FEEDBACK NO. 23

HIGHER BARRING GEAR SPEED OF TD-BFP (TURBINE DRIVEN BFP) 500 MW

1        PROBLEM DETAILS:

The barring gear speed of TD-BFP was observed very high against the recommended value.

2        OBSERVATIONS:

With barring gear valve full open, oil flow to barring gear was quite high and causing higher barring speed. No Orifice was envisaged in the oil supply line. Provision of orifice was thought of.

3        ANALYSIS:

3.1      After providing an orifice of dia 50 mm in oil supply line, the barring speed was still of the order of 600 RPM with barring gear valve full open. In this condition, rotor used to come on barring automatically with the opening of barring gear valve.

3.2      As the speed observed with dia 50 mm orifice was higher, the orifice size was reduced to dia 25 mm with which barring speed reduced to 150-200 RPM. But barring gear was not coming automatically after the valve opening and manual barring was required.

3.3      With dia 50 mm orifice and throttling the barring gear valve, speed was maintaining at 120-150 RPM.

4     ACTION TAKEN:

4.1      Dia 50 mm orifice was provided in the oil supply line.

4.2      Barring gear logic was modified by designers to maintain the speed automatically at around 120-150 RPM by throttling the barring gear valve.

5     REMARKS:

5.1      The problem got resolved after above modification.

5.2      The modification should be incorporated in other similar units also.

 

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