piping engineeringmanilalam

8/13/2019 Piping EngineeringManilalAM

1/62

Piping Engineering

Manilal A M

Assist. Prof. in Chemical Engineering


2/62

Contents

Scope Of Piping Engineering

Pipe Sizing Techniques

Mechanical Design Of Pipes Codes and Standards

Piping Elements

Stress Analysis of Piping Systems

7/17/2013 2


3/62

Various Stresses in Pipes

Pipe Support Selection and Design

Stress Analysis of Piping Systems

Expansion Joints

Jacketed Piping

Basics of Piping Drawings

Plot Plan Fundamentals

Equipment and Piping Layout

Dynamic Analysis of Pipes

7/17/2013 3


4/62

Scope Of Piping Engineering

Life of a Chemical Process

Knowledge Base Required Chemical Engineering

Mechanical Engineering

Metallurgical Engineering

Civil Engineering

7/17/2013 4

CommissioningConcept Beyond

Piping

Engineering


5/62

Major Phases

Techno-Economic Feasibility

Design Phase

Construction Phase

Commissioning Phase

Operation/Production Phase

7/17/2013 5


6/62

Techno-Economic FeasibilityEconomics- guiding principle

Risk factor and pollution considerationFor new plantsChemical Path FeasibilityThermodynamic feasibility

Kinetic feasibilityReaction Path Synthesis Algorithms( Organic

Synthesis)

BFD

Engineering/Technological FeasibilityBatch or Continuous or Combination of both

Detailed processes involvedUnit operations

Unit processes7/17/2013 6


7/62

Process Synthesis

BFD

Decision on Unit Operations

Choices of Equipment

Plant Cost

Operating Cost

Scope of Optimization

Cost Optimal Flow sheet Configuration

Selection of other equipments

Utilities

7/17/2013 7


8/62

End results

7/17/2013 8

Conceptual Design

Equipments and their

Capacities (Roughly)

Capital cost and

Operating Cost

Raw material availability and Cost and

Market prizes of products and by products

Techno-Economically feasible process


9/62

Design Phase

Rigorous Engineering Calculations

Essentially two components

Process Design & Mechanical Design

Process Design

Operating Conditions Equipment Sizes

Simulation Software

Steady State Simulators

Dynamic Simulators

7/17/2013 9

BFD PFD


10/62

PFD

Father drawing

Instead of blocks symbols

Max Possible information about the process

Stream specifications Unique numbering, stream table

Inspection and review of PFD

7/17/2013 10


11/62

Control System Synthesis and Design(CSSD)

Control System Design

System Identification

Manipulated/Controlled variable selection

Controller selection

HAZOP

Identify deviation from expected steady state

Identify hazard

Monitoring instruments

Stand by

Mitigation measures

7/17/2013 11


12/62

Many more to do with the PFD

Hydraulic Calculations

Pressure drop

Compressible/ Incompressible

Single Phase/ Multi phase

Available correlations

Pipe Sizing

Operating Cost

Capital cost

Batch/ Semi batch

Storage tanks

7/17/2013 12


13/62

P&ID

7/17/2013 13

PFD P&ID

Stand-by

Equipments

StorageTanks

Pipe Sizes

Instrumentation

&Control

ValvesOther

Fittings


14/62

P&ID Is the Mother Drawing shows

Relative elevations of equipments

Number of Trays, feed tray location (Distillation

Column)

Cardinal Drawing for various section Stored and updated for the entire life cycle

Basic drawing for

subsequent equipment design

Plant layout

Piping layout

Insulation calculations

Bill of material (BOM)7/17/2013 14


15/62

Bible for Piping Engineer

Details of pipe lines

Material of Construction

Service

Mechanical Design

Pressure vessels

Closures

Flanges

Gaskets Bolts

Man holes and Hand holes

Reinforcing pads7/17/2013 15


16/62

Mechanical Design Stiffening rings

Internally/Externally

Tall vessels

Wind loads

Supports

Seismic effects

Eccentric loads

Considering all these fabrication drawings are issued

7/17/2013 16


17/62

Piping (preliminary )

Pipe wall thickness design

Fix nominal diameter and schedule

for first BoM for pipe length requirement

Design Phase is Over

7/17/2013 17


18/62

Construction Phase

Choice of Plant location Politico-socio-economic considerations

Plant Layout

Unit layout/ Equipment Layout Directly influence Piping layout

Piping (veins and arteries)

Routing

Stress Analysis

Supports7/17/2013 18


19/62

Use of softwares

Civil structures/ Foundations Software model of 3-D layout

Has all the details

BoM for pipes and piping elements Can monitor project implementation

Can act as Complete database

7/17/2013 19


20/62

Commissioning

Not at all a smooth affair Adhoc decisions need to be taken on field

Fabrication errors

Late or non delivery of items Design errors

Steady state design

Evolve a good start up policy using dynamicsimulators

7/17/2013 20


21/62

Normal Operation Phase

Properly designedsmooth run

Need debottlenecking

Minor/major changes

Installation of additional equipment

Bypassing existing equipment

7/17/2013 21


22/62

PIPE HYDRAULICS & SIZING

7/17/2013 22


23/62

PIPING

Pipe sections when joined with fittings, valves, and

other mechanical equipment and properly

supported by hangers and supports, are called

piping.

