pd mechanical dsgn

7/30/2019 Pd Mechanical Dsgn

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Step 1: Specification

Material T in C T out C

34o API Crude oil 40 67

42o API Kerosene 200 90

T in T out

Shell 200 90

Tube 40 67

T mean 145 C

Cp (145C) 2.47 kJ/KgC

Duty 754.7222222 kW 754722.222

Step 2: Physical Properties

Kerosene Inlet Mean Outlet

Temperature 200 145 90

Specific Heat 2.72 2.47 2.26

Thermal Conductivity 0.13 0.132 T

Density 690 730 770

Viscosity 0.22 0.43 0.8

Step 3: Overall Coefficient

For an exchanger for this type, the overall coefficient will be in the range of 300-500 w/mC

See figure 12.1 and table 12.1; so start with 300

Step 4: Exchanger Type Dimension

Tlm = (Thi - Tco) - (Tho -

ln [(Thi - Tco)/(Th

Tlm = 81.89229794

R = Thi - Tho

Tco - Tci

= 4.074074074

S = Tco - Tci


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Thi - Tci

= 0.16875

From figure 12.19, Ft = 0.92

Tm = 75.34091411

Step 5: Heat Transfer Area

Uo = q

AoTm

Ao = q

UoTm

= 33.39142841

Step 6: Layout and Tube Size

Using a split ring floating head exchanger for efficiency and ease of cleaning

Outer Diameter 19.05 mm 0.01905

Internal Diameter 14.83 mm 0.01483Triangular 23.81 mm 0.02381

Long Tubes 5 m 5000

Pitch/ Diameter 1.25

Step 7: Number of Tubes

Area of one tube (neglecting thickness of tube sheet)

= 0.2992367 m

Number of tubes = 111.5886801 Say

So, 2 passes, tube per pass = 55.5 Say

Check the tube-side velocity at this stage to see if it look reasonable

Tube cross sectional area = 0.000172732 m


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Area per pass = 0.009672978 m

Volumetric Flow Rate = Flow of Crude x

3600

= 0.016818708 m/s

Tube Side Velocity, Ut = 1.738731069 m/s

Hence, the velocity is satisfactory, between 1 and 2 m/s.

Step 8: Bundle and Shell Diameter

From Table 12.4, for tube passes, K1 = 0.249

n1 = 2.207

Bundle Diameter, Db = Outer Diameter x (Nt/K1)^(1/n1)

Pt = 1.25do

do = 0.019048 m

Db = 302.150182 mm

For a spliting floating head exchanger the typical shell clearance from figure 12.10 is 53 mm,

Ds = 355.150182 mm

Step 9: Tube Side Heat Transfer Coefficient

Re = xUtxDi

= 6049.309164

Pr = CpxThermal Conductivity

= 53.5880597

L/D = 337.1544167

From figure 12.23, jh = 0.0038


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Nu = jh x Re x Pr^0.33

Nu = 85.52278363

hi = Nu x (Thermal Conductivity/ Internal Di

= 772.7614974

Step 10: Shell-side heat transfer coefficient

As a first trial take the baffle spacing = Ds/5

= 71.03003641

As = 5041.014512

Equilateral triangular pitch

de = 1.1 (Pt - 0.917do)

do

= 13.51957786 mm

Volumetric flow rate on shell side = 0.003805175

Shell side velocity = 0.754845276

Re = 17325.63009

Pr = 8.046212121

Use segmental baffles with a 25% cut. This should give a reasonable heat transfer coefficient

From figure 12.29, jh = 0.0048

hs = 1615.795011 W/mC

Step 11: Overall coefficient

Kw = 55

1/hi = 0.00129406

1/hid = 0.00035

ln do/di = 0.250414945


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1/ho = 0.00061889

1/hod = 0.0002

1/Uo = 0.002930853

Uo = 341.1975878

Step 12: Pressure Drop

Re = 6049.309164

Ut = 1.738731069

From figure 12.24, jf = 0.0053

Pt = 41930.37008 N/m

= 0.42 bar


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Pressure in (bar) Permissible Pressure drop (bar) Fouling Factor (W/m2C)

6.5 1 0.0003

5 1 0.0002

Hours Second

1 3600

W

Crude oil Outlet

C Temperature 67

kJ/kgC Specific Heat 2.07

W/mC Thermal Conductivity 0.134

kg/m Density 812

mNsm- Viscosity 2.86

w/mC

Tci)

o - Tci)]


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m

mm

mm

111 tubes

56


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1

density

19.05 mm

0.302 m

o the shell inside diameter


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meter)

say 71

mm 0.005041 m

0.01352 m

m/s

without too large a pressure drop.


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Mass Flowrate (kg/h)

50000

10000

Mean Inlet

53.5 40 C

2.04 2.01 kJ/kgC

0.134 0.135 W/mC

825.8 840 kg/m

3.52 4.3 mNsm-


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cost estimation

guthrie method

K1 4.8306 log10Cp= 4.274003

K2 -0.8509 Cp= 2033986

K3 0.3187

A 33.4

Fm 1 Cbm= 6691816

Fp 1

b1 1.63

B2 1.66

Cp 2033986


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1

2

3

45

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

2526

27

28

29

30

31

32

33

34

35

3637

38

39

40

41

42

43

44

Heat Exchanged

Transfer Rate, Service

Tube Type

CONSTRUCTION OF ONE S

Corrosion Allowance mm

Tube No.

