Heat Exchangers Design and Construction Chemicoz

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

What are they used for? Heat Exchanger Cooler Heater Condenser 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

Design codes: Code Standard Specifications 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

Main Components 1- Channel Cover 8- Shell 2- Channel 9- Baffles 3- Channel Flange 10- Floating Head backing Device 4- Pass Partition 11- Floating Tubesheet 5- Stationary Tubesheet 12- Floating Head 6- Shell Flange 13- Floating Head Flange 7- Tube 14 –Shell Cover

TEMA Heat Exchanger

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

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

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

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

Example AES

Example AKT

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

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

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

Material Selection Cost & Strength Corrosion Resistance Fabricability Availability

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

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

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

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 : 3 Subsections + mandatory Annex + non mandatory Annex Division 2: Alternative rules Division 3 : Alternative rules of high pressure

ASME code overview

TEMA code overview TEMA classes: TEMA subsections 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

Sample Calculations PR . SE – 0.6 P + CA t = + UT Shell thickness calculations under Internal Pressure: PR . SE – 0.6 P + CA t = + UT 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)

Sample Calculations PR . SE – 0.6 P + CA t = + UT Channel thickness calculations under Internal Pressure: PR . SE – 0.6 P + CA t = + UT 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)

Sample Calculations Body Flanges:

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

Sample Calculations Pairs of flanges 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

Sample Calculations Nozzles and standard flanges: Flange Rating (ASME B16.5) Area replacement calculations Nozzle neck thickness calculations Impingement protection Sample

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

For Triangular pattern 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 For Square pattern For Triangular pattern G: Gasket effective diameter F: Factor

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

Tube-to-Tubesheet joint Expanded Strength welded Seal welded

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

Sample drawing Construction drawing is the design output

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