Interview Questions.

Question 1. What Is A Sis?

Answer :

SIS is a Safety Instrumented System. It is designed to prevent or mitigate dangerous activities by using taking the process to a secure nation when predetermined conditions are violated. A SIS consists of a aggregate of common sense solver(s), sensor(s), and very last detail(s). Other commonplace phrases for SISs are protection interlock structures, emergency shutdown structures (ESD), and safety shutdown systems (SSD). A SIS can be one or extra Safety Instrumented Functions (SIF).Safety-Instrumented-System-Components

Question 2. What Is A Sif?

Answer :

SIF stands for Safety Instrumented Function. A SIF is designed to save you or mitigate a risky event with the aid of taking a system to a tolerable risk degree. A SIF consists of a aggregate of good judgment solver(s), sensor(s), and final detail(s). A SIF has an assigned SIL level depending on the amount of hazard that needs to be decreased. One or extra SIFs contain a SIS.

Computer Science Engineering Interview Questions
Question three. What Is Sil?

Answer :

SIL stands for Safety Integrity Level. A SIL is a degree of protection system overall performance, or probability of failure on demand (PFD) for a SIF or SIS. There are four discrete integrity tiers associated with SIL. The higher the SIL level, the decrease the opportunity of failure on demand for the safety system and the higher the system overall performance. It is important to also notice that as the SIL level increases, commonly the fee and complexity of the gadget also boom.

A SIL level applies to a whole device. Individual merchandise or components do not have SIL ratings. SIL levels are used whilst implementing a SIF that need to reduce an current insupportable technique risk level to a tolerable hazard variety.

Question 4. What Does Functional Safety Mean?

Answer :

Functional protection is a time period used to describe the safety machine this is depending on the ideal functioning of the logic solver, sensors, and final factors to achieve the desired hazard discount stage. Functional protection is finished whilst each SIF is efficaciously performed and the process hazard is reduced to the favored level.

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Question 5. Why Were The Ansi/isa eighty four, Iec 61508, And Iec 61511 Standards Developed?

Answer :

The standards have been a natural evolution for the want to reduce manner hazard and improve protection via a more formalized and quantifiable method. Additionally, and specially for IEC 61508, because the software and usage of software program has evolved and proliferated, there was an expanded want to expand a general to manual machine / product designers and builders in what they had to do to make certain and “claim” that their structures / products have been acceptably safe for their intended makes use of.

Operating System Interview Questions
Question 6. When Do I Need A Sif Or A Sis?

Answer :

The philosophy of the standards shows that a SIS or SIF need to be carried out simplest if there may be no different non-instrumented way of thoroughly getting rid of or mitigating process danger. Specifically, the ANSI/ISA-84.00.01-2004 (IEC 61511 Mod) recommends a multi-disciplined crew method that follows the Safety Lifecycle, conducts a manner risk analysis, designs a selection of layers of protection (i.E., LOPA), and sooner or later implements a SIS when a dangerous event can't be averted or mitigated with some thing other than instrumentation.

Question 7. What Is A Proof-test Interval?

Answer :

Proof trying out is a demand of protection instrumented systems to make certain that the entirety is running and acting as anticipated. Testing should encompass the verification of the entire system, common sense solver, sensors, and final factors. The c program languageperiod is the time frame that the testing happens. The testing frequency varies for each SIS and is dependent on the generation, machine structure, and target SIL degree. The evidence-test c program languageperiod is an important aspect of the opportunity of failure on call for calculation for the device.

Instrumentational Engineering Interview Questions
Question eight. What Is A Process Hazard Analysis (pha) And Who Conducts This?

Answer :

A PHA is an OSHA directive that identifies protection problems and risks within a technique, develops corrective moves to respond to protection issues, and preplans opportunity emergency moves if protection systems fail. The PHA must be performed through a diverse group that has precise understanding in the manner being analyzed. There are many consulting and engineering corporations that also provide PHA services. PHA methodologies can include a What-If Analysis, Hazard and Operability Study (HAZOP), Failure Mode and Effects Analysis (FEMA), and a Fault Tree Analysis.

Question 9. What Voting Configurations Are Required For Each Sil Level?

Answer :

Obtaining a desired SIL level is dependent on a mess of factors. The sort of technology hired, the variety of machine additives, the opportunity of failure on call for (PFD) numbers for every factor, the system architecture (e.G., redundancy, voting), and the proof checking out intervals all play a full-size position in the dedication of a SIL level. There is not a popular answer for what balloting configurations are required for every SIL stage. The balloting architecture need to be analyzed in the context of all the elements mentioned above.

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Question 10. Will A Sil Rated System Require Increased Maintenance?

Answer :

SIL solutions are really no longer usually the most price-powerful answers for reducing system chance. Many instances, enforcing a SIL answer would require extended device, which necessarily will require accelerated renovation. Additionally, it's far in all likelihood that the better the SIL stage, the extra common the proof trying out c language might be, which may also ultimately increase the quantity of machine renovation that is required. This is why the requirements suggest a SIL primarily based answer only when manner hazard can not be decreased through other strategies, as decided with the aid of LOPA.

