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[+] Known bugs & solutions / workarounds

[+] General questions

[+] Modeling issues

[+] Requested / Planned new functionality (Contact feedback@exsilentia.com for status)

Questions and Answers

[+] Known bugs & solutions / workarounds

[+] General questions


The filesize of the exSILentia reports becomes rather large when I include all SIFs of my project. Can you optimize the reports?

The exSILentia reports are dynamically generated in RTF (Rich Text Format). Once you open the report in MSWord select "File" - "Save As" - "Word Document". Once you store the file in the "native" Word format its size will drop drastically (e.g. 80MB to 3MB).

Applies to: exSILentia (All versions)  Keywords: Reports

What can I do if we switch from IEC 61511 to IEC 61508 after many SIFs are entered? Is there any way to update these selections for all SIFs in a project?

exSILentia has a Parameter Update utility. This utility allows you to change some key parameters for all or a selected set of SIFs in a project.

Applies to: exSILentia (All versions)  Keywords: SILver, Change SIF parameter, 61508, 61511

What are the system requirements for exSILentia Standalone?

To use exSILentia your system should meet the following minimum requirements
• Microsoft® Windows 2000 or Windows XP (all service packs installed)
• Personal Computer with Pentium 700 MHz or higher processor
• 256 MB of RAM (512 MB recommended)
• 100 MB of free hard disk space
• CD-ROM drive
• Free USB port
• Microsoft® Internet Explorer 6.0 or later
• Minimum screen resolution of 1024 x 768

Applies to: exSILentia Standalone  Keywords: General, System Requirements

What are the system requirements for exSILentia Online?

User Minimum Requirements:
-Internet Explorer 5.5 with Javascript enabled
-screen resolution of 800x600

User Recommended:
-Internet Explorer 6.0 (or newer)
-screen resolution of 1024x768 or greater

Users must install the Citrix interface agent on his local machine. This may require administrator right access. Citrix ICA client v10 or later should be installed.

Applies to: exSILentia Online  Keywords: General, System Requirements

What are the system requirements for exSILentia Server?

exSILentia Server must be hosted on a Citrix presentation server. Whatever server can run Citrix presentation server 4.0 and up will be suitable to support exSILentia.

In addition Hard Drive Space of at least 1 Gigabytes is recommended

The user requirements are identical to the exSILentia online requirements.
User Minimum Requirements:
-Internet Explorer 5.5 with Javascript enabled
-screen resolution of 800x600

User Recommended:
-Internet Explorer 6.0 (or newer)
-screen resolution of 1024x768 or greater

Users must install the Citrix interface agent on his local machine. This may require administrator right access. Citrix ICA client v10 or later should be installed.

Applies to: exSILentia Server  Keywords: System Requirements

With the stand-alone version of exSILentia, how does the licensing work? I understand there is a USB key, but is it possible for several people in the same office to have the software installed on their individual PCs? We would only ever need one person at a time to use the software, so we would simply move the USB key around as required. Is this possible?

Indeed a USB key is needed for the stand-alone version of exSILentia. It is possible however to have the USB key in a server and the software installed on an unlimited number of PCs. When you startup the software, it will look for the USB key, first locally, then on the network. As soon as one user is connected to the key other users will not be able to startup the tool until the first user disconnects. Alternatively you can move the USB key around as you described, both solutions work.

Applies to: exSILentia Standalone  Keywords: USB, License

We already have done the SIL assessment (SIL selection) and the only thing we want to do is the reliability calculations (SIL verification). Is there a way to do just that without using all tools integrated in exSILentia?

When defining a project within exSILentia users can identify what sub-tools they want to include. If a project only warrants the use of SILver simply deselect the SILect and SIF SRS tool enable checkboxes.

Applies to: exSILentia (All versions)  Keywords: SILver, Existing SIL Assessment

With your exSilentia software, it is possible to consider high demand mode applications for a SIF? If yes how do I do this?

We have the option to consider high demand mode for a SIF.
To be more precise we allow you to specify either the demand interval on the SIF, in which case SILver determines the mode the application is in, or define low demand, high demand, or continuous demand.
You define the demand modes on the "Safety Intrumented Function" screen of SILver.

Applies to: exSILentia (All versions)  Keywords: SILver, High Demand, Demand Mode

What kind of sensor, electronics, actuator, etc. components are listed in the exida equipment database?

