ASIAN BUSINESS CONSULTANTS.

PUNE. INDIA .

TOPICSTOPICSINTRODUCTIONINTRODUCTION

BASIC CONSTRUCTIONBASIC CONSTRUCTION

TYPES & TYPES & NOMENCLATURENOMENCLATURE

BASIC DESIGN RULESBASIC DESIGN RULES

DETAILS OF VARIOUS DETAILS OF VARIOUS PARTSPARTS

PROBLEMS/TROUBLE PROBLEMS/TROUBLE SHOOTINGSHOOTING

MAINTENANCE/ MAINTENANCE/ INSPECTION INSPECTION

CASE STUDIESCASE STUDIES

IntroductionIntroduction

Heat Exchanger is mechanical equipment Heat Exchanger is mechanical equipment in which heat is exchanged between two in which heat is exchanged between two fluids.fluids.

Heat exchange equipment is vital to the Heat exchange equipment is vital to the operation of the Process plant. Its purpose operation of the Process plant. Its purpose is to ensure effective heat transfer as per is to ensure effective heat transfer as per design, functional requirements – resulting indesign, functional requirements – resulting in

LARGE HEAT/UTILITY SAVINGS UN-INTERRUPTED LARGE HEAT/UTILITY SAVINGS UN-INTERRUPTED OPERATION PREVENT UNSCHEDULED OUTAGESOPERATION PREVENT UNSCHEDULED OUTAGESSAFETY, RELIABILITYSAFETY, RELIABILITY

Types of heat Types of heat exchanger exchanger

Based on service Based on service Based on constructionBased on construction

Types of Exchangers Based on ServiceTypes of Exchangers Based on ServiceExchanger:Exchanger:

It is a unit that exchanges heat between two process streams It is a unit that exchanges heat between two process streams without phase change; i.e. liquids are not evaporated nor without phase change; i.e. liquids are not evaporated nor condensed. condensed.

Cooler:Cooler:Cools the process fluids without phase change.Cools the process fluids without phase change.

Condenser: Condenser: Condenses process vapor stream. Condenses process vapor stream.

Re-boiler: Re-boiler: Provides latent heat of vaporization to bottom of distillation/ Provides latent heat of vaporization to bottom of distillation/ fractionation column.fractionation column.

Pre-heater: Pre-heater: Uses steam or hot process stream to heat & or vaporize the feed Uses steam or hot process stream to heat & or vaporize the feed to processing unit. to processing unit.

Types of Exchangers Based on ConstructionTypes of Exchangers Based on Construction

Tubular heat exchangerTubular heat exchanger::

U tube type heat exchanger U tube type heat exchanger

Fixed tubesheet heat exchangerFixed tubesheet heat exchanger

Floating head type heat exchangerFloating head type heat exchanger

Hair pin type Hair pin type

Pipe in pipe heat exchangerPipe in pipe heat exchanger

Fin fan type exchanger Fin fan type exchanger

Plate type heat exchangerPlate type heat exchanger

Spiral plate type heat exchangerSpiral plate type heat exchanger

SHELL AND TUBE HEAT SHELL AND TUBE HEAT EXCHANGERSEXCHANGERS

Why shell-and-tube?Why shell-and-tube?

Scope of shell-and-tubeScope of shell-and-tube

ConstructionConstruction

TEMA standardsTEMA standards

Choice of TEMA typeChoice of TEMA type

Fluid allocationFluid allocation

Design problemsDesign problems

EnhancementEnhancement

Improved designsImproved designs

Why shell-and-tube?Why shell-and-tube?

S&T accounted for 85% of exchangers supplied S&T accounted for 85% of exchangers supplied to oil-refining, chemical, petrochemical and to oil-refining, chemical, petrochemical and power companies. power companies.

Why?Why?Can be designed for almost any duty with a very wide Can be designed for almost any duty with a very wide range of temperatures and pressuresrange of temperatures and pressures

Can be built in many materialsCan be built in many materials

Many suppliersMany suppliers

Repair can be by non-specialistsRepair can be by non-specialists

Design methods and mechanical codes have been Design methods and mechanical codes have been established from many years of experienceestablished from many years of experience

Functions of S&T exchangersFunctions of S&T exchangers

Heating (gas or liquid)Heating (gas or liquid)

Cooling without condensing (gas or liquid)Cooling without condensing (gas or liquid)

Condensing of vapors (partial condensing OR full Condensing of vapors (partial condensing OR full condensing) condensing)

Evaporating liquid (partial or full)Evaporating liquid (partial or full)

Based on the above S&T exchangers are known Based on the above S&T exchangers are known as:as:

Heaters / Coolers / BoilersHeaters / Coolers / Boilers

Condensors / Trim coolers /Trim condensorsCondensors / Trim coolers /Trim condensors

Vaporisers / ReboilersVaporisers / Reboilers

Designation of S & T exchDesignation of S & T exch

TEMATEMA - - R C B –fundamental stdR C B –fundamental stdClass ‘R’ – Used for severe requirement of Class ‘R’ – Used for severe requirement of Petroleum and related processing applications.Petroleum and related processing applications.

Class ‘C’ – Used for moderate requirements of Class ‘C’ – Used for moderate requirements of commercial and process applications.commercial and process applications.

Class ‘B’ – Used for chemical process service.Class ‘B’ – Used for chemical process service.

STATIONARY HEAD TYPES (A, B, C, D)STATIONARY HEAD TYPES (A, B, C, D)

SHELL TYPES (E, F, G, H, J, K)SHELL TYPES (E, F, G, H, J, K)

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

Scope of shell-and-tubeScope of shell-and-tubeMaximum pressureMaximum pressure– Shell 300 bar (4500 psia)Shell 300 bar (4500 psia)

– Tube 1400 bar (20000 psia)Tube 1400 bar (20000 psia)

Temperature rangeTemperature range– Maximum 600Maximum 600ooC (1100C (1100ooF) or even 650F) or even 650ooCC

– Minimum -100Minimum -100ooC (-150C (-150ooF)F)

Fluids Fluids – Subject to materials Subject to materials

– Available in a wide range of materialsAvailable in a wide range of materials

Size per unit 100 - 10000 ftSize per unit 100 - 10000 ft2 2 (10 - 1000 m(10 - 1000 m22))

Can be extended with special designs/materialsCan be extended with special designs/materials

Constructional detailsConstructional details

Shell side:Shell side: Shell, Shell covers, shell Shell, Shell covers, shell nozzlesnozzles

Tube side:Tube side: Tube sheet, Tubes, Baffles, Tie Tube sheet, Tubes, Baffles, Tie rods,rods, Spacers, Impingement Spacers, Impingement plate,plate, Channel shell, Channel Channel shell, Channel cover, Tube side nozzlescover, Tube side nozzles

Non-pressure Non-pressure attachments:attachments: Saddles, structuralSaddles, structural

Associated piping for shell side and tube sideAssociated piping for shell side and tube side

ConstructionConstructionBundle of tubes in large cylindrical shellBundle of tubes in large cylindrical shell

Baffles used both to support the tubes and to Baffles used both to support the tubes and to direct into multiple cross flowdirect into multiple cross flow

Gaps or clearances must be left between the Gaps or clearances must be left between the baffle and the shell and between the tubes baffle and the shell and between the tubes and the baffle to enable assemblyand the baffle to enable assembly

Shell

Tubes

Baffle

Shell-side flowShell-side flow

Shell and tube HX partsShell and tube HX partsShellShell

TubesTubes

Shell coverShell cover

Channel box Channel box

Channel coverChannel cover

Tube sheetTube sheet

Floating headFloating head

BafflesBaffles

Tie rodsTie rods

Major Parts of shell & tube heat exchangerMajor Parts of shell & tube heat exchanger

Tubeside Flow In

Shellside Flow In

Shellside Flow Out

Tubeside Flow Out

Shell

Tube Bundle

Tube Sheet

Channel

Baffles

Nozzle

Exch. Major Parts & Generally used MOCExch. Major Parts & Generally used MOC

Shell: Shell: Carbon steel (CS), Stainless steel (SS), Titanium, Carbon Carbon steel (CS), Stainless steel (SS), Titanium, Carbon steel cladded with SS, Titanium or Monel steel cladded with SS, Titanium or Monel

Channel: Channel: Generally similar to tube MOC. Generally similar to tube MOC. Carbon steel (CS) , Stainless steel (SS), Titanium, Carbon steel (CS) , Stainless steel (SS), Titanium, Carbon steel cladded with SS, Titanium or Monel Carbon steel cladded with SS, Titanium or Monel

Tube sheet: Tube sheet: Carbon steel (CS), Stainless steel (SS), Titanium , Carbon Carbon steel (CS), Stainless steel (SS), Titanium , Carbon steel cladded with SS, Titanium or Monel steel cladded with SS, Titanium or Monel

Tubes:Tubes: Carbon steel (CS), Stainless steel (SS), Admiralty Brass, Carbon steel (CS), Stainless steel (SS), Admiralty Brass, Titanium (Ti) , Monel Titanium (Ti) , Monel Tubes are available in different diameters. Tubes are available in different diameters.

Commonly used OD:Commonly used OD:3/8" - 9.5 mm 5/8” – 16 mm, ¾” - 19.05 mm, 1” – 25.4 3/8" - 9.5 mm 5/8” – 16 mm, ¾” - 19.05 mm, 1” – 25.4 mm, 2” – 50.8 mm mm, 2” – 50.8 mm

Exch. Major Parts & Generally used MOCExch. Major Parts & Generally used MOCGasket: Gasket:

CAF (Asbestos), Iron jacketed gasket with AsbestosCAF (Asbestos), Iron jacketed gasket with AsbestosSpiral wound gasket (SS, Monel, Titanium filled with PTFE, Spiral wound gasket (SS, Monel, Titanium filled with PTFE, Grafoil, Asbestos) Grafoil, Asbestos) Solid flat metal : Soft Iron, Aluminum, Copper, Brass, Monel, Solid flat metal : Soft Iron, Aluminum, Copper, Brass, Monel, SS SS O rings, O rings,

Baffles:Baffles: Types of baffles: Types of baffles: Segmental baffle , Strip baffle, Disc and doughnut baffle, Segmental baffle , Strip baffle, Disc and doughnut baffle, Orifice baffle , Longitudinal baffle Orifice baffle , Longitudinal baffle

Tie Rods & Spacer Tubes: Tie Rods & Spacer Tubes: MOC of baffles, tie rods, spacer tubes are similar to tube MOC of baffles, tie rods, spacer tubes are similar to tube MOC or shell MOC. MOC or shell MOC.

