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computer science
systems analysis design

Questions and Answers of Systems Analysis Design

Figure P18-39 shows two similar unit pulse waveforms. The only difference is that the first pulse is positive from \(-T / 2\) to \(T / 2\), while the second pulse goes from \(+\mathrm{A}\) to
What is the most important criterion to use when selecting sensors for SIF applications?A. Ability to accurately measure the process variable B. IEC 61508 assessment C. Purchase cost D. Manufacturers
A single pressure transmitter (1oo1) is being used in a SIF to initiate a trip when the pressure output signal goes below 6 mA. This transmitter is connected to a safety PLC that is programmed to
A transmitter has failure rates as presented in Table 10-2. A proof test is performed every 5 years during a process shutdown. The proof test coverage is 92% and MTTRDD is 168 hours. After any
What type of flame detector would be selected for a burnermanagement system?
When would a fire and gas function be classified as a SIF?
When would a burner-management system function be classified as a SIF?
Can a relay logic system be used to satisfy the requirements for a SIL 3 SIF? What are some of the issues that must be addressed when using relays as a logic solver?
A safety-rated smart logic module might include what basic functionality?
If an IEC 61508 certified logic solver is selected, what prior use safety integrity justification is required?
A safety PLC has an Ethernet connection port used to send information to a data server in the system. Can this port be used without a cybersecurity risk?
A safety PLC has been certified to IEC 62443-4-1 and IEC 62443-4-2. Is this device guaranteed to be hacker proof?
List the advantages of using PLCs in safety applications, as compared to relays.
A SIF uses two discrete inputs and one discrete output. Based on the failure rates in Table 11-2, what is the total DU failure rate for the logic solver in this safety instrumented function?
What characteristics are required in a safety PLC?
A safety PLC manufacturer has stated that proof testing includes only physical inspection for deterioration and damage, and a check for unauthorized program changes Detailed test of the programmed
What CPT would be expected for a PVST with a timed pulse on a 3/2 pilot-operated spool solenoid valve?
A SIF uses a single, pneumatic, final element assembly consisting of a 3/2 pilot-operated poppet solenoid valve, a spring-return pneumatic piston actuator, and a floating ball valve. The application
A manufacturer has provided a self-certification for functional safety with a dangerous failure rate of 4 FITS for a 3/2 direct-acting poppet solenoid valve. Is this value realistic for the process
A SIF uses a single, pneumatic, final element assembly consisting of a 3/2 pilot-operated spool solenoid valve, a spring-return scotch yoke actuator, and a trunnion ball valve. The application is
A 3/2 solenoid valve is needed for a SIF final element. A CV rating of 0.1 is required. The lowest dangerous failure rate is desired. Which type of solenoid valve is the best choice?
The useful life of a device is often published in what document?
Why are proof test plans needed?
How can operations and maintenance capability be measured?
Proof test recommendations from a device manufacturer are often published in what document?
A set of nonredundant (1oo1) safety equipment is used to implement a SIF. Demands are expected every minute and DTI is 40 seconds. The following failure rate data are obtained by adding the failure
A set of nonredundant (1oo1) safety equipment, with all component devices certified as having systematic capability SC 3, is used in a low-demand application. The longest DTI of the equipment set is
A SIF description includes three valves. To protect against the hazard, valve one must be closed to cut off the fuel supply from natural gas. Valve two must be closed to preserve heat in a process
An overfill protection SIF has been designed with a level sensor, a safety PLC, and a final element assembly. The MT for the process unit is 15 years. The logic solver is programmed to shut down the
A software bug causes a logic solver to fail unpredictably and randomly. Will this failure be considered a random failure or a systematic failure? Why?
A manufacturer states that the failure rate for a pressure switch is constant and the MTBF is 2 years. What does this mean?A. The expected minimum life for the switch is 2 years B. The expected
Each of the 50 transmitters in identical service had a test time of 7,640 hours. During this period, three failures occurred. Calculate the failure rate.
Each of the 50 transmitters in identical service had a test time of 7,640 hours. During this period, no failures occurred. Describe the procedure for calculating the failure rate.
A failure rate report states that a level transmitter did not indicate high level in a storage tank. Proof testing performed each year did not detect the failure. The failure was traced to a failed
A failure report states that a safety transmitter signaled a high pressure in a vessel and initiated a trip. Other pressure measurements did not indicate any high pressure. A diagnostic in the safety
A device has a reliability of 0.95 for an interval of 1 year. What is the unreliability?
An instrument has a failure rate of 0.015 failures per year. What is the unreliability for a 5-year mission?
An instrument has a failure rate of 0.015 failures per year. All failures are immediately detectable. The MTTR is 24 hours. What is steady state unavailability?