There is a wide variety of equipment available in the exida equipment database. Once you use the SILver tool, you will notice dropdown boxes. All equipment items will be accessible from these dropdown boxes. The equipment database has been published by exida as the Safety Equipment Reliability Handbook (SERH) showing all equipment items that are accessible from the tool, the book is over 500 pages, which will give an indication of the large amount of equipment items available.

Applies to: exSILentia (All versions)  Keywords: SILver, Equipment, SERH

With regards to your exSILentia on-line product tool and the built-in equipment reliability database, does the exSILentia database contain all the equipment included in the SERH and all subsequent updates? Can a user add and store their own equipment reliability data and make this accessable to other nominated users, i.e. an asset owner making relaiblity data available to consultants?

The equipment database included in the exSILentia SILver tool contains all the devices found in the Safety Equipment Reliability Handbook (SERH) and all updates. This insures that all SIFs you create will have the most up to date reliability data from exida.

A user can enter custom reliability data by using "MyOwn" devices. At the current time it is not possible to store this data for use in other functions or by other users in the Standalone and Online versions of exSILentia. The Server version of exSILentia can be purchased with the option to have a Custom Equipment Database. The Server version administrator will have the ability to specify additional devices. These devices will then become available for all users.

Note that exida would like to include any devices that you have reliabilty data for its equipment database, given the data passes our quality requirements.

Applies to: exSILentia (All versions)  Keywords: Equipment Data, MyOwn, SERH

Does the exSILentia software cover FMEA and FTA analysis?

the exSILentia tool will enable you to determine a required SIL for a Safety Instrumented Function and calculate the achieved SIL for that Safety Instrumented Function. The calculation of achieved SIL is driven by an equipment database containing failure rates for hundreds of products. In that the exSILentia tool incorporates FMEA techniques used to determine component failure rates and because of the SIF voting selections it incorporates FTA analysis.

Applies to: exSILentia (All versions)  Keywords: FMEA, FTA, SILver, SILect

We are interested in your exSILentia™ Stand Alone Program and would like to order the program soon. Prior to purchase the program, I have a question for the program as follows.
When you have a new updated version for the program, how can we update the program?
- Will you release a patch file per a separate order?
- Should we re-order a complete exSILentia program?
- Is there any annual mainterance fee for the program update and/or equipment database updates?

We add new functionality to exSILentia on a regular basis. Minor increments are free of charge for the version of the tool you purchase (1.1, 1.2). Major Increments (new version of the tool 1.x to 2.x) will require an upgrade charge.

We release the Safety Equipment Reliability Handbook database each quarter, and you will be notified of the updates. One (1) year of Safety Equipment Reliability Handbook database updates is included with the purchase of exSILentia. After the first year a yearly maintenance fee of US $645 is required to receive Safety Equipment Reliability Handbook database updates.

Applies to: exSILentia (All versions)  Keywords: Updates, SERH

The standard proof test for our project changed from 6 months to 1 year. How can I change this is for all my SIFs?

exSILentia has a Parameter Update utility. This utility allows you to change some key parameters for all or a selected set of SIFs in a project.

Applies to: exSILentia (All versions)  Keywords: SILver, Change parameter

Is the user manual of exSILentia contained on the CD-ROM provided or do we have to buy it seperately? If the user manual is contained on the CD-ROM, does it provide enough guidance as to how to handle your software without training?

The user manual is part of the CD-ROM. With the purchase of the exSILentia Standalone tool, you will also receive a printed copy of the manual, you do not have to buy it separately. If you have a good functional safety background the manual will be enough for you to learn to use the tool.

exida offers exSILentia training classes for those who want to get a quick start in using the tool and/or build confidence when using the tool. If you do not have a functional safety background exida recommends you review some of the exida online training classes on SIL verification or attend an exida functional safety training class befoe attending the exSILentia training course.

Applies to: exSILentia Standalone  Keywords: User Manual, exSILentia Training

As described on the website, the exSIlentia SILver calculations and development process have been independently verified and certified for compliance to IEC 61508. If we order the exSILentia program (CD-ROM) is a copy of the certification report included?

The IEC 61508 certification report is actually included on the exSILentia CD-ROM. You can access it through the tools help menu. It is also available directly from the exSILentia website:
http://www.exsilentia.com/exsilentia/exsil-downloads.asp.

