case studies practically observed during the failures or mal operation of actuators of valves and dampers

1. Case studies
A V R N B MANIKYALA RAO

2. Case Study 1
100% FCV Stuck up
Economizer fly ash hoppers choke
Ash accumulation inside the stem
Actuation of Torque switch
Drum level to low
Boiler trip on drum level low low
Turbine trip on inlet steam temperature low low

3. Case Study 2
•Generator tripped on class A lock out
•Generator stator temperature high, Co release
actuated
•I/M working on Co2 release circuit
•Accidental grounding took place on negative
terminal
•Already ground persisting on positive
•Dc earth faults should be cleared as and when
noticed

4. Case Study 3
•Instrument air leakage from the connection
joint of attemperator spray block valve.
•Loss of air supply resulted in to full open
•Attemperator control valve was passing
•The steam temperature came down even
though the control valve was close
•TG trip on temperature low low

5. Case Study 4
• TG trip on loss of excitation
•DAVR dual auto channel and one manual
channel
•Service channel failed Redundant channel
tracking is not proper
•Bump transfer took place instead of bump
less
•Excitation could not be maintained

6. Case Study 5
•2X80 KVA UPS.
•Hot stand by
•In service UPS failed
•Hot stand by could not come in line
•Hot stand by was not taken in line since many
days
•Its healthiness was not tested

7. Case Study 6
•Boiler tripped on drum level low low
•BFP tripped on Suction valve not open
•House keeping workers are working at the
pump and touched the limit switch
• Resulted in to total unit tripping
•Reliability can be improved by adopting 2 out
of 3 logic or taking precautionary measures to
avoid accidental touching by barricading the
area

8. Case Study 7
•Field breaker closing on bypass of speed
interlock
•By passed during cold checks on excitation
system
•TG tripped on Over flux protection resulting
field breaker open
•Never by pass any interlocks
•Effects seriously on equipment and personal
safety

9. Case Study 8
•By pass of furnace pressure high high
•With LC guns cut in Boiler is tripping on Furnace
pressure high high(75mmhg)
•Whenever LC gun Cut in , pressing the Furnace
pressure high high protection
•After some period of operation observed furnace
skin casing damage, resulting in to boiler shut
down for long period
•Remedial measures protection modification with
timer
•Introduction of orifice in LC guns

10. Case Study 9
•Any Case studies experienced
by Participants?

11. THANK YOU