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Recently we hosted an exclusive webinar that explored advanced techniques for Reliability, Availability, and Maintainability (RAM) modeling. Attendees had the chance to go beyond the basics of RBD logic, Mean Time to Failure (MTTF), and Mean Time to Repair (MTTR) and dive into the powerful capabilities of simulation techniques using Availability Workbench.

What We Covered:

• Beyond the Basics: We discussed the limitations of simple metrics like MTTF and MTTR and how to tackle real-world challenges effectively.
• Monte Carlo Simulation: Attendees learned how this technique can predict system behavior under uncertainty and model complex scenarios with confidence.
• Real-World Applications: We demonstrated how to incorporate wear-out failures, maintenance schedules, and rotating equipment into RAM models.
• Optimization Strategies: The session showcased how advanced modeling can enhance both reliability and maintenance strategies.

Key Takeaways:

The webinar provided practical insights for engineers, analysts, and managers who:

• Want to build more sophisticated and accurate RAM models.
• Seek to optimize reliability and maintenance planning with data-driven approaches.
• Are new to Monte Carlo Simulation and curious about its applications in RAM modeling.

Looking Ahead:

If you missed the session, don’t worry! We’ll be sharing more opportunities to learn about advanced RAM modeling techniques in the near future. Stay tuned for updates and announcements.

Stay Connected:

To ensure you don’t miss future events, subscribe to our newsletter: Home Page - Isograph or follow us on: (30) PeakAvenue GmbH: Posts | LinkedIn .

The event was a success, and we’re excited to continue helping professionals unlock the full potential of RAM modeling with Availability Workbench.

Included is a list of questions and answers from this webinar:

