Instrument recommendations – Heath Consultants EI-5 Ethane Gas Identifier User Manual

Page 16

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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

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