Heat Exchangers Design and Construction Chemicoz 1 Introduction

Heat Exchangers Design and Construction Chemicoz 1

Introduction: Shell and tube heat exchangers are one of the most common equipment found in all plants How it works? 2

What are they used for? 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

Design codes: Code Is recommended method of doing something ASME BPV – TEMA Standard is the degree of excellence required API 660 -ASME B 16. 5–ASME B 36. 10 M–ASME B 36. 19 -ASME B 16. 9–ASME B 16. 11 Specifications Is a detailed description of construction, materials, … etc Contractor or Owner specifications 4

Main Components 1234567 - Channel Cover Channel Flange Pass Partition Stationary Tubesheet Shell Flange Tube 8 - Shell 9 - Baffles 10 - Floating Head backing Device 11 - Floating Tubesheet 12 - Floating Head 13 - Floating Head Flange 14 –Shell Cover 5

TEMA Heat Exchanger 6

TEMA Heat Exchanger Front Head Type A - Type B - Type C - Type 7

TEMA Heat Exchanger Shell Type E - Type J - Type F - Type K - Type 8

TEMA Heat Exchanger Rear End Head Types M - Type Fixed Tubesheet S - Type Floating Head T - Type Pull-Through Floating Head 9

Classification: U-Tube Heat Exchanger Fixed Tubesheet Heat Exchanger Floating Tubesheet Heat exchanger 10

Example AES 11

Example AKT 12

Heat Exchangers Mechanical Design Terminology Design data Material selection Codes overview Sample calculations Hydrostatic test Sample drawing 13

Terminology ASME TEMA API MAWP MDMT PWHT NPS – DN – NB – NPT Sch - BWG 14

Design Data Heat Exchanger Data Sheet : TEMA type Design pressure Design temperature Dimensions / passes Tubes ( dimensions, pattern) Nozzles & Connections Baffles (No. & Type) 15

Material Selection Strength Cost & Availability Material Selection Corrosion Resistance Fabricability 16

Strength A – Yield Strength B – Tensile Strength C – Rupture point A B C 17

Strength 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 18

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 Ø Part A : Ferrous material specifications Ø Part B : Non-Ferrous material specifications Ø Part C : Specifications of welding rods, electrodes and filler metals Ø Part D : Properties Sec. VIII: Rules of construction of pressure vessels Ø Division 1 : Ø Division 2: Alternative rules Ø Division 3 : Alternative rules of high pressure 3 Subsections + mandatory Annex + non mandatory Annex 20

ASME code overview 21

TEMA code overview TEMA classes: Ø Ø Ø 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 Ø 10 subsection 22

Sample Calculations Shell thickness calculations under Internal Pressure: t= PR. + 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) 23

Sample Calculations Channel thickness calculations under Internal Pressure: t= PR. + 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) 24

Sample Calculations Body Flanges: 25

Sample Calculations Body Flanges: Ø Trial and error calculations Ø Gasket seating conditions Ø Operating conditions Ø No. of bolts and size Ø Bolt circle diameter Ø Inside and outside diameters Ø Check min. and max. bolt spacing Ø Detailed analysis of the flange Ø Ø Ø Forces calculations Moment calculations Stresses calculations 26

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 27

Sample Calculations Ø Nozzles and standard flanges: § Flange Rating (ASME B 16. 5) § Area replacement calculations § Nozzle neck thickness calculations § Impingement protection Sample 28

Sample Calculations ØTubesheet: • 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 29

Sample Calculations ØTubesheet: • 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 30

Sample Calculations ØTubesheet: • Tubesheet thickness for Shear: T: Effective tubesheet thickness DL: Effective diameter of the tube center parameter DL=4 A/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 31

Tube-to-Tubesheet joint ØExpanded ØStrength welded ØSeal welded 32

Hydrostatic Test Ø Test pressure : 1. 3 X MAWP Ø Test Procedure Ø Gasket change 33

Sample drawing ØConstruction drawing is the design output Sample drawing 1 Sample drawing 2 34

Thank You Chemicoz chemicozz@gmail. com 35