Parr Instrument 6400 - Manual (Page 76)

11
Troubleshooting
P a r r I n s t r u m e n t C o m p a n y 74
c
haPter
11
Troubleshooting
Bomb Exhaust Troubleshooting
The bomb exhaust and sealing is controlled by
movement of the 966DD2 piston inside of the
1140DD bomb seal/release cylinder. This assembly
is mounted on the bottom of the calorimeter air can.
The piston is driven to the up position (exhaust)
by applying oxygen at 30 atm to the 1/8 male con-
nector (344VB). The piston is driven down (bomb
seal) by applying pressure to the 376VB elbow. The
application of the oxygen pressure is controlled by
the A1251DD three station solenoid valves. There
is a flow restrictor, part 527VB, on the inlet side of
this solenoid which limits the maximum flow rate
of oxygen and in turn creates a gradual increase in
pressure at the 1140DD bomb seal/release cylinder
when the solenoid is turned on. Failure of the bomb
to exhaust in a timely fashion can have more than
one cause. Certain causes can be eliminated sys-
tematically by checking the bomb exhaust diffuser,
at the end of the bomb exhaust line, for any restric-
tions in the six small cross drilled holes. This fitting
should be removed from the tubing, inspected
thoroughly and cleaned as required.
Service the O-rings on the 966DD2 Piston
This process is described in the 500 test mainte-
nance section.
Confirm function of the 966DD2 piston
In order to reduce the amount of time it takes to
duplicate and troubleshoot this type of situation,
the I/O diagnostics can be used to pressurize and
exhaust the bomb without having to run lengthy
combustion or pre-tests.
Caution!
This screen allows unconditional and arbitrary
output control for testing purposes. Be aware
that all user and instrument protection is
disconnected while on this screen. This is
very important and you should take proper
precaution.
1. Make sure the 668DD check valve is installed at
the bottom of the cylinder.
2. Lock the head into the cylinder and close the
calorimeter lid.
3. Confirm the Exhaust is off.
4. Turn Bomb Seal on then off to retract the
966DD2 piston.
5. Turn on O2 Fill to begin filling the bomb. The
bomb will be completely filled in one minute,
at which time O2 Fill should be turned off. This
seats the check valve in the head which in turn
seals the contents of the bomb.
6. The calorimeter lid can be unlocked at this time.
7. Activating the Exhaust should initiate a bomb
exhaust within two seconds. If it takes much
longer than two seconds before the bomb be-
gins to vent, then at least one of the following
conditions outlined below exist.
If the bomb exhaust is initiated in a timely manner
but fails to complete in 10 seconds, a blockage or
restriction in the bomb exhaust circuit is indicated.
This must be investigated and corrected.
If the bomb fails to exhaust, the 899DD Head Handle
and SN1632HX 8/32 Hex Nut can slowly be removed
to release the pressure in the bomb. See Figure 14-1.
If the piston moves properly with no applied bomb
pressure, but still fails to initiate an exhaust of a
pressurized bomb in a timely fashion, at least one of
the following conditions exist:
1. The 527VB restrictor is partially blocked.
2. The exhaust line is blocked.
3. There is a gas leak between the outlet of the
solenoid and the 1140DD cylinder. This also
includes the 357HCJB O-ring seal on the piston
inside of the cylinder.
The first condition can be eliminated by cleaning or
replacing the 527VB restrictor.
The second condition can be eliminated by replac-
ing the tubing and clearing all connections.