18: By now, we would have advanced the
Expansion Engine cam position from 7 to about 5 or 4 depending
upon the increase in air pressure in P-2 and P-3. When we
reduce Cam position, the Inlet pressure will go up and the
outlet pressure will come down and vice-versa. But in higher
cam position, more air will be handled by Expansion Engine
but the temperature drop will be less and vice-versa. When
starting the plant, even when the Expansion engine is operated
in cam 7, the pressure will be very high. The pressure at
P-1 will be high (45 to 50 Kgs. /cm2) as the warn air volume
is large. As air contracts due to cooling after the first.
Heat Exchanger, the pressure at P-1 will drop gradually
and the Cam position is adjusted to, maintain a high P-1
pressure. After about 3 - 4 hours operation, the liquid
will appear in Lower Column and P-1 pressure will continue
to drop. The Cam is then shifted to positions 3, 2 .......etc.
to sustain high pressure at P-1 and obtain maximum purity,
when the plant is sufficiently cool.
19: When T-1 is -90 Deg.C. To -100 Deg.C.
And when T-2 is -140 Deg.C. Open V3 valve slightly. Then
watch T-3 temperature. This will start cooling down. By
the time V1 should have been closed to 1 then watching the
pressure of the lower column
20: When T-3 temperature before V3 reaches
-140 Deg.C. / -150 Deg.C. Open V3 slightly more without
upsetting T-3. Half an hour after this, liquid air will
start forming in Lower Column.
21: 1 or 1 Y:z hours after this, liquid
oxygen will start forming in main condenser. Now close the
By Pass Valve V1 - half turn.
22: let is a good practice to drain a little
amount of RL and LO. initially to flush lines by
opening R26 and R27.
23: Now open isolation valves R13 &
_14 and close equalizing valve of level gauge RE. (L2).
The level of Liquid Oxygen will start increasing which will
show in the DP level gauge manometer on the main panel of
the cold box. When L2 25 cms increased and closed fully
V1.
24: When Upper Column level in L2 had increased
to about 50 cm. Start closing V4 and V5 valves. Level,:. will
fall down and again arise.
25: When V4 is about 2 to 3 turns open
and V5 is about 1 to 2 turn open, Oxygen. Purity is to be
analyzed collecting a sample from R27.
26: Oxygen Purity should be more that 99%
before starting the LO. Pump.
27: To increase Oxygen Purity, V5 &
V4 to be slightly closed.
28: After attaining good Oxygen Purity
and having level at 48 em, open oxygen valve V8A and then
V8 valve gradually. Now Liquid Oxygen is allowed to enter
LO.Pump.
29: When level had again risen after a
drop, we are ready to start LO. Pump.
30: Open valve 06.
31: Before starting LO. Pump, check free
rotation by hand. Clean the LO. Pump Piston with C.TC.
32: Start the LO. Pump and check oil pressure
for crank lubrication in P-16 pressure gauge. It should
be above 0.7 kgs. /cm2
33: Now check for flow of Oxygen in vent.
34: Then open 0-5, 0-6 and loosen all bull nose
connections to cylinders. Now, product Oxygen lines will
be purged.
35: Thereafter close 06, 0-6 and tighten
bull nose connections. Keep open cylinders valves, individual's
connection valves and open 0-5. Safety valve at the manifold
is set at 165 kg/cm2 and should be checked prior.
36: Keep constant close watch on the oxygen
pressure gauge on cold box panel and manifold. Rate of production
can be checked by time taken for filling a set of known
capacity cylinders after the trail runs are over. The ambient
conditions vary from place to place and also the relative
humidity. The FAD of the compressor will therefore vary
and the production of oxygen is dependent on the amount
of air entry the column as it is the main feed stock. For
calculating the rated production the output has to be converted
into design suction conditions which are normally 15 to
24 deg C, 760 mm Hg and 50% RH.
