Parr Instrument 1108R User Manual

1108R

Oxygen Combustion Vessel

Operating Instruction Manual

662M

1108R Oxygen Combustion Vessel

Preface 3

Scope 3

Head Seal Modification 3

Related Instructions 3

Customer Service 3

Operating the 1108R Oxygen Combustion Vessel 4

Precautions 4

Special Alloy Construction 4

A Chlorine-Resistant Bomb 4

Other Special Purpose Bombs 4

Allowable Sample Size 5

Attaching the Cotton Thread 5

Liquids in the Bomb 5

Closing the Bomb 5

Filling the Bomb 6

Recovering the Combustion Products 7

An Optional Recovery Procedure 7

Operating Suggestions 11

Poor Combustion 11

Oxygen Charging Pressure 11

Maintenance and Safety Instructions 12

Bomb Maintenance 12

Bomb Repairs and Proof Tests 13

1108R Maintenance Checklist 14

Parts 16

1108R Parts Diagram Key 16

Parts for the 1108R Oxygen Combustion Vessel 17

Parts for the 2901 Ignition Unit 18

Parts for the 1825 Oxygen Filling Connection 19

Samples and Sample Holders 8

Particle Size and Moisture Content 8

Combustion Aids 8

Sample Pellets 8

Combustion Capsules 8

Foodstuffs and Cellulosic Materials 9

Coarse Samples 9

Corrosive Samples 9

Liquid Samples 9

Gelatin Capsules 9

Tape-Sealed Sample Holders 10

Heavy Oils 10

Explosives and High Energy Fuels 10

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Parr Instrument Company

1108R Oxygen Combustion Vessel

Preface

Scope

These instructions cover the procedures to be fol­lowed when using a Parr 1108R Oxygen Combustion
Vessel to determine calorific values of solid or liquid
combustible material in a Parr calorimeter, or when
using an 1108R in a 1901 Oxygen Vessel Apparatus
to prepare solid or liquid samples for chemical
analysis. The user should study these instructions
carefully in order to obtain a complete understand­ing of the capabilities and limitations of an 1108R,
and to be well aware of the precautions to be ob­served in its operation. Calorimeter operations and
the operation of various oxygen vessel accessories
are described in separate instruction manuals listed
below, copies of which are available upon request.

Note About Nomenclature:

Historically, burning a sample enclosed
in a high pressure oxygen environment is
known as Oxygen Bomb Calorimetry and
the vessel containing the sample is known
as an Oxygen Bomb. The terms bomb and
vessel are used interchangeably.

Head Seal Modification

The 1108R differs from the standard 1108 series
oxygen combustion vessel in that the head seals
using a quad ring rather than an o-ring. To insure
proper compression of the quad ring a separate con­tact ring is used in conjunction with the screw cap.

Otherwise the head is similar to the one used in
the 1108P in that a wire is heated to ignite a cotton
thread that in turn ignites the sample.

This model is offered to users that have older
models incorporating this type of seal.

Related Instructions

No. Description

201M Limited Warranty
207M Analytical Methods for Oxygen Bombs
230M Safety in the Operation of Laboratory

and Pressure Vessels

483M Introduction to Bomb Calorimetry

Customer Service

Questions concerning the installation or operation of this instrument
can be answered by the Parr Customer Service Department:

1-309-762-7716 • 1-800-872-7720 • Fax: [phone]

E-mail: [e-mail] • http://www.parrinst.com

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3

1108R Oxygen Combustion Vessel

Operating the 1108R 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 materi­als 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
page 9 or the tape technique.

• 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 10 before starting to use the
bomb, and urge all operating personnel to re­read these instructions often.

Special Alloy Construction

The standard 1108R Oxygen Combustion Vessel is
made of a special niobium-stabilized stainless steel
selected for it’s excellent resistance to the mixed
nitric and sulfuric acids generated in a bomb com­bustion. It is a superior alloy which will withstand
the conditions generated in almost all fuel testing
applications, 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

1108RCL Combustion Vessel described below. It
should be noted that all instructions for the 1108R
apply equally to the 1108RCL as well.

A Chlorine-Resistant Bomb

The 1108RCL Combustion Vessel is the same as the
standard 1108R 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 1108RCL Combustion Vessel instead
of 1108R for its longer service life under extreme
corrosive conditions. Bomb maintenance is also
improved. In most cases, 1108RCL vessels returned
to the factory for scheduled maintenance can be
restored to optimum finish by polishing instead of
having to rebore the cylinder to remove pits.

Other Special Purpose Bombs

Although the 1108R and 1108RCL Combustion
Vessels will handle a broad range of test samples,
Parr also offers other special purpose combustion
vessels, including: a high pressure bomb for ex­plosives, an oversize bomb for large samples and
a semi-micro bomb for small samples. Separate
operating instructions are issued for these special
bombs.

• 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.

