Heath Consultants EI-5 Ethane Gas Identifier - Manual (Page 16)

EI-5 Manual Rev A 13
Hetek recommends that the instrument be kept clean to the typical standards
applied to portable gas detection instruments, as well as meeting the
requirements for dust, water and gas resistance that are inherent to most
handheld instruments. The use of filters, etc. is covered in the Ethane
Identifier User Manual. Of critical importance is the issue of any type of
blockage of the gas transfer system, and the assurance of no entrainment of
oils, liquids, gases or particulates in the gas sample. Any cleaning protocol
would need to address these issues. It is recommended that, should heavy
hydrocarbon vapors be drawn into the separation column, the user leave the
Ethane Identifier on with the selector valve on “Time” position to purging
the column for approximately 30 minutes. The same procedure applies to
remove entrapped moisture in the separation column.
Calibration of the instrument “sensor” is a misnomer. The instrument utilizes
a column that essentially separates the components in a graduated order.
If more than one type of combustible component is present in the sample
the lightest one (smallest molecule) will be released first followed by the
next heavier (larger molecule). The semiconductor reacts to the release of
each component, as the column releases it, as shown on the previous page
(see Typical Elution Times).
Semiconductor sensors cannot be calibrated. There is no mechanism
to move their response. So, at best, the semiconductor sensor can be
challenged with a known concentration of gas, and the results verified. In
the case of the Hetek Ethane Identifier, the response of the semiconductor
as an absolute value is not critical – the response time delta or elution times
are a function of two separate responses by the sensor. The quantification
of the response is not as critical as the time between the two “peaks”. Since
the two responses (peaks) by the semiconductor sensor are within a minute
of each other, the semiconductor sensor is considered consistent over the
time of the evaluation.
The closest to calibration that you can come with the Ethane Identifier system
is to challenge it with a known sample, within the concentration range noted
in the operating manual and check the result. The manual indicates that “the
instrument can provide reliable results with sample concentrations measured
on a C.G.I. of 10 LEL to 75 LEL natural gas. However, for optimum results
attempt to analyze samples in a concentration of about 50 LEL.”
INSTRUMENT RECOMMENDATIONS