Tubesheet-Stationary

Channel or Bonnet

Shell Steel

Rating

Size

Connection

Intermediate

Out

In

No. Passes per Shell

Design Temperature C

Design/ Test Pressure kPa (ga)

Latent Heat kJ/kg @ C

Inlet Pressure kPaVelocity m/s

Pressure Drop, Allow./Calc kPa

Fouling Resistance (Min.)/Calc mC/W

Temperature (In/Out) C

Density kg/m

Viscosity/ Liquid mPa.s

Molecular Mass, Vapor

Molecular Mass, Noncondensable

Specific Heat Capacity kJ/(kgC)

Vapor (In/Out)

Liquid

Steam

Water

Noncondesable

Fluid Name

Surf/ Unit (Gross/Eff)

Thermal Conductivity J/(s.m.C/m)

Service of Unit Oil to Oil Exchange

Size

Fluid Quantity, Total kg/h

Plant Location

Customer

Fluid Allocation

PERFORMANCE OF ONE U

Address


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45

46

47

48

49

50

5152

53

54

55

56 Remark

Weight/ Shell

Code Requirement

Floating Head

Expansion Joint: Carbon Steel

Gasket-Shell Sidev- Inlet Nozzle

Bypass Seal Arrangement

Support: Tube

Baffles: Long

Type: SegmBaffles: Cross

Floating Head Cover


15/21

Material: Carbon Steel

Tubesheet: Floating

Channel Cover

Shell Cover

ELL

ODID

Tube Side

3

2

Shell Side

3

2

0.0003

100

650

0.0002

100

500

Sketch (Bundle/ Nozzle Orien

150#

4.3

840

40

2.26

0.135

Crude Oil

50 000

In

10 000

0.135

2.012.72

0.13

Out

90

770

0.8

In

200

690

0.22

Kerosene

r Item No. E-4

Connected In Parallel

Reference No.

Date: Rev:

Proposal No.

NIT

Shell Side Tube Side


16/21

Type: Flanged

Impingement Protection

InletSpacing: 75 mm%Cut (Diameter/ Area): 25%ented


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ation)

2.86

812

67

Out

0.134

2.07

Series


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19/21

MECHANICAL DESIGN

specification

shell 355.15 mm

tubes 14.83 mm id

19.05 mm od

length 5000 mm

kerosene in the shell, operating pressure 5 bar

crude in the tubes, operating pressure 6.5 bar

material of construction, semi-killed or silicon killed crbon steel

a) Design Pressure: takes 10% greater than operating pressure

shell = 4.4 = 440000 N/m2

tubes= 6.05 =650000 N/m2

design temperature: 200 oC

take this design temperature both shell and tubes. The tubes could reach the kerosene

temperature if there was no flow of crude oil

b) corrosion allowance

kerosene= 2 mm

crude oil= 4 mm

c) end covers used torispherical, header-cover flat plate

d) stressing

from table 13.2, design stress is 105 N/mm2 at 200oC

shell: e= 0.0008 m = 0.8 mm

add corrosion allowance= 2.8 mm

thiss is less than the minimum recommended thickness so round up to 5 mm

header: e= 0.0011 m = 1.1 mm

add corrosion allowance = 5.1 mm

shell end cover, torispherical,

take Rc = 0.3

Rk/Rc = 0.1

Cs = 2.37 take joint factor as 1 formed he


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e = 0.00148 m = 1.5 mm


floating head torispherical:

from figure 12.10 bundle to shell clearance, take as split ring

Db = 53.15 mm = 53

take Rc = 0.3

Rk/Rc = 0.1

Cs= 2.37

e= 0.00206 m = 2.1 mm

add corrosion allowances = 6.1 mm

flat plate (header cover) type e,

Cp= 0.55

Di= 355 mm = 0.35 m

De= 0.4 m

e= 0.167 m = 16.7 mm


all thickness will be rounded to the nearest standard size

e) Tube rating

tube id= 14.83 mm

tube od= 19.05 mm

design stress = 105000000 N/m2

design pressure = 6.05 N/m2

thickness required , e = 0.0000053 m = 0.005

actual wall thickness = 2.11 mm

f) tube sheet thickness should not be less than tube diameter

take thickness as 20 mm

shell od= 365.15 mm say 370 mm

design pressure= = 440000 N/m2

design temperature 200 oC


21/21

refer to table 13.5, 6 bar rating will be satisfactory

floating head od 350 mm

design pressure 6.05 N/m2

design temperature 200 oC

based on the table 13.5 use 10 bar rated flanged

h) supports

use saddle supports

diameter 0.4 m

length 10 m

shell and header volume of steel 0.063 m3volume of shell head, take as flat 0.0004

volume of floating head, take as flat 0.0005

volume of flat plate end cover 0.0026

volume of tube-sheet 0.0026 ignoring the holes

volume of tube 0.115

number of baffles 77

taking baffles as 3 mm thick and ignore the baffle cut

volume = 0.027

total volume of steel

shell 0.063

shell head 0.0004

floating head 0.0005

end cover 0.0026

tube sheet 0.0026

tubes 0.115

baffles 0.027

total 0.2111 m3

taking density of steel as 7800 kg/m3

mass of HE= 1646.58 kg

weight HE= 16152.9498 N

mass of water, ignore volum of tube 1257 kg

weight= 12331.17 N

maximum load on supports= 28484.12 N

29 kN

pd mechanical dsgn

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