4

Parr Instrument Company

1108R Oxygen Combustion Vessel

845DD2 Cotton Ignition Thread

To attach the fuse either twist or tie the cotton thread
to the A40DD2 semi-permanent fuse wire.

Allowable Sample Size

To stay within safe limits, the bomb should never be
charged with a sample which will release more than
8000 calories when burned in oxygen, and the initial
oxygen pressure should never exceed 40 atmo-

spheres (590 psig). This generally limits the mass of

the combustible charge (sample plus benzoic acid,

gelatin, ring 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.

Attaching the Cotton Thread

A cotton thread (845DD2) is used as an auxiliary

fuse to ignite the sample. Ten centimeters of thread
is recommended for this auxiliary thread which is
looped over the heating wire, doubled on itself,
twisted to form a single strand and fed into the
sample cup to lay on the sample.

When contact is made through the heating wire,
the thread will ignite, drop into the sample cup and
ignite the sample.

A38A Head Support Stand

Set the bomb head on the A38A support stand when

attaching the fuse and arranging the sample.

Liquids in the Bomb

Most bomb combustion procedures call for a small
amount of liquid to be placed in the bottom of the
bomb as a sequestering agent and absorbent. If the
amount and type of liquid are not otherwise speci­fied, add 1.0 mL of distilled or deionized water from
a pipet.

Closing the Bomb

Care must be taken not to disturb the sample when
moving the bomb head from the support stand to
the bomb cylinder. Check the sealing ring to be sure
that it is in good condition and moisten it with a bit
of water so that it will slide freely into the cylinder;
then slide the head into the cylinder and push it

down as far as it will go. For easy insertion, push

the head straight down without twisting and leave
the gas release valve open during this operation.
Make sure that the contact ring is positioned flat
on top of the sealing ring. Set the screw cap on the
cylinder and turn it down firmly by hand to a solid
stop. When properly closed, no threads on the
cylinder should be exposed. If the screw cap tends
to bind to the cylinder at this point, indicating that it
might be difficult to open the bomb after it has been
fired, turn the screw cap back slightly – but only a
few degrees – enough to release the binding, since
the bottom thread must remain fully engaged. It
is not necessary to use a wrench or spanner on the
screw cap. Hand tightening should be sufficient to
secure a tight seal.

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5

1108R Oxygen Combustion Vessel

Filling the Bomb

The instructions below
describe a manual system

using the 1825 Oxygen
Filling Connection furnished

with other Parr apparatus.

Oxygen for the bomb can
be drawn from a standard
commercial oxygen tank.
Unscrew the protective cap
from the tank and inspect
the threads on the valve
outlet to be sure they are
clean and in good condi­tion. Place the ball end of
the connection into the
outlet socket and draw up
the union nut tightly with

a wrench, keeping the 0-55

atm gage in an upright position.

The pressure connection to the bomb is made with
a slip connector on the oxygen hose which slides
over the gas inlet fitting on the bomb head. Slide
the connector onto the inlet valve body and push it
down as far as it will go. If it does not slide easily,
a drop of water spread around the inlet valve will
lubricate the sealing rings.

Close the outlet valve on the bomb head; then open
or “crack” the oxygen tank valve not more than
one-quarter turn. Open the filling connection control
valve slowly and watch the gage as the bomb pres­sure rises to the desired filling pressure (usually 30

atm., but never more than 40 atm.); then close the

control valve. The bomb inlet check valve will close
automatically when the residual pressure in the fill­ing hose is released, leaving the bomb filled to the

highest pressure indicated on the 0-55 atm. Gage.

Release the residual pressure in the filling hose
by pushing downward on the lever attached to the
relief valve. The gage should now return to zero. If
the pressure drops slowly and a large amount of gas
escapes when the pressure relief valve is opened,
the check valve in the bomb head is not operating
properly. This trouble will have to be corrected
before the bomb can be used. If too much oxygen
should accidentally be introduced into the bomb,
DO NOT proceed with the combustion. Detach the
filling connection; exhaust the bomb; remove the
head and reweigh the sample before repeating the
filling operation.

1825 Oxygen Filling

Connection

Firing the Bomb

The electric current for
firing the bomb should
be drawn from a Parr
2901EB Ignition Unit

connected to an 115V
50/60Hz grounded elec­trical outlet. (For 230V
50/60Hz use a 2901EE
Ignition Unit). Connect

one of the lead wires
from the calorimeter
to the 10 cm binding
post on the ignition unit
and the 2nd wire to the
middle or “common”
terminal.

When using the bomb in a calorimeter, insert the
421A lifting handle into the two holes in the side of
the screw cap and lower the bomb partially into the
calorimeter water bucket. Press the banana plugs
on the two ignition wires firmly into the terminal
sockets on the bomb head before the head is com­pletely immersed in the water. After connecting
the wires, lower the bomb into the bucket with its
feet spanning the circular boss in the bottom of the
bucket. Remove the lifting handle and shake off any
drops of water back into the bucket. Be careful not to
remove any water from the bucket with the fingers.
When using the bomb alone for analytical purposes
it should be connected to the ignition unit as de­scribed above and held submerged in an A387A or
similar water bath during firing.