Question 11. Can A F&g System Be A Sif Or Sis?

Answer :

A Fire and Gas (F&G) machine that automatically initiates method moves to prevent or mitigate a hazardous event and eventually takes the process to a secure nation may be considered a Safety Instrumented Function / Safety Instrumented System.

However, it's far honestly essential in a F&G system to make sure gold standard sensor placement. If there is inaccurate placement of the fuel / flame detectors and hazardous gases and flames are not correctly detected, then the SIF / SIS will not be powerful.

Correct sensor placement is greater crucial than deciding whether a F&G SIF / SIS must be SIL 2 or SIL 3.

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Question 12. What Is Sil four?

Answer :

SIL 4 is the very best degree of risk discount that may be received thru a Safety Instrumented System. However, within the process enterprise this isn't a sensible degree and presently there are few, if any, merchandise / structures that support this protection integrity level.

SIL 4 structures are normally so complex and steeply-priced that they're now not economically beneficial to implement. Additionally, if a technique includes a lot hazard that a SIL four machine is required to carry it to a secure nation, then fundamentally there may be a hassle in the technique design which wishes to be addressed by using a method exchange or other non-instrumented method.

Computer Science Engineering Interview Questions
Question 13. Can An Individual Product Be Sil Rated?

Answer :

No. Individual merchandise are only appropriate for use in a SIL environment. A SIL level applies to a Safety Instrumented Function / Safety Instrumented System.

Question 14. What Type Of Communication Buses Or Protocols Are Applicable For Sil 2 Or Sil 3 Systems?

Answer :

The form of communique protocol this is suitable for a SIL 2 or SIL 3 device is actually dependent on the form of platform that is getting used. Options encompass, but are not restrained to: 4-20 mA output signal, ControlNet (Allen Bradley), DeviceNet Safety (Allen Bradley), SafetyNet (MTL), and PROFIsafe. Currently, the ISA SP84 committee is operating on developing recommendations for a protection bus, to ensure that the foundations observe IEC 61508, and IEC 61511 requirements. The first gadgets with a safety bus need to be to be had with the aid of 2008. The Fieldbus Foundation is actively concerned within the committee and working on setting up Foundation Fieldbus Safety Instrumented Systems (FFSIS) project to work with companies and give up users to expand protection bus specifications.

Question 15. For General Monitors, How Can I Access The Pfd And Mtbf Data For The Products?

Answer :

The General Monitors SIL certificate have the PFD, SFF, and SIL numbers that correspond to every product. MTBF records may be provided by using request.

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Question 16. Can A Manufacturer State Their Products Are “sil X Certified” Rather Than “appropriate For Use In A Sil X System”?

Answer :

Individual products are simplest suitable to be used in a SIL environment. A SIL degree applies to a Safety Instrumented Function / Safety Instrumented System.

Product certificates are issued both with the aid of the manufacturer (self-certification), or different impartial corporation to reveal that the perfect process is accompanied, calculations had been completed, and evaluation has been completed at the man or woman merchandise to suggest that they are like minded to be used within a machine of a given SIL degree.

Full IEC 61508 certification can practice to a manufacturer’s procedures. Full certification implies that a manufacturer’s product improvement technique meets the standards set forth in the correct parts of sections 2 – three of IEC 61508 (such as hardware / gadget and software). Receiving complete certification from an permitted notifying frame offers the give up person self assurance that the manufacturer’s engineering method has been reviewed and its product’s electric content material, firmware and common sense have been assessed and comply with the pointers set forth in the trendy.

There are only a few nationally authorized our bodies which can trouble nationally approved certifications. Other consulting corporations problem certificate that suggest that the product and / or manner has been reviewed by means of an impartial 1/3 birthday celebration.

Question 17. Can A Manufacturer State Their Products Meet All Parts Of The Requirements Of Iec 61508 Parts 1 To 7?

Answer :

IEC 61508 includes the following elements, underneath the general name Functional Safety of electrical/digital/programmable electronic safety-related systems:

Part 1: General necessities

Part 2: Requirements for electric/electronic/programmable digital protection-associated systems

Part three: Software necessities

Part four: Definitions and abbreviations

Part five: Examples of methods for the determination of safety integrity tiers

Part 6: Guidelines on the utility of components 2 and three

Part 7: Overview of techniques and measures

To be in compliance with the usual, it's miles important to conform to Parts 1 – 3. Parts four – 8 are informative handiest and can be useful in information and applying the usual, however do now not have requirements for conformance.

Manufacturers of merchandise usually meet Section 2 necessities to decide thru a FMEDA evaluation that their merchandise are appropriate for use within a given SIL level.

Companies choosing to certify their engineering strategies and get hold of full IEC 61508 certification may also comply with Section three because it pertains to software program improvement.

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Question 18. What Does Sil X Suitable Mean, Is This A Valid Statement As Per The Standard Iec 61508 Or Can Any Other Wording Be Used?

Answer :

SIL stands for Safety Integrity Level. A SIL is a measure of protection machine performance, or opportunity of failure on call for (PFD) for a SIF or SIS. There are four discrete integrity ranges associated with SIL. The better the SIL stage, the decrease the probability of failure on demand for the protection machine and the higher the gadget performance. It is critical to also be aware that because the SIL stage will increase, typically the price and complexity of the device also increase.

