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Control and Instrumentation GlossaryWe have 22 entries in our Glossary for this letter. SAT - Site Acceptance Test A test of equipment carried out at site following installation of equipment but prior to commissioning. Further Reading SCADA Supervisory Control and Data Acquisition - A term commonly used to describe a PC based software package that allows operator control of a process from a PC and has the PC collecting and storing process information. Often used with PLCs. Further Reading Scale Factor The factor by which the number of scale divisions indicated or recorded by an instrument must be multiplied to compute the value of a measured variable. Further Reading SCE Safety Critical Element Further Reading scf - Standard Cubic Feet Pronounced scuf - a measurement of gas e.g. 20 MMSCF/hr being 20 thousand cubic feet per hour Further Reading Sensitivity The minimum change in a physical variable to which an instrument can respond. Further Reading Sensor An element or device that detects a variable by receiving information in the form of one quantity and converting it to information in the form of that or another quantity. Further Reading Setpoint A variable - expressed in the same units as the measurement - which sets either the desired target for a controller or the condition at which alarms or safety interlocks are to be energised. Further Reading Signal to Noise Ratio Ratio of signal amplitude to noise amplitude. Further Reading SIL - Safety Integrity Level A discrete level (1 to 4) for specifying the safety integrity requirements of the safety functions to be allocated to a loop. SIL 4 being most onerous. Further Reading SIL Ratings Toolbox Page SoR Statement of Requirements Further Reading Sour A sour fluid is a fluid that contains hydrogen sulphide (H2S) at 10 ppm or more. Further Reading SOV Solenoid Operated Valve Further Reading SOx - Sulphur Oxides Sulphur oxide gases (principally Sulphur dioxide - SO2) are formed when fuel e.g. coal and oil; containing sulphur is burned. Further Reading Span The algebraic difference between the upper and lower range values expressed in the same units as the range. Further Reading Stability The ability of an instrument or sensor to maintain a consistent output when a constant input is applied. Further Reading Steady State A characteristic of a condition e.g. value; rate; periodicity or amplitude exhibiting only negligible change over an arbitrary long period of time. Further Reading Stellite Cobalt based alloy commonly applied as coating to valve trims to provide high resistance to wear; corrosion and high temperatures. Further Reading Stonewall The maximum stable flow and maximum head condition for a centrifugal compressor. Further Reading STP - Standard Pressure and Temperature STP is used in many thermodynamic calculations and tabulations and is defined as 0 degrees Celsius and 1 atmosphere of pressure. Further Reading Surge An unstable operating condition when the flow through a compressor is decreased to the point that momentary flow reversals occur. Can lead to major damage of compressor. Further Reading Synchronous An event or action that is synchronized to a reference clock. Further Reading |
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