In all operations, check the bomb for leaks before
firing. If any gas leakage is indicated, no matter how
slight, DO NOT FIRE THE BOMB. Instead remove
it from the water bath; release the pressure and
eliminate the leak before proceeding with combus­tion test. If no leakage is indicated, then stand back
and press the firing button on the ignition unit to fire
the charge.

Caution!
Do not have the head, hands or any parts of
the body directly over the bomb during the
firing period and do not go near the bomb for
at least 20 seconds after the firing.

2901 Ignition Unit

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Parr Instrument Company

1108R Oxygen Combustion Vessel

Fire the charge by pressing the ring button on the

ignition unit, keeping the circuit closed for about 2
seconds. The indicator light will come on when the
button is depressed and will remain on while the
button is depressed.

If the indicator light does not come on when the
firing button is pressed there is either a fault in the
2901 or an open circuit in the system. Check for
voltage between the 10 cm and common terminals
of the 2901. Approximately 23 VAC should be mea­sured. If there is no voltage present, check the fuse
inside the 2901. An open circuit can usually be lo-

cated with an ohmmeter. Flex the lead wires during

any continuity check as the wires may be broken
and making only intermittent contact. If the red indi­cator light glows during ignition but the bomb fuse
does not burn, check the system for a voltage leak
to ground, most likely in the insulated electrode on
the bomb head. Check the electrode using the high
impedance scale on an ohmmeter and replace the
electrode insulator and seal if leakage is indicated.

Recovering the Combustion Products

Let the bomb stand in the calorimeter or water bath
for at least 3 minutes, then lift it out of the water
and wipe with a clean towel. Open the valve knob
slightly to release all residual gas pressure before
attempting to remove the screw cap.

Caution!
Do NOT have any part of the body in the
exhaust path of the bomb.

Gas release should proceed slowly over a period

of not less than one minute to avoid entrainment
losses. After all pressure has been released, un­screw the cap; lift the head out of the cylinder and
place it on the support stand. Do not twist the head
during removal. Pull it straight out to avoid sticking.
Examine the interior of the bomb for soot or other
evidence of incomplete combustion. If such is found
the test will have to be discarded. Wash all interior
surfaces of the bomb and the combustion capsule
with a jet of distilled water and collect the washings.
If any precipitate or residue is present, remove it
with a rubber policeman. Do not filter the washings
as this might remove valuable constituents. Titrate
the washings and measure the unburned fuse wire
as required for calorific tests, then analyze the wash­ings for sulfur and other elements, if required.

An Optional Recovery Procedure

If desired, a luer tting, 518A, can be attached to the

bomb to provide a means for washing the bomb
and recovering the combustion products with a
syringe without opening the bomb and removing
the bomb head. To use this procedure, remove the
standard A420A valve needle and replace it with
an A420A2 needle to which a syringe, 244C, can be
attached.

To recover the combustion products via a luer
fitting, let the bomb stand in a cooling bath for at
least 3 minutes after firing to allow for complete
condensation of all residual vapor. Then remove the
bomb from the water and attach only the barrel of a
244C syringe to the luer fitting. Open the valve and
release the pressure at a slow rate, using at least
a full minute to bring the bomb pressure back to
atmospheric. The attached syringe barrel will help to
retain any condensate spray that might be carried
out of the valve during the exhaust period.

Add 30 mL of distilled water to the attached syringe
barrel and use the syringe plunge to force the
water into the bomb, then close the valve while
holding the plunger down. This will develop suf­ficient pressure within the bomb to seat the inlet
check valve and provide enough positive pressure
to help remove the washings. Agitate and rotate
the bomb in a horizontal position to wet all inner
surfaces, then turn the bomb upside down over
a 600 mL beaker and open the valve to discharge
the washings into the beaker. Tilt the bomb slightly
toward the valve to get as much of the water out as
possible. Repeat this back-flushing procedure two
times, collecting a total of 90 to 100 mL of washings,
then open the bomb and recover any liquid that
may remain in the cylinder. The three complete back
flush and rinse cycles should recover better than 99
percent of the combustion products.

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7

1108R Oxygen Combustion Vessel

Samples and Sample Holders

Particle Size and Moisture Content

Solid samples burn best in an oxygen bomb when
reduced to 60-mesh, or smaller, and compressed
into a pellet with a Parr Pellet Press. Particle size is
important because it influences the reaction rate.
Large particles may not burn completely and small
particles are easily swept out of the capsule by
turbulent gases during the rapid combustion. Com­pression into a pellet is recommended since a pellet
burns less vigorously than a loose sample, resulting
in fewer incomplete combustions.