Tube Pattern, PitchTube Pattern, Pitch: : Triangular, Square Triangular, Square

Tube to tubesheet Joints:Tube to tubesheet Joints: Welded with light expansion, Welded with light expansion, Expanded, expanded with seal welded. Expanded, expanded with seal welded.

Selection Of Heat ExchangerSelection Of Heat Exchanger

It must meet the process requirements It must meet the process requirements

It must withstand the service conditionIt must withstand the service condition

It must be maintainableIt must be maintainable

Exchanger Cost Exchanger Cost

Capital cost of installationCapital cost of installation

Area occupied by the equipmentArea occupied by the equipment

Availability and cost of water Availability and cost of water

Pressure drop Pressure drop

Significance of Different Types of Heat Exch.Significance of Different Types of Heat Exch.

Fixed Tube sheet Exchanger:Fixed Tube sheet Exchanger:

Both tubesheet fixed to shell. Both tubesheet fixed to shell.

Application Best Suited: Application Best Suited:

For cleaner fluid on shell side For cleaner fluid on shell side

Low cost Low cost

Limitations: Limitations:

Temp. difference on shell side & tube side Temp. difference on shell side & tube side should be less than 93 deg c. should be less than 93 deg c.

Fixed Tube sheet DesignFixed Tube sheet Design

Fixed Tubesheet type Heat Exchanger

Front EndFront EndStationary Head Stationary Head

TypeTypeShell TypeShell Type Rear EndRear End

Head TypeHead Type

AA EE MM

Channel and Channel and Removable Cover Removable Cover One Pass Shell One Pass Shell Fixed Tubesheet Fixed Tubesheet

Stationary Head Stationary Head

Significance of Different Types of Heat Exch.Significance of Different Types of Heat Exch. Floating Head Type:Floating Head Type:

One tubesheet floats in shell and bundle may One tubesheet floats in shell and bundle may be removable from shell, back cover can be be removable from shell, back cover can be removed to expose tube ends.removed to expose tube ends.

Application Best Suited: Application Best Suited:

High temperature difference on shell & tube High temperature difference on shell & tube side side

Cleaning possible with floating end cover Cleaning possible with floating end cover

Limitations: Limitations:

Internal gasket offer danger of leakageInternal gasket offer danger of leakage

Only horizontal unitsOnly horizontal units

Typical floating head exchTypical floating head exch

Significance of Different Types of Heat Exch.Significance of Different Types of Heat Exch. U Tube:U Tube:

Only one tube sheet required, tube bends in U Only one tube sheet required, tube bends in U shape, Bundle is removable shape, Bundle is removable

Application Best Suited: Application Best Suited: High temperature difference on shell & tube side High temperature difference on shell & tube side Clean service on tube sideClean service on tube side

Limitations: Limitations: Higher tube side velocities can cause erosion on Higher tube side velocities can cause erosion on tube endstube endsFouling / subsequent cleaning problemFouling / subsequent cleaning problem

Typical U tube exchTypical U tube exch

U Tube type Heat ExchangerFront EndFront End

Stationary Head Stationary Head TypeType

Shell TypeShell Type Rear EndRear EndHead TypeHead Type

CC EE UU

Channel Channel IntegralIntegral with Tube sheet and with Tube sheet and

Removable CoverRemovable Cover

One Pass Shell One Pass Shell U-Tube Bundle U-Tube Bundle

U Tube type Heat Exchanger

Significance of Different Types of Heat Exch.Significance of Different Types of Heat Exch. Hair Pin Type Exchanger: Hair Pin Type Exchanger:

Extended surface due to longitudinal finning. Extended surface due to longitudinal finning. Tube bundle can be removed from shell for Tube bundle can be removed from shell for cleaning. cleaning.

Application Best Suited: Application Best Suited: Smaller transfer area required Smaller transfer area required Suitable for higher pressure requirement Suitable for higher pressure requirement Low space Low space

Limitations: Limitations: Smaller capacity Smaller capacity

Hair Pin type Heat ExchangerHair Pin type Heat Exchanger

Return Bend (welded)

Shell Cover Gasket

Shell

External Fin Pipe

Shell End PieceTwin Flange

Shell Cover

Vent

Drain Sliding Support

Fixed Support

Double Pipe Exchanger

Typical Kettle reboilerTypical Kettle reboiler

Helical exchangersHelical exchangers

Less fouling on Less fouling on shell sideshell sideHigh heat High heat transfertransferHigh capital cost High capital cost and maintenance and maintenance costcost

Applicable Codes & StandardsApplicable Codes & Standards

ASME SEC VIII ASME SEC VIII Rules for Construction of Rules for Construction of

DIV 1/2 DIV 1/2 Pressure VesselsPressure Vessels

TEMA TEMA Standards of the Tubular Standards of the Tubular Exchanger Exchanger

Manufacturer's Manufacturer's AssociationAssociation

API 660API 660 Shell and Tube Heat Shell and Tube Heat Exchangers for Exchangers for

General General Refinery Refinery ServicesServices

API 661API 661 Air-Cooled Heat Exchangers Air-Cooled Heat Exchangers for General Refinery for General Refinery

ServiceService

TETEMMA ClassificationsA Classifications

TEMA Class Application TEMA Class Application ExampleExample______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

__ RR Severe environments Severe environments RefineriesRefineries

CC Moderate service Moderate service BuildingBuilding services,services, commercial,commercial, and generaland general processprocess industriesindustries

BB Chemical process Chemical process ChemicalChemical

manufacturingmanufacturing

TEMA standardsTEMA standardsThe design and construction is usually based on TEMA The design and construction is usually based on TEMA 8th Edition 19988th Edition 1998

Supplements pressure vessel codes like ASME and BS Supplements pressure vessel codes like ASME and BS 55005500

Sets out constructional details, recommended tube Sets out constructional details, recommended tube sizes, allowable clearances, terminology etc.sizes, allowable clearances, terminology etc.

Provides basis for contractsProvides basis for contracts

Tends to be followed rigidly even when not strictly Tends to be followed rigidly even when not strictly necessarynecessary

Many users have their own additions to the standard Many users have their own additions to the standard which suppliers must followwhich suppliers must follow

TEMA Designation System Example

Type “S” Split-RingFloating Head

Type “E” ShellSingle-Pass

Type “A” Channel

23”ShellI.D.

Straight TubeLength 192”

(16’ – 0”)

TEMA Size and Type Normally Written: 23–192 AES

TEMA terminologyTEMA terminology

Letters given for the front end, shell and rear Letters given for the front end, shell and rear end typesend types

Exchanger given three letter designationExchanger given three letter designation

Above is AELAbove is AEL

ShellFront endstationary head type

Rear endhead type

Front head typeFront head typeA-type is standard for dirty tube sideA-type is standard for dirty tube side

B-type for clean tube side duties. Use if possible B-type for clean tube side duties. Use if possible since cheap and simple. since cheap and simple.

B

Channel and removable cover Bonnet (integral cover)

A

More front-end head typesMore front-end head typesC-type with removable shell for hazardous tube-side C-type with removable shell for hazardous tube-side fluids, heavy bundles or services that need frequent fluids, heavy bundles or services that need frequent shell-side cleaningshell-side cleaning

N-type for fixed for hazardous fluids on shell sideN-type for fixed for hazardous fluids on shell side

D-type or welded to tube sheet bonnet for high D-type or welded to tube sheet bonnet for high pressure (over 150 bar)pressure (over 150 bar)

B N D

Shell typeShell typeE-type shell should be used if possible butE-type shell should be used if possible but

F shell gives pure counter-current flow with two F shell gives pure counter-current flow with two tube passes (avoids very long exchangers)tube passes (avoids very long exchangers)

E F

One-pass shellTwo-pass shell

Longitudinal baffle

Note, longitudinal baffles are difficult to seal withNote, longitudinal baffles are difficult to seal with

the shell especially when reinserting the shell afterthe shell especially when reinserting the shell after

maintenancemaintenance

More shell typesMore shell typesG and H shells normally only used for horizontal G and H shells normally only used for horizontal thermosyphon reboilersthermosyphon reboilers

J and X shells if allowable pressure drop can not be J and X shells if allowable pressure drop can not be achieved in an E shellachieved in an E shell

J

HG

X

Split flow Double split flow

Divided flow Cross flow

Longitudinalbaffles

Rear head typeRear head typeThese fall into three general typesThese fall into three general types

fixed tube sheet (L, M, N)fixed tube sheet (L, M, N)

U-tubeU-tube

floating head (P, S, T, W)floating head (P, S, T, W)

Use fixed tube sheet if Use fixed tube sheet if TT below 50 below 50ooC, C, otherwise use other types to allow for otherwise use other types to allow for differential thermal expansiondifferential thermal expansion

You can use bellows in shell to allow for You can use bellows in shell to allow for expansion but these are special items which expansion but these are special items which have pressure limitations (max. 35 bar)have pressure limitations (max. 35 bar)

Fixed rear head typesFixed rear head types

L is a mirror of the A front end headL is a mirror of the A front end head

M is a mirror of the bonnet (B) front endM is a mirror of the bonnet (B) front end

N is the mirror of the N front end N is the mirror of the N front end

L

Fixed tube sheet

Floating heads and U tubeFloating heads and U tube

Allow bundle removal and mechanical cleaning Allow bundle removal and mechanical cleaning on the shell sideon the shell side

U tube is simple design but it is difficult to clean U tube is simple design but it is difficult to clean the tube side round the bendthe tube side round the bend

Floating headsFloating headsT S

Pull through floating headNote large shell/bundle gap

Similar to T but with smaller shell/bundle gap

Split backing ring

Other floating headsOther floating headsNot used often and then with small exchangersNot used often and then with small exchangers

P W

Outside packing to give smaller shell/bundle gap

Externally sealed floating tube sheetmaximum of 2 tube passes

TEMA Types

Design PracticesDesign PracticesComparable heat transfer coefficents on shell and Comparable heat transfer coefficents on shell and tube sides.tube sides.

Hot fluid in tubesHot fluid in tubes

Viscous fluid in shell sideViscous fluid in shell side

Dirty fluid in tubesDirty fluid in tubes

Counterflow preferred Counterflow preferred

Triangular pitches are preferredTriangular pitches are preferred

Velocities >1m/s , <2m/sVelocities >1m/s , <2m/s

Baffle spacing < 1m or shell dia whichever is the Baffle spacing < 1m or shell dia whichever is the lower.lower.

