Process Design Training Pipe Sizing

7/31/2019 Process Design Training Pipe Sizing

1/44

Process Design Training

Line Sizing

Based on GPSA


2/44

Course goals

Understand fluid flow

Understand line sizing criteria

Understand requirements of special lines

Understand network sizing and special programs

Lines or pipes are the arteries of a plant

Cooling water and Fire water systems

Create your own sizing workbook in Excel

Automate the task, by linking simulation outputs

Understand piping engineering guidelines


3/44

Overview:

All Chemical process plants are madeof pipes that transfer fluids from and todifferent equipment

Fluids are:

Liquid

Thelinked imagecannotbedisplayed. Thefilemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfileand location.

Thelinked imagecannotbed isplayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfile and location.

Process Engineers - are they glorified plumbers?

apour Two phase

Slurry

Fluids may flow under pressure orgravity



4/44

Overview

Fluid Flow


5/44

Meet the basics

2 Fluid physicalproperties affectingfluid flow are:

1. viscosity and2. density

Bernoullis Theorem:

Based on law of conservation of energy

Total energy of a fluid at any point abovea datum is the sum of the elevationhead, the pressure head, and thevelocity head

E2

Highly viscous fluids behave differently

Viscosity is a measure of a fluids internal resistance to deformation or shear. Itindicates resistance to flow when acted upon by an external force

Viscosity of most liquids decreases with temperature, whereas that of gasesincreases. Pressure has almost no effect on the viscosity of liquids or near perfectgases. Viscosity of saturated or slightly superheated vapour is changedappreciably by pressure changes

= = + +E1


6/44

Reynolds Number

Reynolds Number

Laminar Flow: At low velocities, fluid moves in a reasonably straight line.Velocity of the fluid is maximum at the center of the pipe and zero atthe pipe wall. Re < 2,100

Turbulent Flow: At higher velocities, fluid particles show a random motiontransverse to the direction of flow. There is always a boundary layer atthe pipe wall where flow is laminar. The velocity profile is nearly

Re = DV/

Turbulent flow is further categorized into partially or fully developed turbulence

Laminar or streamlined flow

Turbulent flow

. ,




7/44

Reynolds Number

Reynolds Number

Laminar Flow: At low velocities, fluid moves in a reasonably straight line.Velocity of the fluid is maximum at the center of the pipe and zero atthe pipe wall. Re < 2,100

Turbulent Flow: At higher velocities, fluid particles show a random motiontransverse to the direction of flow. There is always a boundary layer atthe pipe wall where flow is laminar. The velocity profile is nearly

Re = DV/

20% margin is taken on calculated P to take care of uncertainties in the empirical correlations

Pressure Loss Due to Friction:

Flow results in friction and friction loss. Darcy-Weisbach equation is used to

determine frictional loss. [Also called, Poiseuilles law for laminar flow.]It is valid for both laminar and turbulent flow of any liquid. Changes in elevation,velocity, or density must be accounted for by applying Bernoullis theorem. Forgases consider short line segments, such that density is essentially constant

. ,


8/44

Friction Factor

Friction factor represents the fraction of velocity head lost due to flow

Pipe roughness has no effect on the friction factor in laminar flow, while it

increases loss in turbulent flow

Colebrook proposed a friction factor based on relative roughness, viz/D, ratio of roughness of the pipe wall to diameter


1. Moody friction factor, 4 times higherthan Fanning friction factor. Moodysused largely by Civil engineers and their

hydraulics program

2. Fanning friction factor is used inProcess calculations

It does not mean P calculated by Civil Engineers is 4 times higher!


9/44

Friction Factor

Friction factor represents the fraction of velocity head lost due to flow

Pipe roughness has no effect on the friction factor in laminar flow, while it

increases loss in turbulent flow

Colebrook proposed a friction factor based on relative roughness, viz/D, ratio of roughness of the pipe wall to diameter

Fittings take bulk of the pressure drop. Eye estimates in plant OK as long as all fittings are counted.

Equivalent Length of Valves and Fittings.P is usually accounted by equivalent lengths of the fitting. L/D or K factorcorrection for actual ID or NRe is usually ignored


10/44

Overview

Line Sizing Criteria


11/44

General Guidelines

Minimum andmaximum velocitylimits based onsediments deposit and

erosion; vibration andnoise

Sizing based on economics (fixed cost) Vs P (running cost)

Minimum 2 to avoid small bore pipe rupture.Smaller pipes need additional supports onsleepers/ pipe rack

1. In lines injected with corrosion inhibitors, maintain recommended velocity

2. Low velocity and pressure drop in pump suction and PSV inlet piping

3. To avoid vortex in vessel liquid outlet lines h > 2 VH or V < gh

Optimum size Vs Special Requirements


12/44

General GuidelinesThelinked imagecannotbed isplayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.

