WELCOME ALL 3rd BATCH

GELs TO ‘TECHNICAL

FOUNDATION COURSE’ &

WISH THEM ALL THE

VERY BEST IN ALL THEIR

ATTEMPTS

HEAT EXCHANGERS

A Heat Exchanger is a mechanical

equipment in which heat is exchanged

between two fluids.

Heat exchange equipment is vital to the

operation of the Refinery. Its purpose is to

ensure effective heat transfer as per design,

functional requirements – resulting in

• LARGE HEAT / UTILITY SAVINGS

• UN-INTERRUPTED OPERATION

• PREVENT UNSCHEDULED OUTAGES

• SAFETY, RELIABILITY

Most commonly used Heat Exchangers

in Refinery, Petrochemicals are :

• Shell & Tube Heat Exchangers

• Air Fin Coolers (Fin Fan Coolers)

• Plate Type Heat Exchangers – Utilities

• Speciality types – Packinox type

• Finned / Studded tubes in Convection banks

• Heaters, Boilers Etc.

CONSTRUCTION BASIS

• STATIONARY HEAD TYPES (A, B, C, D)

• SHELL TYPES (E, F, G, H, J, K)

• REAR HEAD TYPES (L, M, N, P, S, T, U)

Example:

a) A : Removable Channel & Cover

E : One Pass Shell

S : Floating Head with Backing Device

b) B : Bonnet integral Cover

E : One Pass Shell

M : Fixed Tube Sheet

c) A : Removable Channel Cover

E : One Pass Shell

P : Outside Packed Floating Head

d) C : Integral with Tube Sheet, Removable Cover

F : Two Pass Shell with Longitudinal Baffle

U : U – Tube Bundle

e) A : Removable Channel Cover

K : Kettle Type Reboiler

T : Pull-through Floating Device

f) A : Removable Channel Cover

J : Divided Flow

W : Welded Tube Sheet

Types according to TEMA

• Class „R‟ – Used for severe requirement of

Petroleum and related processing

applications.

• Class „C‟ – Used for moderate requirements

of commercial and process applications.

• Class „B‟ – Used for chemical process

service.

VARIOUS PARTS

• Shell, Appurtenances (Tube Bundle)

• Stationary Head, Shell, Shell Cover,

Channel Cover, Tube Sheet, Floating Head,

Nozzles, Vents, Drains, Expansion Joints

Etc.

• For details, please Ref: Table N-2, Fig.N-2

in TEMA Standards.

DESIGN

• THERMAL DESIGN

• MECHANICAL DESIGN

• ASME Section VIII Division 1 / TEMA ‘R’

• Other Sections:

Section II A, B, C : Material, Welding Rod,

Consumables

Section V : NDT

Section IX : Welder Qualifications

• Other Unit / Process / Licensor specific requirements

• ASME Sec VIII Div 1 ( UG, UW,

Mandatory, Non-mandatory appendices)

• ASME Sec II A – Ferrous Material Spec‟s

• ASME Sec II C – Welding Consumables

• ASME Sec V – NDT, specific articles

TEMA

Sec 1 : Size numbering, Type designation, Nomenclature of Heat Exchanger components.

Sec 2 : Recommended Fabrication Tolerances, Clearances.

Sec 3 : General Fabrication, Performance Information, Name Plate, Specification Sheets Etc.

Sec 4 : Installation, Operation and Maintenance.

Sec 5 : General Requirements of Shell, Tube Sheet, Covers, Baffles, Support Plates, Gaskets, Channel Cover, End Flanges Etc.

Sec 6 : Vibration Damage Patterns, Failure Regions,

Dimensionless Numbers, Natural Frequencies,

Axial Tube Stress, Effective Tube Mass Damping,

Acoustic Vibration, Design Considerations for

Vibration Aspects.

Sec 7 : Deals with Various Thermal Relations like Fluid

Temperature, Mean Metal Temperatures of Shell

and Tubes.

Sec 8 : Physical Properties of Fluids viz: Density, Specific

Heat, Thermal Conductivity, Viscosity, Critical

Properties Etc.

Sec 9 : General Information on Dimensions, Pressure-

Temperature Ratings, Conversion Factors Etc.

Sec 10 : Deals with Vessel Supports, Lifting Lugs, Wind

and Seismic Design, Plugging of Tubes, Gaskets,

Tube Sheet, Nozzles, Covers Etc.

