Case Study:- Flow Measurement of Boiler Feed Water in Coal Power Plant

Coal based power plants contribute around 40 % of power generation world-wide. This is most used method for generating power.

Coal-fired plants produce electricity by burning coal in a boiler to produce steam. The steam produced, under tremendous pressure, flows into a turbine, which spins a generator to create electricity. The steam is then cooled, condensed back into water and returned to the boiler to start the process over.



Coal Based Power Plant Process Flow Diagram


Measuring the feed water flows to the boiler is of crucial importance for continuous process optimization and to avoid premature failure of the tubes. The water undergoes pre-treatment to avoid problems of scaling , fouling and rusting thereby preventing frequent maintenance or replacement of costly parts of the equipment concerned.



Boiler Feed Water Process Flow Diagram


One of the coal-based power plant with capacity more than 100 MW had problem of failing boiler feed water tubes.

During investigation it was found that the failure of the tubes was attributed to both short term and long-term issues.

Short term tube failures mostly happened during start-up wherein tube metal temperature got extremely elevated ( > 800 deg C ) due to lack of water flow and

Long term tube failures were due to creep rupture a phenomenon occurring over a period.

Client then opted to go for cost effective but reliable solution by deciding to go for flow measurements at several points on water tubes subjected to high pressure and temperature regime using clamp on flow meters. These were thermally isolated from the process tubes but acoustically coupled to measure flow.

The above approach helped in identifying the main cause of tube failure i.e entrapped air and steam in boiler feed water. This was overcome making some process changes.

Client enjoyed following benefits by using clamp on flow meter

  • Measurement in extremely harsh process pressure and temperature where other conventional meters don’t work.

  • Non-intrusive installation hence no pressure loss

  • Reduce inspection and maintenance due to less fatigue of tube

  • Accurate measurement even with entrained gaseous bubbles using advance diagnostics.

Check Out the Clamp-On Flow Meter Video

 



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