inspection of double tube sheet exch.presentation1.ppt

8/14/2019 Inspection of Double Tube sheet exch.Presentation1.ppt

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INSPECTION OF DOUBLETUBESHEET HEAT EXCHANGERS

AT CONFERENCE HALL ON 2 ND DEC.2005

Presented by Mr. Prasad Pathak

For the benefit of business and people


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2

1 Information Double T/S H.E.

2 Thumb rules

3 Introduction

4 Tube Sheet Details

5 Tube To Tube Sheet Joint

6 Tube Sheet To Tube Sheet Joint

7 Requirement Of Mock Up8 Mock Up Testing

6.1 DIM. Report of Mock Up

6.2 Expn. Record of Mock Up

6.3 Pull Out Record of Mock Up

9 Problems Incurred

10 Customers Concurrence

11 Conclusion

CONTENTS


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3

INFORMATION ON DOUBLE TUBE

SHEET HEAT EXCHANGERS

1


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4BUSINESS TRANSITION THE ROAD AHEAD

INTEGRAL DOUBLE TUBESHEETS

HEAT EXCHANGERS

The tube sheet are connected in a manner which:-Distributes axial load.

Distributes radial thermal expansion loads .

The interconnecting element is capable of preventing individual radial growthof tubesheet.

ASSUMPTIONS:

Element is rigid enough to mutually transfer all thermal and mech. radialloads between t/sheets.

Tubes are rigid enough to mutually transfer all mechanical and thermal axialloads between the tubesheets

DOUBLE TUBESHEET EXCHANGERS1


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CONNECTED DOUBLE TUBESHEETS

HEAT EXCHANGERS

The tube sheet are connected in a manner which :-

Distributes axial load between tubesheets by means of cylinder.

The effect of differential radial growth between t/s is a major factor intube stresses and spacing between t/sheets

ASSUMPTION:

Interconnecting cylinder and tubes are rigid enough to mutuallytransfer all mech. and thermal axial loads between the tubesheets.

1 DOUBLE TUBESHEET EXCHANGERS


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SEPARATE DOUBLE TUBESHEET

HEAT EXCHANGERS

The tube sheets are connected only by inter connecting tubes.

The effect of differential radial growth between t/s is a major factor in tube

stresses and spacing between t/sheets

ASSUMPTIONS:-

No loads are transferred between the tubesheets.

1 DOUBLE TUBESHEET EXCHANGERS


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THUMB RULES IN STREAMALLOCATIONS

2


8/378BUSINESS TRANSITION THE ROAD AHEAD

PRACTICAL GUIDELINES FOR OPTIMUM DESIGN

FLUID STREAM ALLOCATIONS:-

The higher pressure fluid normally flows through the tube side. With smallerdiameter and nominal wall thk. the tubes are better able to accept highpressures.

Thus larger diameter is avoided for larger pressures.

Generally corrosive fluids are in the tubeside. This is much less expensive touse the special alloys designed to resist corrosion for tubes than for shell.

Flow of higher fouling fluids through the tubes are easier to clean usingcommon mech. methods than the shell .

THUMB RULES IN STREAM ALLOCATIONHEAT EXCHANGERS2



It is best to place fluids requiring low pressure drops in the shell circuitsince flexible combinations & configurations- affecting tube pitch, baffle useand spacing, and multiple nozzles etc can be used when laying out the shellcircuit.

The fluid with lower heat transfer coeff. normally goes in the shell circuitwith this setup, low-fin tubing, which will increase available surface area,canbe used to offset the low heat transfer.

THUMB RULES IN STREAM ALLOCATIONCONTD HEAT EXCHANGERS2


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INTRODUCTION

3



HEAT EXCHANGERS3

Usually we come across inspection of straight tube and U tube HeatExchangers with single Tube sheet at either ends or single Tube sheet at oneend(U tube HE).

TEMA provides option for using Double Tube sheet HE to get a bettercontamination-proof joint.( ref.TEMA RCB pg.55-62)

Such design of exchangers are popular in Pharma industries whereintermixing of shell side and tube side fluid are totally to be avoided forprocess reasons.

It would be worthwhile attempting to describe how the double tube sheetavoids intermixing. Pl. refer the figure.

INTRODUCTION



HEAT EXCHANGERS3 INTRODUCTION

HEAT EXHCHANGER DETAILS



HEAT EXCHANGERS

TYPICAL JOINT DOUBLE TUBESHEET

INTRODUCTION3

Inner T/SOuter T/S

ChannelShell

Tubes

Shell



GENERAL DETAILS ABOUT THE JOB INCLUDING OVERALL DIMNS. :

HCL Hydrogenation Heater for Reliance Industries Limited ,HaziraPROCESS FLUID:- SHELL SIDE - HCL / TUBE SIDE - STEAM*U Tube Double Tube sheet HE.

DIMENSIONS :

Overall Length 6931 mm.

SHELL ID 440 mm x 12 Thk, TUBESHEET 476 ODMATERIAL :

Shell / Dish end SA 516 Gr 70

Tube sheet SA 350 Gr LF2 46mm & 71mm ThK

U Tubes SA 334 Gr 6 19.05 OD x 2.77 mm thk

HEAT EXCHANGERS

* SINCE THE PROCESS FLUID WAS STEAM, CUSTOMERCONFIRMATION OF IBR WAS SOUGHT.

