Ion Science Hydrosteel 6000 - Manual (Page 7)

Hydrosteel 6000 MANUAL Ion Science Ltd
Page 7 of 39
Unrivalled Detection. www.ionscience.com
About Hydrosteel 6000
Principle of Operation
Collecting a hydrogen sample
Hydrosteel 6000 enables measurements to be made of gaseous hydrogen flux emanating from a steel
surface. The steel surface can be of variable curvature and surface condition.
To make the measurement, a stream of ambient air is drawn across the steel surface by a high performance
low-power-demand pump. This test-
gas stream is confined within a specially designed ‘collector plate’
contained in the probe assembly which is attached to the steel surface. The probe assembly and collector
plates vary according to application. The probe types are listed with their features in Section
– Application
specific measurements.
The collected hydrogen is conveyed through narrow bore tubing, into the measurement analyser, and across
the face of a very sensitive amperometric detector.
Determining the level of the collected hydrogen
The zero hydrogen datum point for Hydrosteel 6000 measurement is the background hydrogen
concentration in air at sea level, namely 0.5 ppm
1
. Rapid diffusion, and hence rapid dispersion of hydrogen
in air, results in a very low and stable background prevailing in the ambient air of most environments, even
indoors. This condition enables the Hydrosteel 6000 to be used in measuring a very small flux of hydrogen
emanating from steel as a result of its interaction with hydrogen occluders and hydrogen occluding
processes. The integrity of the measured data is circumscribed by drift in the ambient air hydrogen content,
and this drift is usually very low.
The flow of the test-gas stream F across the steel surface is carefully regulated by means of restrictions, and
a flow bypass, between the pump and the detector to ensure that it remains smooth and constant. An
additional feature of the flow bypass is to ensure that in the event of a probe blockage, the pump is not
working against a negative pressure differential. Flow regulation is particularly important as the flux J of
hydrogen emanating from the steel is given by:
J = c x F / A
where A is the effective area over which hydrogen is captured, and c the enhanced hydrogen concentration
resulting from hydrogen entrainment.
Output from the amperometric sensor is an electric current, which is proportional to the concentration of
hydrogen presented to it. This current is amplified and scaled for display, and logging, as a hydrogen flux.
To summarise, the prowess of Hydrosteel 6000 technology stems from capturing the hydrogen flux from a
well-defined area of steel surface in a known flow of air, and measuring the very small enhancement in
hydrogen concentration entrained in the air stream. By this means, the very small hydrogen flux commonly
emanating from steel can be quantitatively measured, easily, rapidly and reliably.
Application specific measurements
Hydrosteel can be used to locate, map, and monitor hydrogen flux as detailed in Section
– Deployment
Methods on the next page. Hydrosteel engages interchangeable probes to enable attachment to steel of
diameter greater than 2 in., 5 cm, and surface temperatures from -40 to +500 ºC, -40 to 930 ºF. The
interchangeable probes are classified as follows:
LT-R: Low Temperature
– Roaming Probe
This probe utilises a collector plate 6 in., 15 cm across to deliver the maximum sensitivity, and is
magnetically attached to steel of 3.5 in., 9 cm diameter or greater, of surface temperatures up to 130
o
C, 265
o
F for short periods (quick spot measurements only), and 110
o
C, 230
o
F for general use (for extended
periods please consider use of AT-S probe). To ensure efficient hydrogen capture in wet or windy conditions,
the LT-R probe incorporates a flexible seal around its perimeter.