Glossary: Analytical sampling systems

June 15, 2010

Common analytical sampling systems
 terms and definitions

ADSORPTION: The tendency of some types of molecules to stick to solid surfaces, including the insides of tubing, so they do not show up in analytical readings.

ANALYZER: A sophisticated device that measures the amounts of different chemical components in a sample.

CALIBRATION: A method of testing and adjusting the analyzer’s readings to ensure they are accurate.

DEADLEG: A tee formation with a block at the end so there is no through-flow of fluid. A deadleg holds the old sample, allowing a small portion of it to mix with the new sample, resulting in potential contamination.

FAST LOOP: A circuit or loop of tubing flowing from the process line to a certain point in a sampling system and then back to the process line. It ensures that the sample arriving at a certain point in the sample system is timely and fresh.

FIELD STATION: The place in a sampling system where sample pressure is reduced by means of a regulator.

FLOWMETER: A component that measures the flowrate of liquids and gases through a process system.

FLOW COEFFICIENT: (Cv ) The relative ease with which a fluid flows through a component. The higher the Cv , the lower the pressure drop.

MANIFOLD: An assembly of valves typically within a single block allowing for a compact design with a limited number of connections.

MIXING VOLUME: A reservoir with a separate inlet and an outlet, such as a filter or knockout pot. Fluid flows through a mixing volume, slowly, but it flows. It is a potential source of contaminating the new sample.

MPC: (Modular Platform Components) Fluid system components such as valves, filters and adapters that mount easily (with screws) on a substrate that provides the flow path from one component to the next.

NeSSI: (New Sampling/Sensor Initiative) A sampling system vision and specification (ANSI/ISA 76.00.02) with miniature modular sampling components, smart transducers, field mounting capabilities, and easy integration into plant control systems.

PAT: (Process Analytical Technology) Defined by the U.S. Food and Drug Administration as a mechanism to design, analyze and control pharmaceutical manufacturing processes through the measurement of Critical Process Control Parameters (CPP).

PRESSURE: Force per unit area, commonly expressed in pounds per square inch (PSI) or bar.

PROCESS LINE: A large pipe in a plant that moves the liquid or gas product from one step or process to another.

SAMPLING SYSTEM: A system employed in many industries that draws a sample from a process line and prepares it for analysis in an analyzer.

STREAM SELECTOR: A valve assembly that enables multiple sample streams to share a single analyzer.

TIME DELAY: The total amount of time that elapses as a sample travels from the latest step in the process line through the sampling system to the analyzer, including time required for analysis in the analyzer.

TUBE FITTING: A leak-tight mechanical connection between two pieces of tubing (or tubing and a component) that may be assembled with simple tools and reassembled numerous times.

VALVE: A device used to regulate, direct, or shut off the flow of fluids within a process system.

The terms and definitions for this issue’s Word Search come from Swagelok Company, a manufacturer of fluid system technologies, including analytical sampling systems.

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