DESIGN STEPSDESIGN STEPS

Thermal (process) designThermal (process) designMechanical designMechanical design

Data for process designData for process design

Operating fluids: their properties (chemical, Operating fluids: their properties (chemical, physical and thermal properties)physical and thermal properties)Operating conditions: Inlet / outletOperating conditions: Inlet / outlet

temperature/flow/pressuretemperature/flow/pressureHeat duty : Heat transfer requirementHeat duty : Heat transfer requirementHeat transfer co-efficientsHeat transfer co-efficientsFouling factorsFouling factorsBasic equation for thermal design isBasic equation for thermal design is

Q = U A F (LMTD)Q = U A F (LMTD)

Process design stepsProcess design steps

Select a basic typeSelect a basic type

Select tentative set of Select tentative set of modify design modify design

design parametersdesign parameters parametersparameters

Rating of designRating of design

thermal perf/pressurethermal perf/pressure not OK not OK

drop calculationsdrop calculations

evaluation of design okevaluation of design ok go to mechanicalgo to mechanical

Q, delta P accept?Q, delta P accept? designdesign

ModesModes of Heat Transferof Heat Transfer

ConductionConduction

Convection Convection

RadiationRadiation

Fourier's law for Heat conduction

Q = -k A (dT/dx)

Q = heat duty, BTU/hr

k = thermal conductivity of the material, BTU/hr-ft 2 - o F/ft

A = Area perpendicular to the heat flow, ft2

dT/dx = temperature gradient in direction of heat flux, ºR/ft

Thermal conductivities of material are determined experimentally or can be estimated using empirical methods when experimental data is not available, as is generally the case with liquid and gas mixtures.

Equation for Convection

Heat transfer by convection can be described by an equation similar to the equation for conduction.

Q = h A T

where

Q = heat duty, BTU/hr

h = heat transfer coefficient due to convection, BTU/hr-ft 2 - oF

A = surface area, ft 2

DT = temperature difference between the surface and the bulk fluid, oF

The heat transfer coefficient due to convection depends on the properties of the fluid, geometry of the surface and flow rate. It can be determined experimentally or, given the amount of data available, be calculated by using the dimensionless groups; Nusselt, Prandtl, Reynolds, and Grashof numbers.

Stefan - Boltzmann law: Energy emission by radiation

Q = s e AT 4

Q = emitted energy, BTU/hr.

s = radiation coefficient for a black body, BTU/ft. 2 -hr.- o R 4

e = emissivity, dimensionless

A = surface area of emitting body, ft.2

T = surface temperature of emitting body, oR

e= ranges from 1.0 for a black body to 0.02-0.04 for polished metal surfaces.

Shell & Tube Heat Exchangers

•Floating Head Design

•U-tube Design

•Fixed Tube Sheet Design

•Kettle Design

Heat transfer involving unfired shell and tube heat exchangers or air fins is mainly concerned with convection as the mechanism.

By BjBy Bj 5959

Shell and Tube Exchanger

2 pass tube, 1 pass shell

Bonnet/Dome

Tube sheet

Tube sideoutlet

Tube sideinlet

Shell sideinlet

Shell sideoutlet Tubes

Shell

Partition plate

Baffles

Baffle Designs

By BjBy Bj 6161

Thermal Design

•Area required for heat exchangeSurface area of tubes required for transferring the heat duty

•Heat duty

Quantity of heat to be transferred from hot stream to cold stream

By BjBy Bj 6262

Calculation of heat duty

Q = m Cp T

Q Heat duty (Joules/hr)m Mass flow rate (Kg/hr)Cp Specific heat (Joules/Kg deg C)T Temperature difference between inlet and outlet

By BjBy Bj 6363

Area required for heat transfer

A = Q (U* Tln)

Q Heat duty (Joules/hour)U Overall Heat transfer coefficient (Joules/m2 hr deg C)Tln Log mean Temperature difference (deg C)A Area required for heat transfer (m2)

Heat transfer coefficients - Typical

Heat transfer coefficients - Typical

Units- BTU/hr ft2 deg F

By BjBy Bj 6666

Log Mean Temperature Difference (LMTD)T1

T2 t1

t2

T1 = T1-t2

T2 = T2-t1

Tln = (T1 - T2)/ ln(T1/ T2 )

Fouling refers to any change in the solid boundary separating two heat transfer fluids, whether by dirt accumulation or other means, which results in a decrease in the rate of heat transfer occurring across that boundary. Fouling may be classified as

1. Corrosion fouling. 2. Biofouling. 3. Particulate fouling. 4. Chemical reaction fouling 5. Precipitation fouling (ex.—Scaling).

Fouling And Scaling

1. Corrosion fouling. The heat transfer surface reacts chemically with elements of the fluid stream producing a less conductive, corrosion layer on all or part of the surface.

2. Biofouling. Organisms present in the fluid stream areattracted to the warm heat-transfer surface where they attach, grow,and reproduce. The two subgroups are microbiofoulants such as slimeand algae and macrobiofoulants such as snails and barnacles.

3. Particulate fouling. Particles held in suspension in the flow stream will deposit out on the heat-transfer surface in areas of sufficientlylower velocity.

4. Chemical reaction fouling (ex.—Coking). Chemical reaction of the fluid takes place on the heat-transfer surface producing an adhering solid product of reaction.5. Precipitation fouling (ex.—Scaling)A fluid containing some dissolved material becomes supersaturated with respect to this mate- by using, in concert with adequate velocities, some form of extendedsurface.

By BjBy Bj 7070

Velocity in Cooling Water tubes

•Velocity of 1 to 2 m/s is considered ideal.•Higher velocities increase erosion.•Lower velocities increase deposition of salts and results in scale formation.•Scale formation reduces heat transfer.

By BjBy Bj 7171

Calculation of Velocity of Cooling water velocity in tubes

•Using Ultra sonic flow meter.•Equipments required- Ultrasonic flow meter•Data required Hx Dimensions

•By heat balance•Equipments required- Thermometer•Data required Hx Dimensions,Shell side flow,inlet and outlet temperatures

By BjBy Bj 7272

Monitoring of Heat Exchanger for fouling

A = Q (U* Tln)

Equation used

Data required•Hx Dimensions.•Inlet and outlet temperatures.•Operating Heat duty

U (Overall heat transfer coefficient) is calculated and monitored

Example 7.3 Kerosene (shell) / Crude oil (tube) HX ref DQ kern Page 151

Data In Shell or tubeHot fluid Kerosene S (Enter S if in shell) (Enter T if in tube)Cold fluid Crude oil T (Enter S if in shell) (Enter T if in tube)Shell side dataKerosene inlet temp 390 deg FKerosene outlet 200 deg FKerosene flow 43800 lbs/hrKerosene density 0.73 gm/cc 45.57 lb/ft3Kerosene Cp 0.605 BTU/lb deg FKerosene ka 0.0765 BTU/hr sqft deg F/ftKerosene viscosity 0.97 cP 2.328 lb/hr ftKerosene fouling factor 0.001 1/BTU/hr sq ft deg FTube side dataCrude oil inlet temp 100 deg fCrude oil outlet 170 deg fCrude oil density 62.43 lb/ft3 1 gm/ccCrude oil Cp 1 BTU/lb deg FCrude oil ka 0.348 BTU/hr sqft deg F/ftCrude oil viscosity 1 cP 2.4 lb/hr ftCrude oil viscosity at wall temp 1 cP 2.4 lb/hr ftCrude oil fouling factor 0.002 1/BTU/hr sq ft deg F

Thermal design - DATA

Thermal design - Calculations

CalculationsHeat duty 5034810 BTU/hrAssume U 75 BTU/hr sqft deg FFlow Path C (Enter C for counter flow , P for parallel)LMTD 152.20 deg FInitial Area estimate 441.08 sq ft

Heat Transfer Coefficient tube side

Heat transfer coefficient tube sideAssume Tube dimensionsoutside dia 1 inch 0.083 ftTube length 8 feettube thickness 0.083 inchInside dia 0.834 inch 0.070 ftTube sheet allowance 6 inchnet tube length available 7.5 feetNo of tubes 224.64 tubes say 225.00Tube velocityTube side flow rate 71925.8571 lbs/hrAssume no of tubes 44 should be > 225.00Assume no of tube passes 4 passesno of tubes per pass 11 tubes/passTube velocity 7.67 ft/secMass flow rate in tube 1723585.65 lb/hr sq ftReynolds number 49912Prandtl number 6.90Heat transfer coeff tube side 1475.94 BTU/hr sqft deg fhio 1230.93 BTU/hr sqft deg f

Heat Transfer Coefficient shell side

Film coefficent Shell sideAssume Tube pitch 1.25 inchPitch type T (Enter T for Triangular and S for square)Assume shell ID 12 inch 1 ftClearance between tubes 0.25 inchAssume baffle spacing 5.5 inchCross flow area 0.092 sq ftshell side Mass flow rate 477818.18 lb/hr sq ftShell side Eq tube dia 0.71 inch 0.06 ftReynolds number 12159.52Prandtl number 18.41heat transfer coeff shell side 216.63 BTU/hr sqft deg f

Heat Transfer Coefficient Overall

Overall heat transfer coeffcientU 113.29 BTU/hr sqft deg fArea required 291.99 sq ftArea assumed 92.15 sq ft

Applicable design Applicable design codes/standards/practices codes/standards/practices

TEMA –Tubular Exchangers Manufacturer's TEMA –Tubular Exchangers Manufacturer's AssociationAssociationASME Codes Sec-VIII-Div I and IIASME Codes Sec-VIII-Div I and IIASME Sec –II A , B ,C ,D- Materials , Welding ASME Sec –II A , B ,C ,D- Materials , Welding consumables, propertiesconsumables, propertiesASME Sec –IX – Welder qualificationASME Sec –IX – Welder qualificationASME Sec –V - NDTASME Sec –V - NDTANSI standardsANSI standardsNACE standards/ recommended practicesNACE standards/ recommended practicesAPI standardsAPI standardsProcess Licensor's guidelinesProcess Licensor's guidelines

TEMA guidelinesTEMA guidelines

Not to exceed Inside Diameters of 100 inches (2450 Not to exceed Inside Diameters of 100 inches (2450 mm)mm)Product of Nominal Dia (inches) and Design Product of Nominal Dia (inches) and Design Pressure (psi) not to exceed 1,00,000 (17.5 x 10Pressure (psi) not to exceed 1,00,000 (17.5 x 1066 kpa) kpa)Not to exceed Design Pressure of 3000 psi (2068 Not to exceed Design Pressure of 3000 psi (2068 kpa)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)

Materials used for S&T Materials used for S&T exch:exch:

ShellShell :: CS / SS / Non-ferrous typesCS / SS / Non-ferrous typesTubesTubes :: CS / AS / SS / Non-ferrousCS / AS / SS / Non-ferrousTube SheetTube Sheet :: Forgings / PlatesForgings / PlatesNozzle PipesNozzle Pipes :: CS / AS / SSCS / AS / SSNozzlesNozzles :: CS / AS / SSCS / AS / SSGasketsGaskets :: CAF, Spiral Wound, IJA, CAF, Spiral Wound, IJA, Ring Joint typeRing Joint typeFastenersFasteners :: CS / AS / SSCS / AS / SSName PlateName Plate :: SSSS

Allocation of fluidsAllocation of fluids

Put dirty stream on the tube side - easier to clean Put dirty stream on the tube side - easier to clean inside the tubesinside the tubes

Put high pressure stream in the tubes to avoid thick, Put high pressure stream in the tubes to avoid thick, expensive shellexpensive shell

When special materials required for one stream, put When special materials required for one stream, put that one in the tubes to avoid expensive shellthat one in the tubes to avoid expensive shell

Cross flow gives higher coefficients than in plane Cross flow gives higher coefficients than in plane tubes, hence put fluid with lowest coefficient on the tubes, hence put fluid with lowest coefficient on the shell sideshell side

If no obvious benefit, try streams both ways and see If no obvious benefit, try streams both ways and see which gives best design which gives best design

Allocation-shell & tube side Allocation-shell & tube side fluidsfluids

Fouling Fouling : Depends of type of fluid, extent : Depends of type of fluid, extent of fouling, facilitate cleaningof fouling, facilitate cleaningFlow rateFlow rate: lower flow in tubes: lower flow in tubesCorrosionCorrosion: more corrosive in tubes: more corrosive in tubesViscosity Viscosity : high viscosity in shell: high viscosity in shellPressure :Pressure : high pressure in tubes high pressure in tubesTemp:Temp: high temp in tubes (MoC) high temp in tubes (MoC)HT coefficient:HT coefficient: lower HTC fluid in shell lower HTC fluid in shell

Which type ? - + and - Which type ? - + and -

ParameterParameter Fixed TSFixed TS U tubeU tube FL headFL head

Bundle removalBundle removal NoNo YesYes YesYes

Provision for expansionProvision for expansion NoNo YesYes YesYes

Tube inside cleaningTube inside cleaning YesYes DifficultDifficult YesYes

Tube outside cleaningTube outside cleaning NoNo YesYes YesYes

CostCost LowLow LowLow HighHigh

Selection of shell typesSelection of shell types

E type shell ( single E type shell ( single pass) pass)

General duties General duties

K type shell K type shell Shell side fluid Shell side fluid boiling/phase separation boiling/phase separation

F type shell F type shell For more passes of shell For more passes of shell side side

G or H type shellG or H type shell Thermosyphon type Thermosyphon type reboilers reboilers

J or X type shell J or X type shell When shell side pressure When shell side pressure drop is restricting drop is restricting

Selection of tube side typesSelection of tube side types

B type front headB type front head Front end stationary headFront end stationary head

A type front headA type front head When frequent cleaning of When frequent cleaning of tube side is requiredtube side is required

M type rear headM type rear head Fixed tubesheet typeFixed tubesheet type

L type rear headL type rear head With A type and odd No. of With A type and odd No. of tube passestube passes

K type rear headK type rear head Kettle type exchangersKettle type exchangers

S type rear headS type rear head Floating head typeFloating head type

Shell-to-bundle clearance (on diameter)Shell-to-bundle clearance (on diameter)

0.5 1.0

1.5 2.0 2.50

Shell diameter, m

Cle

aran

ce,

mm

0

150

100

50

Fixed and U-tube

P and S

T

Shell thicknessShell thickness

pp is the guage pressure in the shell is the guage pressure in the shell

t t is the shell wall thicknessis the shell wall thickness

is the stress in the shellis the stress in the shell

From a force balanceFrom a force balance

pDs

t

p

t

2t pDs tpDs2

hence

Typical maximum exchanger sizesTypical maximum exchanger sizes

Floating HeadFloating Head Fixed head & U Fixed head & U tubetube

DiameterDiameter 60 in (1524 mm)60 in (1524 mm) 80 in (2000 mm)80 in (2000 mm)

LengthLength 30 ft (9 m) 30 ft (9 m) 40 ft (12 m)40 ft (12 m)

AreaArea 13 650 ft13 650 ft22 (1270 m (1270 m22)) 46 400 ft46 400 ft22 (4310 (4310 mm22))

Note that, to remove bundle, you need to allow at least Note that, to remove bundle, you need to allow at least as much length as the length of the bundleas much length as the length of the bundle

ExampleExample

BESBES

Bonnet front end, single shell pass and split Bonnet front end, single shell pass and split backing ring floating headbacking ring floating head

Example 1Example 1Debutaniser overhead condenserDebutaniser overhead condenser

Hot sideHot side Cold sideCold side

FluidFluid Light hydrocarbonLight hydrocarbon Cooling Cooling waterwater

CorrosiveCorrosive NoNo NoNo

Pressure(bar)Pressure(bar) 4.94.9 5.05.0

Temp. In/Out (Temp. In/Out (ooC)C) 46 / 4246 / 42 20 / 3020 / 30

Vap. fract. In/OutVap. fract. In/Out 1 / 01 / 0 0 / 00 / 0

Fouling res. (mFouling res. (m22K/W)K/W) 0.000090.00009 0.000180.00018

Example 2Example 2Crude tank outlet heaterCrude tank outlet heater

Cold sideCold side Hot sideHot side

FluidFluid Crude oilCrude oil SteamSteam

CorrosiveCorrosive NoNo NoNo

Pressure(bar)Pressure(bar) 2.02.0 1010

Temp. In/Out (Temp. In/Out (ooC)C) 10 / 7510 / 75 180 / 180180 / 180

Vap. fract. In/OutVap. fract. In/Out 0 / 00 / 0 1 / 01 / 0

Fouling res. (mFouling res. (m22K/W)K/W) 0.00050.0005 0.00010.0001

What is this?What is this?

Shell-side enhancementShell-side enhancementUsually done with integral, low-fin tubesUsually done with integral, low-fin tubes– 11 to 40 fpi (fins per inch). High end for 11 to 40 fpi (fins per inch). High end for

condensationcondensation– fin heights 0.8 to 1.5 mmfin heights 0.8 to 1.5 mm

Designed with o.d. (over the fin) to fit into the Designed with o.d. (over the fin) to fit into the a standard shell-and-tubea standard shell-and-tube

The enhancement for single phase arises The enhancement for single phase arises from the extra surface area (50 to 250% extra from the extra surface area (50 to 250% extra area)area)

Special surfaces have been developed for Special surfaces have been developed for boiling and condensationboiling and condensation

Low-finned TubesLow-finned TubesFlat end to go into tube sheet and Flat end to go into tube sheet and intermediate flat portions for baffle locationsintermediate flat portions for baffle locations

Available in variety of metals including Available in variety of metals including stainless steel, titanium and inconelsstainless steel, titanium and inconels

Tube-side enhancement using insertsTube-side enhancement using inserts

Spiral wound wire and twisted tapeSpiral wound wire and twisted tape

Increase tube side heat transfer coefficient but Increase tube side heat transfer coefficient but at the cost of larger pressure drop (although at the cost of larger pressure drop (although exchanger can be reconfigured to allow for exchanger can be reconfigured to allow for higher pressure drop)higher pressure drop)

In some circumstances, they can significantly In some circumstances, they can significantly reduce fouling. In others they may make things reduce fouling. In others they may make things worseworse

Can be retrofittedCan be retrofitted

Twisted tape

Wire-wound inserts (HiTRAN)Wire-wound inserts (HiTRAN)

Both mixes the core (radial mixing) and Both mixes the core (radial mixing) and breaks up the boundary layerbreaks up the boundary layer

Available in range of wire densities for Available in range of wire densities for different dutiesdifferent duties

BafflesBafflesProvided for bundle stiffnessProvided for bundle stiffness

Direct flow – Heat transferDirect flow – Heat transfer

TypesTypes

Plate bafflesPlate baffles

Rod bafflesRod baffles

Helical bafflesHelical baffles

Conventional Shell-side FlowConventional Shell-side Flow

Shell-side axial flowShell-side axial flow

Some problems can be overcome by having axial flowSome problems can be overcome by having axial flow

Good heat transfer per unit pressure drop but Good heat transfer per unit pressure drop but – for a given duty may get very long thin unitsfor a given duty may get very long thin units– problems in supporting the tubeproblems in supporting the tube

ROD baffles (Phillips petroleum)ROD baffles (Phillips petroleum)

introduced to avoid vibrations by providing additional introduced to avoid vibrations by providing additional support for the tubessupport for the tubes

also found other advantagesalso found other advantages– low pressure droplow pressure drop– low fouling and easy to cleanlow fouling and easy to clean– high thermal effectivenesshigh thermal effectiveness

ROD bafflesROD bafflesTend to be about 10% more expensive for the Tend to be about 10% more expensive for the

same shell diameter same shell diameter

Twisted tube (Brown Fin tube)Twisted tube (Brown Fin tube)Tubes support each otherTubes support each other

Used for single phase and condensing duties in Used for single phase and condensing duties in the power, chemical and pulp and paper the power, chemical and pulp and paper industriesindustries

Shell-side helical flow (ABB Lummus)Shell-side helical flow (ABB Lummus)Independently developed by two groups in Independently developed by two groups in

Norway and Czech RepublicNorway and Czech Republic

Comparison of shell side Comparison of shell side geometriesgeometries

Twistedtube

Segmentalbaffles

Helicalbaffles

RODbaffles

Good p Y N Y YHigh shell N Y Y NLow fouling Y N Y YEasycleaning

Y With squarepitch

With squarepitch

Y

Tube-sideenhance.

Included With inserts With inserts With inserts

Can givehigh

Y N N Y

Lowvibration

Y With specialdesigns

With doublehelix

Y

Tube typesTube types

Straight tube and U tubeStraight tube and U tube

Spiral tubesSpiral tubes

Finned tubes: enhanced heat transferFinned tubes: enhanced heat transfer

Circumferentially finned/Longitudinally finnedCircumferentially finned/Longitudinally finned

Helically finnedHelically finned

Tube layoutsTube layouts

Typically, 1 in tubes on a 1.25 in pitch or 0.75 in tubes on Typically, 1 in tubes on a 1.25 in pitch or 0.75 in tubes on a 1 in pitcha 1 in pitch

Triangular layouts give more tubes in a given shellTriangular layouts give more tubes in a given shell

Square layouts give cleaning lanes with close pitchSquare layouts give cleaning lanes with close pitch

pitchTriangular30o

Rotatedtriangular60o

Square90o

Rotatedsquare45o

Tube layout pattern and pitchTube layout pattern and pitch

Purpose of Tube to Purpose of Tube to Tubesheet jointTubesheet joint

To join tubes and tubesheet and keep To join tubes and tubesheet and keep the tubes structurally stable and the tubes structurally stable and support the skeleton assembly under support the skeleton assembly under design conditions.design conditions.To prevent intermixing of shell and To prevent intermixing of shell and tube sheet fluids.tube sheet fluids.To take care of Longitudinal, To take care of Longitudinal, Compressive, Mechanical and Compressive, Mechanical and Thermal axial loads coming on tubes.Thermal axial loads coming on tubes.

