A.
Applicability
and Frequency
1.
The boiler flexibility test will apply to all ships powered by steam
boilers equipped with automatic combustion and feedwater control systems,
provided that fuel oil burners are of the wide range (mechanical, steam atomization) type. Boiler flexibility test results shall be:
a.
Entered in the engineering log.
b.
Entered on data sheet 11 of the OLV manual.
c.
Data sheets must be retained onboard at least one year.
d.
Entered on Boiler Water Chemistry Work sheet Log.
e.
Entered on PMS card.
2.
A complete set of readings shall be taken and recorded for all propulsion equipment on line at the start of
and completion of each ramp load change.
Though not recorded on the data sheets, this information is required for
diagnostic evaluation of deficiencies.
3.
Ramp load change of 70 percent of full power in 45 seconds, within a
range of 15‑25% low end and 85‑95% high end.
4.
Flexibility tests shall be accomplished with the boiler control systems
in the full automatic mode.
5.
Pre-test Conditions
a.
Verify that all interacting systems such as forced draft blowers and
governors, main feed pumps and associated controls, auxiliary exhaust system,
fuel oil pump pressure regulators, and fuel oil burners are operating properly.
b.
There shall be sufficient fireroom auxiliary equipment on the line to
support the 100 percent single boiler steaming rate.
c.
The test boiler shall have all burners in service using normal underway
sprayer plates.
d.
All automatic controls in the machinery space (except for the idle
boiler combustion control system) shall be in the automatic mode.
e.
Prior to conducting boiler flexibility test, it shall be determined that
forced draft blowers are parallel to within 300 RPM under steady state steaming
conditions at both upper and lower boiler load conditions.
f.
Visual smoke indicators shall be in good working conditions and free of
soot or dirt on optical surfaces.
6.
Verify that the calibration of the following gages that are to be used
in the test are current:
a.
Boiler steam drum pressure
b.
Burner fuel oil pressure
c.
HP Turbine first stage steam pressure
7.
Boiler water gages shall be provided with scales or otherwise marked
with numerals at half inch intervals from the specified normal water level from
minus 8 to plus 10.
8.
In the event that both initial and final flexibility test loads cannot
be attained with one boiler in operation, a second boiler may placed
on-line. When two boiler are in operation
in the machinery space, the boiler to be tested shall be in full automatic
control and the other boiler shall be under remote manual combustion
control.
This
boiler shall be adjusted to the firing rate necessary to maintain the steaming
rate required to establish the desired initial steaming rate on the boiler to
be tested; this firing rate should then
be maintained through the flexibility test which follows.
B.
Testing
Procedures
1.
Determination of boiler load.
2.
Divide the design boiler full power fuel oil rate by the total number of
burners per boiler (Figure 1).
CE -
WALLSEND FUEL OIL BURNER
STEAM ATOMIZATION - DIESEL
FUEL MARINE (MIL-F-16684)
|
CONDITION |
FULL POWER |
|
Rating, % F.P. (oil rate) |
120 |
|
Total Oil Flow, lb/hr/boiler |
13,180 |
|
No. Burners in Operation |
4 |
|
Sprayer Plate Size |
5X 80555589 |
|
Oil Flow per Burner, lb/hr |
2,740 |
|
Fuel Oil Pressure, psi |
290 |
|
Atomizing Stm. Pressure, psi |
150 ±15 |
|
Press. Drop Across Register, in. H2O |
21 |
Figure
1
1.
Multiply the oil rate determined in step (a) by lower limit of percent
boiler full power to be achieved during the boiler flexibility test (15 to 25
percent) to obtain a per-burner fuel
oil rate for this lower unit.
2.
Using the sprayer plate capacity curve for the sprayer plates in service
read the values of fuel oil rate calculated in step (b) and obtain the
corresponding fuel oil burner pressure from the other axis of the curve. This fuel oil pressure will provide the
required lower limit oil rate with all burners in service (Figure 2).
|
Figure
2 |
3.
To obtain a per-burner fuel oil rate for the upper limit of percent
boiler full power to be achieved during the boiler flexibility test (85 to 95
percent), multiply the value of per-burner oil rate determination in step (a)
by the upper limit percent of boiler full power.
4.
Enter the sprayer plate capacity curve at the fuel oil rate calculated
in step (d) and obtain the corresponding fuel oil burner pressure. This
fuel oil pressure will provide the required upper limit oil rate with all
burners in service.
B.
Throttle
Manipulation
1.
Manually adjust the main turbine throttle to the position required to
obtain the steady state lower limit fuel oil pressure. This throttle position will establish the
initial load for conducting the boiler flexibility test. Mark the throttle at this position. When
conditions have stabilized the initial load, slowly open the main turbine
throttle to the position required to obtain the upper limit burner fuel oil
pressure. This throttle position will
establish the final load for conducting boiler flexibility test. Mark the
throttle at this position. The number
of turns of the throttle required to change the load from the initial value to
the final value should be recorded.
2.
Drill the throttleman in moving the throttle to produce a linear change
in steam pressure between the upper and lower throttle position limits in the
prescribed time interval of 45 seconds.
The rate of change of throttle position must be regulated by the
throttle operator to maintain a smooth, continuous linear change of turbine
steam pressure as indicated by the specified gage. It is important to note that linear changes in steam pressure may
require variations in the rate of change of throttle opening and closing.
C.
Conducting
the Boiler Flexibility Test
1.
When steady-state conditions have been attained, the throttle should be
manipulated in a manner to impose the boiler flexibility test load change on
the boiler being tested. During the
period of this test, the boiler plant in the other machinery space(s) shall be
operated at a steady state steaming condition.
The ship shall maintain course throughout the entire procedure.
D.
Guidelines
for interpretation of boiler flexibility test results
1.
