K465i Operations and Maintenance
P/N 1212831 Rev C
Page 4-26
Copyright
©
2012
Veeco Instruments, Inc. Confidential
All Rights Reserved
OPERATING PRECAUTIONS
It is recommended that the Palladium cell be operated at all times in accordance with
recognized, safe practices for hydrogen-handling equipment. When using hydrogen, be
aware of the properties of the gas. For example, hydrogen:
Is combustible at concentrations between 4% and 75% in air.
Detonates at concentrations between 18% and 59% in air.
Has an auto ignition threshold (in air) of 500°C.
Will be ignited with an electrical discharge exceeding the energy equivalent to 200
mA @ 24 VDC.
Please consult your qualified safety personnel for required safe operating procedures and
practices. The following general safety precautions are recommended:
Use only grounded electrical connections.
Do not operate instruments in the presence of fugitive hydrogen.
Permit only qualified and trained personnel to make component replacements.
Always disconnect electrical power before removing unit cover.
Allow time for hot internal surfaces to cool.
Avoid the use of spark producing electrical equipment near the purifier cell.
Operate the unit only in a well-ventilated area that is equipped with hydrogen
detection instrumentation, an alarm system, and a fire protection system that meets
the criteria of NFPA 30.
Post
No Smoking
signs in areas where hydrogen can be present.
Exposure to hydrogen feed-gas streams of unknown quality is inadvisable and may result in
damage to the membrane. In particular, ensure that corrosive contaminates as halogens
and halides are absent from the feed-gas stream. Do not allow sulfur compounds or
unsaturated hydrocarbons in the feed gas as these compounds will poison the surface of the
palladium alloy membrane. If a cell becomes partially poisoned, as indicated by a drop in
the hydrogen purification rate, reactivation may be possible.
Gases such as N
2
, CO, CO
2
, H
2
O, NH
3
, and CH
4
are not injurious to the palladium membrane
but will reduce the transfer rate by reducing the hydrogen partial pressure. Other materials,
although not damaging, may likewise reduce the ability of the cell to transfer hydrogen at
the rated capacity. Specifically, it is known that oils, orK465i GaNic compounds, solvents,
greases, pipe compounds, and fitting lubricants (particularly those containing lead) will
decrease the capacity of the hydrogen purifier. Mercury, lead, zinc and iron salts should not
come in contact with the palladium alloy tubes.
Oxygen in a concentration greater than 1,000 ppm, although not a surface poison, may
cause damage to the palladium membranes. The palladium alloy is an excellent catalyst for
the reaction of hydrogen and oxygen, and an exothermic reaction will occur when these two
gases are present. The presence of oxygen in the hydrogen feed gas can cause severe
overheating and damage to the purifier. For example, a concentration of 1,000 ppm of
oxygen will cause a temperature rise of 30°C when reacted with hydrogen. If it suspected
that the hydrogen feed gas stream may contain oxygen at a concentration above 1,000
ppm, an
Oxygen-Removing Purifier
can be installed in the feed line to the
Hydrogen Purifier
.