An instrument has a failure rate of 0.015 failures per year. Failures are detected once per year when a periodic inspection is performed.Assuming perfect restoration, what is the PFavg?
A valve has a failure rate of 0.06 failures per year. A periodic inspection performed once a year can detect 60% of the failures. The valve is operated for 10 years before it is removed from service
During an annual inspection of an SIS, 5 of the 112 safety functions had a dangerous failure on the solenoid valve. What number should be assigned to the probability of dangerous failure for this
A system has a transmitter, a controller, and a valve. The probability of failure for the next 5 years equals 0.15 for the transmitter, 0.008 for the controller, and 0.19 for the valve. For the next
An instrument has an MTTF of 28,000 hours and an MTTR of 48 hours.What is the MTBF?
A device has a failure rate of 5 • 10-6 failures per hour. None of the failures are detected by any automatic diagnostics. The device is inspected every 2 years, and all failures are detected
A system is repairable. Since all failures are immediately recognizable, the restore time averages 48 hours. The percentage of downtime must be calculated for a 20-year expected system life. What is
For a gas burner to work without failure, one of two identical fans, the burner, and the controls must function without failure. The reliability of a fan is 0.9. The reliability of the burner is
A system has the following series-reliability block diagram:Failure rates are:λAC Power = 0.002 failures per year λDC Power Supply = 0.004 failures per year λLevel Switch = 0.02 failures per year
In Exercise 5.2, what is the reliability of the system for a 1-year time interval?A. 0.869 B. 0.131 C. 0.125 D. 0.9869 E. 0.877
A system has the following reliability block diagram: A B AC Power Motor
A system has four components with the RBD below. If the power supply has a 1-year reliability of 0.95 and the controller has a 1-year reliability of 0.99, what is the system reliability for 1 year?A.
Draw the Markov model for the system in Exercise 5.5.
Based on the system illustrated in the figure below, draw a fault tree to represent a safe failure (spurious trip) due to the failure of the TX1/2 subsystem; that is, the top event is “Nuisance
What is the P matrix for the Markov model in Figure 5-18? 5 Fail Energized 3 2. Degraded Detected 1 0 3 Comm. Loss 4 Degraded Undetected 2 Fail Safe 5 Figure 5-18. Example Markov model 24
Draw a Markov model for the system in Figure 5-6. Common Symbols Additional Symbols OR Gate AND Gate Event or Resulting Fault Basic Event Figure 5-6. Fault Tree Symbols Incomplete Event Inhibit Gate
A solenoid valve is energized in normal process operation. It is deenergized when a dangerous condition is detected and vents air from a pneumatic actuator. If the solenoid coil fails short circuit
A valve is designed to close on trip in a SIF. If this valve had a failure where internal seals were damaged and could not completely stop flow, how would this failure be classified?
A ball valve without an actuator cannot fail in such a way that it causes a false trip. What is the safe failure rate for the ball valve?
A flame detector used in burner management application falsely sees a flame when there is none. How would that failure mode be classified?
A gas detector used in a flammable gas shutdown function falsely indicates the presence of flammable gas. How would that failure mode be classified?
A safety PLC communicates shutdown status to the operator via a communication link. If this link fails to communicate, how would that failure mode be classified?
A SIF has a remote actuated valve energized and open. The valve must close when a demand is detected. The valve is fitted to a piston-type pneumatic actuator that has an O-ring seal around the
A manufacturer field-return data system shows six failures were reported in the last 5 years, with a total estimated operating time of 939,256 hours. If it is assumed that 40% of actual field
Based on data from a manufacturers field-return data system, an estimated 15 field failures occurred. If the estimate of field operational hours for the device is 3,000,000 hours, what is the point
A site-failure data-collection system has been established. Failures are recorded when a work order is generated to send a failed device to the manufacturer for analysis and/or repair. What potential
Cycle testing using the B10 method results in a dangerous failure rate of 0.2 FITS for a solenoid valve. Is this failure rate prediction valid for use in a low-demand process industry application?
A component database is created to perform FMEDA. The data have been calibrated based on cycle test results. Would the result from this FMEDA be suitable for low-demand process industry applications?
A component database created for FMEDA is based on process industry field failure data. Would this database be expected to generate realistic process industry failure data predictions?
Does FMEDA-based failure rate data include failure rates due to anticipated human error?
What is the failure rate of an electronic switching regulator in low power applications using environmental profile 1 from the Electrical Mechanical Component Reliability Handbook (EMCRH), as shown
What is the failure rate of a mechanical elastomer ring, U-Cup, used in a dynamic application at 350 kPa (kilopascal) in an environmental profile 1 from the EMCRH, as shown in Figure 7-4?
