatly simplify the data collection process involved in fault tree analysis.

Ready to aid your FTA process with NEXGEN? Schedule a demo with us using the link below.