Heat Exchangers

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  • Words: 1,105
  • Pages: 35
By: Baher EL Shaikh Mechanical Engineer EMetahnex

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Shell and tube heat exchangers are one of the most common equipment found in all plants  How it works? 

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Classification according to service .



Heat Exchanger Both sides single phase and process stream



Cooler

One stream process fluid and the other cooling water or air



Heater

One stream process fluid and heating utility as steam



Condenser

One stream condensing vapor and the other cooling water or air



Reboiler One stream bottom stream from a distillation column and the other a hot utility or process stream 3



Code

Is recommended method of doing something

ASME BPV – TEMA 

Standard

is the degree of excellence required API 660-ASME B16.5–ASME B36.10M–ASME B36.19-ASME B16.9–ASME B16.11



Specifications

Is a detailed description of construction, materials,… etc Contractor or Owner specifications

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1- Channel Cover 2- Channel 3- Channel Flange 4- Pass Partition 5- Stationary Tubesheet 6- Shell Flange 7- Tube

8- Shell 9- Baffles 10- Floating Head backing Device 11- Floating Tubesheet 12- Floating Head 13- Floating Head Flange 14 –Shell Cover 5

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 Front

Head Type

A - Type

B - Type

C - Type

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Shell Type

E - Type

J - Type

F - Type

K - Type 8



Rear End Head Types

M - Type Fixed Tubesheet

S - Type Floating Head

T - Type Pull-Through Floating Head

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 U-Tube  Fixed

Heat Exchanger

Tubesheet Heat Exchanger

 Floating

Tubesheet Heat exchanger

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AES 11

AKT 12



Terminology



Design data



Material selection



Codes overview



Sample calculations



Hydrostatic test



Sample drawing

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ASME : American Society of Mechanical Engineers  TEMA : Tubular Exchanger Manufacturer Association  API : American Petroleum Institute  MAWP : Maximum Allowable Working Pressure  MDMT : Minimum Design Metal Temperature  PWHT : Post Weld Heat Treatment  NPS – DN – NB – NPT  Sch - BWG 

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Heat Exchanger Data Sheet :



TEMA type



Design pressure



Design temperature



Dimensions / passes



Tubes ( dimensions, pattern)



Nozzles & Connections



Baffles (No. & Type)

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B 

A – Yield Strength



B – Tensile Strength



C – Rupture point

A

C

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Creep Strength a slow plastic strain increased by time and temperature (time and temperature dependant) for stressed materials



Fatigue Strength The term “fatigue” refers to the situation where a specimen breaks under a load that it has previously withstood for a length of time



Toughness The materials capacity to absorb energy, which, is dependant upon strength as well as ductility

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ASME code Overview Sec.I Power Boilers Sec.II Materials Sec.III Nuclear Fuel Containers Sec.IV Heating Boilers

ASME BPV code

Sec. V Non Destructive Examination Sec. VI Operation of heating boilers Sec. VII Operation of power boilers Sec. VIII Pressure vessels Sec. IX Welding and Brazing Sec. X Fiber-Reinforced plastic PV Sec. XI Inspection of nuclear power plant Sec. XII Transport tanks 19

ASME code overview 

Sec. II: Materials 

Part A : Ferrous material specifications



Part B : Non-Ferrous material specifications



Part C : Specifications of welding rods, electrodes and filler metals Part D : Properties





Sec. VIII: Rules of construction of pressure vessels 

Division 1 :



Division 2: Alternative rules



Division 3 : Alternative rules of high pressure

3 Subsections + mandatory Annex + non mandatory Annex

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ASME code overview

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TEMA code overview 



TEMA classes: 

Class R: Generally severe requirements for petroleum and related processing applications



Class C: Generally moderate requirements of commercial and general processing applications



Class B: Chemical Process service

TEMA subsections 

10 subsection

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Sample Calculations 

Shell thickness calculations under Internal Pressure:

PR t= + CA + UT . SE – 0.6 P       

t : Min. Required Shell Thickness P : Design Pressure of Shell Side S: Max. Allowable Stress of Shell Material R: Shell Inside Radius (corroded conditions) E : Joint Efficiency CA: Corrosion Allowance UT: Under Tolerance (if applicable)

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Sample Calculations 

Channel thickness calculations under Internal Pressure:

PR t= + CA + UT . SE – 0.6 P       

t : Min. Required Channel Thickness P : Design Pressure of Tube Side S: Max. Allowable Stress of Channel Material R: Channel Inside Radius (corroded conditions) E : Joint Efficiency CA: Corrosion Allowance UT: Under Tolerance (if applicable)

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Sample Calculations 

Body Flanges:

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Sample Calculations 

Body Flanges: 

Trial and error calculations 

Gasket seating conditions



Operating conditions



No. of bolts and size



Bolt circle diameter



Inside and outside diameters



Check min. and max. bolt spacing



Detailed analysis of the flange 

Forces calculations



Moment calculations Stresses calculations



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Sample Calculations 

Precautions in body flanges design and installations:



Pairs of flanges



Bolt holes shall straddle center line



Corrosion Allowance



Cladding



Bolts shall be multiple of 4



Bolting shall be allowed to be removed from either side



Calculated thickness not include the RF

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Sample Calculations  Nozzles and standard flanges: 

Flange Rating (ASME B16.5)



Area replacement calculations



Nozzle neck thickness calculations



Impingement protection

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Sample Calculations  Tubesheet: • Tubesheet is the principal barrier between shell side and tube side • Made from around flat piece of metal with holes drilled for the tubes

• Tubes shall be uniformly distributed • Tubesheet thickness shall be designed for both sides • Tubesheet shall be designed for bending stresses and shear stresses • Corrosion allowance

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Sample Calculations  Tubesheet: • Tubesheet thickness for bending

T: Effective tubesheet thickness S: Allowable stress P: Design pressure corrected for vacuum if applicable at the other side η: Ligament efficiency G: Gasket effective diameter F: Factor For Square pattern

For Triangular pattern

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Sample Calculations  Tubesheet: • Tubesheet thickness for Shear:

T: Effective tubesheet thickness DL: Effective diameter of the tube center parameter

DL=4A/C

C: Perimeter of the tube layout A: Total area enclosed by the Perimeter C P: Design pressure S: Allowable stress do: Outside tube diameter

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Tube-to-Tubesheet joint  Expanded

 Strength welded  Seal welded

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Hydrostatic Test  Test pressure : 1.3 X MAWP  Test Procedure  Gasket change

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Sample drawing  Construction drawing is the design output

Sample drawing 1

Sample drawing 2

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Baher EL Shaikh [email protected]

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