Adev triple range, Operation of Hydrogen-Cooled Generators and Hydrogen Purity Monitoring Insure Safe. The complete system with sampling system for atex areas. A package from a single source of supply.

1. Hydrogen analysis on
hydrogen cooled generators
www.adev.it info@adev.it

2.  Hydrogen Purity Monitoring Insure Safe
 Operation of Hydrogen-Cooled Generators

3. Application
• On Hydrogen-cooled generators, Hydrogen is circulated through hollow conductors in the
generator to remove the heat that is generated by copper losses in the stator and rotor.
Hydrogen is used since it’s a good heat transfer agent. During normal or on-line operation,
Hydrogen purity must be maintained at a level between 95 and 99%, a level at which it’s
non-explosive and will not support combustion.
• In the start-up phase of a Hydrogen-cooled generator, the hollow conductors and, in fact,
the inside of the generator itself will contain ambient air which must be purged with an
inert gas (e.g. CO2 or N2) prior to introducing Hydrogen. Conversely, on shutdown the
Hydrogen has to be purged with the inert gas before air is introduced.

4. • In short, there are two basic requirements/applications for Hydrogen
purity monitoring; first, to maintain Hydrogen purity for normal operation
above the UEL (Upper Explosive Limit) of 74% H2 in Air and second, to
monitor inert gas purge cycles; on start-up, to insure air is purged out
before Hydrogen is added; and on shutdown, to insure Hydrogen is
purged out prior to introducing air, to prevent explosive levels of H2 which
will result in plant equipment damage/shutdown and possible injury to
plant personnel.

5. CO2
Solution
ADEV model 8866TRTriple Range thermal conductivity analyzer for binary mixtures is
designed and thus ideally suited to providing the highly sensitive and accurate analyses for
the required measurement:
in in
CO2
with the great advantage that all measures can be made with a unique analyzer, simply
setting the wanted range in accordance to the phase. Operation that can be manually
made by a local selector or remotely by customer DCS.
H2 Air
in
H2Air

6. In some cases, nowadays the use of N2 as inert gas is preferred to CO2. In this case,
the thermoparamagnetic Oxygen analyzer model 8863 in necessary for an accurate
measure of Air in N2 because with thermal conductivity measuring principle the
sensitivity of Air respect to N2 is not enough.
H2 Air N2
in in in
H2 Air N2

7. • To satisfy the first basic requirement, that of monitoring Hydrogen purity during
normal operation so that it’s maintained above the UEL of H2 (Upper Explosive
Limit of H2 in Air = 74%), operationally above 93% H2, the range 85-100% H2 in Air
is applicable (or other on customer specification).
• For the second basic requirement, monitoring the inert gas purge cycles, the range
0-100% H2 in CO2 will apply.
• The third offered range gives the possibility to better verify the inerting phase,
checking the range 0-100% CO2 in Air (or N2 in Air with the addiction of the
thermoparamagnetic Oxygen analyser model 8863 as explained before).

8. • As pictured, an analyser is supplied with a control unit which can be panel
mounted either at the sampling site or in a control room.The control unit
also can provide a current output signal, alarms, reading in engineering
units and free contacts to identify the range selection.

9. Different approaches to the measure
Alternative approaches can be used, depending on the type
of inert gas used
A. For CO2 purge gas
B. For N2 purge gas

10. A. For CO2 purge gas
Solution 1: A model 8866 analyser can be used for any number of generators to
monitor start-up and shutdown, in order to follow CO2 purge gas from
air level to 100% CO2 (and vice versa). Calibration range will be:
1. 0-100% CO2 in Air
Solution 2: A model 8866 Dual Range analyser is recommended for each
generator to monitor intermediate levels of H2 during purging and air
intrusion during continuous operation. Ranges are:
1. 0-100% H2 in CO2
2. 75-100% H2 in Air

11. Solution 3: A model 8866TRTriple Range analyser, including all functions in a
unique analyser, with ranges customer selectable. Example of
possible triple ranges are:
1. 0-100% CO2 in Air 1. 0-100% Air in CO2
2. 0-100% CO2 in H2 2. 0-100% H2 in CO2
3. 100-75% H2 in Air 3. 75-100% H2 in Air
Note that the starting point 75% can be 85% or as per customer specification.The
calibration is easy and, on the simplest range (suppose range 2), the current output is
related to the selected range (manually or remotely) and it’s identified by a free contact
for each range and by a lighted indication on the main control unit.