A SIL degree applies to an entire device if it reduces the hazard in the quantity similar to the precise SIL level. Individual merchandise or additives do now not have SIL rankings. SIL ranges are used when implementing a SIF that must lessen an existing intolerable manner risk stage to a tolerable chance variety.

Only the end consumer can make certain that the protection system is applied to be compliant with the requirements. It is up to the person to ensure that methods had been followed well, the evidence testing is carried out efficiently, and suitable documentation of the design, manner, and tactics exists. The system or gadget have to be used in the way in which it turned into intended so one can effectively gain the favored chance discount level. Just shopping for SIL 2 or SIL 3 appropriate additives does no longer ensure a SIL 2 or SIL 3 gadget.

Operating System Interview Questions
Question 19. Using A Sil three Logic Solver Means That I Have A Sil three System?

Answer :

No. When the use of a SIL 3 common sense solver, it is crucial that the complete machine is designed to conform to SIL three requirements. The PFD for the complete system is vital. If a user installs a SIL three logic solver however does now not employ appropriate redundancy or does now not incorporate additives into the system with accurate PFD calculations, then the complete device won't observe a SIL three level. “A chain is best as sturdy as its weakest hyperlink.”

Question 20. Sil three Suitable Products Are Better Than Sil 1 Or Sil 2 Suitable Products?

Answer :

This isn't always proper. While a better SIL stage corresponds to a lower chance of failure on call for, a SIL 2 suitable product may be flawlessly applicable for use in a SIL 3 environment if, as an instance, the proof trying out c programming language is multiplied or if redundancy is used. It could be very critical for an stop-user to recognize the working necessities of the products inside a given SIL surroundings to ensure that after hooked up, the goods maintain their SIL suitability degrees. Incorrect set up, evidence testing, or configuration of the products may want to make the SIL suitability stage inaccurate.

Desktop Engineer Interview Questions
Question 21. There Are Many Agencies That Are Capable Of Issuing Sil Certifications?

Answer :

There are very few nationally accredited bodies which can difficulty nationally authorised certifications, such as FM, TUV, and Sira. Many unaccredited consulting firms difficulty certificate that suggest they have reviewed the product and / or process for conformance to positive parts of the IEC 61508 fashionable. The preferred does now not mandate that certain organizations or organizations are able to certify products and systems. Rather, it's far recommended that evaluation is either carried out or demonstrated via an unbiased 1/3 celebration.

Question 22. A Vendor Can Determine Whether A System Meets The Requirements Of Iec 61511?

Answer :

No. Only the give up consumer can make certain that the protection device is implemented to be compliant with the standards. It is up to the consumer to make sure that methods have been accompanied well, the proof testing is performed efficaciously, and suitable documentation of the layout, process, and tactics exists. The system or gadget must be used inside the manner wherein it changed into intended which will efficiently gain the preferred threat discount stage. Just buying SIL 2 or SIL 3 appropriate components does not ensure a SIL 2 or SIL 3 device.

Question 23. A Customer Must Purchase A Complete Sil Based Solution, Even If Some Functions Do Not Require A Sil Level?

Answer :

For most applications there will best be a few SIF features being treated by using the device, and the sizable majority of the circuits may not need to be SIL rated at all. If the customer specifies SIL 2 or SIL three for the whole device he may additionally add huge fee with very little advantage or development in protection.

Industrial Automation Engineer Interview Questions
Question 24. How “protection” And “reliability” Are The Same Thing?

Answer :

No. Safety and reliability are often linked however are not the identical element. Safety is defined in the IEC 61508 requirements as “freedom from unacceptable threat.” A secure gadget have to protect from dangers whether or not it's miles acting reliably or not. Safety engineering assures that a safety device plays as wanted, even if portions fail. In fact, protection engineers expect that structures will fail, and design thus.

Reliability is a degree of the way well the system does exactly what it is intended to do when operated in a selected manner. A dependable machine won't always be a secure system. The assignment in functional protection is to make certain that a machine is both dependable and safe.

Instrumentational Engineering Interview Questions
Question 25. Explain Sil And Sis And How They Relate?

Answer :

Safety Instrumented System (SIS): Instrumented machine used to enforce one or greater safety instrumented capabilities. An SIS consists of any aggregate of sensors, common sense solvers, and very last factors. This can consist of safety instrumented control functions, protection instrumented protection features, or each. In many industrial processes, specially those in the chemical or oil & gasoline industries, involve inherent risk due to the presence of dangerous chemicals or gases. Safety Instrumented Systems are in particular designed to defend personnel, device, and the environment by using decreasing the chance or the effect severity of an recognized emergency occasion.

Safety Integrity Level (SIL): SIL is a quantifiable dimension of hazard used as a way to set up safety overall performance objectives for SIS structures. IEC requirements specify four feasible Safety Integrity Levels (SIL1, SIL2, SIL3, SIL4); but, ISA S84.01 simplest recognizes up to SIL3 ranges.