Parr Instrument 1108 - Manual (Page 4)

1108 Oxygen Combustion Vessel
P a r r I n s t r u m e n t C o m p a n y 4
Operating the 1108 Oxygen
Combustion Vessel
Precautions
Combustion with oxygen in a sealed bomb is a very
effective and reliable method for releasing all heat
energy obtainable from a sample and for preparing
hydrocarbon compounds and carbonaceous materi-
als for analysis, but there are certain precautions
which must always be observed when using this
equipment. In particular:
• Do not overcharge the bomb with too much
sample or with a sample which might react with
explosive violence.
• Do not overcharge the bomb with too much
oxygen. The initial charging pressure should not
exceed 40 atm (590 psig).
• Do not fire the bomb alone on an open bench
without providing a protective cooling medium.
The bomb should be completely submerged in
water during firing.
• Do not fire the bomb if gas bubbles are
released from any point on the bomb when it is
submerged in water.
• Do not ignite a volatile sample without using
one of the sealed sample holders described on
pages 8-9.
• Stand away from the bomb during and do not
handle the bomb for at least 6 minutes after
firing.
• Keep the bomb in good condition at all times.
Any parts that show signs of weakness or
deterioration must be replaced promptly.
• Read the maintenance and safety instructions
beginning on page 12 before starting to use the
bomb, and urge all operating personnel to re-
read these instructions often.
• Screw caps and cylinders are stamped so that
each cylinder and screw cap can be identified as
a matched set. We recommend that you maintain
the match of cylinders and screw caps for your
safety and ease of use.
Special Alloy Construction
The standard 1108 Oxygen Combustion Vessel is
made of a special columbium-stabilized stainless
steel selected for it’s excellent resistance to the
mixed nitric and sulfuric acids generated in a com-
bustion. It is a superior alloy which will withstand the
conditions generated in almost all fuel testing ap-
plications, yet neither it nor any other stainless steel
will resist the corrosive atmospheres produced when
burning samples containing halogen compounds.
For these applications, Parr offers the 1108CL Oxygen
Combustion Vessel described below. It should be
noted that all instructions for the 1108 apply equally
to the 1108CL as well.
A Chlorine-Resistant Bomb
The 1108CL Combustion Vessel is the same as the
standard 1108 model, but with a head and cylinder
made of an alloy with superior corrosion resistance
to the free chlorine and halogen acids released
when burning chlorinated samples. Users who
analyze waste materials and combustible solvents
are urged to select the 1108CL Combustion Ves-
sel instead of 1108 for its longer service life under
extreme corrosive conditions. Bomb maintenance
is also improved. In most cases, 1108CL returned
to the factory for scheduled maintenance can be
restored to optimum finish by repolishing instead of
having to rebore the cylinder to remove pits.
1108B Oxygen Combustion Vessel
The 1108B and 1108BCL Combustion Vessels are
identical to the 1108 and 1108CL models except for
the screw cap and cylinder. The 1108B and 1108BCL
have a heavy duty screw cap allowing for higher
energy release per sample. The cylinder has been
adapted to comply with Indian Standard IS 1350.
Other Special Purpose Bombs
Although the 1108 and 1108CL Combustion Vessels
will handle a broad range of test samples, Parr also
offers other special purpose combustion bombs,
including: a high pressure bomb for explosives, an
oversize bomb for large samples and a semi-micro
bomb for small samples. Separate operating instruc-
tions are issued for these special bombs.
Allowable Sample Size
To stay within safe limits, the bomb should never be
charged with a sample which will release more than
8000 calories (1108) or 10,000 calories (1108B) when
burned in oxygen, and the initial oxygen pressure
should never exceed 40 atmospheres (590 psig).
This generally limits the mass of the combustible
charge (sample plus benzoic acid, gelatin, firing oil
or any combustion aid) to not more than 1.1 grams.
When starting tests with new or unfamiliar materials
it is always best to use samples of less than 0.7 of a
gram, with the possibility of increasing the amount
if preliminary tests indicate no abnormal behavior.
To avoid damage to the bomb and possible injury
to the operator, it should be a standing rule in each
laboratory that the bomb must never be charged
with more than 1.5 grams of combustible material.