7/17/2013 23


24/62

Why Pipe Sizing Is Important?

30% of total cost of process plant

Significant amount of operating cost

Significant amount of maintenance cost

7/17/2013 24


25/62

Pipe Sizing involves

Lots of experience

Engineering foresight and judgment

Not mere theory

7/17/2013 25


26/62

Pipe Sizing Procedures

1. Velocity considerations

2. Available pressure drop considerations

3. Economic considerations

Degree of difficulty: 3>2>1

P calculation is an integral part of 2 & 3 For (1) it is needed to quantify energy requirements

7/17/2013 26


27/62

Pressure drop calculations

Types of flow Phase

Horizontal, Inclined

Through straight run pipes/ complex routings

Isothermal/ Non-isothermal

Incompressible/ compressible

Laminar/Turbulent

7/17/2013 27


28/62

BERNOULLIS EQUATION

Statement of Law of Conservation of Energy

Sum of the pressure head, velocity head and

elevation head is constant everywhere along theflow path.

7/17/2013 28

22

222

12

211

Zg

v

g

P

Zg

v

g

P


29/62

g

P

1

g

P

2

g

v

2

2

1

g

v

2

2

2

1Z

2Z

Fig. 17/17/2013 29


30/62

Frictional Pressure drop

BE need to be modify Skin friction

Form friction

7/17/2013 30

PZ

g

v

g

PZ

g

v

g

P

22

222

12

211


31/62

Single Phase Pressure Drop Calculation Single Phase Flow

Laminar Transient

Turbulent

Reynolds Number

Re< 2000 - Laminar

2000


32/62

Alternate definitions

G = linear mass velocity

W = mass flow rate in lb/h,D = pipe ID in inches

7/17/2013 32

DGRe

DWRe 31.6


33/62

Darcys Equation

7/17/2013 33

gD

vfP D

2

)( 2

For turbulent flow region, use friction factor chart -

),(

FactorFrictionsDarcy

RoughnessPipeRff

f

eD

D

ratioDdifferentforRvsf eD )(


34/62

Fanning's Equation

7/17/2013 34

gDvfP F

2)4( 2

FD

F

ff

anningf

4

FactorFrictionsF

Another friction factor used in pressure drop

calculation is the Churchill friction factor

CFD fff 84


35/62

Be sure which chart you are using!!!

Linear region of for Laminar flow

7/17/2013 35

eRvsf

e

C

e

F

e

D

Rf

Rf

R

f

8

16

64

M th ti l l ti


36/62

Mathematical correlationsAll equations are based on

7/17/2013 36

)(FactorFrictionsDarcy Df

3400000eRpipe,Smooth

50000eRpipes,commercialRough

21

210

126.1ln656.19

108.56

RegionTurbulent

64

RegionLaminar

f

Rf

Rf

Rf

e

e

e

D

M h i l l i


37/62

Mathematical correlations

Blazius Equation, for fully developed flow

7/17/2013 37

21

2.0

25.0

888.027.0

1656.19

,3400000

046,0

3164.0

fRD

f

flowturbulentdevelopingRwithpiperoughorsmoothfor

Rf

equationBlasiusAnother

Rf

e

e

e

e


38/62

Mathematical correlations

Colebrook- White Equation

7/17/2013 38

mmpipesteelcommercial

fR

f

pipessmoothFor

fRdf

De

D

DeD

05.0

51.2log2

1

51.2

71.3log2

1


39/62

Roughness Factor

7/17/2013 39


40/62

Calculation of Actual Pressure Drop

Use this in BE to get actual pressure drop

If Piping contains valves and fitting Equivalent pipe length of fittings

Equivalent pipe length for entrance and exit effect

Add all these and use in BE

Temp and Pressure Effects?

