parr 1108 Operating Instructions Manual Download

Page: 6 / 20

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

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 elimi-
nate the leak before proceeding with combustion
test. If no leakage is indicated, adjust the water flow
rate so that the bomb will be covered by a continu-
ous flow of cold water during the firing period, then
stand back and press the firing button on the igni-
tion unit to fire the charge.

Caution:

Do not have the head, hands or any

parts of the body directly over the bomb dur-

ing the firing period and do not go near the

bomb for at least 20 seconds after the firing.

Filling the Bomb

The instructions below de-
scribe a manual system us-
ing 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 out-
let to be sure they are clean
and in good condition. Place
the ball end of the connec-
tion into the outlet socket
and draw up the union nut
tightly with a wrench, keep-
ing 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 eas-
ily, a drop of water spread around the inlet valve
will lubricate the sealing rings. Older bombs use a
threaded connector with a knurled coupling which
must be turned finger tight.

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 con-
trol 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. 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. The bomb inlet check valve will close
automatically when the oxygen supply is shut off,
leaving the bomb filled to the highest pressure indi-
cated on the 0-55 atm. Gage. 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 trou-
ble will have to be corrected before the bomb can
be used. If too much oxygen should accidentally be
introduced into the bomb,