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Raj Kumar

Manager ARP

SEISMIC ANALYSIS OF 660MW CONDENSER USING FINITE

ELEMENT METHOD

,BHEL Delhi

Date:13.06.2014

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Background of your Organisation

BHEL was established in 1964. Heavy Electrical (India) Ltd was merged with BHEL in 1974.[5] In 1982, it entered into power equipments, to reduce its dependence on the power sector. It developed the capability to produce a variety of electrical, electronic and mechanical equipments for all sectors, including transmission, transportation, oil and gas and other allied industries.[5] In 1991, it was converted into a public limited company. By the end of 1996, the company had handed over 100 Electric Locomotives to Indian Railway and installed 250 Hydro-sets across India.[5]

It is engaged in the design, engineering, manufacture, construction, testing, commissioning and servicing of a wide range of products, systems and services for the core sectors of the economy, viz. Power, Transmission, Industry, Transportation, Renewable Energy, Oil & Gas and Defenc

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SEISMIC ANALYSIS OF 660MW CONDENSER USING FINITE ELEMENT METHOD

• INTRODUCTION:-

The 660MW Condenser is one of the crucial components among the power plant

equipment manufactured by BHEL. To ensure its satisfactory and uninterrupted

operation, it should be protected from natural calamities e.g. earthquake, tsunami,

volcanic eruption etc. The 660MW Condenser was slated to be installed in Barh district

of Bihar, which falls under Seismic Zone IV, according to IS 1893: Part 1-2002 . The 3D

CAD model of the condenser was developed and imported into Hypermesh software

for the purpose of carrying out Seismic Analysis.

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• GENERAL DESCRIPTION OF CONDENSER:-

The condenser is a box type construction with divided water box design which

facilitates the operation of one half of the condenser while the other half is under

maintenance. The steam space is of rectangular cross-section condensing surface.

The condenser is provided with integral air cooling section from where air and non

condensable gases are drawn out with the help of air evacuation equipment.


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• METHODOLOGY FOLLOWED FOR SEISMIC ANALYSIS

Superimposition of the Results of Static Analysis over RSA Results

Response Spectrum Analysis(RSA)OS-ANALYSIS

Modal Analysis OS-ANALYSIS

Static Analysis under Gravity by using OS-ANALYSIS

Meshing in HyperMesh

3D CAD Modeling

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• 3D CAD MODELING AND MESHING

The 3D CAD model of 660MW Condenser was created, and imported in Hypermesh for

meshing. For all the condenser parts, except pipes and bearings ,shell model was

generated from the solid 3-D CAD models in Hypermesh software using mid-surface

extraction method. The surfaces so created were meshed with 4-noded(Quad) and 3-

noded(Tria) shell elements. The bearings and its assemblies were meshed with

tetrahedral elements. The pipes were meshed with 1-D beam and truss elements. The

connectivity between 3-D element and 2-D ,and ,2-D and 1-D elements was maintained

using rigid elements. The 0-D element like mass elements were used to define the LP

turbine load ,water and tube load on the condenser

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Full Condenser Assembly - CAD Shell Model

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Isometric View of Condenser Assembly - FE Shell Model

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Isometric View of Dome Internal stiffening - FE Shell Model

Top View of Condenser Assembly - FE Shell Model

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CONTACT SURFACE CREATED FOR LP HEATER SADDLE PLATE

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RIGID LINKS CREATED BETWEEN BEARINGS AND BOTTOM PLATE

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2D MESHING OPTIONS USED IN HYPERMESH

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3D MESHING OPTIONS USED IN HYPERMESH

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STATIC ANALYSIS UNDER GRAVITY BY USING OS-ANALYSIS:-

The Finite Element model thus generated was checked for errors due to loss of

accuracy during meshing, missing mass etc. to ensure the correctness of the

analysis. Jacobian and Aspect Ratio were considered as the criteria for checking

mesh quality. The FE model, thus, generated was analysed using Optistruct

Analysis. Static analysis with “1g” in vertical downward direction (for self weight

loading condition) was carried to get the stress and displacements under dead

weight conditions.

BOUNDARY CONDITIONS:

1.The bottom surface of Condenser Support has been constrained in all

directions.

2.The upper surface of Condenser Support has been partially constrained that is

given below in the Fig. 15

3.The Turbine mass has been incorporated as lumped mass on the upper edges of

Upper Dome Wall.

4.The tube load and water load has been applied as mass elements per node on

each of the 42 Shell Internal Details Plates and 4 Water Chambers.

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RESULTS :-

Stress Plot of Condenser under Self Weight

Displacement Plot of Condenser under Self

Weight

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MODAL ANALYSIS BY USING OS-ANALYSIS:-

Modal Analysis was performed on the finite element model of Condenser to extract its

natural frequencies. 1089 modes were extracted between the frequency range 0-50Hz.

RESPONSE SPECTRUM ANALYSIS BY USING OS-ANALYSIS

Response Spectrum for Barh region was generated with the help of IS 1893: 2002 code.

In the Response Spectrum Analysis, 100% value of spectral acceleration values were

assigned in the East-West,North-South direction and 66.67% value in Vertical direction.

The excitation was given in all the three directions simultaneously. The directional

combination and modal combination were implemented by ALG(Algebric )method and

SRSS(Square root of sum of squares) respectively.

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0

0.02

0.04

0.06

0.08

0.1

0.12

0 10 20 30 40 50 60

Sei

smic

Co

effi

cien

t (A

h)

Frequency (f)

Seismic Coefficient(Ah) Vs Frequency (f) Graph

RESPONSE SPECTRUM GRAPH

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RESPONSE SPECTRUM TABLE IMPORTED IN HYPERMESH

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RSPEC CARD CREATED FOR PERFORMING RESPONSE SPECTRUM ANALYSIS

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TABDMP CARD CREATED FOR PERFORMING RESPONSE SPECTRUM ANALYSIS

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CREATION OF LOADSTEP FOR RESPONSE SPECTRUM ANALYSIS

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COMBINED RESULTS OF STATIC ANALYSIS AND RESPONSE SPECTRUM ANALYSIS BY USING OS-ANALYSIS

The results of Static Analysis of Condenser under self-weight were combined with those of Response Spectrum Analysis and a combined analysis was performed.

Following Load Cases were considered:

1. For Design Basis Earthquake (DBE)2. For Maximum Considered Earthquake ( MCE)

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STRESS PLOT OF 1D BEAM ELEMENTS IN HYPERVIEW

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Displacement Plot of Condenser under the effect of combined Dead and Seismic load

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Stress Plot under the effect of combined Dead and Seismic load

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CONCLUSION:-

The design of 660MW Barh Condenser has been found to be strong and good

enough to withstand the seismic forces in the event of an Earthquake(DBE). Based

on the results of abovementioned Analyses, it has been observed that the

equipment possesses at least a minimum strength to withstand minor

earthquakes

(< DBE) which occur frequently, without damage; resist moderate

earthquakes(DBE) without significant damage and can withstand a major

earthquake (MCE) without collapse.

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