Materials such as coal burn well in the as-received
or air-dry condition, but DO NOT BURN BONE-DRY
SAMPLES. A certain amount of moisture is desir­able in order to control the burning rate. Very dry
samples may burn so rapidly that a flame might
reach the seals or the soft valve seat in the bomb
head, igniting these parts and possibly causing a
serious burn-out through the head. Moisture con­tents up to 20% can be tolerated in many cases, but
the optimum moisture is best determined by trial
combustions. If moisture is to be added, drop water
directly into a loose sample or onto a pellet after the
sample has been weighed; then let the sample stand
for awhile to obtain uniform distribution.

2811 Pellet Press

offers a convenient means for preparing samples
in this manner. Pellets produced in this press are
ejected into a stainless steel receiver from which
they can be lifted and handled easily with a pair of
forceps. Most pellets for use in the 1108R Oxygen
Combustion Vessels are made in a one-half inch di­ameter size, but smaller diameters can be produced
in the same press using interchangeable punch and
die sets. Complete pellet making instructions are
furnished with each press.

Combustion Aids

Some samples may be difficult to ignite, or they
may burn so slowly that the particles become chilled
below the ignition point before complete combus­tion is obtained. In such cases benzoic acid, white oil
or any other combustible material of known purity
can be mixed with the sample. Ethylene glycol,
butyl alcohol or decalin may also be used for this
purpose. It must be remembered, however, that a
combustion aid adds to the total energy released in
the bomb and the amount of sample may have to be
reduced to compensate for the added charge. If ben­zoic acid is added as a combustion aid, it must be
added in a pellet form, .2 gm pellets. Never combust
benzoic acid in powder form.

Sample Pellets

One of the most useful techniques for handling
powdered samples is to compress the material into
a tablet or pellet before it is weighed. Pellets are
easier to handle than loose samples and they burn
slower in the bomb, thereby reducing the chances
for incomplete combustion. The Parr pellet press

Combustion Capsules

Non-volatile samples to be tested in Parr oxygen
bombs are weighed and burned in shallow capsules

measuring approximately 1” diameter and 7/16”

deep. These are available in stainless steel, fused

silica and platinum alloyed with a 3-1/2% rhodium.

Stainless steel capsules are suitable for all tests

except those in which a non-metallic (fused silica)

holder is desired or where the superior corrosion

resistance of a Pt-Rh cup is required. Fused silica

capsules should be used for samples containing
dissolved metals which can ignite a stainless steel
capsule and cause serious bomb damage.

Stainless steel capsules will soon acquire a dull grey
finish after repeated use in an oxygen bomb due to
the formation of a hard, protective oxide film. This
dull finish not only protects the capsule but it also
promotes combustion and makes it easier to burn
the last traces of the sample. It is recommended,
therefore, that capsules be heated in a muffle fur-

nace at 500°C for 24 hours to develop this protective

coating uniformly on all surfaces. This treatment
should be performed after a capsule has been

8

Parr Instrument Company

3601 Gelatin Capsules

43A6 Combustion Capsule with

Adhesive Tape Seal

1108R Oxygen Combustion Vessel

43AS Combustion Capsules

polished with an abrasive to remove any ash or
other surface deposits. Heating in a muffle furnace
is also a good way to destroy any trace of carbon
or combustible matter which might remain in the
capsule from a previous test. After heating, place the
capsules in a clean container and handle them only
with forceps when they are removed to be weighed
on an analytical balance.

Capsules should be monitored for wear. Do not use
the capsule if the wall or base thickness is less than

0.025”.

Foodstuffs and Cellulosic Materials

Fibrous and uffy materials such as vegetable bers

may have to be packed into the combustion capsule
and moistened to slow the burning rate, but food­stuffs and cellulosic samples generally burn with
little difficulty. Partial drying may be necessary if the
moisture content is too high to obtain ignition. But
if the sample is heat sensitive and cannot be dried,
a water soluble combustion aid such as ethylene
glycol can be added to promote ignition.

Coarse Samples

In most cases it may be necessary to burn coarse
samples without size reduction since grinding or
drying may introduce unwanted changes. There
is no objection to this if the coarse sample will
ignite and burn completely. Whole wheat grains
and coarse charcoal chunks are typical of materials
which will burn satisfactorily without grinding and
with no additives or special procedure.

Corrosive Samples

Although the Parr bomb is made of corrosion resis­tant alloys, repeated use with high sulfur samples or
with samples containing over 20 mg of chlorine may
corrode the metal surfaces and produce a dull film
on the inner walls of the bomb. Materials containing
appreciable amounts of caustic; such as dried black
liquor from a pulp mill, may also damage the bomb,
with the caustic attacking the alloy capsule and
causing the metal capsule and the bomb electrodes
to ignite and burn. These corrosive attacks on the
bomb can be reduced by using smaller samples
and by increasing the amount of liquid placed in the
bottom of the bomb. If a corrosive film develops on
the bomb surfaces it should be removed by proper
polishing before it grows to a point where deep
pitting occurs.

