Topic: Process Analyzers
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Flue Gas Analyzers, Gas Chromatographs, Analyzer Flow Switch/Monitors and More
Model Predictive Control -- Where Have We Been and Where Are We Going -- Part 3
McMillan, Weiner and Darby Discuss Practical Considerations in MPC Setup, Maintenance and Improvement to Meet Economic Objectives
5th-Generation Thermox WDG Flue Gas Combustion Analyzer
Mounts Directly to the Process Flange, and Is Heated to Maintain All Sample-Wetted Components Above the Acid Dewpoint
Modular Still Matters
The Process Analyzer Industry and One of Its Largest User Communities Must Get Away from Building "Steel Copies of Wooden Bridges"
White Papers: In Depth Research
Reliable Multilayer Piezo Actuators - Development and Testing
Piezoelectric multilayer actuators are the driving force behind the most challenging nanopositioning applications. These types of actuators have been in use for about two decades and have reached maturity several years ago. Continuous improvements are based on long term tests and exact knowledge of the environmental operating conditions and failure modes allows to push the limits of this technology even further.
The paper presents the results of an extensive study involving up to four environmental chambers and more than 1,000 actuator samples to develop a grid of 13 humidity and temperature conditions. Weibull-analysis is used at every condition to determine the DC-voltage dependent lifetime of the co-fired PICMA multilayer actuators. In addition to the (most critical for precision positioning applications) DC tests, behavior under large-signal AC-conditions with up to 1010 cycles for different functions as well as temperature-conditions was also evaluated. Three patented design features of the latest actuator generation are based on the findings.
How to Manage Vaporization in an Analytical System
Author: Doug Nordstrom, Tony Waters, Swagelok
If the analyzer in your analytical system requires gas but your sample is liquid, the only option is to convert the liquid to gas. This process is called vaporization or flash vaporization. The objective is to convert a sample of all liquid to all vapor instantly - without changing the composition.
It is not easy to vaporize a sample, nor is it always possible, so make sure it's really necessary and possible before you try. You should always analyze a liquid in a liquid phase unless there are strong reasons for analyzing in a vapor phase.
If you proceed with vaporization, it's important to understand the difference between evaporation and vaporization. Evaporation occurs gradually with an increase in temperature. Vaporization occurs instantly with a drop in pressure. It's not possible to vaporize a sample by increasing temperature. Heat causes evaporation, and adding more heat simply makes evaporation happen faster.
In a mixed sample, evaporation will allow some compounds to evaporate before others, resulting in fractionation. Vaporization, done properly, ensures that all of the compounds vaporize at the same time, preserving the sample's composition.
However, it is possible for things to go wrong when vaporizing. Instead of flashing the whole sample into a vapor, you could unintentionally cause a combination of vaporization and evaporation. The result would be fractionation. Once a sample of mixed compounds fractionates, it is no longer suitable for analysis. With fractionation, a common scenario is for lighter molecules to evaporate first and travel on toward the analyzer, while the heavier molecules remain behind in the liquid phase. Even if at some later point in the process a fractionated sample appears to be all gas, the mixture will not be of the same molecular proportions as it was before fractionation. It will no longer accurately represent the product taken from the process line.
Let's take a closer look at the process of vaporization and how we can manipulate the variables -- temperature, pressure, and flow -- to ensure proper vaporization and an accurate analytical result.
How to Use a Regulator to Reduce Time Delay in an Analytical System
Author: Doug Nordstrom, Mike Adkins, Swagelok
Process measurements are instantaneous but analyzer responses never are. From the tap to the analyzer, there is always a time delay. Unfortunately, this delay is often underestimated or misunderstood.
Time delay is defined as the amount of time it takes for a new sample to reach the analyzer. One way to control time delay is with a regulator. Regulators control pressure, and pressure in an analytical system is closely related to time. In the case of gas systems with a controlled flow rate, the lower the pressure, the shorter the time delay.
Delay may occur in any of the major parts of an analytical instrumentation (AI) system, including the process line, tap and probe, field station, transport line, sample conditioning system, stream switching system, and analyzer.
Ensuring an Accurate Result in an Analytical Instrumentation System Part 2: Calibrating the Analyzer
Author: Doug Nordstrom and Tony Waters, Swagelok Company
In many analytical instrumentation systems, the analyzer does not provide an absolute measurement. Rather, it provides a relative response based on settings established during calibration, which is a critical process subject to significant error. To calibrate an analyzer, a calibration fluid of known contents and quantities is passed through the analyzer, producing measurements of component concentration. If these measurements are not consistent with the known quantities in the calibration fluid, the analyzer is adjusted accordingly. Later, when process samples are analyzed, the accuracy of the analyzer's reading will depend on the accuracy of the calibration process. It is therefore, imperative, that we understand how error or contamination can be introduced through calibration; when calibration can - and cannot - address a perceived performance issue with the analyzer; how atmospheric pressure or temperature fluctuations can undo the work of calibration; and when and when not to calibrate.
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