PPT-on-false-air.ppt

 Brief of False/Excess Air
 Needs of Identification &
Practices
 How To Attack
 Remedial Actions
 Summary
Flow of Presentation

What
Does
It
Mean
s
Any undesired extra air ingresses
or intruded in the sealed
systems i.e.. boiler flue gas path
or ACC vacuum system,
FALSE / EXCESS AIR

POSSIBLITIES/REASONS FOR FALSE AIR
ENTRY
The major possibilities & invitations for a FALSE
AIR entry is our closed circuit systems which are
in negative pressure for example the huge boiler
flue gas ckt ,LP turbine & its auxiliary ckt or
even ACC vacuum ckt., even a pin hole in these
vast ckts gives a wonderful invitation to this
problem as the air has the tendency to flow from
a positive to negative(lower) pressure region
without any external efforts. Our plants are
designed for these circuits which has to be
excellently leek proof to avoid this major culprit.

CHANGE IN FLUE GAS COMPOSITION WITH
EXCESS AIR

Needs for identification &
Practices

Why False Air Needs Our Attention ?
 Air ingressment is a common problem in power plant
which is affecting the plant performance by following
ways.
 Heat loss .
 Fan efficiency loss & overload .
 Flue gas emission,
 Difficulty in maintain operating parameters.
 Affecting vacuum in acc.
 Increase plant down time.
 Loss of repeated maintenance and rework hours.
 Ultimately production loss & monitory loss

Affected areas of Power Plant
 Air cooled Condenser vacuum circuit
 Boiler flue gas circuit

Vacuum system – Air cooled condenser

Major parameters of ACC
 Vacuum - 8500 mmwc
 Media- Two phase mixture of Steam
 Temperature- 55oC
 Surface area – 62000 mtr2 ( consist 4.5 meter duct also)
 Leakage/False air – 0.03% ( 110 kg/Hr air)

 Vacuum + 1500 MMWC to - 250 mmwc
 Media – Flue gases
 Leakage /False air – 0.5 to 1.0% O2/ 4% excess
air
Temperature – 350 deg C
 Surface area –25000 mtr2
Major parameters of Boiler

How to attack on False Air
Planning
Measurement
Monitor
Control & Review
Compare

Steps for managing the false air
Steps
for
Managin
g
1. Identiication of area of leakage
2. Resources availability
3. Make the schedule of Measurement
4. Measurement of Excess air / O2
5. Solution to attend it online/offline
6. Long term technological solution
7. Points to be taken care during
a. Design b.
Fabrication
c. Erection & Commissioning d.

1.Identify the area to be covered
 The first & the foremost important activity is to
define the system boundary,
 Total areas affected to be divided in different zones
based on the similarity and continuity.
 Fix the design/target value of parameter in that
area.
 Convert the losses in money term

2. Resources
 Dedicated team for measurement
 Maintenance cum operation team for attending
it on temporary basis
 Instruments for leak detection & measurement

3. Make the schedule of
Measurement
 Daily measurement,
 Manual measurement
 On line measurement
 Weekly measurement
 Measurement Schedule before stoppage of
equipment.
Boiler O2 measurement by portable flue gas analyser 01.05.12
Left Pass Right Pass
S.No
.
Description Unit
DCS O2 @
Eco. Inlet
Field O2 (by
portable O2
analyser)
Field O2
(equivalent)
DCS O2 @
Eco. Inlet
Field O2 (by
portable O2
analyser)
Field O2
(equivalent)
O2 measurement
1 Eco. Outlet ( APH inlet) %

4. Methods for Excess air / O2
measurement
 Take the measurement by portable O2
 On line O2 meter
 Ultrasonic leak detector
 Physical round
 Sound
 Load on fans
 Change in system drop
 Thermography of the affected zone

Measurement by portable
instruments
Excess Air ingressment
measurement at
Economizer outlet
Ultrasonic Leak
detection system
Thermo graphic method

5 Solution for attending it online
 By Welding
 Closing man hole
 By applying the Putty
 By changing the gaskets
 By reducing the gap between seals
 By tightening the glands
 Adjusting the dampers
 Adjusting the Rotary air lock

6. Long Term Technological
Solution
 Welding techniques
 Quality control on welding
 Design of flanges
 Design of Man holes
 O2 online measurement in false air prone
area
 High temperature knife valve fixing/Air
tight valve fixing

Monitoring & measures taken at SMP
Online O2 Analyzer
at Economizer
Outlet
Air tight motorized
gate at ID Duct &
measurement
tappings