Liquid Samples

Non-volatile samples are treated in the same
manner as solid materials. Oils and other liquids
which are not volatile at room temperature can be
weighed directly into open combustion capsules.
The cotton thread should be positioned just slightly
above the surface of the sample or just touching the
surface.

Gelatin Capsules

Volatile liquid samples to be burned in an oxygen
bomb can be handled conveniently in Parr 3601

Gelatin Capsules. These 0.9 mL capsules consist

of two cups which telescope together with a fric­tion fit adequate to retain most liquids. Corrections
must be made for the heat of combustion of gelatin

www.parrinst.com

9

1108R Oxygen Combustion Vessel

(approximately. 4600 cal/g) if the capsules are used

for calorimetry, and for the sulfur content of the
gelatin (approximately. 0.35%) if used for sulfur de­terminations. Blank tests must be run to determine

the exact amounts. Gelatin capsules should always

be stored in sealed bottles and handled with due
regard for their hygroscopic nature.

The blank tests should be repeated at frequent
intervals since values determined on a weight basis
will change if there are variations in the moisture
content of the gelatin.

Tape-Sealed Sample Holders

Volatile samples can be handled in a standard 43AS
combustion capsule with a flat top rim, or in a 43A6
platinum capsule with a spun rim by covering the
top of the capsule with a disc of adhesive plastic
tape. To seal a capsule; stretch a piece of tape across
the top and press it firmly against the rim with a
flat blade, then trim the excess with a sharp knife.
The seal obtained in this manner will be adequate
to retain most volatile samples. The tape used for
this purpose should be free of chlorine and as low
in sulfur as possible. Borden “Mystic Tape” No.
M-169-C, or 3M Transparent Tape No. 610 are recom­mended for this purpose. Equivalent tape can be

obtained from Parr under Part No. 517A. The weight

of the tape disc must be determined separately and
a correction applied for any elements in the tape
which might interfere with the determination. This
can be done by running a blank test with the tape
alone using a sample weighing about 1.0 gram. Tape
should always be stored in a sealed container to
minimize changes in its moisture content.

Use the following procedure when filling and
handling any of these tape-sealed sample holders;
Weigh the empty cup or capsule; then cover the top
with tape, trim with a knife and press the trimmed
edge firmly against the metal rim. Also cut and
attach a small flag to the disc; as illustrated at the
top of page 9. Puncture the tape at a point below the
flag, then reweigh the empty cup with its tape cover.
Add the sample with a hypodermic syringe; close
the opening with the flag and reweigh the filled
cup. Set the cup in the loop electrode and arrange
the cotton thread so that it touches the center of the
tape disc.

Just before closing the bomb, prick the disc with
a sharp needle to make a small opening which
is needed to prevent collapse of the disc when

pressure is applied. Fill the bomb with oxygen to the

usual charging pressure, but add oxygen slowly so

that the tape will not collapse into the cup. Fire the

bomb and complete the test in the usual manner.

Low volatile samples with a high water content,
such as urine or blood, can be burned in an open
capsule by absorbing the liquid on filter paper pulp
or by adding a combustion aid, such as ethylene
glycol or by freeze drying the sample.

Heavy Oils

Oils and other liquids which are not volatile at room
temperature can be weighed directly into open
combustion capsules. The cotton thread should be
positioned just slightly above the surface of the
sample or just touching the surface.

Several precautions must be observed when testing
heavy oils because of the intense heat which they
develop. If the wall of the metal combustion capsule
is thin, or if some of the sample happens to have
been spread on the thin rim of the capsule, it is pos­sible that the metal may become heated to the point
where it will ignite. This condition is serious because
of the excessive heat liberated when metal burns in
oxygen. Also, the molten metal oxides may damage
the interior of the bomb. In extreme cases the bomb
electrodes may also ignite and burn with similar

results. For these reasons, be sure that any capsule

holding a heavy oil is in good condition and not
worn thin from prior usage. Also, bend the straight
electrode so that it does not project over the cup
where it will receive the full flame from the sample.
It is always desirable to tilt the capsule slightly in the
loop holder so as to direct the flame away from both
electrodes. Some operators prefer to use a 10 to 13
mL platinum crucible for holding heavy oil samples
because the added depth in a crucible promotes
slower combustion and a milder flame.

Explosives and High Energy Fuels

Special precautions must be observed when testing
materials which release large volumes of gas upon
ignition, or which detonate with explosive force.
Although most slow-burning gun powders and rocket
propellants can be tested in the conventional 1108R
Oxygen Combustion Vessel, the user must under­stand that this bomb is not designed to withstand
the shock pressures produced by primers and high
explosives. It is much safer to test these materials in a
Parr 1104 High Pressure Oxygen Combustion Vessel.