what are the differences between MTTF and MTBF? i usually input MTBF for failure data.	MTTF (mean time to failure) is the average time between start up (or installation) of a new asset and the point of first failure. MTBF (mean time between failure) is the average time from one failure to the next. Strictly speaking, MTBF = MTTF + MTTR. MTTF and MTBF are often very similar as MTTF >> MTTR. This may be why the terms are sometimes used interchangeably.
how does the number of intervals work and what's its implication on the output result	The number of intervals has two functions. 1) It is the number of time increments in the profile plots. For example, if you set a lifetime of 10 years and 10 intervals, the program will plot system parameters like cost, downtime, etc, on a plot with 10, 1-year time intervals on the x axis. 2) It is the interval used when calculating net present value (NPV) and cost escalation. In the settings, you can specify a NPV yield % to be discounted from the system cost and an escalation % to be added to various other costs (e.g. labor, spares, etc). These % discounts/escalations will be applied per interval.
i was thinking, sometimes supplier only provided us lifetime for a product, can i treat it as MTTF and input to the RBD? or as what Jonathan mentioned, it's the same as MTBF in Isograph program?	It may be best to consult with the supplier about their exact meaning. Is it the recommended time to replace the component, or is it the average expected time of failure?
There was a possibility to "seed" the random number generator	You may set a random number seed. This acts as a trigger for the random number generator. It is an integer. The same sequence of "random" numbers will always be returned as long as the seed is not changed. This is important as it means that any change you observe in your results will be due to a change in your model, and not because of a different sequence of random numbers.
Isn't the tank just an additional cold standby redundancy with a very short life time?	Temporary backup may be modeled using a Buffer distribution. When defining a failure model, you may select Buffer as the failure distribution (same place where I selected Bi-Weibull). Now you will be able to set Time to Fill and Time to Empty. Placing the block in parallel with a pump block for example would provide back up for the TTE specified. There are also different regimes for how the buffer is refilled, e.g. only refill after pump is repaired, change refill rate based on capacity available, etc.
Would you say that AvSim is a combination of the module RCMCost and RBD?	In a sense, yes. The failure models are very similar to causes in RCMCost, and are simulated in the same way. Combining ideas like RBDs and rules allows us to model the dependency between failures in a way that is not possible in RCMCost.
1) How AVsim handles multiple products? (where there is equipment that handles fluid A or B in the same RBD).	In the Project Options there is a Products tab. Here you may define up to 4 different product streams. The program can then perform capacity analysis for all the products defined.
(2) Does the process relationship of fluid A with respect to fluid B have to be included, or does everything refer to 100% of each fluid separately?	Each fluid would be treated independently. For example, if a block can carry 50% or A but only 20% of B, the loss of that block (assuming no redundancy) would result in the loss of the specified amount of each product.
6 months maintenance then good as new, with a 6 months wear out, cancels out no?	It does! I chose a simple example to illustrate clearly the relationship between maintenance and wear out. Naturally it may not be so simple in the real world, especially when balancing costs and losses due to maintenance against those due to failure.
Does the equipment rotation rule take into account planned maintenance as well as component failures?	Yes, a PM would trigger rotation, but only if the PM causes the block to become non-operational. This is a setting in the properties of the task where you can tell the program if the asset needs to be shut down for maintenance or if it can remain operational during the task.
Have you also done the analysis with as good as old?	Yes. This results in a substantial increase in downtime. In fact the result is similar to the model without PM since the PM now has no impact on the condition of the system. (there is a slight difference owing to a change in sequence of events)
Is there a way to find the output results for a specific Phase only, and disregarding the downtime during the other Phases?	Phase results are limited to costs only. However, This could be achieved using the profile intervals discussed in an earlier answer. The program will store downtime for each interval, allowing you to output a custom report that omits the downtime from one or more intervals if you wish.
Could you explain a case for Availability vs. Production Capacity using AVsim? How can I activate it in my AVsim?	It would depend on what is required from the model. A straightforward system availability analysis would look only at downtime, i.e. only instances of a complete outage of the system would be considered. A capacity analysis would be useful where it is necessary to consider degradation of a system, i.e. failures that do not necessarily bring down the whole system, but impact its ability to operate at maximum production. To activate a capacity analysis, create a Consequence (Add >> Resource >> Consequence) and select the Loss of Capacity option in the properties dialog. Next, double click the system-level block in the project tree and select the new consequence from the Consequence drop-down box. Now, when you run the analysis, the results will include the average lifetime capacity. It will also be possible to produce a capacity profile plot report. Note that you can adjust the max capacity of each block by double clicking and selecting the Rules tab.
Is the integration with EAM tools already in place or are you planning to do that?	Integration is available for SAP and Maximo. These portals primarily work with the RCMCost module, as it can accept asset hierarchies of the kind stored in such tools. However, AvSim can still make use of other data downloaded from an EAM, such as spares, labor, work history and maintenance strategies. If you are a user of RCMCost as well, the asset hierarchy download from the EAM system could be converted to a simple RBD using an option in the Tools menu.
How can you control when a repair task is done after an inspection finds a failure? I have seen it be repaired based on when it would have failed but in the real world you would like to control when it is repaired.	At present there is no means to specify exactly when the preventative task would happen. The reason the secondary task is deferred until the point when the failure would have happened is that this allows the program to determine if there is enough time available to requisition the resources needed for the preventative task. Say, for example, the PM requires a spare, but it would take a week to get the spare and the failure is set to happen after 5 days, the program would advance the clock to the point of failure, find that the resources have not arrived and trigger a failure event instead.
How can we add the backup time of a tank by available liquid level (example 4 hours) in the event of a pump failure?	Please see previous answer describing Buffer models.
(a) ¿Cómo AVsim maneja varios productos? (ejemplo algunos equipos con fluido A y otros equipos con fluido B en el mismo RBD). / (b) ¿o es necesario adicionar la relación entre la capacidad máxima de los fluidos?	Please see previous answer regarding different product streams.
Please comment a case about Availability Vs. Production Availability using AVsim? Could you clarify if it is activated at Level 1 (more general) by adding a particular block or if a selection is activated at the Project Level of the options menu?	Please see previous answer regarding activating capacity analysis in AvSim.
How do we incorporate the Ramp Time into our model?	Ramp time may be added in the properties or each corrective and planned maintenance task. It is immediately below the Task Duration field in the Task Properties dialog.

If you have any questions, please feel free to contact me.

Best Regards, Jeremy

Maintenance is a critical aspect of ensuring operational reliability, but how often do we stop to consider if we’re overdoing it—or worse, not doing enough? Most organizations understand the importance of maintenance but lack the right tools to optimize it. The result? Suboptimal maintenance strategies that can cost millions in unnecessary expenses, equipment downtime, or even premature failures.

That’s where Isograph’s RCMCost software comes in. This powerful tool takes the guesswork out of maintenance planning and puts data-driven decisions at the forefront, helping organizations find the sweet spot between too little and too much maintenance.

Why Optimizing Maintenance Matters

Too much maintenance can be just as costly as too little. Many companies are making maintenance decisions based on intuition or overly conservative plans that don’t reflect real-world conditions. Over-maintaining assets can lead to wasted resources, while under-maintaining them can result in unexpected breakdowns and expensive repairs. The key is striking the perfect balance—something that Isograph’s RCMCost is designed to help you achieve.

