Transcript Header to Stub Weld Failures

FOCUS POINTS FOR SITES TO
IMPLEMENT TOWARDS BOILER TUBE FAILURES
PREVENTION
(Actionable points for site based on failure analysis )
SCOPE: BOILER PRESSURE
PARTS(HEADERS,TUBES,LINKS, PIPES etc)
1
Header to Stub Weld Failures
Headers stubs are probably getting strained during
transportation, improper handling, erection (overloading)
resulting into failures taking place at various stages from
boiler hydro test to boiler going into operation.
 All the header stubs are to be checked for leakage, sweating
etc during site hydro tests. After attaining full pressure &
completion of hydro test , system pressure may have to be
brought down at lower working pressure & this checking
needs completion on all the headers before draining the
system.
 Failures are to be reported to units with sufficient details
and findings as and when experienced.
2
Tube to Tube Butt Joint Failures
 Welders performance monitoring has to be done on
continued basis & to be re-qualified at regular interval as
applicable.
 Edge preparations by machining & automation of welding
needs due consideration.
 Process quality audit at sites by external agency is to be
introduced.
 Failure data along with failed tube samples are to be sent to
Trichy unit for analysis for taking suitable corrective &
preventive measures.
3
Attachment Weld Failures
 Attachment welding shall necessarily be done by qualified
welders at site.
 Failure data along with failed samples may be sent to unit
for analysis for taking suitable corrective & preventive
measures.
4
Fly Ash Erosion Failures
 Excess gaps in back pass, especially between steam cooled
wall and LTSH/economiser is to be informed to units for
advice & corrective measures to be taken up.
 Refractory work has to be ensured as per drawing.
5
Steam Erosion Failures
 Proper functioning of thermal drain valve, lance tube
retract mechanism and proper closing of poppet valve after
blowing are to be ensured.
 Proper functioning of ASLD is to be ensured to minimise
secondary damages.
 Also educate our customers suitably in this regard.
6
Choking Failures
Boilers in operation , it has been observed that foreign
materials have been left out in the headers resulting into
choking, starvation & resultant failure.
 All the headers shall be inspected (by boroscope) before
welding the last member to the header.
 Sub contractor personnel may have to be appraised about
the consequence of leaving unwanted material inside
headers/pipes/tubes.
7
Raw Material Defect Failures
 All the failed tube material samples shall necessarily be sent
to Trichy Unit for analysis for taking suitable corrective &
preventive measures.
8
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