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Parr Instrument Company

1108R Oxygen Combustion Vessel

Operating Suggestions

Poor Combustion

The difference in combustion characteristics of the
wide variety of materials which may be burned in
an oxygen bomb make it difficult to give specific
directions which will assure complete combustions
for all samples. However, two fundamental condi-

tions may be stated. First, some part of the sample

must be heated to its ignition temperature to start
the combustion and, in burning, it must liberate suf­ficient heat to support its own combustion regard­less of the chilling effect of the adjacent metal parts.
Second, the combustion must produce sufficient
turbulence within the bomb to bring oxygen into the
fuel cup for burning the last traces of the sample.

An incomplete combustion in an oxygen bomb is
nearly always due to one or more of the following
causes:

1. Excessively rapid admission of gas to the bomb
during charging, causing part of the sample to
be blown out of the cup.

2. Loose or powdery condition of the sample which
will permit unburned particles to be ejected
during a violent combustion.

8. Insufficient space between the combustion
cup and the bottom of the bomb. The bottom
of the cup should always be at least one-half
inch above the bottom of the bomb, or above
the liquid level in the bomb, to prevent thermal
quenching.

9. Excessive moisture or non-combustible material
in the sample amounts to approximately 20
percent or more of the charge it may be difficult
to obtain complete combustion. This condition
can be remedied by adding a small amount of
benzoic acid or other combustion aid.

Oxygen Charging Pressure

Operators sometimes disagree as to the most
desirable oxygen charging pressure. As a rule, it is
best to use the lowest gas pressure that will give
complete combustion. Lower pressures permit
higher gas temperatures and greater turbulence,
both of which help to secure better combustion. The
range of charging pressures for Parr oxygen bombs

usually falls between 25 and 35 atmospheres, and it

should never exceed 40 atmospheres.

3. The use of a sample containing coarse particles
which will not burn readily. Coal particles which
are too large to pass a 60-mesh screen may not
burn completely.

4. The use of a sample pellet which has been made
too hard or too soft. Either condition sometimes
causes spalling and the ejection of unburned
fragments.

5. The use of an ignition current too low to ignite
the charge.

6. Insertion of the cotton thread below the surface
of a loose sample. Best results are obtained by
barely touching the surface or by having the
cotton thread slightly above the sample.

7. The use of insufficient oxygen to burn the
charge, or conversely, the use of a very high
initial gas pressure which may retard the
development of sufficient gas turbulence within
the bomb.

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11

1108R Oxygen Combustion Vessel

Maintenance and Safety Instructions

Bomb Maintenance

Under normal usage Parr oxygen bombs will give
long service if handled with reasonable care. How­ever, the user must remember that these bombs
are continually subjected to high temperatures and
pressures which apply heavy stresses to the sealing
mechanism. The mechanical condition of the bomb
must therefore be watched carefully and any parts
that show signs of weakness or deterioration should
be replaced before they fail. Otherwise, a serious
accident may occur.

Do not fire the bomb if gas bubbles are observed
anywhere indicating a possible gas leak. Disas­semble the parts and install new seals immediately.
The bomb head parts which require closest attention
and most frequent replacement are: the 410A quad
ring head gasket, all the 238A sealing rings, the

415A O-ring and the 20VB PCTFE valve seat in the

needle valve.

When replacing the 410A head gasket, remove the
104A2 contact ring and position the new 410A flat
upon the head.

The 20VB valve seat in the needle valve deteriorates
with use, not only in the needle area but on the
underside of the seat as well. Leakage and a possible
serious burn-out can result from a worn or damaged
seat if it is not replaced promptly. As a basic rule,
the 20VB valve seat and the two 238A O-rings on

the valve needle should be replaced after every 500

firings or every six months, whichever occurs first.
If the bomb is used for samples containing chlorine,

these parts should be replaced after every 250 rings.

To replace the valve seat, unscrew the 397A com­pression nut; remove the valve stem and the old
seat, and disassemble all of the parts. Drop a new
20VB valve seat into the body and push it down
into place. Slide a 7VBCM Monel washer, two 238A
O-rings and the 378A packing cup onto the A420A
valve needle assembly with the needle pointed
upward; then adjust the parts on the needle so
that the tip of the needle is flush with-or slightly

recessed into-the bottom of the packing cup. Insert
this assembly into the 396A outlet valve body and
press it firmly against the valve seat by tightening
the 397A compression nut to 100 inch-pounds of
torque.

A Parr 475A Service Clamp offers a convenient

means for clamping the bomb head firmly in a vise
without damaging the head when replacing any of
the bomb head parts.

Keep the 397A compression nut on the valve needle

tightened rmly at all times. Frequent tightening

is important. This nut, if slightly loose, may allow a
leak to develop during the rapid pressure rise upon
ignition. This type of leak may not be detectable
before firing; but if it develops, the hot gases can
ignite the 20VB valve seat and burn through the
head.