Applies to: exSILentia (All versions)  Keywords: Certification, IEC 61508

Are there any other advantages to the stand-alone version compared with the on-line version? I can see the following benefits:
(a) obviously we would own the software for ever
(b) databases are stored locally instead of on exida’s servers
(c) no delays when using the software due to browser page refresh issues
(d) ability to depreciate an outright software purchase which couldn’t be done with a hire fee
(e) Report generation hopefully would work faster, no downloads of large files

Disadvantages of the off-line version include less portability (can’t work at home unless you take the USB key with you).

The list provided pretty much sums up the advantages of the standalone. We would like to add that the user interface of the standalone is also more user friendly than the on-line version simply because of the “dynamic” limitations of the web.

Yes working from home, you’ll need a laptop and the USB key. Note that exida offers discounts if you purchase more than one license at the same time.

Applies to: exSILentia (All versions)  Keywords: Tool comparison, USB key

When I purchase the exSILentia tool is the Safety Equipment Reliability Handbook included or is there extra cost?

Included with the purchase of the exSILentia tool you get 1 year of equipment database updates. After the first year there is a nominal fee of US $645 per year. Any tool updates within the version e.g. 1.x will be included with your purchase.

The tool does not come with a hardcopy of the Safety Equipment Reliability Handbook. There are however special packages available in the exida online store that include the tool, the book and free shipping.

Applies to: exSILentia (All versions)  Keywords: SERH

If I order exSILentia stand alone I will also get the exida equipment database. Your website states that during the first year after purchase equipment database updates are included, after a year I will have to pay a fee. What is the fee for getting the equpment database updates in subsequent years?
Relating to that are all versions / updates of exSILentia free after I order the current version or only minor releases? If only minor releases are include is there some kind of discount/reduced price if I already have the current version and there is a new major release coming out?

Indeed equipment database updates are included during the first year after purchase. After the first year exida charges US $745 per year for equipment database updates.

The exSILentia standalone minor revisions / updates are free and available for download via www.exSILentia.com. Any Major revision / new version (1.x to 2.x) will require you to upgrade, if you want to continue receiving software upgrades. There will be a discount / reduced price / upgrade price for existing exSILentia users when a Major revision is released.

Applies to: exSILentia Standalone  Keywords: Updates, Equipment Database

[+] Modeling issues


How can I model a Safety Instrumented Function in SILver that uses hard relay based logic?

While we are working on a modification plan to include relay logic as one of the Safety PLC selection options, we currently do not have that ability (directly). There is a workaround however; instead of selecting a logic solver from the dropdown you should select “MyOwn”. This will allow you to enter your own logic solver.

Applies to: exSILentia (All versions)  Keywords: SILver, MyOwn, Relay Logic, Logic Solver

What should I do if a component is not found in SILver's list of devices?

There may be several reasons why an equipment item is not listed.

1. If the data is available, the equipment item may not be listed in the equipment database since the data did not meet exida's quality requirements.

2. exida may not be aware that data for a specific equipment item is available. Please let us know and we will add the device once we review the reliability data and confirm the data is adequate for use in functional safety calculations.

Please contact exida at serh@exida.com for more information.

If reliability data is not available for a device, please contact the manufacturer and explain that his equipment is used in functional safety applications where reliability data is required to determine safety integrity level applicability. exida can help the manufacturer perform a Failure Modes, Effects, and Diagnostic Analysis to determine the reliability data for an equipment item.

If you have reliability data that is proprietary you can use this data by selecting a "MyOwn" device and enter the data manually.

Applies to: exSILentia (All versions)  Keywords: SILver, MyOwn, Equipment

I have some SIFs that are energize-to-trip. SILver states that it handles de-energize-to-trip functions only. How can I analyze the energize-to-trip functions?

The limitation of SILver to de-energize-to-trip functions is caused by the reliability data in the equipment database. To be more precise the reliability data for digital equipment. As an example a short on a switch would be considered dangerous in a de-energize-to-trip application whereas the shorting of the switch would initiate the safety function in an energize-to-trip application and therefore would be safe.

Other than the reliability data there is virtually no difference in the reliability calculations, a 1oo2 configuration uses the same Markov model for energize-to-trip as for de-energize-to-trip. The main difference is the way the components will be connected in the process.

