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STARTING OIL PUMP IN
SERVICE PROBLEM AT
NTPC,TTPS UNIT#5 ,110 MW UNIT
Objective
To study the Main oil pump discharge
pressure not sustaining when unit isrunning on load
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Brief Description of TG Lub
oil System When the Turbine Generator is on BarringGear and on Full speed No load ( FSNL ) ,
Starting oil pump ( SOP ) supplies Lub oil to allbearings , Governing system , Airside seal oilsystem, MOP suction .
When the machine is rolled to 3000 rpm ,
Main oil pump ( MOP ) takes over the duty ofsupplying Lub oil to TG Bearings , Governingsystem , Airside seal oil system .
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Observations :
• As we switch off the SOP after unit issynchronized to Grid , MOP dischargepressure is taking a dip of 4-5 Kgf/cm2
from 10.5 Kgf/cm2 to 5.5 –
6.5 Kgf/cm2which is resulting in Auto start of SOP .
• If the SOP is not coming into service ,
Turbine is getting tripped and the unit # 5has tripped 2 times so far because of thisaccount.
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Problem faced : • When the SOP is switched off either at
FSNL ( 3000 rpm ) or when the unit is
on load ,
• MOP Discharge pressure is not holding
at a constant value , but it is varying by
4-5 Kgf/cm2 resulting in dip of
discharge pressure . Hence the TurbineGenerator is getting tripped .
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Major jobs carried out during
Annual OH – 2009 of Unit # 5 No Turbine cylinders were overhauled
6 Nos of TG Lub oil system NRV's serviced
2 Nos of SOP Discharge valves , MOP Suction isol. valve, MOP Disch. to Lub oil coolers isol. valve serviced
TG Lub oil cooler bundles replaced with New design
( Finned tubes ) bundles of M/s Laxmi EngineeringIndustries ,( Bhopal ) Pvt Ltd make
Air side and Gas side Seal oil pumps replaced with Newpumps of M/s Tushaco make Gear pumps
2 out of 3 Logic has been introduced in this overhaul by
C&I in DDCMIS Generator Rotor , Seal Rings replaced during Gen.
Rotor thread out operation
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Post Overhauling works 2 Nos of NRV’s one in MOP suction line
from SOP Discharge , SOP Discharge to
Gov. system oil line were replaced with
New ones – No change in SOP running status while unit is on Load
ONE no. of SOP replaced with overhauled
pump – No change in SOP running status while unit is on Load
•
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Brain storming
/Recommendations
• Oil Injector which is providing MOP
suction needs inspection • All NRV ‘s in TG Lub oil system
servicing • MOP Inspection & Seal rings
replacement if required • Governing system inspection • Lub oil Orifices inspection/rectification
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Suggestions to solve the above
problem by the Esteemed
members We welcome your valuable suggestions
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REPEATED FAILURE OF OMEGA
PIPE GASKET AT NTPC , TTPSSTAGE – 2 UNITS ( 2*110 MW )
• Brief Introduction of the Problem : What is OMEGA pipe ?
– It is nothing but an IP Turbine Steam Inlet pipe in the
form of symbol OMEGA . – Omega pipe is having LHS & RHS Steam inlet pipes
and a common inlet on the IP cylinder facing – Steam leakage was observed from LHS Flange of
Omega pipe in Dec ,2008 & Jul , 2009 in Unit # 5
– Resulting in Unit # 5 Outage on 2 occasions
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Observation of the Problem : • Steam leakage from LHS Flange of
Omega pipe of Unit # 5 was due to
the failure of Old Serrated Gasket of
material SS – 316 .
• May be due to thermal shocks
during Load changes/Transient
operating conditions.
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Remedial measures : A New modified Gasket with more outside
diameter to hold between the Studs beingused .
Camprofile gasket with Graphite sheathingon both sides used with higher OD toarrest the leakage .
Support system for the IP Steam chestLHS /RHS will be thoroughly inspectedduring next Annual Overhaul .