What Isograph’s RCMCost Brings to the Table

RCMCost leverages a quantitative, verifiable approach to maintenance optimization. With this tool, companies can determine the optimal maintenance frequency for their assets, reducing costs while maintaining reliability. RCMCost doesn’t rely on guesswork; it uses real-world data, sophisticated simulation techniques, and a wealth of industry expertise to make informed recommendations.

Some key features of RCMCost include:

• Data-Driven Maintenance Decisions: RCMCost uses actual performance and failure data to generate insights.
• Integration with Leading Systems: The software seamlessly syncs with popular systems like SAP and Maximo, ensuring a smooth flow of information.
• Sophisticated Simulation Techniques: Model your assets under various maintenance scenarios to predict outcomes and costs with precision.

See RCMCost in Action

Want to see how RCMCost can save your organization time and money? Take a look at our recent webinar:

During this session, we showcase how RCMCost works and provide a live demonstration of how it calculates the optimal maintenance frequency for your assets. You’ll also see how easy it is to integrate with your existing systems, and how simulation techniques can transform raw data into savings.

Maintenance is essential, but doing it right is critical. By leveraging tools like Isograph’s RCMCost, your organization can reduce costs, increase reliability, and make better maintenance decisions based on real-world data—not just intuition. Sometimes the easiest way to make more money is to simply work smarter.

Have any question please contact me:

There’s always something new to learn by revisiting the fundamentals. While this schematic and fault tree logic may seem straightforward, watching someone else break down the logic can offer fresh insights. In this session, our Senior Technical Advisor, Dr. David Wiseman, will give you a glimpse into his approach to analyzing the logic in this simple schematic.

Webinar recap, we'll guide you through building a Functional Safety Model in FaultTree+. Using a generic IEC 61508 Safety Integrated System as an example, we'll demonstrate how to create and structure your model effectively, whether you are following IEC 61508, IEC 61511, ISO 26262, or ARP 4754.

Schematic Example:

This was one of our most popular webinars to date.

"The only bad question is the one left unasked."

We always encourage a safe environment where open communication and the idea that asking questions is key to learning and growth. The nice thing about the Q&A from this meeting is that some of the questions were answered by our technical staff and some of the questions were answered by users of our products.  I appreciate the involvement and participation of the users in this meeting!

Our next meeting on November 12 will introduce more advanced RAM modelling. RAM models can be quite simple, using only RBD logic, MTTF and MTTR data. But using Monte Carlo Simulation (MCS) opens up the possibility of modelling more complex behaviors, such as wear out, maintenance, rotation, etc.

Register here: HERE

List of Questions and Anwers from the meeting:

Question	Answer
Shouldn't the top event be "Block Valve FC1 and Block Valve FC2 fail to close when required"?	In a Fault Tree, the TOP gate represents the Hazard or system failure you wish to model. In this instance it is a dangerous failure of the high integrity pressure protection system (HIPPS). In a simple system like this, the failure of the valves to close would be the a cause of the problem, but does not describe the hazardous scenario. Furthermore, in a more complex system, this would be rto specific a description and would fail to account for other possible causes of the hazard.
Is the description within the top event too vague?	As above, it is important to have a description encompasses the hazardous scenario. Though there is an argument to me made that 'Dangerous failure of HIPPS' would be a better description, as the HIPPS could also fail in a safe state if the valves where to fail closed, or the sensors were to send a spurious high pressure signal!
valve x 'or' valve y fail instead of 'and'	In this system, the valves close to stop the flow. Only one valve is required for this function, meaning that a dangerous failure only occurs if both valves fail to close. Hence the use of an AND gate. Bear in mind that a fault tree deals in failure, not success - i.e. what combination of failures would lead to a failure.
it is only parallel for the "unwanted open" state. for "unwanted closed" it is actually series	The Special Function menu has a Convert Fault Trees to Dual Trees option. This reverses the logic. (e.g. AND becomes OR, etc)
Is variant management possible in RWB?	Yes, RWB Enterprise Version allows for version control and comparison.
Sir David, in the system, how would you model the potential interactions between them that could lead to a cascading failure? Is there a specific approach to address these risks in Isograph?	This is actually best modelled using a numerical method, such as Monte Carlo simulation. FTA uses probability calculations which do not account for dynamic behaviors (e.g. failure rate of A dependent on status of B). The next webinar will go into this in more detail.
Is the description within the top event too vague?	Please see 5.
Is it un/reasonable to have different events using different failure rate models?	It is perfectly reasonable - even common - to have different events use different models. This was only a simple example that used one model type.
Will that still result into a meaningful calculation?	Yes, the calculation would still be meaningful.
Can we configure configuration factor CMooN per IEC 61508?	I believe this is covered by the IEC 61508-6 beta factor calculation feature. It allows you to select the level of MooN voting and adjusts the beta factor accordingly. This feature is accessed via the CCF model properties dialog, by select the Apply IEC Model option.
What is Modularization>? How to select?	Modularization is the process by which the software solves the probability of each gate independently where possible, before using it in the calculation higher up the tree. This process is applied automatically by the program, and dramatically improves calculation efficiency and, for some very complex trees, improves accuracy as well. Note that modularization is only performed for gates with no dependencies. (e.g. no shared events, no CCF models, etc) Modularization may be turned on/off in the properties dialog of each gate.
Is Route 2H included for HFT?	Route 2H is not currently included. However, we have this logged as a likely update to a future version of the Fault Tree software.
Is it possible on the software to look at the calculations for the various individually calculated figures? this would allow problem solving should something not be as expected	Yes. It is possible to instruct the program to store results for any and all gates in the tree. This Retain Results option may be turned on for individual gates in the properties dialog, or globally via the Analysis menu. It is also possible to display results for individual events using the View options dialog. (View, Options menu option)
Are there are any plans to produce a monte-carlo based FT analysis and if not, why?	MCS-based FTA is possible in the AvSim module of Availability Workbench.
Thanks Rachel! Does this work like a standard RAM package would I.E. using block diagrams? Or can it run FTs dynamically, i.e. for 500 cycles using distributions as required?	AvSim will let you build either RBD or FT diagrams.
For more complex FT models, is it possible to get a Results Report (in Excel or similar format) with all Gates / Events Unavailability?	Yes. All results from both gates and events may be displayed in the form or a report and exported to CSV, which may then be opened in Excel.
Similarly, is it possible to get a Results Report (in Excel or similar format) with all combinations of cut-sets and associated unavailability?	There is a cut set report template provided with the software that will display all cut sets for a selected gate. While it is possible to show sets for all gates in one report, this would require a custom report template.
You might cover it later, but can the tool identify the optimum inspection interval to achieve a target HIPPS failure rate?	For this I recommend the Special Sensitivity analysis. I think I mentioned briefly but did not have time to show it in detail. This is a feature that allows you to iteratively change an event parameter, such as proof test interval, and see the impact on a top gate result parameter. This would help you to select an optimum interval.
For bigger FT models is it possible to export a FT model structure (to pdf or picture format) without using printscreen?	Yes, you can open the Diagram report and then print to PDF using the built in export functionality in the Reporting tool.
How do you quantify the degradation of materials in different conditions? For example, if a tube is exposed to salt water, the degradation of the tube is much higher compared to fresh water. Is there a way to incorporate this into a fault tree?	The Weibull failure model provides some scope for dealing with fatigue and wearout, as does the built in Markov analysis tool. (not covered in the presentation) Note that the FTA is still only performing a probability calculation, so would only use a mean or point probability for the wear out event. It cannot be modelled dynamically. For this you would need a numerical solution like Monte Carlo simulation.
can the library function be used in RBD as well?	Yes, the project library functionality is available in all modules of RWB. The parts libraries work with Prediction, FMECA, RBD and FTA.
i mean the library of data that we used in one project, not the generic data library	Please see above.
so data i used in FT, can also become library for RBD?	Yes, generic failure models created in FTA can be used in RBD and vice versa, including via a library.
Within RWB FT+ is there an option to model exponential distributions, if so how?	The Rate model (and related models, like MTTF and Rate-MTTR) follow an exponential distribution, i.e. probability has an exponential relationship to time.
What is the unavailability resolution (%) of availability workbench?	This will depend on the amount of statistics collected. The lifetime simulations you can perform, and the more failure events occur during an analysis, the lower the statistical error will be.
Can you import data/libraries from Availability Workbench directly into RWB, and vice versa?	Yes. Using 'File, Save as…' you can save an AWB project using the .awbx file format. This can then be opened in RWB using the Import AWB Project File option in the File menu. The reverse is also true. FTA and RBD data may be exchanged with AvSim, and FMECA data with RCMCost.
i am using your company workbench availability for RAM study, what is the difference between this one and that one?  are there any way to import  database from one to the other?	The primary difference is that AWB uses simulation to calculate results, making it ideal for RAM modelling, maintenance and spares optimization, and life cycle costs. RWB uses standard probabilistic methods for reliability analysis, making it well suited to functional safety analyses, amongst others. Regarding exchange of data between tools, please see above.
Will this webinar be made public?	Yes. A link to the YouTube video will be provided.

I look forward to any questions, comments or ideas you have for future meetings.

Best Regards,