Key SIL (Safety Integrity Levels) Terms

The global value of SIL (Safety Integrity Levels) to the process industries has increased significantly over the years. For many companies, SIL is still an elusive term sometimes misunderstood and implemented incorrectly. To fully understand SIL and its consequences, it is essential to comprehend the necessary words, acronyms, and phrases often used and how they relate to the pursuit of functional safety.  The following are some of the most commonly used:

Dangerous failure

Failure with the potential to bring the safety instrumented system into a dangerous or non‐functional state.

FMEDA

Failure Modes Effects and Diagnostic Analysis

HFT

Hardware Fault Tolerance, ability of a hardware to continue to perform a required function in the presence of faults or errors.

MTBF

Mean Time Between Failures

PFD

Probability of Failure on Demand, Probability of hazardous failures for a safety function on demand.

Safety Function

The ability of a system to carry out actions necessary to maintain a defined safe state for a process, equipment, or a plant.

Safety‐Related System

A safety‐related system performs the safety functions that are required to maintain a safe condition (for example, a flow meter, a burner, and a PLC).

SFF 

Safe Failure Fraction, percentage of failures that do not have the potential to put the safety‐related system in a hazardous state.

SIL

Safety Integrity Level, IEC 61508 defines four Safety Integrity Levels (SIL1 through SIL4). Each level corresponds to a level of probability for the failure of a safety function.

SIS 

Safety Instrumented System, implementation of one or more safety instrumented functions.

Piping Specialties / PSI Controls

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Terms and definitions courtesy of Kurz Instruments

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The Operation of the Cash Valve B Series, Type E-55, Type PBE-1, Type PBE-2, and Type PBE-5

Cash Valve is a leading manufacturer of pressure regulating and back pressure valves offering products for steam, air/gas, liquid, and cryogenic applications. Products range in size from 1/8" - 2" for threaded NPT connections and up through 6 inches for flanged configurations. Temperatures range between cryogenic up through 800°F, and materials of construction are offered with iron, brass, bronze, carbon and stainless steel depending on your application.

For more information about Cash Valve, contact Piping Specialties, Inc. by calling 800-223-1468 or by visiting their web site at https://psi-team.com. 

A Free Technical Paper Explaining Refractive Index

Refractive index measurement is a measurement of the speed of light in a medium. The speed of light (usually denoted by c) is 299 792 458 m/s in a vacuum. In other media, the speed of light is lower, and the refractive index (R.I.) of a medium is how much slower the light's speed is in the medium.

The detection of liquid concentrations by optical means is not new. The law of refraction was mathematically formulated first by Ibn Sahl in 984 but not known in Europe. Instead, its discovery misattribution goes to the Dutch astronomer and mathematician Willebrord Snellius (Snell), who rediscovered the law and published it in 1621. The first laboratory instrument to accurately measure liquids' refractive index was developed by Ernst Abbe in 1874.

This technical paper, courtesy of Vaisala K-Patents, is a technical explanation and understanding of the refractive index.

For more information about industrial refractometers, contact Piping Specialties / PSI Controls by calling 800-223-1468 or by visiting their web site at https://psi-team.com.