You can model energize-to-trip functions; however you need to be careful when selecting equipment from the equipment database.

Applies to: exSILentia (All versions)  Keywords: SILver, Energize-to-Trip

How can I calculate the PFDavg of a single device?

To calculate the PFDavg of a single device, select the device in SILver and select "<none>" for all other devices in the group. This will exclude everything except the device you would like to analyze.

Applies to: exSILentia (All versions)  Keywords: SILver, PFDavg

How do I model the configuration shown in the accompanying figure?

The easiest way to model this is by considering the three relays part of the sensor (after all they are on the same channels).

A) Define a single sensor group with 1oo3 (assuming 1oo3 voting), diverse technology. For leg 1 and 2 select temperature transmitter with RTD for Sensor and for leg 3 select a Level Switch for sensor. For all three legs select an IS Barrier for Interface Module 1 and a Relay for Interface Module 2.

B) Define a final element group with the final element being a relay.

C) For the logic solver select a "MyOwn" logic solver. Instead of entering the failure rates for a single wire, you also need to consider the power supply needed to power this SIF. Compared to the power supply the wire is negligible; therefore enter the following data for your "MyOwn" logic solver;

Component: Power Supply
Voting: 1oo1
Failure Rates (1/hr)
* Safe Detected = 0
* Safe Undetected = 2.48E-06
* Dangerous Detected = 0
* Dangerous Undetected = 3.21E-08

Architectural Constraint Type: A
Beta (%): 0

Applies to: exSILentia (All versions)  Keywords: SILver, Relay Logic

[+] Requested / Planned new functionality (Contact feedback@exsilentia.com for status)


I have a Logic Solver that is not in your equipment database. I have all the failure rates for CPU, Power Supply and I/O modules. Do you have plans to allow entering all module / channel failure rates for a Logic Solver, so we can take advantage of the automatic channel calculation?

Yes. We intend to allow the user to specify all detailed failure rates for a Logic Solver in a future version of exSILentia through an advanced user option. We also will continue to support the current option to enter only a single set of failure rates for the Logic Solver.

Applies to: exSILentia (All versions)  Keywords: SILver, Logic Solver

I understand that reliability data in your Equipment Database may be updated from time to time. Is there any way to have SILver or exSILentia alert me when new data is available and allow me to update my SIFs?

exSILentia / SILver currently does not alert you to equipment data changes. However, we are planning on adding this feature in the version 2 release of exSILentia.

Applies to: exSILentia (All versions)  Keywords: SILver, Equipment Database

I think it is great that you show the PFDavg and MTTFS contributions for each part. I would, however, like to see a chart, or bar graph like in exSILentia Standalone, that shows the contributions of each Group to the Part PFDavg or MTTFS. This way I can see which Sensor Group or Final Element Group is contributing the most to my PFDavg or MTTFS. Are there plans to include this in the online version as well?

Yes. We intend to add a page to show the contributions that each group makes to the part PFDavg and MTTFS. Note that the group contribution bar graphs are already part of the reports that are generated by the online version of exSILentia.

Applies to: exSILentia Online  Keywords: SILver, PFDavg, MTTFS

I would like the ability to generate a "Bill of Materials" based on the SILver design selections in my project. Do you have plans for this?

Yes. We intend on adding a Bill of Materials Report to exSILentia. We are also working together with some Safety PLC manufacturers to automatically generate (part of) the logic solver programming.

Applies to: exSILentia (All versions)  Keywords: SILver, Bill of Materials

Our process requires us to document both the person responsible for each phase of the Safety Lifecycle, and the person responsible for reviewing each phase. Would you be able to add entry fields to indicate the reviewer?

Yes, we are planning to add additional fields for reviewers in addition to the current fields for analysts. In addition users will be able to specify tool users and user roles, engineer / analyst vs. reviewer.

Applies to: exSILentia (All versions)  Keywords: Reviewer

Over the course of a project, the reliability data in the Equipment Database may change. Is there anyway in the reports to identify which version of the Equipment Data was used to generate the results?

Currently this is not possible. However, we are working on a method of versioning the data in the Safety Equipment Reliability Handbook (SERH) so that it can be saved with the project, and also displayed in the Reports.