Types of tube-tubesheet joint Types of tube-tubesheet joint

Expanded jointExpanded joint

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.

Types of tube-tubesheet joint Types of tube-tubesheet joint

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.

Types of tube-tubesheet joint Types of tube-tubesheet joint Seal weld is used to supplement an expanded tube

joint to ensure tube joint leak tightness.

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 to tube sheet joint Tube to tube sheet joint parametersparameters

Tube MoC, hardnessTube MoC, hardnessTube sheet MoC, hardnessTube sheet MoC, hardnessGroove shapeGroove shapeCleanliness of tube and tubesheetCleanliness of tube and tubesheetType of expander, torque valuesType of expander, torque valuesAmount of expansionAmount of expansion4-5% for SS4-5% for SS7-8% for CS7-8% for CS10-12% for old tubes re-used10-12% for old tubes re-used

How thermal stresses are How thermal stresses are taken care of?taken care of?

By properly selecting the type of exchangerBy properly selecting the type of exchangerFor e.g., fixed tubesheet exch: max delta T shall For e.g., fixed tubesheet exch: max delta T shall be 38 deg C as thumb rule.be 38 deg C as thumb rule.Expansion joint on shell can take care thermal Expansion joint on shell can take care thermal expansionexpansion

How thermal stresses are How thermal stresses are taken care of?taken care of?

Provision of internal Provision of internal bellows on one pass bellows on one pass tube – vertical exch:tube – vertical exch:

U tube designU tube design

Floating head design Floating head design

GasketsGaskets

Provided to seal the joints against leakProvided to seal the joints against leak

Spiral wound with asbestos fill or graphite fillSpiral wound with asbestos fill or graphite fill

Metal jacketedMetal jacketed

Ring joint typeRing joint type

Camprofile typeCamprofile type

CAF – only for less critical servicesCAF – only for less critical services

Material Material

SS 304, SS 316 SS 304, SS 316

Problems of Conventional S & TProblems of Conventional S & T

Zigzag path on shell side leads toZigzag path on shell side leads to

Poor use of shell-side pressure dropPoor use of shell-side pressure drop

Possible vibration from cross flowPossible vibration from cross flow

Dead spotsDead spots– Poor heat transferPoor heat transfer

– Allows foulingAllows fouling

Recirculation zonesRecirculation zones– Poor thermal effectiveness, Poor thermal effectiveness,

Problems encountered in Problems encountered in HX operationHX operation

Poor heat transferPoor heat transfer

Plugged tubes due to foulingPlugged tubes due to fouling

Low velocitiesLow velocities

High coolant temperaturesHigh coolant temperatures

Air pockets in HXAir pockets in HX

Tube leaksTube leaks

Corrosion , erosionCorrosion , erosion

Sudden extra expansionSudden extra expansion

High pressure drops High pressure drops

Fouling of tubes/shell side with depositsFouling of tubes/shell side with deposits

Problems in S&T ExchProblems in S&T Exch

FoulingFouling - shell side or tube side - shell side or tube side

LeaksLeaks – Tube leak/Gasket leak/ roll leak – Tube leak/Gasket leak/ roll leak

Corrosion /ErosionCorrosion /Erosion - Tube side/ shell side - Tube side/ shell side

Vibration /Stress related problemsVibration /Stress related problems

Inherent design deficienciesInherent design deficiencies

What is fouling?What is fouling?

Fouling is any kind of deposit on HT surface that Fouling is any kind of deposit on HT surface that reduces heat transfer. Fouling is indicated byreduces heat transfer. Fouling is indicated byHigher pressure dropHigher pressure dropLower heat dutyLower heat duty

Fouling can be due toFouling can be due to

Sedimentation: Cooling water depositsSedimentation: Cooling water depositsProcess generated: polymerization/cokingProcess generated: polymerization/cokingCorrosion products: oxide (rust) scalesCorrosion products: oxide (rust) scalesMicrobiological fouling: bacterial actionMicrobiological fouling: bacterial actionDesign discrepanciesDesign discrepancies

FoulingFoulingShell and tubes can handle fouling but it can be reduced Shell and tubes can handle fouling but it can be reduced

byby

keeping velocities sufficiently high to avoid depositskeeping velocities sufficiently high to avoid deposits

avoiding stagnant regions where dirt will collectavoiding stagnant regions where dirt will collect

avoiding hot spots where coking or scaling might avoiding hot spots where coking or scaling might occuroccur

avoiding cold spots where liquids might freeze or avoiding cold spots where liquids might freeze or where corrosive products may condense for gaseswhere corrosive products may condense for gases

High fouling resistances are a self-fulfilling High fouling resistances are a self-fulfilling prophecyprophecy

Factors affecting foulingFactors affecting fouling

Velocity- flow- lower velocity, higher foulingVelocity- flow- lower velocity, higher foulingChemical reaction productsChemical reaction productsCorrosion productsCorrosion productsTemperatureTemperatureBundle geometry- baffles dead spacesBundle geometry- baffles dead spacesFluid properties -> viscosity, purityFluid properties -> viscosity, purity

Fouled CW exchangerFouled CW exchanger

External and HCBN foulingExternal and HCBN fouling

How to minimize foulingHow to minimize fouling

Design stage ( fouling factors)Design stage ( fouling factors)Allocation of correct fluidsAllocation of correct fluidsControl of process parametersControl of process parametersBundle geometry changes Bundle geometry changes Frequent cleaningFrequent cleaningAdvanced methods ( online cleaning, inserts)Advanced methods ( online cleaning, inserts)

Leaks in S&T ExchLeaks in S&T Exch

TUBE LEAKS: can be due toTUBE LEAKS: can be due toCorrosion of tube side fluidCorrosion of tube side fluidCorrosion of shell side fluidCorrosion of shell side fluidCorrosion products- under deposit corrosionCorrosion products- under deposit corrosionVibration damageVibration damageErosion damagesErosion damagesStress crackingStress crackingInherent flaws, material defectsInherent flaws, material defects

Causes of tube leakCauses of tube leak

TUBE LEAK

VIBRATION /STRESS CORROSION DESIGN/ MATERIAL DEFICIENCY

INCORRECT MATERIALINCORRECT DESIGN

POOR MATERIAL QUALITY

TUBE VIBRATION

MECHANICAL STRESSES

FLOW PROBLEMS

MECHANICAL

STRESSES

STRESS CORROSIONCRACKING

UNDER DEPOSIT CORROSIONGENERAL THINNING

PITTING

Causes of gasket leakCauses of gasket leak

Wrong gasket type or rating or sizeWrong gasket type or rating or sizeInsufficient tighteningInsufficient tighteningNon-uniform tighteningNon-uniform tighteningThermal stresses across fasteners- differential Thermal stresses across fasteners- differential thermal expansion or contractionthermal expansion or contractionThermal shocksThermal shocksOver pressurizationOver pressurization

Causes of roll joint leaksCauses of roll joint leaks

Insufficient expansionInsufficient expansionImproper cleaning of tubes & tube sheet holesImproper cleaning of tubes & tube sheet holesDamaged grooves of tube sheet holeDamaged grooves of tube sheet holeThermal shocks Thermal shocks Poor inspectionPoor inspectionPoor weld quality in case of seal welded or Poor weld quality in case of seal welded or strength welded jointsstrength welded jointsOver pressurizationOver pressurization

Leak is suspected when intermixing of shell side Leak is suspected when intermixing of shell side and tube side fluids is observed. Normally, if and tube side fluids is observed. Normally, if leakage rate is very high, assume tube leak. leakage rate is very high, assume tube leak. Gasket leaks can be moderate and roll leaks Gasket leaks can be moderate and roll leaks can be less in amount can be less in amount

1) U TUBE EXCHANGER:1) U TUBE EXCHANGER:For tube leaks as well as roll leaks drop bonnet, For tube leaks as well as roll leaks drop bonnet, pressurize shell side.pressurize shell side.Gasket leaks can be visible outsideGasket leaks can be visible outside

How to identify leaks?How to identify leaks?

How to identify leaks- How to identify leaks- cont’dcont’d

2) FLOATING HEAD EXCHANGERS:2) FLOATING HEAD EXCHANGERS:There are 5 gaskets in FH exchanger. 4 gaskets There are 5 gaskets in FH exchanger. 4 gaskets are visible and hence leak is visibleare visible and hence leak is visibleIf no leaks are there, drop dome cover, If no leaks are there, drop dome cover, pressurize tube side and check for floating head pressurize tube side and check for floating head gasket leak.gasket leak.For tube leak/ roll leak identification, use TEST For tube leak/ roll leak identification, use TEST RINGS on floating head side and pressurize RINGS on floating head side and pressurize shell sideshell side

Causes of corrosionCauses of corrosion

Corrosion of shell side and tube side can be Corrosion of shell side and tube side can be due to any / combination of following:due to any / combination of following:Chlorides: can corrode CS materials at any Chlorides: can corrode CS materials at any temperature temperature pitting corrosion pitting corrosionChlorides can result in Stress corrosion Chlorides can result in Stress corrosion cracking in SS materials under favorable cracking in SS materials under favorable stressed conditions and temperaturestressed conditions and temperatureAcids: organic / inorganic acids, wet H2S, Acids: organic / inorganic acids, wet H2S, carbonic acids, formic acids carbonic acids, formic acids low pH low pHAlkalies: caustic Alkalies: caustic high pHhigh pHInorganic substances: Sulphur, NH4ClInorganic substances: Sulphur, NH4Cl

Causes of corrosion-Causes of corrosion-cont’dcont’d

AminesAmines can corrode non-ferrous materials can corrode non-ferrous materialsGalvanic corrosion: dissimilar metals Galvanic corrosion: dissimilar metals mostly due to design problemsmostly due to design problemsGeneral corrosion: uniform thinningGeneral corrosion: uniform thinning oxidation ( rusting)oxidation ( rusting)Erosion/ corrosionErosion/ corrosion due to high due to high velocity( turbulence) , high concentration of velocity( turbulence) , high concentration of some inorganic salts ( NH4HS)some inorganic salts ( NH4HS)Under deposit corrosionUnder deposit corrosion pitting (localized) pitting (localized)High temperature oxidationHigh temperature oxidationDe alloyingDe alloying