Thelinked imagecannotbe displayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.

Thelinked imagecannotbed isplayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.

1. Avoid bends close to control valve / pump outlet/ steam injection points.Usually leads to high erosion, rupture and plant fire

2. Liquid lines with check valve or quick closing valve OR poorly sizedcondensate lines may lead to water hammer and pipe rupture

Optimum size Vs Special Requirements


13/44

Liquid & Gas Lines

High velocity sonic flow maylead to pipe failure and fire

Liquid lines are usually sized on velocitycriteria

Special criteria based on fluid/ service such asNH3, C2=, NaOH, H2SO4, sea water etc

In saturated liquid, high velocity leads toflashing/ cavitation

In gas high P may lead to choked flow with


Size high P gas lines in segments

1. Gas lines are sized to limit pressure drop (gas compressor being energyexpensive than liquid pumping!)

2. Where adequate pressure drop is available, then noise limits velocity incontinuous service and 50-70% sonic velocity limit in intermittent service

3. Use inlet or outlet density if P is


14/44

Special Lines

Modulating steamtraps like float orthermostatic asopposed to bucket

discharge condensatecontinuously. Use aLCV with a boot asappropriate

Simplified formulae, such as Hazen andWilliams are available for water

Manning equation is used to size gravity flowlines

With recip pumps, design based on maximuminstantaneous or pulsating flow

Steam condensate lines may have high

All drain lines are gravity flow lines

Rules of Thumb

Pump suction line 1 or 2 sizes bigger than inlet nozzle.Should be sized to start standby pump viz n+1 pumps

Tank outflow line 1 or 2 sizes bigger than inlet line

.

But all traps do not open at the same time

If this pipe runs liquid full,vacuum d/s valve may

cause flashing, vibrationand pipe failure.

Use gutter or self-ventingsizing methods

10m


15/44

Liquid Network

Instead of sizing a single line, attimes, you may have to size agroup of pipes forming anetwork

Example: From suction todischarge point of a pump, tocalculate the pump head, horseower and NPSH re uirements


SourceDestinat

ion

Source

Destination

Town water and cooling water supply provide interesting network analysis


16/44

Water Supply Network

Cooling Water Network



Cooling Tower& Pumps

Coolers

Cooling water or hot water/ oil network are classical examples of network programs

Resistance in series R = R1 + R2

Resistance in parallel 1/R = 1/R1 + 1/R2Total R, then flow = Head/ R

Flow

He

ad

Head

Resistance


17/44

Gas Transmission Lines

Steady-state, isothermal gas flow:

Q = 38.77 (Ts/Ps) E ff [(P1^2P2^2)/S Lm TavZav]^0.5 d^2.5

Different equations proposed, all based on empirical data, providedifferent solutions to the transmission factor or ff . To adjustmeasured flow against calculated flow E is tweaked

Special equations are used to size pipelines

1. AGA Equations (a) partially and (b) fully turbulent flow with two differenttransmission factors

2. Weymouth Equation, takes ff as a function of the diameter. Good for shortpipelines as in gathering systems. Good results when compressibility is taken.Not valid in partially developed turbulence

3. Panhandle A for partially developed and Panhandle B for fully turbulent flows

For low pressure lines, Oliphant or Spitzglass Formula may be used


18/44

Comparison of Gas Transmission FactorsThelinked imagecannotbed isplayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.

Results differ widely. Go by what is an accepted practice in your plant


19/44

Two Phase LinesThelinked imagecannotbedisplayed. Thefilemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfileand location.

Baker, Gregory-Aziz-Mandhane ,Taitel-Duckler maps

Two phase lines are difficult todesign and operate

Flow regimes and terrain profileinfluence P, slug size andliquid hold-up

Correlations are usually developed for air-water system in pipes


20/44

Two Phase LinesThelinked imagecannotbe displayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.