Can an FMEDA be used to predict the proof test coverage of a specific proof test?
A LOPA has indicated that a demand would occur every 10 years on average for a particular process hazard. Although most automatic diagnostics execute every minute, the worst-case time period for
A set of nonredundant (1oo1) safety equipment is used to construct an element used in a SIF. Demands are expected every minute. Automatic diagnostic time is given as 30 seconds.What is the HFT? What
A set of nonredundant (1oo1) safety equipment is used to construct an element used in a SIF. Demands are expected every minute. Diagnostic time is given as 1 second. The equipment is programmed to
A device is to be used as an element in a SIF in low-demand mode. The failure rates are given as:What is the SFF? If this were a Type B component in a 1oo1 architecture, what SIL level would the
A dual redundant (2oo2) design has what level of HFT?
A 2oo3 safety architecture has what level of HFT?
A motor controller is required as the final element in a SIL 2 safety function. The only product available with IEC 61508 certification will not meet functional requirements. What steps must be taken
Two smart transmitters have been selected for a SIF design. The logic solver is programmed to trip if either transmitter indicates a dangerous condition (1oo2). The manufacturer’s data sheet lists
Two smart transmitters are intended to be used for a SIF design. The IEC 61508 certificate states “systematic capability of SC 2.” Can two of these transmitters be used for a SIL 3 application?
A final element assembly is being designed consisting of a solenoid valve, a pneumatic actuator, and a trunnion ball valve. The IEC 61508 certificate for the solenoid valve states that the product
International safety standards require that operating companies follow the SIS safety life cycle specifically as outlined in the respective standard.A. True B. False
The SIS safety-life-cycle process can:A. Reduce SIS costs B. Increase process safety C. Help insure that regulations are met D. Provide an example of “good engineering practices”E. All the above
Why should a company pay attention to IEC 61508 and IEC 61511?A. It is legally required in some countries B. It can save money on safety systems C. Owners/operators often require compliance D. A
According to the SIS safety life cycle in IEC 61511, when should a process hazards analysis be conducted?A. After the project scope is defined and the piping and instrumentation drawings (P&ID) are
In the SIS safety life cycle, an SRS is done:A. After defining the project scope B. After the hazard and risk analysis phase C. Throughout the phases of the life cycle D. After overall safety
Which of the following methods is not usually part of the analysis phases of the safety life cycle?A. LOPA B. SIL verification analysis C. Hazard and operability study (HAZOP)D. Risk analysis
What parts of the SIS safety life cycle are subject to functional safety management?I. The analysis phase II. The operation phase III. Only the phases before commissioning IV. The design phase A.
In the analysis phase of the SIS safety life cycle, the following activity is performed:A. Install the SIS B. Analyze risk C. Decommission the SIS D. Operation and validation planning E. SIS
When does the safety life cycle end?A. It never ends B. When the project is fully commissioned C. When the safety system is decommissioned D. When the safety system is proven through use
Compared to control system design, there are special considerations and additional requirements for SIS design, including:I. The need to meet international standards II. Careful consideration of
An SIS typically performs the following functions:I. Reads sensors and performs optimization calculations II. Generates outputs to maintain process variables close to set points III. Executes
An SIS may include:A. Sensors B. Logic solvers C. Final elements D. All the above
In a de-energize-to-trip system, a loss of power supply failure is considered:A. Impossible B. Fail-danger C. Not a failure D. Fail-safe
How does a SIF most typically reduce risk?A. Reduces the likelihood of harm B. Reduces the magnitude of harm C. Satisfies legal requirements D. Satisfies managerial requirements
Which safety standards address SIL selection methods?I. IEC 61508 II. IEC 61511 III. ISO 9000 IV. ISA-84.00.01-2004 A. I and IV only B. I, II, and IV only C. All four items D. I and II only
Should a fire and gas system that performs a mitigation function be classified as an SIS?A. Yes – It reduces risk.B. No – These systems are not classified as an SIS.
A cause-and-effect diagram illustrates logic for a function where two valves will be closed and a pump will be de-energized when either of two pressure sensors detects that pressure in a vessel is
The complex power \(S_{\mathrm{L}}\) delivered to the load \(Z_{\mathrm{L}}\) in Figure P16-17 is \(20+j 20 \mathrm{kVA}\). The source produces an average power of \(22 \mathrm{~kW}\) and the line
In the balanced three-phase circuit in Figure P16-42 , the line impedance is \(Z_{\mathrm{W}}=1+j 5 \Omega /\) phase and the average power delivered to the load is \(25 \mathrm{~kW}\) at a lagging

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