Vibration problemsVibration problems

Vibration could be due to:Vibration could be due to:Geometry ( design) problem and/orGeometry ( design) problem and/orProcess conditionsProcess conditions

Vibration can result in:Vibration can result in:Tube to tube collision-> wear and thinningTube to tube collision-> wear and thinningBaffle hole enlargement & tube thinningBaffle hole enlargement & tube thinningTube breakage near tube sheetTube breakage near tube sheetMaterial defect propagationMaterial defect propagationAcoustic resonance Acoustic resonance

Prone areas:Prone areas:Nozzle entrance, Near tube sheet, Nozzle entrance, Near tube sheet, Unsupported length between baffles, U bendsUnsupported length between baffles, U bends

How to minimize vibration problems ?How to minimize vibration problems ?Operating for the purpose intended.Operating for the purpose intended.Proper flow conditions Proper flow conditions Design/ geometry modificationsDesign/ geometry modifications

Vibration problems-Vibration problems-cont’dcont’d

-

Velocity Velocity

Resonance Instability

Flow-induced vibrationFlow-induced vibrationTwo types - RESONANCE and INSTABILITYTwo types - RESONANCE and INSTABILITY

Resonance occurs when the natural frequency Resonance occurs when the natural frequency coincides with a resonant frequencycoincides with a resonant frequency

Fluid elastic instabilityFluid elastic instability

Both depend on span length and velocityBoth depend on span length and velocity

Tu

be

dis

pla

cem

ent

Avoiding vibrationAvoiding vibration

Inlet support baffles - partial baffles in first few tube Inlet support baffles - partial baffles in first few tube rows under the nozzlesrows under the nozzles

Double segmental baffles - approximately halve cross Double segmental baffles - approximately halve cross flow velocity but also reduce heat transfer coefficientsflow velocity but also reduce heat transfer coefficients

Patent tube-support devicesPatent tube-support devices

No tubes in the window (with intermediate support No tubes in the window (with intermediate support baffles)baffles)

J-Shell - velocity is halved for same baffle spacing as J-Shell - velocity is halved for same baffle spacing as an E shell but decreased heat transfer coefficients an E shell but decreased heat transfer coefficients

Avoiding vibration (cont.) Avoiding vibration (cont.)

Inlet support baffles

Double-segmental baffles

No tubes in the window - with intermediate support baffles

TubesWindows with no tubes

Intermediate baffles

Key fabrication stepsKey fabrication steps

Material Identification (Pressure parts)Material Identification (Pressure parts)FormingFormingWeldingWeldingReview of WPS / PQR / Welder QualificationReview of WPS / PQR / Welder QualificationNDTNDTStage and Final InspectionsStage and Final InspectionsMock-up AssemblyMock-up AssemblySkeleton AssemblySkeleton AssemblyTube BundleTube BundleInsertion of Tube Bundle into ShellInsertion of Tube Bundle into ShellTestingTestingPaintingPaintingDocumentationDocumentationPacking / Protection / DispatchPacking / Protection / Dispatch

Various Testing/Examinations Various Testing/Examinations UsedUsed

Visual ExaminationVisual ExaminationDye Penetrant ExaminationDye Penetrant ExaminationMagnetic Particle ExaminationMagnetic Particle ExaminationRadiographic ExaminationRadiographic ExaminationUltrasonic ExaminationUltrasonic ExaminationCheck Tests (Chemical, Mechanical, Special Tests)Check Tests (Chemical, Mechanical, Special Tests)Tests for determining pullout load ‘Fr’ valueTests for determining pullout load ‘Fr’ valuePneumatic TestsPneumatic TestsHydraulic TestsHydraulic TestsSpecial Tests (IGC, NACE related, Hardness, Eddy Special Tests (IGC, NACE related, Hardness, Eddy Current Testing, Helium Leak test Etc.)Current Testing, Helium Leak test Etc.)Pre-shipment checksPre-shipment checks

Maintenance ActivitiesMaintenance Activities

Identify leak type and location: hydrotestingIdentify leak type and location: hydrotestingAttend leak : Attend leak : – gasket leak- re-tighten or replacegasket leak- re-tighten or replace– retubing or plugging leaky tubesretubing or plugging leaky tubes– re-expansion of tube sheet joint/ re-weldingre-expansion of tube sheet joint/ re-welding

Cleaning of tube side /shell side as per Cleaning of tube side /shell side as per requirementsrequirementsInstall new bundles/ shell as per requirementInstall new bundles/ shell as per requirementOffer statutory tests as per schedule (IBR Etc.)Offer statutory tests as per schedule (IBR Etc.)Timely modifications in shell side/ tube side as Timely modifications in shell side/ tube side as per CTS/CES/FDC/Licensor requirementsper CTS/CES/FDC/Licensor requirements

Steps of retubingSteps of retubing

Cut tube and clean the tube sheet holes thoroughlyCut tube and clean the tube sheet holes thoroughlyDo mock up test at workshopDo mock up test at workshopSelect the required % expansion for retubing -CESSelect the required % expansion for retubing -CESMeasure tube OD, ID and tube sheet hole diameters.Measure tube OD, ID and tube sheet hole diameters.Insert the tubes. Set 3 mm max projection outside tube sheet. Insert the tubes. Set 3 mm max projection outside tube sheet. Then expand the tubes by expander tool.Then expand the tubes by expander tool.Measure final expanded ID. Calculate the % expansion.Measure final expanded ID. Calculate the % expansion.7-8% for CS, 4 to 5% for SS and non ferrous7-8% for CS, 4 to 5% for SS and non ferrousExpansion in % will be the following x 100Expansion in % will be the following x 100

(Tube ID after expn-tube ID before expn-Tube hole dia+tube (Tube ID after expn-tube ID before expn-Tube hole dia+tube OD) /(Tube OD- Tube ID before expan)OD) /(Tube OD- Tube ID before expan)

Points regarding hydrotestPoints regarding hydrotest

Isolate all instrument connectionsIsolate all instrument connectionsBe sure of hydrotest pressure (1.3 x DP)Be sure of hydrotest pressure (1.3 x DP)Pressure gages – calibrated, proper rangePressure gages – calibrated, proper rangeVenting thru highest pointVenting thru highest pointPressurize from bottom in steps Pressurize from bottom in steps Go to test Pr, hold 10 min, then come to 2/3 TPGo to test Pr, hold 10 min, then come to 2/3 TPHold for 30 min, then vent from topHold for 30 min, then vent from topAfter complete venting, drain from bottomAfter complete venting, drain from bottomDrying and preservationDrying and preservation

SITE INSTALLATIONSITE INSTALLATION

Civil jobs : foundation / pedestal/ structuresCivil jobs : foundation / pedestal/ structuresInspection as received condition- check for Inspection as received condition- check for N2 purging of shell & tube sidesN2 purging of shell & tube sidesPhysical installation : LevelingPhysical installation : LevelingSite Checks: ITP format fill upSite Checks: ITP format fill upAlignment to upstream downstream tube Alignment to upstream downstream tube side / shell side pipingside / shell side pipingInsulation wherever necessaryInsulation wherever necessaryPassivation for future usePassivation for future use

Inspection relatedInspection related

Maintain history (of failures, reliability issues)Maintain history (of failures, reliability issues)Recommend repair, replacement based on Recommend repair, replacement based on inspection findingsinspection findingsRecommend insurance sparesRecommend insurance sparesResolve corrosion, other degradation issues Resolve corrosion, other degradation issues through TRIPODthrough TRIPODFulfill statutory requirements (as applicable) –Fulfill statutory requirements (as applicable) –IBR , Factory Act IBR , Factory Act

ORDERING INFORMATIONORDERING INFORMATIONWe provide : PR / PO / Datasheet / Drawings / We provide : PR / PO / Datasheet / Drawings / Other relevant Specifications (Licensor`s or Other relevant Specifications (Licensor`s or client`s specifications)client`s specifications)Supplier provide: QAP / ITP, Stage, Final Supplier provide: QAP / ITP, Stage, Final Inspections reportsInspections reportsThird party inspection agencyThird party inspection agencyShall be as per Heat Exchanger Specification Shall be as per Heat Exchanger Specification SheetSheetPerformance / Construction details, MOCPerformance / Construction details, MOC

Pre-order requirementsPre-order requirements

Vendor surveyVendor surveyEnlistmentEnlistmentMonitoring performanceMonitoring performanceAppraise purchase departmentAppraise purchase departmentReview technical bidsReview technical bids

Cost of Heat ExchangersCost of Heat ExchangersSize / type of Heat ExchangerSize / type of Heat ExchangerMaterial of constructionMaterial of constructionType of tube to tube sheet jointsType of tube to tube sheet jointsInspection, NDT requirements based on Inspection, NDT requirements based on severity of serviceseverity of serviceImported / indigenousImported / indigenousLocation of Manufacturer vs. userLocation of Manufacturer vs. userGovernment / statutory regulations (IBR Etc.)Government / statutory regulations (IBR Etc.)Quantity, lead timeQuantity, lead time

Rule of thumb on costingRule of thumb on costingPrice increases strongly with shell diameter/number of tubes Price increases strongly with shell diameter/number of tubes because of shell thickness and tube/tube-sheet fixing because of shell thickness and tube/tube-sheet fixing

Price increases little with tube lengthPrice increases little with tube length

Hence, long thin exchangers are usually bestHence, long thin exchangers are usually best

Consider two exchangers with the same area: fixed tube Consider two exchangers with the same area: fixed tube sheet, 30 bar both side, carbon steel, area 6060 ftsheet, 30 bar both side, carbon steel, area 6060 ft22 (564 m (564 m22), ), 3/4 in (19 mm) tubes3/4 in (19 mm) tubes

LengthLength DiameterDiameter TubesTubes CostCost

10ft10ft 60 in60 in 31393139 $112k (£70k)$112k (£70k)

60ft60ft 25 in25 in 523523 $54k (£34k)$54k (£34k)

AIR FIN COOLERSAIR FIN COOLERS

What are Air fin coolersWhat are Air fin coolers

Air fin coolers are heat transfer equipment used for Air fin coolers are heat transfer equipment used for removing heat from process fluid to the atmosphere removing heat from process fluid to the atmosphere for:for:

Cooling orCooling or

Condensing ( by removing latent heat of vaporization) Condensing ( by removing latent heat of vaporization) or or

Partial condensingPartial condensing

The Air fin cooler assembly consists of The Air fin cooler assembly consists of

Tube bundle for process fluid flow and heat transferTube bundle for process fluid flow and heat transfer

Fan assembly for providing air flow to remove heatFan assembly for providing air flow to remove heat

Significance of Different Types of Heat Exch.Significance of Different Types of Heat Exch. Fin Fan Cooler Fin Fan Cooler

No shell required, Header ends similar shell & No shell required, Header ends similar shell & tube type. tube type.