Do not use extreme force when closing the needle
valve. A moderate but firm turn on the valve knob
should be sufficient to stop all gas flow. Excessive
needle pressure will deform and possibly close the
gas passage. If this happens, unscrew the valve
body and replace the 20VB valve seat. Accumulated
salt deposits may also clog the gas passage, making
it difficult to release pressure at the end of a run.
To avoid this, clean the passage through the valve
needle and deflector nut with a small drill.

The 238A sealing ring in the insulated electrode
should be replaced with the same frequency as the
20VB valve seat. Also, keep the 411A terminal nut
tight at all times. As the 238A sealing ring ages and
hardens it becomes a partial electrical conductor,
permitting misfires and producing unwanted heat­ing effects. Periodic replacement will eliminate this
potential problem.

The threads on the screw cap should be checked
routinely for any burns or other deformity. After
long use, the threads on the screw cap may become
worn to the point where they will no longer provide
a safe closure for the bomb, and the screw cap will
have to be replaced. The following procedure can be
used to check the extent to which the threads have
become worn:

12

Parr Instrument Company

1108R Oxygen Combustion Vessel

1. Assemble the bomb with the head in the cyl­inder and count the number of turns required
to bring the screw cap down firmly against the
head.

2. Then open the bomb; remove the head and
replace the screw cap, but turn it down to only
one-half of the turns previously counted. This
will usually be about four turns.

3. With the screw cap in this position, use a dial
gage to measure the vertical deflection when
lifting the screw cap upward. If this measure-

ment exceeds 1/32 inch (0.030”), the screw cap is

unsafe and should be discarded.

4. The cylinder can then be returned to the fac­tory for inspection. If the threads on the cylinder
are in good condition, a new screw cap can be
custom-fitted to the cylinder.

Never under any circumstances use oil on the
O-rings which seals the bomb head or on any of the
valves or fittings which handle compressed oxygen.
This precaution applies to all of the oxygen bombs
parts to the oxygen filling connection as well.

Although Parr oxygen bombs are made from alloys
which will withstand most corrosive gases, these
bombs will not resist chlorine, fluorine or bromine
in the presence of moisture. If samples yielding
appreciable amounts of these elements are burned
in a Parr bomb, the interior surfaces may become
etched or corroded. In such cases the bomb should
be emptied and washed as quickly as possible after
each combustion.

Bomb Repairs and Proof Tests

The 20VB valve seat, 410A, 415A, and the four 238A
O-rings should be replaced after every 500 rings,

or every six months, whichever occurs first. If the
bomb is used for samples containing chlorine, these

repairs should be made after every 250 rings.

Parr oxygen bombs can be returned at any time for
repair and testing. A factory test is recommended

after every 5000 rings, or after any of the following
conditions; (a) red with an excessive charge, (b)
ignition of any internal components, (c) machined
by any source other than the factory, (d) damaged

by corrosive vapors that might have exceeded 80%

of the corrosion allowance, or (e) any changes in the
threads on the bomb cylinder and/or screw cap.

When returning a bomb to the factory, ship it to:

Parr Instrument Company

Attn: Repair Department

211- 53rd Street
Moline, Illinois 61265

A purchase order covering the repair work should be
included with the shipment or mailed to the same
address as no repairs will be started without specific
instructions. Be sure to include a return shipping
address and the name and telephone number of the
individual to be contacted if questions arise con­cerning excessive repair costs or other problems.
Individual repair parts can be ordered from any Parr
dealer or direct from the factory.

If the interior of the bomb should become etched
as mentioned above, the resistance of the metal
to further attack can be improved by restoring the
surface to its original highly polished condition.
Bombs needing repolishing or other repair work can
be returned to the factory. A periodic overhaul and
test at the factory will help to keep any Parr oxygen
bomb in first-class condition.

See page 14 for a Maintenance Checklist.

www.parrinst.com

13

1108R Oxygen Combustion Vessel

1108R Maintenance Checklist

Refer to page 11-13 & 16-17 of the 1108R Operating Instruction Manual for assembly instructions and parts
diagram.

Replace 840DD2
Heating Wire

Clean electrodes

Replace the following:

410A

415A

238A (4)

143AC

50 to 100 Test Maintenance

Date Date Date Date

500 Test Maintenance

Date Date Date Date

20VB

Examine and replace if worn or cracked.

143AC

401A

96AC

14

Parr Instrument Company

Notes

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15

1108R Oxygen Combustion Vessel

Parts

1108R Parts Diagram Key

KEY ITEM DESCRIPTION

1 103A SCREW CAP

2 410A QUAD-RING BUNA-N

394A19 OXYGEN VESSEL HEAD, BARE

3

394A19CL

101A OXYGEN VESSEL CYLINDER

4*

101ACL

5 395A2 INLET VALVE BODY

6 415A O-RING 7/16 ID BUNA-N

7 238A O-RING 3/16 ID BUNA-N

8 403A CHECK VALVE

9 411A TERMINAL NUT

10 143AC INSULATOR, DELRIN

11 906DD2 CAPSULE HOLDER

12 388A SPACER

13 SC1932SC10 SOCKET HEAD SET SCREW

14 655DD ELECTRODE SPACER

15 404A2 DEFLECTOR NUT

16 1095DD ELECTRODE

17 1095DD2 ELECTRODE, INSULATED

19 401A SLEEVE INSULATOR

20 96AC ELECTRODE INSULATOR

A420A

23 407A VALVE KNOB

24 398A LOCK NUT

25 400A VALVE NEEDLE

OXYGEN VESSEL HEAD,
BARE FOR CHLORINE SER-

VICE

OXYGEN VESSEL CYLINDER
FOR CHLORINE SERVICE
(1108RCL)