7/17/2013 40

lengthEffectivePcalculatedPfrictionalNet


41/62

Over Design

Recommend next higher size than calculated

Design for 30%extra flow rate

Design for 30% less pressure drop

7/17/2013 41


42/62

Two Phase Calculations

Depend on flow regimes 7 flow regimes are identified

Bakers procedure

Bakers parameters

7/17/2013 42

P

YX BandB

5.0

315.0

)(

16.2

32

)()(531

vl

vY

l

l

l

vlvlX

A

WB

WWB


43/62

7/17/2013 43

dyne/cmliquid,oftensionSurface

cPliquid,ofViscosity

,sec

lb/ftdensity,Liquid

lb/ftdensity,Vapourlb/hrate,flowLiquid

lb/hrate,flowVapour

2

3

3

l

l

l

v

l

v

ftareationalcrossInternalA

W

W


44/62

Flow regimes

7/17/2013 44


45/62

Bakers Chart

7/17/2013 45


46/62

Correlations for

Lockhart Martinelli Method Lockhart Martinelli modulus (X)

From fig obtain YL and YV

7/17/2013 46

P

VL PPX /2

twotheoflargestthetake

)()(

)()(

LLLV

LLLV

PYP

PYP


47/62

7/17/2013 47

Pi Si i


48/62

Pipe Sizing

Based on Velocity Considerations

Simplest approach

Liquid - 1-3 m/s

Gases/Vapour - 10-30 m/s

7/17/2013 48

ocities)linear velRecomandedrate,Flow(fD


49/62

Based on Available Pressure Drop

Most involved/important method Sized to meet process requirement

Acceptable maximum hydraulic pressure drop

A minimum pipe size, which causes at the mostthis pressure drop is recommended

Trial and error procedure

7/17/2013 49


50/62

Assume a commercial pipe size (NB)

Fix the schedule number (pressure design decides it)

Obtain the ID

Calculate hydraulic P If P> acceptable level

Take a higher pipe size and repeat the calculations

Recommend, minimum pipe size meeting the Prequirement

7/17/2013 50


51/62

Situations demanding this method

Suction pipe sizing for a pump Flow of volatile liquid through pipes

Feed to distillation column

Lines having control valves

Lines from thermo-siphon reboiler

7/17/2013 51

Economic Pipe Sizing


52/62

Economic Pipe Sizing

Least Annual Cost Approach

If the previous two constraints are not stringent

Go for Economic pipe sizing

Economics is governed by

Capital cost

Operating Cost

Figures given below shows the Amortized cost,

Annual operating cost and Total cost, each vs NPS

7/17/2013 52

Optimum Pipe Dia


53/62

Optimum Pipe Dia

The cost of unit length of run pipe of diameterD is calculated as

Let F be the fraction of cost of accessories perunit length

The Total Capital cost =

Annualized Capital cost =Where AMis the amortization factor

7/17/2013 53

5.1353.0 XDCD

DCF)1(

DM CFA )1(


54/62

If annual maintenance cost if a fraction G of

the capital cost,

Total pipe cost is

Annualized capital + maintenance cost, CP,

Operating Cost

7/17/2013 54

DM CFGA )1)((

5.1)1)((353.0 XDFGAC MP

E

PYKWCF 0000542.0


55/62

7/17/2013 55

pumpingofcostAnnualC

kW.h)(perpower,electricofcost

yearperoperationofhoursefficiencypump

lb/ftdensity,

lb/h,rateflow

psidrop,pressurehydraulic

F

3

K

YE

W

P


56/62

The P can be calculated as

So, the cost of moving the fluid per year is

7/17/2013 56

84.4

16.084.1

1325.0D

WP

ED

YKWCF 284.4

16.084.2

2840000


57/62

Total Annual cost of unit pipe length is

So,

7/17/2013 57

ED

YKW

XDFGAC MT

284.4

16.084.2

5.1

2840000

)1)((353.0

0)dD

dC

@(Dofvalue

asobtainedbecanCminimizeswhich

T

T

Optimum

Optimum

D

D

On solving


58/62

On solving

Most of the quantities in the above expression

are project specific.

The expression is further simplified withrepresentative values of AM,G,F,E,X,Y and K

as

7/17/2013 58

169.0

337.0

027.0479.0

1

0657.0

FGA

YKWD

M

opti

027.0142.0479.0

027.0142.0479.0

276.0

717.1

SQD

orSQD

LAC

LAC


59/62

7/17/2013 59

kWhK

yearhY

ftX

E

F

G

AM

/$0218.0

/7880

/$32.1

55.0

75.6

01.0

143.0

169.0

D

169.0

D

)01.0/(728.0F

2196,0F

factorsCorrection

a

Y

i i i h l i l


60/62

Given optimum Dia how to select commercial

size?

Concept of cross over diameter

If, DLAC>DC DH

If, DLAC


61/62

But.

It is an industrial practice to

recommend a pipe of one size

higher than what is arrived at by

any of the above procedures.

7/17/2013 61


62/62

Thank You

piping engineeringmanilalam

Documents