Application Best Suited:Application Best Suited: High level of heat removal is required High level of heat removal is required Where cooling water not available. Where cooling water not available. Where ambient temp is low Where ambient temp is low

Limitations: Limitations: Problem of frequent fouling and corrosion. Problem of frequent fouling and corrosion. Higher investmentHigher investment4 to 10 times more ground space in shell & tube 4 to 10 times more ground space in shell & tube typetype

Mechanical componentsMechanical components

Tubes, tube supportsTubes, tube supports

Inlet & outlet header boxes ( tube sheet , plug sheet)Inlet & outlet header boxes ( tube sheet , plug sheet)

Header plugs with gasketsHeader plugs with gaskets

Side covers, air sealsSide covers, air seals

Plenum and plenum coversPlenum and plenum covers

LouvresLouvres

chimneyschimneys

Steam coilsSteam coils

Drive unit:Drive unit:

Fan assemblyFan assembly

Motor and Gear box/ belting, vibration switchesMotor and Gear box/ belting, vibration switches

Materials of constructionMaterials of construction

Tubes and headers with header plugs:Tubes and headers with header plugs:

Carbon steelCarbon steel

Killed CS - H2 and wet H2S servicesKilled CS - H2 and wet H2S services

Chrome-Moly steelsChrome-Moly steels

Stainless steelsStainless steels

Fins:Fins:

AluminiumAluminium

Structures, plenum, fan rings, tube supportsStructures, plenum, fan rings, tube supports

Structural CS with galvanisingStructural CS with galvanising

Gaskets: plain metal gasketsGaskets: plain metal gaskets

Air-Cooled Heat ExchangersAir-Cooled Heat ExchangersForced-draftForced-draft – Air forced across tube bundle by fan located Air forced across tube bundle by fan located

in air plenum below bundle. (Fin fan coolers)in air plenum below bundle. (Fin fan coolers)

Induced-Draft Induced-Draft – Fan located above hood covering tube bundle.Fan located above hood covering tube bundle.– Air pulled across tube bundle and exhausted Air pulled across tube bundle and exhausted

through hood. (PTA Air fin coolers)through hood. (PTA Air fin coolers)

Humidified Forced-Draft Humidified Forced-Draft – Air humidified before forced across tubes.Air humidified before forced across tubes.– Evaporation draws heat from air and cools air Evaporation draws heat from air and cools air

below temperature of process fluid.below temperature of process fluid.

Horizontal Tube, Induced-Draft Air-Cooled Heat ExchangerHorizontal Tube, Induced-Draft Air-Cooled Heat Exchanger

Inlet Nozzles

Return Headers

Fan Ring

Supports

Drive Assembly

Tube BundleOutlet

Nozzles

Outlet Headers

Inlet Headers

Hood or Plenum

Fan

Air-Cooled Heat Exchangers

Typical Air-Cooled Heat ExchangerTypical Air-Cooled Heat Exchanger

Header

Nozzle

Header

Tube spacer Side Frame

Fins

Tube Support (bottom)

Tube

Air SealLifting LugTube Keeper

(top)Air Seal

Air Seal

Air-Cooled Heat Exchangers

Typical Forced-Draft Air-Cooled Heat Exchanger

SupportsPlenum

Fan RingFan

Outlet Nozzles

Inlet Headers

Drive Assembly

Outlet Headers

Inlet Nozzles Tube Bundle

Return Header(s)

Air-Cooled Heat Exchangers

Humidified Forced-Draft Heat Exchanger

Tube Bundle

Fine Water Mist

Hot Air

Header

Plenum Chamber

Forced Draft Fan

Water Header Nozzles (above

fan Typical)

Header

Partition Plate

Process Nozzle

Process Nozzle

Water Header Nozzles (below fan Sometimes)

Types of arrangement of Types of arrangement of fanfan

General arrangementGeneral arrangement

Types of arrangement of Types of arrangement of fanfan

Air Fin Coolers

Types of draftsTypes of drafts

FORCED DRAFT:FORCED DRAFT:

Fan is placed below bundleFan is placed below bundle

Low HPLow HP

Possibility of recirculation of hot airPossibility of recirculation of hot air

Easy accessibility to motorsEasy accessibility to motors

Lesser air distribution compared to induced draftLesser air distribution compared to induced draft

INDUCED DRAFT:INDUCED DRAFT:

Better draft and hot air is not recirculatedBetter draft and hot air is not recirculated

Poor accessibility for maintenancePoor accessibility for maintenance

Fins protectedFins protected

Higher HPHigher HP

Drive/plenum typesDrive/plenum types

M

M

MG

Transition plenum Box type plenum

Types fan and fan drivesTypes fan and fan drives

FIXED PITCHFIXED PITCH

Pitch can be varied only on stoppage, cheaperPitch can be varied only on stoppage, cheaper

VARIABLE PITCHVARIABLE PITCH

Automatic controlled. Save power , better control, Automatic controlled. Save power , better control, costlycostly

FAN DRIVE:FAN DRIVE:

Belt drivenBelt driven

Gear box drivenGear box driven

MOTOR:MOTOR:

Fixed speed: moderate controlFixed speed: moderate control

Variable speed: better temp control, cost, save powerVariable speed: better temp control, cost, save power

Purpose of Tube to Purpose of Tube to Tubesheet jointTubesheet joint

To join tubes and tubesheet and keep the To join tubes and tubesheet and keep the tubes structurally stable and support the tubes structurally stable and support the skeleton assembly under design conditions.skeleton assembly under design conditions.To prevent intermixing of shell and tube To prevent intermixing of shell and tube sheet fluids.sheet fluids.To take care of Longitudinal, Compressive, To take care of Longitudinal, Compressive, Mechanical and Thermal axial loads coming Mechanical and Thermal axial loads coming on tubes.on tubes.

Types of tube-tubesheet joint Types of tube-tubesheet joint

Expanded jointExpanded joint

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.

Types of tube-tubesheet joint Types of tube-tubesheet joint

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.

Types of tube-tubesheet joint Types of tube-tubesheet joint Seal weld is used to supplement an expanded tube joint

to ensure tube joint leak tightness.

Recommended to use for following cases where

1. intermixing of shell and tube side fluid causes safety hazards.

2. Lethal fluids are used.

Tube to tube sheet joint Tube to tube sheet joint parametersparameters

Tube MoC, hardnessTube MoC, hardnessTube sheet MoC, hardnessTube sheet MoC, hardnessGroove shapeGroove shapeCleanliness of tube and tubesheetCleanliness of tube and tubesheetType of expander, torque valuesType of expander, torque valuesAmount of expansionAmount of expansion4-5% for SS4-5% for SS7-8% for CS7-8% for CS10-12% for old tubes re-used10-12% for old tubes re-used

Bundle typesBundle types

Header typesHeader types

Removable bonnet headerRemovable bonnet header

Easy cleaningEasy cleaningEasy access to tubesEasy access to tubesHeader only or tube sheet Header only or tube sheet can be replacedcan be replacedGasket is big and uniform Gasket is big and uniform tightening is reqdtightening is reqdDesign for long flanges is Design for long flanges is difficult for high difficult for high temperatures and pressurestemperatures and pressuresRemoval of piping for Removal of piping for openingopening

Removable cover plate Removable cover plate headerheader

Easy cleaningEasy cleaningEasy access to tubesEasy access to tubesGasket is big and uniform Gasket is big and uniform tightening is reqdtightening is reqdDesign for long flanges is Design for long flanges is difficult for high difficult for high temperatures and temperatures and pressurespressures

Plug type headerPlug type header

Easy cleaning of tubesEasy cleaning of tubesNo long flanges and long No long flanges and long gasketsgasketsSelected tubes can be Selected tubes can be attendedattendedHigh pressure design High pressure design possiblepossibleGood for H2 serviceGood for H2 serviceHeader cleaning is difficultHeader cleaning is difficult

SPLIT TYPE HEADER

Embedded ( G type)Embedded ( G type)

Helical groove is cut on tube & fins are woundHelical groove is cut on tube & fins are wound

Displaced groove metal is forced on each side of finDisplaced groove metal is forced on each side of fin

Extruded type:Extruded type:

Fins are extruded from outer Aluminium tubeFins are extruded from outer Aluminium tube

Footed (L) typeFooted (L) type

Fins are tension wrapped over the tubeFins are tension wrapped over the tube

Each fin butts against the adjacent finEach fin butts against the adjacent fin

Finning typesFinning types

BIMETALLIC

EXTRUDED

"G" EMBEDDED

"L" WRAP-ON/

Maximum working temperature:

300°C/570° F

400°C/750° F

120°C/250° F

Atmospheric corrosion resistance:

Excellent Poor Acceptable

Mechanical resistance:

Excellent Acceptable Poor

Price index: 125 105 100

Fin typesFin types

•. 

                                      

Routine checks of fin Routine checks of fin coolerscoolers

Tube bundle:Tube bundle:

Check for any visual leaks from tubes or header plugsCheck for any visual leaks from tubes or header plugs

Check louvers for operabilityCheck louvers for operability

External fouling / bowing of tubesExternal fouling / bowing of tubes

Drive unit:Drive unit:

Vibration of fansVibration of fans

Check belting for cracks/ loosenessCheck belting for cracks/ looseness

Check fan blades for deflectionCheck fan blades for deflection

Check hubs for any cracksCheck hubs for any cracks

Check all fastenersCheck all fasteners

LubricationLubrication

Header arrangement typesHeader arrangement types

D type:D type:

Low pressure dropLow pressure drop

Uneven two phaseUneven two phase

Even single phaseEven single phase

Piping unsymmetricalPiping unsymmetrical

E typeE type

Better symmetryBetter symmetry

Better even flow in two phaseBetter even flow in two phase

Slightly higher pressure dropSlightly higher pressure drop

Header arrangement typesHeader arrangement types

C type:C type:

High pressure dropHigh pressure drop

Best even distributionBest even distribution

Costly but very symmetricalCostly but very symmetrical

Control of fin fan coolersControl of fin fan coolers

1. Manually operated louvers. 2. Electrically or pneumatically operated louvers. 3. Pneumatically actuated automatic variable-pitch fans. 4. Variable-frequency fan drives. 5. Warm-air recirculation systems for freezing/pour point control in cold climates. 6. Steam coils.

