2. 2
PDM BRO Activities
The following is a list of Predictive Maintenance (PDM)
activities related to Boiler Reliability Optimization
(BRO).
Infrared Casing Leak Survey
Valve Leakage Survey (IR and Ultrasonic Acoustics)
On-line Acoustic Leak Detection (Confirmation)
Foreign Material Exclusion IR Scan
Ultrasonic Boiler Leak Detection Air Test
Condenser Air In Leakage Detection
Condenser Tube Sheet Leak Check
3. 3
PDM BRO Activities
• Infrared Casing Leak Survey – The use of an infrared imager to
detect and document casing leaks in need of repair. Performed periodically
as well as pre and post outage.
– Casing
– Expansion Joints
– Ductwork
• Advantages: Improves identification of combustion gas leaks over previous
methods that rely on visual inspection. This reduces repair costs by
pinpointing areas of concern and thus reducing the amount of lagging and
insulation needed to be removed. Scaffolding and other items can also be
minimized. Casing repairs improve the unit’s operating performance by
reducing the amount of combustion air lost from these leaks. In balanced
draft units, casing leaks can bias the oxygen and excess air readings used to
control the furnace combustion. Identifying and repairing these leaks leads to
more stable combustion. FD and ID Fans are not overloaded to compensate
for these losses of combustion air. Repairing these leaks also improves safety
by eliminating toxic gases and burn sources. Leaks can also be identified
from outside hazardous areas and at extended distances.
• Restrictions: Time consuming and often requires balanced draft units to
operate at a positive (slight) pressure. Areas inspected often have restricted
access due to heat, boiler gases, and other hazards.
6. 6
PDM BRO Activities
• Valve Leakage Survey (IR and Ultrasonic Acoustics) – Performed
periodically as well as pre and post outage.
– Boiler Drains
– Sootblower Poppit valves
– Safety valves
• Advantages: A Non destructive inspection that does not require valve
disassembly or changes to a unit’s operation. It can identify leaking valves,
which in turn, allows for effective planning and scheduling of maintenance
repairs. Repairing of these valves can improve unit performance by reducing
the loss of steam and thus improving the unit heat rate. Safety concerns
about valve failure, especially on tandem double-block valves and steam
supplies, are reduced because these can be checked with the unit in-service.
• Restrictions: Time consuming with valves to be inspected in areas that
often have restricted access due to heat, boiler gases, and other hazards.
Operations often must accompany PDM personnel to check if a valve is
properly closed.
9. 9
IR Valve Survey
Up stream boiler drain valve appears to be leaking
through. (Source Tanners Creek)
10. 10
PDM BRO Activities
• On-line Acoustic Leak Detection (Confirmation) –
Continuous monitoring systems like Triple 5 that listen for active tube
leaks inside the boiler may sometimes have false positive leak
indication due to external sources of ultrasonic sound. These
external sources from such things as casing leaks, air supply line
leaks, stream leaks around valve packing, etc. can be identified with
the use of portable ultrasonic acoustic sound equipment such as a
UE Ultraprobe or CSI Sonicscan.
• Advantages: Confirming that On-line Acoustic Leak Detection
systems have detected small tube leaks before they become larger
can mean the difference between a forced outage or not. Identifying
external sources improved confidence in the data being provided and
less chance of false positive alarms.
• Restrictions: Only used to identify external sources of ultrasonic
acoustic sound that may produce a false positive. Elimination of
these external sources may need to be made before confirmation is
assessed.
12. 12
PDM BRO Activities
• Foreign Material Exclusion (FME) IR Scan –
Using Infrared Thermography to inspect for boiler tube flow
restrictions.
• Advantages: Required post work verification for supercritical boiler
water walls. Effective non destructive method, it can detect potential
failures due to tube starvation/pluggage during an outage. This
allows for repairs that can prevent a forced shutdown. Large areas
can be inspected with little effort.
• Restrictions: Requires establishment of flow in the furnace/boiler
and a temperature change between condensate and tubes. Must be
performed by a qualified thermographer and boiler expert. Not all
areas are accessible for scanning.
13. 13
FME IR Survey
IR image of plugged tube
Borescope image of
plugged tube
(Source Tanners Creek)
14. 14
PDM BRO Activities
• Ultrasonic Boiler Leak Detection Air Test –
Performed during boiler tube air tests.
• Advantages: Very effective when compared to previous methods in
terms of detection and time required to perform inspection. Ultrasonic
equipment can detect tube leaks that cannot be heard by the human
ear. Background noise is drastically reduced by the use of specialized
headphones. It can detect tube leaks over large distances.
• Restrictions: Techniques used require specialized training and
experience. Large leaks that do not create turbulent air may not be
detected.
16. 16
PDM BRO Activities
• Condenser Air In Leakage Detection – Performed
on main and auxiliary condensers and associated equipment and
piping. Air in the condenser can raise the dissolved oxygen in the
condensate and carry over to the boiler causing tube damage usually
from water side corrosion.
• Advantages: Performed with the unit in service, allows for better
control of cycle and boiler chemistry. This reduces the possibility of
water side boiler tube damage. It also improves unit heat rate by
improving condenser backpressure which also reduces boiler wear
due to less fuel being burned for any given unit load.
• Restrictions: Techniques used require specialized training and
experience. Repairs often are made off line. Often used in conjunction
with IR and trace gas detection.
17. 17
Condenser Air In Leakage
85.5°F
144.3°F
100
120
140
100.9°F
116.1°F
105
110
115
AR01: 100.8°F
AR02: 103.1°F
93.1°F
186.4°F
100
120
140
160
180
SP01: *156.6°F
IR examples of Condenser
Air In Leakage sources.
Confirm with Ultrasonic
Acoustics or Trace Gas.
18. 18
PDM BRO Activities
• Condenser Tube Sheet Leak Check – Performed
only on those condenser tube sheets that can be partially isolated in
service.
• Advantages: Very effective when compared to previous methods in
terms of detection and time required to perform inspection. Ultrasonic
equipment can detect air being sucked into the condenser through a
tube leak that cannot be heard by the human ear. Background noise
is drastically reduced by the use of specialized headphones. Allows
for in service repairs.
• Restrictions: Techniques used require specialized training and
experience. Often used in conjunction with IR and trace gas
detection.
19. 19
Condenser Tube Sheet Check
Modified Ultrasonic Acoustic detector used to detect
condenser tube leaks on line. (Source Big Sandy)
20. 20
Summary
• Predictive Maintenance (PDM) Technologies provide
valuable tools that can and should be used for Boiler
Reliability Optimization (BRO).
• Most are In-Service tools that can detect or confirm
potential problems that my become a safety, operational,
maintenance and/or regulatory issue difficult and
expensive to repair.
• Combining these technologies with existing condition
determination methods such as Non Destructive
Examination (NDE) or visual inspection will improve the
overall Boiler Reliability.
21. 21
Conclusion
• Plant Predictive Maintenance (PDM)
personnel (some locations call them CBM)
should be consulted and included in BRO
activities where PDM tools and Technologies
are required.
• IF YOUR PLANT IS NOT USING THESE
TOOLS TO IMPROVE YOUR BRO
PROGRAM THEN OPPORTUNITIES ARE
BEING LOST.
