Spectrex Xenon 700 SIL Open-Path Gas Detection System - Manual (Page 18)

SafEye TM Xenon 700S SIL Gas Detector
6 Principle of Operation
2.3.6 Gas and Mixture Selection and Setting
At the 3.4µ spectral band of the SafEye, the least sensitive gas is pure
(100% vol) methane and the most sensitive gases are various mixtures of
Methane with heavier alkanes where the Methane percentage is less than
90%. For pure Ethane the sensitivity is close to the high sensitivity gases
and for pure Propane it lies somewhere between the two extremes. Every
SafEye has 4 built-in gas calibration settings that can be changed by
function set up The setting for each SafEye is detailed on the calibration
datasheet provided with each unit.
The calibration settings are designed for use in various applications. Models
701, 702, 703 are calibrated to 4 different gases as follows:
Table 2: Gas Calibrations
Gas Type Description
Gas 1 Pure methane and is for use in methane storage and piping
applications
Gas 2 92% methane, 4% propane and 4% ethane (default)
Universal oil and gas production mixture to be used in all
cases where methane concentration in the mixture does not
exceed 98%. It can also be used for pure Ethane
applications.
Gas 3 LPG - 60% Propane and 40% Butane.
Gas 4 99% methane and 1% propane and is for use in detecting
methane mixture with heavier gases where the methane
component can vary between 100% to 95%. It is also good
for protecting areas where a leak can be either pure
methane or pure propane.
Model 721, 722, 723 are calibrated to one gas only Gas 1 – Ethylene 100%.
The four internal gas calibrations cover most of the flammable gas detection
applications. Actual selections should be made by the user in consultation
with experts to provide for safety requirements. However, for special cases
where none of the four calibrations are appropriate, Spectrex, through local
agents can advise how to calibrate a SafEye Detector to any specific gas.
2.3.7 Flash Source
The Xenon Flash Source was originally introduced in the first SafEye
development and was designed to overcome false alarms, which were
experienced by early generations of the open path system. The new SafEye
Xenon 700S employs the latest generation of flash bulbs to provide even
more power and extended operation life (10 years).