CASE STUDY OF BRAZING OF LACING WIRE OF LOW PRESSURE

TURBINE OF UNIT 5

At

KORBA EAST THERMAL POWER STATION

Submitted by

NARENDRA PATEL

EASE KORBA

KTPS KORBA EAST AT A GLANCE

Korba east thermal power station is operated by Chhattisgarh state power Generation Company limited.

Korba east thermal power station, Korba was commissioned its first unit of 50 Mw capacity on 5 –Sep -1966 with the collaboration with Russian government and added three more units by 31st Oct 1968. It has increased its capacity to 440 mw capacity by adding two unit of 120 mw capacity by 1981 with the help of Bharat heavy Electrical Limited and with a boiler of its own and one boiler of ABL.

Korba east thermal power station has always welcomed new ideas and concepts for improvising its efficiency. Reformation of process is a regular feature at KTPS. The plant’s officials are always ready to adopt newer technologies and believe in continual improvement and setting newer bench marks. EWAC Association goes hand in hand from last 3 decades. EWAC services are regarded very high at Korba east thermal power station. Various technologies have been offered to the plant which has been very well accepted by the plant

ABOUT THE JOB

The fifth unit of Korba east thermal power station was commissioned on 27-apr-1976 and is running successfully for a period of nearly four decades supplying continuous service to the state of Chhattisgarh (which was earlier a part of Madhya Pradesh). The power plant is built with the help of Russian technology.

During the capitol over hauling it was found that there were very small cracks developed at the joint of blade and lacing wire and pitting marks are observed on of 5th and 6th

stage blade of low pressure turbine.

(Low pressure turbine)

Position of crack in the valve

Application details

Nature of problem- crack developed in joint area of lacing and blade and pitting marks due to erosion by steam.

Working parameters

Base metal- Alloy steel

Recommended electrode- Eutecrod 1801

The Salient features of Eutecrod 1801 is as follows

Low melting temp of 600 degree Celsius which ensures that the blades never got over heated to form any distortion and cracks.

Silver bearing alloy due to which it is very thin flowing so that it can fill very intricate gaps in the joint.

Especially designed for dissimilar metal combinations. It has a tensile strength of 90,000 Psi which ensure a high

safety of margin.

STEP BY STEP WELDING PROCEDURE

1st step-

Dye penetration test is done on all blades to find the cracks and pitting marks. It was found that almost all blades of 5th and 6th stages had developed small cracks at the lacing wire area and pitting marks were also present at blade tips.

Dye penetration test

2nd step-

After the cracks are found out it is removed by grinding. Due to which the parent material is also exposed and also the oxides are also removed from the surface

Grinding is being done

Surface after grinding

3 rd step-

Eutector 1801 flux is applied on the freshly prepared surface.

Function of flux

It dissolves the oxides and removes it to the surface of molten filler metal.

Spread ahead of the filler metal and so protect the metal surface from oxidation.

Promotes capillary of the filler metal.

Flux being applied before brazing

4 th step-

Now the brazing area is broadly heated with an excess acetylene flame till the flux liquefies. When the flux liquefies filler rod is introduced into the joining area and is melted with the flame and deposited at the joint.

Brazing is being done

Joints after brazing

5th step-

The joints are cooled slowly and all the flux residues are removed. Then with the help of grinder the surface profile is matched.

Final view of the turbine blades after the excess material is removed by grinding

For Further Information Please Contact

NARENDRA PATEL

EASE KORBA

Ph-07509572413

Mail- np.ewac@gmail.com

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