APPLICATIONS
Work Aid 1A: Resources Used to Evaluate the Instrument Air Pressure and Quality for Gas Chromatograph Analyzers
This Work Aid contains guidelines to evaluate whether the instrument air pressure and quality are acceptable for the gas chromatograph analyzer.
1. Is instrument quality air available (not plant air)?
Yes Instrument air quality is acceptable for use with a gas chromatograph analyzer.
No Stop. The instrument air quality is not is appropriate for use with a gas chromatograph analyzer. Either use an alternate source of instrument air or select another type of analyzer.
2. From the ISS, obtain the instrument air supply pressure (Item 17).
3. From the AMDS, obtain the valve air pressure requirement.
4. Is the valve air pressure requirement less than the instrument air pressure after the pressure drop in the air supply piping and tubing is taken into consideration?
Yes The instrument air pressure is high enough to operate the valves in the gas chromatograph analyzer.
No Is plant nitrogen available at a pressure that is higher than the valve air pressure requirement?
Yes Use plant nitrogen to operate the gas chromatograph analyzer valves. Confirm that the analyzer is configured for separate oven and valve supply.
No Use inert cylinder gas to operate the gas chromatograph analyzer valves. Cylinder gas can be supplied from the carrier gas cylinders (if inert) or a dedicated set of inert gas cylinders.
4. From the AMDS, obtain the oven air pressure and flow requirements.
5. Is the oven air pressure requirement less than the instrument air pressure after the pressure drop in the air supply piping and tubing is taken into consideration?
Yes The instrument air pressure is high enough to operate the gas chromatograph analyzer oven.
No Stop. A gas chromatograph analyzer cannot be used in this application. Either use an alternate source of instrument air or select another type of analyzer.
6. Is the oven air flow requirement less than the instrument air supply capacity?
Yes The instrument air supply capacity is sufficient to operate the gas chromatograph analyzer oven.
No Stop. A gas chromatograph analyzer cannot be used in this application. Either use an alternate source of instrument air or select another analyzer.
Work Aid 1B: Resources Used to Evaluate the Measurement Response Time for Gas Chromatograph Analyzers
This Work Aid contains guidelines to evaluate whether the gas chromatograph analyzer’s response time and the sample handling system’s transport lag time are acceptable for the required measurement response time.
1. From the ISS, obtain the required analyzer response time (Item 55) and the required sample transport lag time (Item 56).
2. From the Specific Application Data Sheet (SADS), obtain the specified analyzer response time.
3. From the sample handling diagram, obtain the calculated sample transport lag time.
4. Calculate the required measurement response time as follows:
MRTReq = required analyzer response time (Item 55) + required sample transport lag time (Item 56)
5. Calculate the actual measurement response time as follows:
MRTAct = specified analyzer response time (SADS) + calculated sample transport lag time 6. Is MRTAct < MRTReq?
Yes The analyzer response time and sample handling system lag time provide a measurement response time that is acceptable for this application.
No The analyzer response time and sample handling system lag time do not provide a measurement response time that is acceptable for this application. Either simplify the gas chromatograph analyzer application or choose another analyzer. The application of the gas chromatograph analyzer can be simplified by reducing the number of components that are measured. If the number of measured components cannot be reduced, contact the gas chromatograph analyzer manufacturer for other options that can be considered to simplify the application.
Engineering Encyclopedia Instrumentation Evaluate Gas Chromatograph Analyzers
Work Aid 1C: Resources Used to Evaluate the Phase of the Process Sample for Gas Chromatograph Analyzers
This Work Aid contains guidelines for evaluating whether the phase of the process sample should be a liquid or a gas at the gas chromatograph analyzer.
1. Is the phase of the process sample a gas at process sample supply tap?
Yes Is the dew point of the gas calibration sample below the minimum ambient storage temperature at the maximum supply pressure of the calibration sample cylinder?
Yes The gas calibration sample is acceptable for this application.
No The gas calibration sample is not acceptable for this application. A liquid calibration sample should be used and vaporized in the sample handling system for delivery to the gas chromatograph.
No Continue.
2. Is the bubble point temperature of the liquid process sample higher than the oven temperature at the sample inject valve?
Yes Is the bubble point of the liquid calibration sample above the maximum ambient or storage temperature at the minimum supply pressure of the calibration sample cylinder?