Relevant standardsRelevant standards

API 661API 661

API 632- WinterizationAPI 632- Winterization

API 631- Noise measurementAPI 631- Noise measurement

ANSI: B1.1 threadsANSI: B1.1 threads

ASNI: B16.5 - flangesASNI: B16.5 - flanges

AISC standards - structuresAISC standards - structures

AGMA for gear boxesAGMA for gear boxes

ASTM standards for tubesASTM standards for tubes

NACE standards for particular servicesNACE standards for particular services

Collection of process dataCollection of process data

Bundle design temp = 343 max which shall be 28+ maximum Bundle design temp = 343 max which shall be 28+ maximum process fluid tempprocess fluid temp

Design pressure = as per client or inlet pressure + 10% + 25 psiDesign pressure = as per client or inlet pressure + 10% + 25 psi

Calculation of heat transfer coefficients ( air side & process side). Calculation of heat transfer coefficients ( air side & process side). Consider fouling factors also.Consider fouling factors also.

Arrive at No of tubes and rowsArrive at No of tubes and rows

Select tube length, thickness, OD, pitch as per API guidelinesSelect tube length, thickness, OD, pitch as per API guidelines

Select headers . For differential temp> 110 deg, use split header Select headers . For differential temp> 110 deg, use split header onlyonly

Select drive unitSelect drive unit

Louver selection as per specific requirementsLouver selection as per specific requirements

Steam coil selection based on calculationsSteam coil selection based on calculations

Design guidelines as per API 661Design guidelines as per API 661

Process stream flow rateProcess stream flow rate

Process fluid chemical and physical propertiesProcess fluid chemical and physical properties

Inlet outlet temperaturesInlet outlet temperatures

Air side and Process side fouling factorsAir side and Process side fouling factors

Inlet pressure and allowable pressure dropInlet pressure and allowable pressure drop

Environment conditionsEnvironment conditions

Design variables:Design variables:

Air flow rate --> fan capacityAir flow rate --> fan capacity

Air outlet temperature/ flow ratesAir outlet temperature/ flow rates

Tube Nos/ rows/ passes Tube Nos/ rows/ passes

Design parameters requiredDesign parameters required

Key fabrication stepsKey fabrication stepsMaterial Identification (Pressure parts)Material Identification (Pressure parts)Tube manufactureTube manufactureFinningFinningWelding of header box and nozzlesWelding of header box and nozzlesReview of WPS / PQR / Welder QualificationReview of WPS / PQR / Welder QualificationNDT of header box/ nozzlesNDT of header box/ nozzlesStage and Final InspectionsStage and Final InspectionsTube Mock-up AssemblyTube Mock-up AssemblyTube expansion / seal weldingTube expansion / seal weldingTestingTestingPaintingPaintingDocumentationDocumentationPacking / Protection / DespatchPacking / Protection / Despatch

Various Testing / Various Testing / Examinations UsedExaminations Used

Visual ExaminationVisual ExaminationDye Penetrant ExaminationDye Penetrant ExaminationMagnetic Particle ExaminationMagnetic Particle ExaminationRadiographic ExaminationRadiographic ExaminationUltrasonic ExaminationUltrasonic ExaminationCheck Tests (Chemical, Mechanical, Special Tests)Check Tests (Chemical, Mechanical, Special Tests)Tests for determining pullout load ‘Fr’ valueTests for determining pullout load ‘Fr’ valuePneumatic TestsPneumatic TestsHydraulic TestsHydraulic TestsSpecial Tests (IGC, NACE related, Hardness, Eddy Special Tests (IGC, NACE related, Hardness, Eddy Current Testing, Helium Leak test Etc.)Current Testing, Helium Leak test Etc.)Pre-shipment checksPre-shipment checks

Tube Internal Fouling:Tube Internal Fouling:

Indications of fouling:Indications of fouling:

High process outlet temperatureHigh process outlet temperature

Higher power consumption of fansHigher power consumption of fans

Depends on: process stream properties, corrosion Depends on: process stream properties, corrosion products, process stream components, coke fines etcproducts, process stream components, coke fines etc

External foulingExternal fouling:: Because of external dust/ soot Because of external dust/ soot

Tube bowing:Tube bowing: flow maldistribution , fouling flow maldistribution , fouling

Plug header gasket leak:Plug header gasket leak:

Improper plug Improper plug

Damaged threads: mechanical / corrodedDamaged threads: mechanical / corroded

Improper tighteningImproper tightening

Problems:AFC tube bundleProblems:AFC tube bundle

Tube Leak: CorrosionTube Leak: Corrosion

Impurities / corrodants in the stream ( Cl-, NH3, H2S, S )Impurities / corrodants in the stream ( Cl-, NH3, H2S, S )

Under deposit corrosionUnder deposit corrosion

Erosion -> high velocity/ turbulence/ erodantsErosion -> high velocity/ turbulence/ erodants

Operating beyond operating windowsOperating beyond operating windows

Improper wash water systemImproper wash water system

Roll leak: Roll leak:

In adequate expansionIn adequate expansion

Bad grooves in tube sheetBad grooves in tube sheet

Thermal shocks Thermal shocks

Fouling and resultant severe tube bowingFouling and resultant severe tube bowing

Poor design ( high differential temperature )Poor design ( high differential temperature )

Problems:AFC tube bundle-Problems:AFC tube bundle-cont’dcont’d

Maintenance activitiesMaintenance activitiesIdentify leak type and location: hydrotestingIdentify leak type and location: hydrotestingAttend leak : Attend leak : – Nozzle gasket leaks - tighten or replace gasketNozzle gasket leaks - tighten or replace gasket– Plug gasket leak- re-tighten or replace plug or Plug gasket leak- re-tighten or replace plug or

replace gasketreplace gasket– Retubing Retubing – Plugging ( 5% per pass) - taper plug / “J” plug with Plugging ( 5% per pass) - taper plug / “J” plug with

welding of tube sheet holewelding of tube sheet hole– re-expansion of tube sheet joint/ re-weldingre-expansion of tube sheet joint/ re-welding

Cleaning of tubes as per requirementsCleaning of tubes as per requirementsInstall new bundles/ shell as per requirementInstall new bundles/ shell as per requirementTimely modifications in shell side/ tube side as per Timely modifications in shell side/ tube side as per CTS/CES/FDC/Licensor requirementsCTS/CES/FDC/Licensor requirements

Steps of retubingSteps of retubingCut tube and clean the tube sheet holes thoroughlyCut tube and clean the tube sheet holes thoroughlyDo mock up test at workshopDo mock up test at workshopSelect the required % expansion for retubing -CESSelect the required % expansion for retubing -CESMeasure tube OD, ID and tube sheet hole diameters.Measure tube OD, ID and tube sheet hole diameters.Insert the tubes. Set 3 mm max projection outside tube Insert the tubes. Set 3 mm max projection outside tube sheet. Then expand the tubes by expander tool.sheet. Then expand the tubes by expander tool.Measure final expanded ID. Calculate the % expansion.Measure final expanded ID. Calculate the % expansion.7-8% for CS, 4 to 5% for SS and non ferrous7-8% for CS, 4 to 5% for SS and non ferrousExpansion in % will be the following x 100Expansion in % will be the following x 100

(Tube ID after expn-tube ID before expn-Tube hole dia+tube OD)(Tube ID after expn-tube ID before expn-Tube hole dia+tube OD) ( Tube OD- Tube ID before expan( Tube OD- Tube ID before expan))

Factors affecting performance Factors affecting performance / Reliability/ Reliability

Fouling of bundleFouling of bundle

Leaks - gasket leaks or tube leaksLeaks - gasket leaks or tube leaks

Tube bowing Tube bowing

Flow maldistributionFlow maldistribution

Process upsets ( flow , temp, pressure)Process upsets ( flow , temp, pressure)

Wash water system problemsWash water system problems

Fan vibrationsFan vibrations

Blade problemsBlade problems

Drive unit / transmission unit problemsDrive unit / transmission unit problems

Ambient conditionsAmbient conditions

Inspection activitiesInspection activities

Maintain history (of failures, reliability issues)Maintain history (of failures, reliability issues)Recommend repair, replacement based on inspection Recommend repair, replacement based on inspection findingsfindingsRecommend insurance sparesRecommend insurance sparesResolve corrosion, other degradation issues through Resolve corrosion, other degradation issues through TRIPODTRIPOD

Pre-order requirementsPre-order requirements

Vendor surveyVendor surveyEnlistmentEnlistmentMonitoring performanceMonitoring performanceAppraise purchase departmentAppraise purchase departmentReview technical bidsReview technical bids

Cost of Air fin coolersCost of Air fin coolersSize / type of bundle, drive unit, transmissionSize / type of bundle, drive unit, transmissionMaterial of constructionMaterial of constructionType of tube to tube sheet jointsType of tube to tube sheet jointsInspection, NDT requirements based on severity of Inspection, NDT requirements based on severity of serviceserviceImported / indigenousImported / indigenousLocation of Manufacturer vs. userLocation of Manufacturer vs. userQuantity, lead timeQuantity, lead time

INDIANINDIAN

GEA Energy systemsGEA Energy systems

GEI HamonGEI Hamon

FOREIGNFOREIGN

GEA BTT -FranceGEA BTT -France

OLMI - ItalyOLMI - Italy

Some ManufacturersSome Manufacturers

Plate and Frame Exchangers

Plate heat exchangerPlate heat exchanger

WeldedWeldedSemi weldedSemi weldedGasketedGasketed

Compact designCompact designEasy maintenanceEasy maintenanceUsed for fouling serviceUsed for fouling serviceHigh heat transferHigh heat transferCostlyCostly

Plate-and-Frame Heat ExchangerPlate-and-Frame Heat Exchanger

Cin

Separating Sheet

BinAout Nozzle

Header

Corrugated Sheet

Side Bar

Distributor

Effective Length

Effective Width

Heat Transfer Section

Distribution Section

Cout

Ain Bout

B

A

A Two-Pass Plate and Frame Flow Arrangement

Plate-and-Frame Heat ExchangerPlate-and-Frame Heat Exchanger

Spiral Flow-Spiral Flow Heat Spiral Flow-Spiral Flow Heat ExchangerExchanger

References:Perry’s Hand Book of Chemical Engineers

Heat Transfer - D Q Kern

Applied Process Design for Chemical and Petrochemical Industries - Ludwig

TEMA - Design code

ASME - Section VIII Div I

Thank Thank

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