Appendix C – Functional Testing Using Gas
Senscient ELDS™
Rev 15
149
GB
Second, prevent further flow of gas into the Gassing Cell by closing the valve on the cell inlet
(11)
to which the gas cylinder is connected.
Finally, close off the outlet valve on the Gassing Cell, thereby sealing off the cell ready for
(12)
use.
Ideally, the test gas concentration should be selected to generate a reading from the unit that is
between 0.5× and 1× full scale.
The integrated LFL.m concentration in the cell can be calculated using the following formula:
Int(LFL.m)ELDS = Lcell * (Concv/v / LFLv/v)
Int(LFL.m)ELDS = 0.236 * (Concv/v / LFLv/v)
Where:
Int(LFL.m)ELDS = Integrated LFL.m reading output by Senscient ELDS™
Lcell
= Length of cell in metres (0.236m for the Senscient Calibration Cell)
Concv/v
= Gas concentration in %v/v
LFLv/v
= Lower Flammability Limit of the gas in %v/v
The integrated ppm.m concentration in the cell can be calculated from the following formula:
Int(ppm.m)ELDS = Lcell * Concppm
Int(ppm.m)ELDS = 0.236 * Concppm
Where:
Int(ppm.m)ELDS = Integrated ppm.m reading output by Senscient ELDS™
Concppm
= Gas concentration in ppm by volume
CAUTION
Tests performed using the Gassing Cell cannot be used to evaluate the response time of an
ELDS OPGD - the Gassing Cell is ONLY suitable for verifying the steady-state response to
target gas(es). The reason for this is that when a Gassing Cell is introduced into the beam-path
of an ELDS OPGD system, the windows, window guards and walls of the Gassing Cell
significantly reduce the signal reaching the ELDS Receiver unit. In order to make measurements
following such significant changes in signal levels, the Receiver unit has to adjust the detector
amplifier’s gain to compensate for the signal changes. Adjusting the amplifier gain to a new level
and allowing this to stabilize takes time; and the amount of time taken varies depending upon
exactly how the Gassing Cell was introduced.
Consequently, do NOT interpret the time taken to respond to target gas inside a Gassing Cell as
being indicative of the time taken to respond to a genuine leak or release of target gas into the
beam-path of an ELDS OPGD. The time taken to respond to target gas inside a Gassing Cell is
longer than the response to a genuine leak / release will be, and is also more variable. The
response time for real leaks / releases is tested by Senscient using special equipment and
procedures that enable the genuine speed of response to be measured, which equipment and
procedures do not make use of the Gassing Cell..
Summary of Contents for Senscient ELDS 1000 series
Page 58: ...Installation Commissioning 58 Senscient ELDS Rev 15 GB 2 x Mounting Brackets ...
Page 140: ...Certification 140 Senscient ELDS Rev 15 GB 9 1 2 Control Drawing CENELEC ATEX ...
Page 142: ...Certification 142 Senscient ELDS Rev 15 GB 9 1 4 Control Drawing CSA US Canada ...
Page 159: ...Appendix D Manufacturer s EC Declarations Senscient ELDS Rev 15 159 GB ...
Page 160: ...Appendix D Manufacturer s EC Declarations 160 Senscient ELDS Rev 15 GB ...
Page 184: ...For local MSA contacts please visit us at MSAsafety com Because every life has a purpose ...