VALVE NEEDLE WITH KNOB

(NOS. 23, 24, 25)

KEY ITEM DESCRIPTION

26 397A COMPRESSION NUT

27 396A OUTLET VALVE BODY

28 7VBCM WASHER MONEL

29 378A PACKING CUP

30 20VB VALVE SEAT PCTFE

31 PA1332RD04 6-32 X 1/4 RHMS

32 840DD2

33 1095DD3 ELECTRODE W/ SETSCREW

34 PC1332SC02 6-32 SHSS (ELECTRODE)

35 906DD2 CAPSULE HOLDER

36 43A_SERIES CAPSULE

37 104A2 COMPRESSION RING

* Sold as complete assembly, see Complete
Assemblies table

Complete Assemblies

ITEM DESCRIPTION

AA101A OXYGEN VESSEL CYLINDER

AA101ACL

A416A6 OXYGEN VESSEL HEAD ASSEMBLY

A416A6CL

OXYGEN VESSEL CYLINDER
OR CHLORINE SERVICE (1108RCL)

OXYGEN VESSEL HEAD ASSEMBLY
FOR CHLORINE SERVICE (1108RCL)

60" IGNITION WIRE
(2.0" PER USE)

16

Parr Instrument Company

1108R Oxygen Combustion Vessel

Parts for the 1108R Oxygen Combustion Vessel

23

24

25

1

26

27

28

29

30

15

9

12

13

7

7

14

10

19

9

7

5

7

8

6

37

2

3

15

14

20

4

16

31

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17

32

31

33

34

35

36

17

1108R Oxygen Combustion Vessel

ISO WARNING SYMBOL

34E2

174F

REF

2005E

11

10
12

Parts for the 2901 Ignition Unit

200F11

1157E
139E21
W/ SA1332RP04

711

(LOAD)

12

TN1632HL

6

6

8

115V

9

5

8

2

115V

9

1

10

MOUNT TRANSFORMER

W/(4) UP18DM04

190F
GROUND SYMBOL
REF

2000E

12V

12V

3

7

8

5

11

4

12

A1580E

1

(3) TN1332HL

4

3

7

6

2014E

95F

(3) A59A2

(10 cm)

(COMMON)

2901 Ignition Unit

2

A3299HC
CHASSIS
REF

1557E REF

2

1

1574E

Item Description

A1673E2 Kit Electric Parts for 2901EB/EE
1203EEE Cord 10A/220V Cont Europe Plug
1202EEE Cord 13A/220V BS Plug
2000E Transformer, 120/240 VAC 24V

XB0010 1/8ID Shrink Tubing Black

34E2 Cord w/ 115VAC Plug 18-3SJT
A3299HC Box Assembly, Ignition Unit 115V
A3299HC2 Box Assembly, Ignition Unit 230V

2005E Strain Relief Pigtail Black
2005E2 Strain Relief Pigtail Black, for 230V

139E21 Fuse 3AG Slo-Blo 250V 5.0 Amp (115 volt units)
139E8 Fuse 3AG Slo-Blo 250V 2.5 Amp (230 volt units)

1157E Fuse Holder, 3AG x 1/4 Tab
SA1332RP04 6-32 x 1/4 RHMS Phillips 18-8

(7 cm)

A3299HC
COVER
REF

1575E
1576E

18

Caution!
For continued protection against possible hazard, replace fuses with same type and rating of fuse.

Parr Instrument Company

1108R Oxygen Combustion Vessel

Parts for the 1825 Oxygen Filling Connection

1825 Oxygen Fill Connection

Item Description

4VB3 Packing gasket
6VBBB Packing cover, brass
8VB2 Packing nut

9VB1 Union nut, brass, CGA540
20VB Valve seat, PCTFE
21VBBB Lantern ring, brass

53A Oxygen gage, 3-1/2”, 0-60 atm

112VB4AK Valve needle
124VB Union nipple, brass, CGA540
A140VB Toggle relief valve
A150VB Valve knob
188A2 Filling connection body, bare
243VB Tube connector, male
438VB Elbow connector, 45°, male
A476A3 Slip connector with O-rings
394HCJE O-ring for A476A3 slip connector (2 required)
HX0012TB024 Pressure tubing, 1/8” OD, Nylon, 5-ft

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19

662M R01 10/10/14