INTRODUCTION3


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TUBE SHEET DETAILS

4


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TUBE SHEET DETAILS

TubeSheet - SA 350 Gr LF2. X 476 dia.

First T/s 46mm( inner) & second 71 mm ( outer).

Each T/s having two grooves of 3mm width and 0.4mm depth.

148 No of holes each of Dia. 19.25mm on 25.4mm traingular pitch.

4 HEAT EXCHANGERS


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TUBE TO TUBE SHEET JOINT

5


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TUBE TO TUBE SHEET JOINT5

Tube SA 334 Gr 6 Size 19.05mmx 2.77 mm ThkFully expanded joint.

8 to 10% expansion% Thinning check and air test after expansion.

HEAT EXCHANGERS


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TUBE SHEET TO TUBE SHEETJOINT

6


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TUBE SHEET TO TUBE SHEET JOINT6

Full penetration joint with 25 mm gap in between the Tube sheets.

NDT as per drawing MPINDT suggested PT and UT in addition to MPI.

HEAT EXCHANGERS


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REQUIREMENT OF MOCK UP

7


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WHY THE MOCK UP WAS REQUIRED TO BE DONE:

( TEMA DOESNT CALL FOR SUCH TESTS FOR U -TUBE EXCHANGERS)

To establish expansion parameters.

To check % thinning after expansion

To check axial load (pull out ) of tubes after expansion.

To check proper flow of tube material in the T/s grooves afterexpansion.

To freeze the sequence of the expansion of the T/s to Tube joint.

REQUIREMENT OF MOCK UP7 HEAT EXCHANGERS

SINCE TUBE SHEET ASSLY HAD DOUBLE EXPN. PORTION,IT WAS ESSENTIAL TO DEMONSTRATE THE EXPANSION

ACHIEVED IN THE INNER TUBESHEET.


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MOCK UP TESTING

8


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MOCK UP TESTING

DESCRIPTION OF THE MOCKUP:-

Tube sheets with same configuration as required in job.

17 No of holes used.

Pull out test carried out on Hole nos. 4,9&14 ,surrounded by at least tworows.

Expansion in two stages.

% expansion checked in both Tube sheets with bore gauge.

ADDITIONAL TESTS DONE ON THE MOCKUP:

After satisfactory expansion, the joint with annular space was seal weldedfirst and then subjected to pneumatic test at 2.0 kg/cm2(g). pressurefollowed by hydro test at 33.0 kg/cm2(g) and the results were leak tight.

8 HEAT EXCHANGERS


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DIM. REPORT OF MOCK UP8.1 HEAT EXCHANGERS


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EXPN. RECORD OF MOCK UPHEAT EXCHANGERS8.2


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PULL OUT RECORD OF MOCK UPHEAT EXCHANGERS8.3


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The pull out loads were found to be satisfactory when the tests were done :-

1. Required load - 56 kn actual 80 kn

2. Macro test was conducted after sectioning to confirm the proper flowof tube material in the grooves after expansion, the flow of material was

satisfactory.

3. Hardness test were done on the inner expanded & unexpandedsurface of the tube and was with in 187 bhn.

8.4 HEAT EXCHANGERSPULL OUT RECORD OF MOCK UP

CONTD..


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PROBLEMS INCURRED

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PROBLEMS INCURRED9.1

REQUIREMENT OF EXTRA LONG DIAL BORE GAGE FOR THE INNERTUBESHEET:

In mock up stage , both ends of the tube sheets were accessible and henceit was easy to check % expansion in both the tube sheets separately.

In actual job, only one end was accessible. So it required a long bore gaugeto check the expansion. Since the fabricator was not having the long boregauge,expansion of the outer T/s was checked and reported. The same wasreferred to client for concurrence and was accepted by them based onsatisfactory mock up results.

HEAT EXCHANGERS

PROBLEMS INCURRED


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NDT SPECIFIED FOR THE EQPT WAS 100% RADIOGRAPHY :-

BV insisted the above requirement for the T/S TO T/Sheet weld joint

Due to the joint geometry, radiography could not be realised. UT was thenext suggested alternative. Again due to joint configuration /lesser widthof joint & limitation of scanning area only a small portion could be

examined leaving out the critical root penetration.

To counter this, special care for the root pass was undertaken by keeping3 visible ports for examining the root penetration visually. The rootpenetration was found satisfactory.

As per approved QAP only MP examination was specified for this jointand hence accepted on this basis.

HEAT EXCHANGERSPROBLEMS INCURRED

CONTD..9.1


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BV INSPECTION REPORT9.2 HEAT EXCHANGERS


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BV INSPECTION REPORTCONTD..HEAT EXCHANGERS9.2


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CUSTOMERS CONCURRENCE

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CUSTOMERS CONCURRENCE 10 HEAT EXCHANGERS


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CONCLUSION

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CONCLUSION

TEMA does not give too much details about such type of Double T/s HE.

Maximum care was taken to do all possible testing and checks toestablish fool proof joint.

Still a better version of checks and testing may be possible.

Any additional information and experience on this topic is welcome.

HEAT EXCHANGERS11

inspection of double tube sheet exch.presentation1.ppt

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