Applies to: exSILentia (All versions)  Keywords: SILver, Equipment Database

Are you planning to include Hardwire or relay selections in the Logic Solver Part of SILver?

Yes. We are working on a modification plan to include relay logic. If you currently need to include a relay as your logic solver use the workaround described in the modeling issues section of this FAQ.

Applies to: exSILentia (All versions)  Keywords: SILver, Relay, Logic Solver

Many of my SIFs are actually based on the same Sensors or Final Elements. Right now, when I need to change one of these common Groups I have to change it in each of the SIFs that use it. Is there anyway to link these groups so that I only need to change them in one place?

In exSILentia you are already able to identify Groups as reusable. This is intended to be used for groups in different SIFs that represent identical hardware. Once you have identified a group for reuse, you can select that group from a dropdown list when you specify a new SIF. When you make changes to a reused group in any of the SIFs the changes will be applied to all SIFs where the group is used.

exSILentia version 2 will have a group copy functionality that will allow users to copy groups between and within a SIF.

Applies to: exSILentia (All versions)  Keywords: SILver, Reuse Groups

My Risk Graph requires the "P" Parameter (Probability of Averting the Hazard) for Economic and Environmental Impact receptors in addition to the Personnel Safety. Do you have any plans to add the P Parameter to the Risk Graphs in exSILentia?

Yes. We plan to add these fields to make the Risk Graph more flexible in version 2 of exSILentia.

Applies to: exSILentia (All versions)  Keywords: SILect, Risk Graph

I have a rather complex configuration that is not in your list of voting architectures. How can I combine my data to generate the correct results?

You can use a little probability trick to convert a calculated average Probability of Failure on Demand and MTTFS to failure rates for use in a subsequent SIF. Use SILver to generate your PFDavg and MTTFS, then convert that to a dangerous undetected failure rate and a safe undetected failure rate using the following approximation formula FailDU = (2 * PFDavg) / Proof Test Interval and FailSU = 1 / (MTTFS * 8760) respectively [8760 to convert from years to hours].

We are also planning to develop this ability directly into exSILentia, where we will allow you to save the output of a Group or Part as a "MyOwn" device for use in another Group.

Applies to: exSILentia (All versions)  Keywords: SILver, Complex voting, MyOwn

Do you have plans to provide a utility that will allow importing SIF information from HAZOP reports?

We already have a PHA import utility that is currently sold as a separate tool. exSILentia version 2 will include optional modules or plug-ins. The PHA import utility will then be fully integrated with exSILentia.

The PHA import utility works with PHA Pro, PHA Works and CSV files.

Applies to: exSILentia (All versions)  Keywords: HAZOP, SIF List

Do you have plans to support additional Languages in the exSILentia Reports (Specifically German)?

Yes, we plan on expanding the languages of our reports to include German and Portuguese in exSILentia version 2. We also have been expanding the ability of the reports to handle extended characters for use in Korean, Chinese, Japanese and other languages.

Applies to: exSILentia (All versions)  Keywords: Reports, Language

I notice that if I deselect Architectural Constraints exSILentia will warn about this. Is there any way to generate a list of possible problems in my configuration? For Instance if Architectural Constraints are turned off, can exSILentia tell me that this SIF is not compliant with IEC 61508, IEC 61511 and/or ANSI/ISA 84.00.01:2004.

We are planning to add an "Error / Compliance" checker utility to exSILentia. The intent is to add the "error / compliance report" to the analysis report but also make it available as a separate report.

Applies to: exSILentia (All versions)  Keywords: Error checking, Standard Compliance

We use Hazard Matrix as our SIL Selection method; however, our Hazard Matrix method also utilizes Layer of Protection analysis. Does exSILentia support this?

exSILentia does not support this directly. You would have to do a Layer of Protection analysis separate and enter the resulting frequency in the Hazard Matrix. We intend to add the ability to associate IPLs with Hazard Matrix and Risk Graph directly.

Applies to: exSILentia (All versions)  Keywords: SILect, LOPA, Hazard Matrix, Risk Graph

Do you have any "helpful hints" or something similar for exSILentia?

We are planning to add a "News and hints" feature to exSILentia that will provide updated information about the tool and try to give you helpful hints about using the tools.

Applies to: exSILentia Online  Keywords: Hints, News
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