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)

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.

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.

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.

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.

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.

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.

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.

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