The two basic purposes for conducting a boiler flexibility test are as
follows.
2.
To ensure that shipboard boiler automatic combustion and feedwater
control systems are correctly installed and adjusted to maintain boiler steam
pressure, water level and combustion within specification requirements during
both steady-state and transient conditions.
3.
To obtain reference data suitable for verifying continuous satisfactory
performance of boiler automatic combustion and feedwater control systems.
4.
The test requirements will reflect the following consideration of the
ability of the boiler, supporting machinery and control systems to maintain
boiler steam pressure, water level and combustion conditions during both
steady-state and transient conditions.
E.
General
information
1.
Flexibility test results must be evaluated prudently. Failure to meet one or more of the test
criteria does not necessarily mean that the affected boiler cannot be steamed safely
in the full automatic mode. For
example, if the transient boiler water level deviation exceeded the allowable
limit by half an inch, this may indicate that the boiler control system is not
functioning properly. However, correction of the problem could be delayed. On the other hand, if during the transient
test, boiler water level barely stayed in the gage glass, this would indicate a
condition that could lead to serious boiler damage and should be corrected as
soon as possible.
2.
When evaluating the results of a boiler flexibility test, past test
results may be use to determine if any significant degradation of system
performance has occurred. To be used in
this manner, numerical values of the test parameters must be recorded rather
than simply noting whether the test results were satisfactory or
unsatisfactory.
3.
Any outside factors that significantly influence test results should be
noted. Significant influencing factors
in this context are defined as any factors that change test results from
satisfactory to unsatisfactory.
Two examples of outside factors that
can significantly effect test results are rolling of the ship and any problems
that prevent generating the smooth ramp load change. When outside factors significantly affect test results, the test
should be rerun following correction of the problem.
F.
Test
Requirements
1.
Main boilers and their associated control systems shall meet the
following performance requirements during a 70 percent "ramp" load
change of boiler full power in 45 seconds, which is a range of 15 to 95 percent
of boiler full power:
2.
To obtain reference data suitable for verifying continuous satisfactory
performance of boiler automatic combustion and feedwater control system.
G.
Performance
Criteria
1.
Level one boiler flexibility test must meet all of the following:
a.
Steady state stability
b.
controlled system pressure - Within +/‑5 psig of set point
c.
water level - Within +/‑1" of normal water level
d.
forced draft blower - parallel within 300 RPM
e.
Transient Response (max. allowable deviation)
f.
Steam pressure - Minus 8% of steam drum pressure on the increase and
plus 3% of steam drum pressure on the decrease
g.
Water level - Within +/- 4" from the normal water level
h.
Stack Condition - Smokeless
i.
Stabilize within four minutes - From the start of the load change, and
remain stable for an additional two minutes.
j.
For levels 2, 3, and 4, criteria refer to Figures 3 and 4.
|
TEST
PARAMETERS |
BOILER FLEX TEST LEVEL |
|||||
|
STEADY STATE STABILITY |
I |
II |
III |
IV |
||
|
Steam Pressure
Deviation from Setpoint (PSIG) |
±5 |
±10 |
±10 |
±15 |
||
|
Water Level Deviation
from Normal (INCHES) |
±1 |
±1½ |
±2 |
±2½ |
||
|
FDB Parallelism - If
Applicable (RPM) |
300 |
400 |
500 |
600 |
||
|
TRANSIENT RESPONSE |
|
|
|
|
||
|
Steam Drum Pressure
Deviation (%) (See Below) |
Drum Controlled from
set-point pressure |
UP |
-8% |
-9% |
-10% |
-12% |
|
|
|
DOWN |
+3%** |
See
Note 1 |
See
Note 2 |
See
Note 5 |
|
|
Superhtr or common Hdr
from starting Drum Press |
UP |
-6% |
-7% |
-8% |
-10% |
|
|
|
DOWN |
+2% |
See
Note 3 |
See
Note 4 |
See
Note 5 |
|
Water Level Deviation - See Table 2 for applicable
variation. (INCHES) |
±4 |
±4 |
+5,
-4_ |
+6,
-5_ |
+7,
-6 |
|
|
|
±5 |
±5 |
+5_,
-5_ |
+6_,
-5_ |
+7,
-6 |
|
|
|
±6 |
±6 |
+6_,
-6 |
+6_,
-6 |
+7,
-6 |
|
|
|
+6,
-5 |
+6,
-5 |
+6_,
-5_ |
+6_,
-5_ |
+7,
-6 |
|
|
Settling Time - See definition enclosed. |
4 min. |
4.5 min |
5 min |
6
min |
||
|
Stack Condition (Black or White smoke) |
Clear |
Lt.
Haze |
Haze* |
Dark* |
||
NOTES: SVS -
Superheater Safety Valve Setting (See Boiler Tech. Man.)
1. SVS X 0.33 - (0.31 X Stm Drum Setpoint)
2. SVS X 0.67 - (0.66 X Stm Drum Setpoint)
3. SVS X 0.33 - (0.317 X Starting Drum
Pressure)
4. SVS X 0.67 - (0.633 X Starting Drum
Pressure)
5. SVS must not lift to comply with level IV
requirements.
* Revised from previous acceptance criterion.
** +4% for LHA - 1 and LHD - 1 classes.
Figure
3
|
LEVEL
I WATER LIMIT VARIATIONS |
|
|
+5, -5 |
+6, -6 |
|
CV - 62 - 64, 67 |
AOE - 1 - 4, 6 |
|
AE - 22 - 23, 27 - 29, 32-35 |
LHA - 1 - 5 |
|
AFS - 4 |
LHD - 1 CLASS |
|
AO - 177 - 180, 186 |
|
|
LPH - 9 - 12 |
|
NOTE:
1. Level I requirements for all other ships are
+4, -4 inches.
Figure
4