Yes The liquid calibration sample is acceptable for this application.
No The liquid process sample must be vaporized in the sample handling system and handled as a gas. This is not a viable liquid application.
No Is the dew point temperature of a vaporized process sample lower than the oven temperature at the sample inject valve?
Yes The vaporized liquid process sample can be handled as a gas for this application.
No Can the oven temperature be raised above the dew point, without affecting the analysis?
Yes The liquid process sample can be handled as a gas.
No This is not a viable gas application. For this
application the sample may be vaporized and a liquid knock out used.
3. Is the dew point of the gas calibration sample below the minimum ambient storage temperature at the maximum supply pressure of the calibration sample cylinder?
Yes The gas calibration sample is acceptable for this application.
No The gas calibration sample is not acceptable. For this application a liquid calibration sample should be used and vaporized in the sample handling system for delivery to the gas chromatograph analyzer.
GLOSSARY
analyzer response time The length of time required for the analyzer to completely analyze a sample and produce an output signal.
analyzer sensitivity The ratio of the change in the analyzer response with a corresponding change in the process sample.
annulus A ring-like part.
background components Components other than the component of interest in a mixture.
British Thermal Unit (BTU) The amount of heat that is required to raise the temperature of 1 lb. of water from 60° to 61° F.
calorific value The heat value of a gas at standard conditions (14.7 psia and 60°F).
carrier gas A gas that provides a stable transport and detection medium for the sample components.
catalytic cracking A petroleum refining process in which large alkanes are broken down by a catalyst into smaller, branched-chain alkanes
suitable for use in gasoline.
chromatogram The output from a gas chromatograph analyzer, which is displayed on a recorder.
column A long, narrow tube that contains an absorbent material.
column loading Deterioration or buildup of unwanted sample components in the column.
contaminant A component in the process sample that will cause degradation or deterioration of the analyzer measurement.
frequency The number of complete waves passing a point in a given amount of time.
Hertz (Hz) The unit of frequency, given as the number of cycles per second; 1 Hz = 1 s-1.
hydrocracking Catalytic cracking in the presence of hydrogen.
ideal gas A gas in which the volume occupied by the gas molecules is negligible compared with the total volume of the system.
linearity The extent to which any signal modification process, as detection, is accomplished without amplitude distortion.
LNG Liquefied natural gas.
LPG Liquefied petroleum gas.
mobile phase The carrier gas.
Engineering Encyclopedia Instrumentation Evaluate Gas Chromatograph Analyzers
net calorific value The gross calorific value that is generated by combustion less the latent heat that is carried by the products of combustion . octane number The octane quantity of a fuel defined as the fuel’s resistance to
knock.
partition coefficient The ratio of the amount of the gas in the air and the amount of gas in the liquid.
peak resolution The peak separation divided by the peak width.
reforming A process for upgrading naphthas into high-octane gasoline and petrochemical feedstocks.
Reid Vapor Pressure (RVP) A measure of the vapor pressure of a sample of gasoline at 100°F. The results are reported in pounds. This test is usually carried out in accordance with ASTM Method D 323.
sample transport lag time The amount of time that is required for a sample to travel from the sample tap to the analyzer.
slip stream A small stream of solution drawn off from a larger solution stream.
specific gravity The ratio of the density of a fluid to the density of water.
standard temperature and pressure
Standard conditions at a pressure of 14.7 psia and a temperature of 60°F.
stationary phase The absorbent material inside the chromatograph column.
stoiciometrically Pertaining to the substances that are in the exact proportions required for a given reaction.
thermal conductivity Thermal conductivity is the intrinsic property of a material (gas, liquid, or solid) to transfer heat. (The quantity of heat in calories that is transferred in 1 second in a gas between two surfaces of area 1 cm2 that are placed 1 cm apart when the temperature difference between the two surfaces is 1°C.) thermal cracking A process that uses heat to break down the residue, or
bottoms, from vacuum distillation and sometimes the heavy gas oils that result from catalytic cracking.
Vapor to Liquid Ratio (V/L), The partition coefficient, usually designated as K, which is equivalent to y/xm where y is the mole fraction of a given component in the vapor phase that is in equilibrium with x, the tool fraction of the same component in the liquid phase. K is a function of temperature, pressure, and composition of the particular system.