WET STEAM - CARRYOVER & SUPERHEATER FAILURE

Steam Drum with Internals like Baffles, Cyclone and Demister is always designed to supply Dry Steam inlet to Primary Super heater coils in boiler operating condition on the entire boiler steam loading range. Steam Drum design with incorrect internals and its fitment may lead to wet steam entry to Primary Super heater coils

These impacts on cost as final steam temperature achievement is a big task & specific steam consumption increase. Further, super heater coil replacement, emergency shutdown, tube failure are maintenance aspects & losses

These deficiencies may be arising during engineering design, boiler capacity enhancement modification & retrofit, erection, boiler repair & maintenance

CASE History: LOW FINAL SUPERHEATER TEMPERATURE & SUPER HEATER TUBE FAILURE
A boiler was modified for capacity enhancement. The cyclone and demister increased in steam drum, no. of super heater coils increased, water wall area increased. During operation, repeated super heater tube failures with swelling, Bulged & long term overheat symptoms and low final steam temperature issues were noticed.

Few other boiler consultants provide an idea to customer for installation of:
1. Header with turbo separator in between steam drum & primary super heater
2. Increase No. of Cyclone and demister
3. Increase no. of stage / pass in super heater
4. Chemical cleaning of Alloy Super heater coils
5. Replacement of all steam drum internals & demister with new design

On our detailed investigation and analysis, outcome as given below:
1. Wrong installation of Feed water pipe in steam drum
2. Poor design of cyclone
3. Choking of demister pads
4. Steam short circuiting through baffles
5. Steam short circuiting through demister
6. Heavy Water carryover to Primary Super heater
7. Internal thick scale deposit in super heater coils
After implementation of above correction to avoid water carryover, desired final steam temperature achieved.

We suggest to reviewing before start the boiler operation: 1. Boiler technical details & auxiliaries before starting 2. Use of water treatment chemicals & Boiler water chemistry parameters as per standard code. 3. Steam drum level operation control within the safe limits 4. Boiler Startup & Shutdown procedure 5. Avoid Water Carryover, Priming & Foaming during boiler operation

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M/s Unite Energy Corporation LLP, Ghaziabad, U.P., India is keen to provide the Boiler Spares, Sales & Services, Retrofit & Site Repairs of Boiler & Auxiliaries, Performance Evaluation, Fabrication, Erection & Commissioning, Design Modification & Feasibility Study, Consultancy & troubleshooting support to mitigate the irregularities in the plant and improvise performance of the plant.