TEMA Basis

• Not to exceed Inside Diameters of 100 inches

(2450 mm)

• Product of Nominal Dia (inches) and Design

Pressure (psi) not to exceed 1,00,000 (17.5 x 106

kpa)

• Not to exceed Design Pressure of 3000 psi (2068

kpa)

INTENT OF THESE PARAMETERS IS TO LIMIT THE

MAXIMUM WALL THICKNESS TO APPROXIMATELY

3 inches (76 mm) AND MAXIMUM STUD DIAMETER

TO 4 inches (102 mm)

MATERIAL

Shell : CS / SS / Non-ferrous types

Tubes : CS / AS / SS / Other special types

Tube Sheet : Forgings / Plates

Nozzle Pipes : CS / AS / SS

Nozzles : CS / AS / SS

Gaskets : CAF, Spiral Wound, IJA, Ring Joint type

Fasteners : CS / AS / SS

Name Plate : SS

ORDERING INFORMATION

• PO / PR / Datasheet / Drawings / Other

relevant Specifications

• QAP / ITP, Stage, Final Inspections

• Shall be as per Heat Exchanger

Specification Sheet

• Performance / Construction details, MOC

• CDD

FABRICATION (Key Steps)

• Material Identification (Pressure parts)

• Forming

• Welding

• Review of WPS / PQR / Welder Qualification

• NDT

• Stage and Final Inspections

• Mock-up Assembly

• Skeleton Assembly

• Tube Bundle

• Insertion of Tube Bundle into Shell

• Testing

• Painting

• Documentation

• Packing / Protection / Despatch

Various Testing / Examinations Used

• Visual Examination

• Dye Penetrant Examination

• Magnetic Particle Examination

• Radiographic Examination

• Ultrasonic Examination

• Check Tests (Chemical, Mechanical, Special Tests)

• Tests for determining pullout load „Fr‟ value

• Pneumatic Tests

• Hydraulic Tests

• Special Tests (IGC, NACE related, Hardness, Eddy Current Testing, Helium Leak test Etc.)

• Pre-shipment checks

INSTALLATION

• Shell, Tube Bundle

• Site Checks

• Alignment to upstream downstream tube

side / shell side piping

• Validation tests

• Passivation and Insulation

Maintenance Activities

• Identify leaks

• Repair, rectify, plug leaks

• Validation tests

• Cleaning as per requirements

• Replacement of tube bundle, retubing

• Attend leaks from gasket joints, piping, fittings

• Offer statutory tests as per schedule (IBR Etc.)

Problem Areas

• Performance related (CTS will monitor)

• Corrosion, Erosion related

• Leaks, reliability related

• Other issues (vibration Etc.)

TUBE TO TUBE SHEET JOINT

Purpose of Tube to Tubesheet joint

• To join tubes and tubesheet and keep the tubes

structurally stable and support the skeleton assembly

under design conditions.

• To prevent intermixing of shell and tube sheet

fluids.

• To take care of Longitudinal, Compressive,

Mechanical and Thermal axial loads coming on tubes.

Selection of Tube to Tubesheet joint

Tube to Tube sheet joints are selected based on the

effective tube longitudinal, compressive stress, and loads

caused by differential thermal expansion between shell

and tubes.

Tube to tube sheet joint loads are calculated as per Clause

7.25, section 5 of “TEMA”.

Types of Tube to Tubesheet joints

1. Expanded

2. Seal Welded

3. Strength Welded

DEFINITION

Expanded tube joint is the tube to tube sheet

joint achieved by mechanical or explosive

expansion of the tube into the tube hole in the

tubesheet.

Welded tube joint is a tube to tubesheet joint

where the tube is welded to the tube sheet.

Welded tube joint can be either strength weld or

seal weld.

As per ASME Sec VIII Div 1 UW-20

Strength weld is one in which the design strength of

the weld is greater than or equal to the maximum

allowable axial tube strength.

A strength weld shall be designed to transfer all of

the longitudinal, mechanical and thermal axial loads

in either direction from the tube to the tubesheet as

well as provide tube joint leak tightness.

Tube

Tube sheet

TYPICAL SKETCH SHOWING STRENGTH WELD

As per ASME Sec VIII Div 1 UW-20

Seal weld is one which has not been designed

to be a strength weld. A seal weld is used to

supplement an expanded tube joint to ensure

tube joint leak tightness.

It is recommended to use for following cases

where

1. intermixing of shell and tube side fluid

causes safety hazards.

2. Lethal fluids are used.

3. Hydrogen service with partial pressure

greater than 6.8 bar

Tube

Tube sheet

TYPICAL SKETCH SHOWING SEAL WELD

ASME SEC VIII DIV 1 - NON MANDATORY

APPENDICES - APPENDIX A

BASIS FOR ESTABLISHING ALLOWABLE

LOADS FOR TUBE TO TUBESHEET JOINT

CONSIDERATION

Effect of different co-efficients of expansion of tube

and tube sheet material.

Joint integrity at service conditions.

SHEAR LOAD TEST

The value of Fr is calculated by carrying out shear

load test on the joint.

In this T-T/s joint shall be loaded until mechanical

failure of the joint or tube occurs. Essential

requirement is that the load should be transferred

axially.

Min of three specimens shall constitute a test. Any

retest shall include a min of nine additional

specimens from the tube from which the original

specimens are taken. All previous test data shall be

rejected.

Fr (test) = 0.8 * L (test) / (At * St)

Where

fr = test efficiency

L (test) = lowest axial load at which failure of the

tube specimen occurs in lb

St = min tensile strength of tube material in psi

At = nom cross sectional area of the tube wall in Sq

in.