12. B. For N2 purge gas
Solution 1: A model 8863 Oxygen analyser can be dedicated or shared among all
generators to monitor start-up and shutdown.
Calibration range will be:
1. 0-100% Air in N2
Solution 2: A model 8866 Dual Range analyser is recommended for each
generator to monitor intermediate levels of H2 during purging and air
intrusion during continuous operation. Ranges are:
1. 0-100% H2 in N2
2. 75-100% H2 in Air

13. Solution 3: ATriple Range package including a model 8866 sensing unit + a model
8863 thermoparamagnetic sensing unit combined with a unique
control unit with ranges customer selectable. Example of possible
triple ranges are:
1. 0-100% Air in N2 1. 0-100% Air in N2
2. 0-100% N2 in H2 2. 0-100% H2 in N2
3. 100-75% H2 in Air 3. 75-100% H2 in Air

14. With the selection of the proper
analyser equipment,
commensurate with the purge gas
used, it can be see from the
following expected sequence of
events that the application of
ADEV gas analysis will insure both
safe shutdown and start-up.
~ 100% H2
inside
Normal operative phase
Range 75-100% H2 in air
of solution 2 Active
Range 75-100% H2 in air
of solution 3 Active
Range 75-100% H2 in air
of solution 2 Active
Range 75-100% H2 in air
of solution 3 Active
With CO2 purge gas With N2 purge gas
Inlet of H2
Step 1
Inerting phase
Inlet of CO2
or N2
Outlet of H2
Range 0-100% H2 in N2
of solution 2 Active
Range 0-100% H2 in N2
of solution 3 Active
Range 0-100% H2 in CO2
of solution 2 Active
Range 0-100% H2 in CO2
of solution 3 Active
Shutdown
With CO2 purge gas With N2 purge gas
Inlet of Air
Outlet of CO2
Or N2
Step 2
Air equalizationWith CO2 purge gas With N2 purge gas
Range 0-100% Air in N2
of solution 1 Active
Range 0-100% Air in N2
of solution 3 Active
Range 0-100% CO2 in air
of solution 1 Active
Range 0-100% CO2 in air
of solution 3 Active

15. ~ 100% H2
inside
Normal operative phase
Range 75-100% H2 in air
of solution 2 Active
Range 75-100% H2 in air
of solution 3 Active
Range 75-100% H2 in air
of solution 2 Active
Range 75-100% H2 in air
of solution 3 Active
With CO2 purge gas With N2 purge gas
Inlet of H2
Step 1
Inerting phase
Inlet of CO2
or N2
Outlet of Air
Range 0-100% Air in N2
of solution 1 Active
Range 0-100% Air in N2
of solution 3 Active
Range 0-100% CO2 in air
of solution 1 Active
Range 0-100% CO2 in air
of solution 3 Active
Start-UP
With CO2 purge gas With N2 purge gas
Air
inside
Inlet of H2
Outlet of CO2
Or N2
Step 2
Inlet of HydrogenWith CO2 purge gas With N2 purge gas
Range 0-100% H2 in N2
of solution 2 Active
Range 0-100% H2 in N2
of solution 3 Active
Range 0-100% H2 in CO2
of solution 2 Active
Range 0-100% H2 in CO2
of solution 3 Active

16. Highlights
• High speed of response Such that any changes in concentration are detected initially in less than 1
second, this permitting operator intervention to circumvent equipment
malfunction or personal injury.
• High sensitivity To insure accurate, repeatable, reproducible and meaningful
measurements which permit continuous on-line operation and safe start-up
and shutdown...through the use of reliable solid-state design.
• Excellent stability Where measurement integrity in minimally affected by the external
operating environment...through rugged construction.
• Application flexibility Since the control unit can be panel mounted either at the analyser location or
remotely in a control room (this last solution will also result in lower costs)

17. Sample and conditioning system
• Complementing the analysers is the availability of a wide selection of
sampling system components, such as filters, flow meters, needle valves
etc…, resulting in a complete package from a single source of supply.
• Further, these components and the analysers can be supplied on a panel (or in
a cabinet), including mounting and wiring, thus keeping installation costs to
the minimum.

18. Hydrogen analysis on hydrogen cooled
generations
by
www.adev.it info@adev.it
Via S.Eurosia, Cesano Maderno (MB) 20811 Italy
Tel. +39 0362641684 - Fax. +39 0362575058