Leak Proof - ACC Vacuum system
Leak proof Man-holes
Leak Proof Expansion
Bellows

Leak Proof – Boiler flue gas system
Leak proof Man-holes
Leak Proof knife edge
gate in Bed Ash Drain

Leak Proofing Agents
Gasket
Champion 54
Valve Carbine
Compound
Sealing Rope
& Liquid

Helium leak detection (Tracer
Method)

SMP Practices – For Helium Leak
Detection
Calibration Observation

Off line attending the jobs
 Planning as per leak list received from process.
 Replacement of worn out parts
 Replacement of leaky gaskets
 Change of glands etc.
 Checking of dampers from inside for full closing
and full opening
 Clearance checking of equipment like rotary air
locks,
 DP test
 Kerosene leak test
 UT test for high thickness welding more than 24
mm

7a. Points To Be Taken Care During
Design
 Guarantee from supplier for design.
 Finalize the proper QAP plan
 Metallic bellow suitable for application
 Higher margin for start and stop shocks.
 Proper man hole design is required
 All flanges to be seal welded from inside
 Proper gasket design
 Provision for 100 % sealing.

7a. Points To Be Taken Care During
Design
 Provision 100 % leak test or pressure test.
 Design & material care need for expansion bellows.
(Eg:- FAILIURE OF SEC. Air nozzle bellows)
 Special care in seal box design in lower
combustor.(100%approach,bothside welding , leak test
&pr. Test facilities
 Approach for both side welding.& Design for both side
welding ( fins , seal boxes, ducts)
 Envisage minimum site welding ,
 Avoid bolted joints( guillotine damper is bolting).

Seal welding for leak proofing

7b. Points important during
Fabrication.
 Secondary responsibility of checking of welding to be given to
operation and maintenance team during fabrication itself.
 Fabrication should be strictly as per design
 QAP- to be finalized before start of activity.
 Qualified welders only to be engaged which can be checked by
third party.
 Engagement of third party for quality check. They should have
authority to stop the work
 Only reputed brand of electrode to be used for fabrication and they
should be specified before start of work
 High temperature gasket suitable for that temperature only to be
used like champian-54 etc.
 Deploy qualified welders & experienced fitters.

7c. Points to be taken during
erection and commissioning
 Secondary responsibility of checking of welding to be
given to operation and maintenance team during
fabrication itself.
 Leak test
 Smoke test
 Permanent supports to checked for duct and sliding
/movement to be kept free
 All temporary supports to be removed from duct before
startup.
 Pressure test
 Fit up inspection before welding clearance.

Proper Fit-up (Before Welding)

Ultrasonic inspection(pulse-echo)
0 2 4 6 8 10
Initial Pulse
Crack
Echo
Back surface echo
Oscilloscope or Flaw detector screen
Plate
Crack
High frequency sound waves are introduced into a material and they are reflected back
from surfaces or flaws.
Reflected sound energy is displayed versus time, and inspector can visualize a cross
section of the specimen showing the depth of features that reflect sound.

Use of Approved welding Electrodes

Proper welding of stiffeners ,
support erection & insulation of the
ducts

Exhaust device water fill test done
in SMP

Liquid penetrate inspection
 A liquid with high surface wetting characteristics is applied to
the surface of the part and allowed time to seep into surface
breaking defects.
 The excess liquid is removed from the surface of the part.
 A developer (powder) is applied to pull the trapped penetrate
out the defect and spread it on the surface where it can be
seen.
 Visual inspection is the final step in the process. The
penetrate used is often loaded with a fluorescent dye and
the inspection is done under UV light to increase test
sensitivity.

7d. Points to be taken care during O&M
 Dedicated man power for leak arresting
 Pressure test during long shut down before stop of the equipment.
 Timely replacement of regular wear area
 Parts to be replaced with proper quality
 Involvement of maintenance team for identification of leakage
 Maintain all operating parameters as designed.
 Ensure proper expansion as per design.
 Root cause analysis of all failures followed with corrective and
preventive actions.
 Don’t deviate from the drawing and technical spec. During
maintenance.
 Expansion provision must be taken care during maintenance work.
 Provide adequate training/guidance to the persons involved.

Summary
 Quantification of losses in money term with
target value
 Dedicated team for identification and attending
it during normal running.
 List and tagging of leakage before stoppage of
equipment for shut down
 Dedicated team during shut down for attending
leakages in time bound manner.
 Proper online instruments like O2
measurement, Leak detector etc.

Continue… Summary
 Pressure test
 Smoke test
 Vacuum test
 Thermo graphic audit of affected area
 One size higher design for leak prone items
 Design consideration
 Strict checking by O and M team during
fabrication and erection.

PPT-on-false-air.ppt

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