Parr Instrument 1108R - Manual (Page 6)

P a r r I n s t r u m e n t C o m p a n y 6
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 condi-
tion. 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 pres-
sure 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 fill-
ing 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.
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 elec-
trical 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 com-
pletely 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 de-
scribed 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 combus-
tion 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.
1825 Oxygen Filling
Connection
2901 Ignition Unit