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Chain conveyor troubleshoot guide

  Problem Identification & Corrective Action Sl No. Problem Potential Cause Solution 1 Chain rises off from sprocket 1.Excess chain slack. 2.Excess wear at the bases of sprocket teeth. 3.Excess chain extension. 4.Foreign material stuck to the bases of sprocket teeth. 5.Reverse rotation of conveyor 6.Uneven chain tightening of chain 1.Adjust the amount of slack equally at both sides. 2.Carryout hard facing of the sprockets 3.Replace the elongated chain parts. 4.Remove the foreign material from the bases of the teeth. 5.Avoid reverse rotation of the conveyor when chain tightened is uneven 2 Chain separates poorly from the sprocket. 1.Sprocket misalignment. 2.Excess chain slack. 3.Excess wear at the bases of sprocket teeth. 4.Uneven chain tightening of chain 1-Adjust alignment. 2-Adjust the amount of slack.

Why does load hunting occur in steam Turbines??

 If Turbine does not maintain the load as per set load, then this condition is called load hunting.Following are the some potential reasons for load hunting

1-Problems associated with actuators:

These are related to leakages in actuators, piston stuck up, oil holes elongation etc. Because of these issues there will interruption or fluctuation of secondary oil flow through actuators, this creates the problems of actuator miss-operation & eventually load hunting.

2-Improper calibration of actuators:

This results into mismatch of actuator opening & given set point or valve demand

3-Lower control oil pressure than required:

Actuators are designed for specific pressure of control oil, if the control oil pressure at actuator inlet becomes less, then there will be more chances of mal function of actuator.

4-Fluctuation of control oil pressure/flow:

Fluctuation of control oil pressure or flow due to malfunction of pump or line PRV may lead to actuator misoperation & hence creates load hunting.

5-Control oil line leakages:

Leakages in control oil line welding & flange joints will lead to fluctuation of flow & pressure causing actuator malfunction & load hunting.

6-Contamination in oil

Foreign particles present in oil lead to improper functioning of actuators, which causes load hunting

7-Burs or scoring marks on actuator spindle & control valves spindles:

Burs or any rough scoring marks on spindles will lead to improper operation of actuator & valves

8-Passing of control valves:

This is the major reason for load fluctuation & Turbine over speed

9-Improperly set control valve cones:

During turbine HP valve assembly after maintenance, HP control valve cones should be set as per factory set readings, if it is disturbed, then there will be issues related to load hunting, low load at more HP demand or over speed.

10-Damage or broken control valves spindle & discs (cones):

Spindle damage or disc damage makes uncontrolled operation, as there will be wrong response from control valves to governor.

11-Wrongly tunes P&IDs in Governor: The disturbed values in P&ID tuning will result into heavy load hunting

12-Malfunction of Governor: This is very rare, but certainly results into load fluctuation of Turbine trip

13-Sudden changes in inlet steam pressure & extraction steam pressure

14-Fluctuation of grid frequency

15-Failure of Turbine inlet & extraction pressure sensor

For related articles on power plant Operation & Maintenance click here

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