IEC 61511: 2016 Process Industry Sector
IEC 61511 is a technical standard that sets out practices in the engineering of systems that ensure the safety of an industrial process through the use of instrumentation. It entails requirements for users of process control and instrumentation for component / element or sub-system safety.…
IEC 61508 functional safety standard indicates Safety Integrity Levels (SIL) needs to be evaluated by three design barriers:
Systematic Capability is achieved when the equipment…
IEC 61508 and IEC 61511 functional safety standards allow Safety Integrity Levels (SIL) to be used four ways by end users:
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Systematic Capability is achieved when the equipment used to implement any safety function achieves two goals: the design process has used procedures intended to prevent systematic design errors (fault avoidance) and the design has systematic design control mechanisms such as a diagnostic for incorrect software execution (fault control). The rigor…
Architectural constraints are limitations that are imposed on the hardware selected to implement a safety-instrumented function, regardless of the performance calculated for a subsystem. Architectural constraints are specified (in) according to the required of the subsystem, type of components used, and of the subsystem’s components. (Type A components are simple devices…
PFDavg (the average Probability of Failure on Demand) is the probability that a system will fail dangerously, and not be able to perform its safety function when required. PFDavg can be determined as an average probability or maximum probability over a time period. IEC 61508 and IEC…
PFH (Probability of dangerous Failure per Hour) is the probability that a system will fail dangerously, and not be able to perform its safety function when required. PFH can be determined as a probability or maximum probability over a time period of an hour. IEC 61508 and
Failure rates are the number of failures per unit time for a piece of equipment which are usually assumed to be a constant value. They can be broken down into several categories, such as safe and dangerous, detected and undetected, and independent/normal and common cause. Failure rates are often…
Failures In Time or Failure UnIT
FIT is the number of failures per billion hours for a piece of equipment.
It is mentioned in both IEC 61508 and IEC 61511 standards as a preferred unit of measurement expressed by 109 hours.
Example: 5 FIT is expressed as 5 failures within 109 hours .
When you…
The Greek symbol lambda, λ, represents failure rates in functional safety, usually expressed in the unit of measurement of FITS.
λ can be expressed as a total failure rate for a device (λT), or it can be broken down into more specific groupings:
The Greek symbol λD represents dangerous failure rates in functional safety, usually expressed in the unit of measurement of FITs, and can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).
λD is the number of dangerous failures per…
The Greek symbol λDD is the detectable dangerous failure rate in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).
λDD is the number of…
The Greek symbol λDU is the undetectable dangerous failure rate in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).
λDU is the number of dangerous undetected failures…
The Greek symbol λS represents safe or spurious failure rates in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).
λS is the number of safe…
There are organizations that are small enough to follow an informal or even undocumented process and still produce a product of sufficient quality to meet market needs. When these organizations attempt to develop a safety product, they inevitably fall short of meeting the requirements of IEC 61508. A formalized…
While correcting a CFSP exam, I read a question which went something like this:
If you purchase all IEC 61508 certified equipment for a low demand safety instrumented function, then to meet the requirements of IEC 61511:
A. No other design verification is needed
B.…
exida has discovered yet another forged functional safety certificate. You can read about another occurrence in a previous blog entry.
The company name on the forged certificate is ISP SA DE CV, Cunduacan, Tab., Mex. How could someone…
Functional Safety Assessments (FSA) focus on the relevant functional safety standards that are to be applied to a product in the appropriate industry. These are standards such as IEC 61511 in the process automation industry, or ISO 26262 in the automotive industry. And IEC 61508 is like an umbrella…
I got a copy of the IEC 61508 certificate for a solenoid valve today from an engineer who thought something was wrong. Although the certificate was from a well known certification company, the certificate gave a “Dangerous Failure Rate” of 1.7 FITS (1.7 * 10-9 failures per…