Fr for various joints is provided in Table A-2 of

Appendix A of ASME SEC VIII DIV I.

Tube holes in Tube sheets ( RCB 7.43)

•Tube hole affects the mechanical strength and leak

tightness of an expanded tube to tubesheet joint

In general

•A rough tube hole provides more mechanical

strength than a smooth tube hole. This is influenced

by a complex relationship of modulus of elasticity,

yield strength and hardness of the materials being

used.

•A smooth tube hole does not provide the mechanical

strength that a rough tube hole does, but it can

provide a pressure tight joint at a lower level of wall

reduction

Contd..

Very light wall tubes requires a smoother tube hole

finish than heavier wall tubes

Significant longitudinal scratches can provide leak

paths through an expanded tube to tubesheet joint

and should therefore be removed.

Tube wall reduction

Tube wall reduction depends on number of factors.

Some of these are

• Tube hole finish (1/32 “ to 1/64” over the OD of

tubes)

• Presence or absence of tube hole serrations

• Tube hole size and tolerance.(RCB 7.41 table)

• Tube sheet ligament width and its relation to tube

dia and thickness

• Tube wall thickness

Contd..

• Tube hardness and change in hardness during cold

working.

• Tube OD Tolerance

•Type of expander used

• Type of torque control and final tube thickness

control.

• Length of expanded joint.

• Compatibility of tube and tube sheet materials

• Groove width should be 1/8” and groove depth

should be 1/32”.

Length of Expansion (RCB 7.511)

Not less than two inches or tubesheet thickness minus

1/8” whichever is smaller. In no case shall the

expanded portion extend beyond the shell side face of

the tubesheet.

Expansion of tube joints to be done after carrying out

required PWHT.

Testing of T-T/s joint

Following tests are carried out during/after tubing

1. Check tube ID before and after expansion.

2. Carry out DP if the joint is welded

3. Check by Pneumatic test / helium as per requirement

4. Check by hydrotest at test pressure

MOCK UP TESTS

1. DP Checks in case of welded

2. Pneumatic

3. Hydrotest

4. Pull out test

5. Determination of fr value

6. WPS / PQR / Welder competence

7. Quality of consumables

PETROKEMYA RECOMMENDATION

Conditions Tube-to-tubesheet joints Design P, Design T

bar G deg C

< 41 < 350 Use expansion with grooves.

> 41 < 350 Use expansion with seal weld.

any > 350 Use strength weld and contact

expansion ( without grooves ),

> 50 - Expansion shall be performed for

the entire thickness of the

tubesheet. Caution shall be taken

not to expand tubes beyond

backface of tubesheets.

In any of the following conditions, TTS joints

shall be seal welded as a minimum :

* Where mixing of shell and tube side fluids could

possibly cause problems such as explosion or

contamination.

* Where exchanger contains lethal substances.

* Cyclic service.

* H2 service where hydrogen partial pressure

exceeds 6.8 bar.

Contd..

Reduction ratio of tube thickness shall be …..

* 5-10% for CS, LAS and high alloy tube

material.

* 4-8% for copper alloy tube materials.

Notes :

* Expansion of TTS joints shall be performed

after any heat treatment in which the temperature

of the joint exceeds 200oC.

* All strength welds shall have a minimum of two

layers.

Contd..

List of exchangers upgraded as per Petrokemya

recommendations

ME-AY281-S13

ME-AY-281-S14

ME-AY281-S03/04/05

ME-AY281-S20

ME-RF413-S04

For other exchangers joint upgradation will be carried

out while procuring new bundles. QAP has been

modified accordingly.

FORWARD PATH

• Selection of vendors

• Incorporating additional inspection requirements as part

of PR spec.

• Review/approval of QAP/ITP for each P.O. With

adequate intervention points for TPI (Hold,

Witness,Review)

• Witnessing of final Hydrotests / Review of TPI reports

at vendor shop.

• Upgradation of existing joints during opportunity

shutdown / new supplies.

• Supervision/ procedure compliance during retubing /

repair in CES Workshop

Inspection related issues

• Maintain history (of failures, reliability issues)

• Recommend repair, replacement based on

inspection findings

• Recommend insurance spares

• Resolve corrosion, other degradation issues

through TRIPOD

• Fulfill statutory requirements (as applicable) –IBR

cases

Some Manufacturers

• L & T – Mumbai

• Godrej & Boyce – Mumbai

• ISGEC – Yamuna Nagar

• BHPV - Vizag

Pre-order requirements

• Vendor survey

• Enlistment

• Monitoring performance

• Appraise purchase department

• Review technical bids

Cost of Heat Exchangers depend on

• Size / type of Heat Exchanger

• Material of construction

• Type of tube to tube sheet joints

• Inspection, NDT requirements based on severity

of service

• Imported / indigenous

• Location of Manufacturer vs. user

• Government / statutory regulations (IBR Etc.)

• Quantity, lead time

THANK YOU