Principle of Operation
16
SafEye
TM
Open Path Detection System User Guide
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 2 extremes. Every
SafEye has 4 built-in gas calibration settings that can be changed by
function setup. 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:
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% and 95%. It is also good for protecting areas where
a leak can be either pure methane or pure propane.
The 4 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 4 calibrations are appropriate, SPECTREX,
through local agents, can advise on how to calibrate a SafEye detector to
any specific gas.
2.3.7
HART Protocol
The SafEye 300 uses the HART Protocol.
HART communications is a bi-directional industrial field communications
protocol used to communicate between intelligent field instruments and
host systems. HART is the global standard for smart instrumentation and
the majority of smart field devices installed in plants worldwide are HART-
enabled.
HART technology is easy to use and very reliable.
Through the HART connection, the SafEye is able to perform:
•
Detector set-up
•
Detector troubleshooting
•
Detector health and status
For more details, refer to the
HART Manual TM899030
.