Flow regimes - horizontal and vertical

Dispersed

bubble

aerated

turbulent

slug flow

annular

mist



21/44

Two Phase Lines

Liquid Slugs 4 mechanisms

1. Wave formation at G/L interface in stratified flow. When liquid wavesgrow large and fill the pipe cross section, a slug flow is formed

2. Slugs form due to terrain. Liquid collects at low points and blocks gasflow. Gas pressure rises and blows the accumulated liquid as a slug

3. Changes in inlet flow rate, as during start-up or ramp-up can causeslugs. As flow rate increases, liquid inventory in the pipeline

Several methods are available to predict random and pigging slugs

1. Greskovich - Shrier and Brill methods for calculating wave induced slugs

2. Schmidt for terrain generated slugs

3. Cunliffe for inlet flow rate generated slugs and

4. McDonald and Baker method for analyzing pigging dynamics

,

4. Pigging can cause large slugs as the liquid inventory of the line isswept ahead of the pig


22/44

CONGRATULATIONS

Now you are an Expert in Plumbing


23/44

Question 1

With head or supply pressure remaining the same, how muchthe flow will increase when you double the pipe size

1. Will remain the same

2. Will double

3. Will quadruple

Let us check it out if Expert1 is really good in training as he claims


24/44

Question 2

A centrifugal pump designed for 500 m/h and 10 bar head,will always deliver it

1. True.

2. False.

Looks like, Expert1 is really good in training as he claims


25/44

Question 3

A recip pump designed for 50 m/h and 10 bar head, willalways deliver it

1. True.

2. False.

Thanks for helping to keep my reputation high!!


26/44

Sizing in Excel

Enter data


27/44

Excel for sizing

You can use Excel toperform simple linesizing, pump sizingand distribution

network calculationsLine Size

Pump Size

Create your first line sizing workbook

Excel allows you to study different sizes, take output toa Line List, interact with project database.

You can link your simulation output to Excel andautomate the task.

The possibilities really are endless.

Network Analysis


28/44

Be kind to your users: start with design basis

When you write yourprogram, its a goodidea to provide theformulae and criteria

for selection.

Let us look at a typical Excel sheet

Make your workbook user friendly

This way, anyone who shares your worksheet canunderstand what it all means (and you can understand ityourself, later on).


29/44

Lesson 3

Process Piping

Engineering Guidelines


30/44

Standard Pipes

Min pipe size = 2 toavoid broken pipes onimpact

Pipes come in standard diametersand wall thickness

Smaller diameter pipes can holdmore internal pressure.

Generally flanges limit theallowable pressure


Small bore piping safety engineers nightmare

Allowable Working Pressures - ASTM A106, grade B seamless pipe - PetroleumRefinery Piping Code to ANSI B31.3-2002Corro allow = 0.05 at 200F

2 Standard Schedule 40 1,469 psig 150# Flange 260 psig8 1,09824 Sc 20 282


31/44

Piping

Some clients opt for full rating,that is upping designconditions to suit, flange rating

Lines are hydrotested, exceptlarge low pressure lines thatare pneumatically tested.Molten K and Na lines are nothydrotested to avoid explosionon contact with water in

Size pipes

Based on operating pressure and temperature,decide design pressure and temperature

Based on selected material, then decide ANSI

flange rating 150 ~ 1500# and ID

Decide on steam/ electrical tracing and hot /cold/ noise insulation requirements

The task is not over with finding diameter.

Design temperature shall consider site black body temperature as a minimum.Steam traced lines shall consider steam condensing temperature. Designminimum temperature shall consider low temperature reached on blowdown.

Design pressure shall consider vapor pressure of LPG at max site temperature,pipe shut-off head, upstream PSV set point and full/ half vacuum as applicable.

Pipes numbered with Sequence No - ANSI Rating - Material code - Insulation

p ng w a es con ons


32/44

Piping

1. Mark gravity flow lines, linesthat should slope or shouldnot have pockets, clearly.

2. Tap off from top

3. Min length for meter runs

and vessel inlet

4. 2 pressure equalisationvalves are given acrossvalves >4 to avoid opening

Check access to valves, instruments and samplepoints

Check slope and no pocket requirements

In liquid lines with slurry, sand or polymer solution,

ensure LR bends, flushing points and cleaningaccess

Symmetrical piping where equal flow required

Piping will locate valves such as control valve andPSV where maintenance access is available. This mayvoid desired slope or inlet pressure drop requirements.

Check piping 3D drawings of all PSV, thermosyphonand pump inlet lines

Spec blinds should be in horizontal runs

valves against high P, that

could result in high velocityand seat cutting/ damage

5. Check high point vents andlow point drains.

6. Eccentric reducers flat ontop in pump suction but atbottom u/s of control valves

,

valves and flow orifices/ turbine meters

The task is not over with finding diameter.


33/44

Piping

Usually piping class decides:

Material of construction

Piping type - seamless, ERW, forged or cast

Pipe schedule (wall thickness) / ANSI Rating

Thelinked imagecannotbed isplayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfile and location.Thelinked imagecannotbedisplayed. Thefilemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfileand location.

Thelinked imagecannotbe displayed.T hefilemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.

Thelinked imagecannotbedisplayed. Thefilemay havebeen moved,renamed,or deleted.Verify thatthe link pointsto thecorrectfileandlocation.

