42
Calculating and Entering the Flow Values Manually
If the flow values are to be calculated manually, the procedure listed below must be followed.
Enter Adjust Ratio Mode with oxygen trim disabled as outlined above.
1.
Select the high fire position. This will cause the display to show A(n), where n is the number of
the high fire profile point.
2.
Wait until the oxygen reading has stabilized, the value can be viewed using the engineer’s key.
3.
Record the
excess air
value at location x in the table. For single fuel profiles, this value may be
found using the Engineer’s Key parameter EK88 (provided the hydrocarbon ratio has been
entered into the appropriate option parameter (36.4 - 36.6) for this fuel). For multiple fuel pro-
files, the tables in section 0 will aid an estimate to be made, using the current oxygen reading.
4.
Select the profile position immediately below high fire. This will cause the display to show A(n
-1).
5.
Wait until the oxygen reading has stabilized and record the
excess air
value at location a1 in the
table
6.
Move air dampers 1 and 2 (if fitted) up until they stop, so that they are at the setpoint immedi-
ately above the current position.
Do not press enter.
7.
Wait until the oxygen reading has stabilized, then record the
excess air
value at location b1 in
the table, relating to the current profile position
8.
Repeat the above for all other profile positions including low fire (profile position A3), record-
ing each time the values at locations a and b in the table. When extra air is added at P3, the time
taken before the flue oxygen reading starts to increase should be measured and entered into
option parameter 30.7.
9.
After completing the table for all Excess Air values a and b, complete the Excess Air + 100 col-
umn, by adding 100 (i.e. y = x + 100, c = a + 100 and d = b + 100.
10.
Complete the Ratio column by dividing c by d (i.e. e = c/d).
11.
Complete the Airflow column by multiplying e by the previous value of f (i.e. f
x
= ex f
x
-1).
12.
If the system will be applying trim to the fuel, the fuel flow column must be completed. This is
achieved by multiplying the airflow at each point by the ratio of excess air + 100 at high fire
divided by the excess air + 100 at the actual point (i.e. gx = f
x
(y/c
x
)).
Example of table completed for A10 (high fire) to A8. In practice, the table must be filled out down
to A3 (low fire).
Profile
Position
Excess Air
Ex. Air + 100
y = x + 100
c = a + 100
d =b + 100
Ratio
Airflow
Fuelflow
High fire
= A10
x
10
y
110
99.9%
99.9%
1 = A9
a
1
b
1
8
33
c
1
d
1
108
133
e
1
+c
1
/d
1
0.812
f
1
= e
1
(99.9)
81.1%
g
1
= f
1
(y/c
1
)
82.6%
2 = A8
a
2
b
2
9
20
c
2
d
2
109
120
e
2
+c
2
/d
2
0.908
f
2
= e
2
(f
1
)
73.7%
g
2
= f
2
(y/c
2
)
74.4%
