Purchasing Hydrogen; Valves; Hydrogen Generator - Thermo Scientific TSQ 9000 Hardware Manual

Preface
Hydrogen Safety Precautions

Purchasing Hydrogen

xxii TSQ 9000 Hardware Manual
Tubing connections should be clamped to barbed or press-fit type connections. Hose
clamps or jubilee clamps must not be used.
• Valves—All valves must be suitable for hydrogen service and for the specific operating
conditions. Valves, including regulators, must not be used for hydrogen, unless they are
designed and identified for such a use. Ball valves are often chosen because of their
superior leak tightness through the valve seat. Pneumatic operators are usually chosen for
remotely operated valves so that potential ignition sources (electricity) are remote from
the valve.
Manual shutoff valves should be provided near each point of use, within immediate reach.
If a hydrogen cylinder or hydrogen generation system is located within immediate reach,
a separate point-of-use shutoff valve is usually not necessary.
Line regulators that have their source away from the point of use should have a manual
shutoff valve near the point of use.
An emergency gas shutoff device in an accessible location outside the use area should be
provided in addition to the manual point-of-use valve in each educational and
instructional laboratory space that has a piped gas supply system.
If necessary, the piping system should have uninterruptible pressure relief. The pressure
relief system should be designed to provide a discharge rate sufficient to avoid further
pressure increase and should vent to a safe location outside or to a ventilation system
exhaust.
Use the following guidelines when purchasing hydrogen:
• Hydrogen Generator—Because it minimizes the amount of hydrogen present and reduces
the degree of hazard, a hydrogen generator (also called an electrolyzer) is the safest way to
purchase hydrogen in the quantity used in GC/MS.
However, to minimize the degree of hazard, the hydrogen generator must only be
operated in a non-explosive environment because hydrogen buildup can be ignitable.
This means that your ventilation system for the room or lab hood must maintain an air
exchange rate that is at least two orders of magnitude greater than the maximum
hydrogen production rate of the hydrogen generator. Be sure to follow the manufacturers'
directions about proper use and maintenance of the regulator.
To prevent the possibility of releasing hydrogen, the hydrogen generator should be set to
shut down if:
– There is a loss of flow to the ventilation system
– A hydrogen detector alarms at 25% of the lower flammable limit of hydrogen in air.
The oxygen exhausted by the electrolyzer should be vented to the outside as well.
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