Pipe Fittings

Plant piping is usually welded to minimize leaks.

Bends and reducers are usually welded

Flanged (bolted) connections are used to take out a component that may requireservicing e.g relief valve, control valve


34/44

Piping

Piping class also decides:

Flange - slip on, weld neck

Facing - Flat FF, Raised Face RF, Ring Type Joint RTJ

Pipe schedule (wall thickness) / ANSI Rating

Corrosion allowance

Type of valves ball, gate, globe

S ecs for askets, bolts etc


Thelinked imagecannotbe displayed. Thefilemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfileand location.

Thelinked imagecannotbe displayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfile andlocation.

Slip-on

Construction requirement like, stress relieving, radiography, dyepenetration, hardness test for welding etc


Thelinked imagecannotbedisplayed. Thefilemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfileandlocation.



Raised Face RTJ

Pipe Fittings


35/44

Insulation

Heat or cold loss to conserve energy

Personnel protection to avoid injury on accidentalcontact

Noise or vibration reduction, in high velocity/compressor piping

Insulated pipes are covered with vapor barriers andmetal casing as required


Insulation pays back in 3 months

What type ofinsulation?

Insulation comes inpreformed shapes,mattress or loose.

Foot traffic usually damages yard piping insulationThelinked imagecannotbe displayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.



36/44

Heat tracing

Steam or electrical resistance orself-limiting electrical tracing

1. To maintain temperature toavoid congealing or wax

deposition2. In intermittent operation lines

3. To avoid cooling and

Thelinked imagecannotbedisplayed. Thefilemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfileand location.Thelinked imagecannotbe displayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.

Steam tracing requires steam supply and condensate collection headers

and gas to glycol dehydrationSteam Tracing Number of tracers:

General: 1 for 2-4; 2 for 6-20. Solidification 25-65C: 1 for 2-3; 2 for 4-8.Solidification 65-150C: 2 for 2; 3 for 4-8; 6 for 10-12; 8 for 14-18.

Max run length is 50m for . 1 steam header for 3-5 tracers; 2 for 16-30.Condensate header is of same size.

Steam Vs Electrical: Capex: 0.3-0.6 : 1; Opex: 2-20 : 1


37/44

Heat tracingThelinked imagecannotbed isplayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.


Steam tracing requires steam supply and condensate collection headers

H i


38/44

Heat tracing

Thelinked imagecannotbed isplayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrectfile and location.Thelinked imagecannotbe displayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.

Electrical resistance heaters canheat fluids during start-up

Self-regulating tapes requiredtemperature during shutdown/

normal operation



Electrical tracing is relatively simple

V l


39/44

Valves

Service decides type ofvalve

Shut-off: Ball, Gate, Plug,Butterfly and diaphragm

Throttling: Angle, globe,needle

Check: Swing, lift, pistonand foot

Gate:

Rising stem in non-corrosive;non rising steam in waterservice

Solid Vs split wedge. Split cantake care of thermalcontraction on cooling

Valves help regulate or isolate fluid flow

u por

open Not quick acting

Takes more space

Not good in slurry service

Install vertically to avoid gatefalling in closed position


V l


40/44

Valves

Globe Good for throttling

Install vertically

Angle

In high P serviceDiaphragm

Made of elastomer

Good for slurr

Ball or Plug

Ball valves widely used in upstreamindustry; gate in d/s

Quick closing

Limited to


41/44

Check valves

Swing checkFull unrestricted flow. No good in pulsatingflow

Wafer check - similar to butterfly. Good for

pulsating flow. No chatteringLift or piston check - similar to globe. Good for

high velocity (gas) flow



,

lead to backflow, rupture and fatal incidents




Check valves minimize back flow. All valves leak............!

Remote operated valves


42/44

Remote operated valves

Remote operated valves can beused to isolate an equipment orsection of a plant remotely.

They are usually operated by a

motor (MOV) or electricalsolenoid (SOV) or air / hydraulicactuators

ROVs help quick isolation, shutdown and blowdown bringing the plant to a safe state

For quick opening and closing; Battery limit

Emergency shutdown.

For large valves - 10 (150~300#), 6 (600~1500#)

ROVs can be automated to close on high level or pressureThelinked imagecannotbed isplayed.The filemay havebeen moved,renamed,or deleted.Verify thatthelink pointsto thecorrect fileand location.

Spectacle blinds


43/44

Spectacle blinds

Note: All valves,including check valvesleak in service.

To provide positive isolation, usually for entryinto confined spaces and in hazardousservices

Spades are used in small bore pipes (


44/44

Thank you

Trust you found it interesting andof value .

Documents

Process Design Training Pipe Sizing