Piping.ppt

8/13/2019 Piping.ppt

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Power Plant FundamentalPiping SystemPiping System - What is that?

Concept - Layout Development Piping Components & their access requirement. Straight length requirements. Orientation of various tapings, components, etc. Piping Drains & Vents Insulation. Material & Sizing, PDT/VDT selection. Critical piping system consideration. Pipe Stress Analysis.

Pipe SupportsSpecial Considerations

Piping Designers Input Output GET-DET Training Prog.,2003-Somnath Kundu1


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Let us first Discuss about WHAT IS PIPEPIPING SYSTEM

It is a Tubular item made of metal,plastic, glass etc. meant for conveyingLiquid, Gas or any thing that flows.It is a very important component for anyindustrial plant. And its engineering playsa major part in overall engineering of aPlant.In next few pages we shall try tofamiliarize about pipe and itscomponents.


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PIPING SYSTEMNow we will try to understand stepby step how a piping system isformed based on the requirements

We shall start with a plane whitesheet


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This is the plane white

sheet we start with

Let us start drawing a

simple piping system

In any plant various fluids flow through pipes

from one end to other.

Now let us start with a plant where we see three

tanks.

Tank-1, Tank-2 and Tank-3

We have to transfer the content of Tank no. 1 to

the other two tanks.

We will need to connect pipes to transfer the

fluids from Tank-1 to Tank-2 and Tank-3

LET US BRING THE PIPES.


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We have just brought the pipes, now we

need to solve some more problems.

Pipes are all straight pieces.

We need some

branch

connections

We need some bend

connections

To solve these

problems we need the

pipe components,

which are called

PIPE FITTINGS


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These are the pipe fittings,

There are various types of fittings for various

purposes, some common types are -

Elbows/Bends, Tees/Branches,

Reducers/Expanders, Couplings, Olets, etc.

Anyway, the pipes and

fittings are in place, but the

ends are yet to be joined withthe Tank nozzles.

We now have to complete theend connections.

These, in piping term, we call

TERMINAL CONNECTIONS.


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These are flanged joints

This is a welded joint

So far this is a nice arrangement.

But there is no control over the flow from Tank-1

to other tanks.

We need some arrangement to stop the

flow if needed

To control the flow in a pipe line weneed to fit a special component.

That is called - VALVE


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There are many types of valves, categorized

based on their construction and functionality,

Those are - Gate, Globe, Check, Butterfly, etc.

Other than valves another important

line component of pipe line is a filter,

which cleans out derbies from theflowing fluid. This is called a

STRAINER


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Here we see a more or less functional piping

system, with valves and strainer installed.

Let us now investigate some aspects of pipe

flexibility.

If this tank nozzle

expands, when

the tank is hot.

In such case we need to fit a flexible

pipe component at that location,

which is called an EXPANSION

JOINT


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When some fluid is flowing in a pipe we may

also like know the parameters like, pressure,

temperature, flow rate etc. of the fluid.

To know these information we need

to install INSTRUMENTSin thepipeline.


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There are various types instruments to measure various

parameters. Also there are specific criteria for installation

of various pipe line instruments.Next we shall look

into how to

SUPPORTthepipe/and its

components.


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Here are some of the pipe supporting arrangements.

There can be numerous variants. All depend on

piping designers preference and judgement.

Let us see some OTHERtypes of supports


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We have just completed a pipe line design.

We shall rewind and check how it is really done in practice.

First the flow scheme is planned,

1) What, 2) From what point, 3) To which point

Pipe sizes are selected, pipe material and pipe wall thickness are selected.

Types of Valves are planned

Also the types of instruments required are planned

We represent the whole thing in a drawing which is called Piping andInstrumentation Drawing, in short P&ID. For P&ID generation we use CADME

software.

By this time you have already come to know that while we prepare P&IDs in

CADME, we enter all the pipe lines system information in the drawing.

So the CADME drawing is an Intelligent drawing which under its surface carries allthe information about a pipe like, Pipe size, Flowing Fluid, etc.

Let us see a P&ID prepared in CADME


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This is screen picture of

P&ID made by CADME

If we click on any line it will

show the Data embedded.


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These are the embedded

data of this line


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Let us look in to a simple P&ID for understanding of P&IDs.

This is part

P&ID for DM

water transfer

system

Click to see Iso


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After the P&ID is ready we start the layout work.

Preferable

Not Preferable

We use PDWBsoftware to route piping in the Plant virtual 3D space.

We call this as piping modeling or physical design.

While development of piping layout we have to consider the following

Piping from source to destination should be as short as possible with minimum

change in direction.

Should not hinder any normal passage way. Also should not encroach any

equipment maintenance space.

Here we carryout pipe routing / layout in Virtual 3D environment.


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While carrying out pipe routing we also need to consider the following

Example of Straight length requirement for Flow Orifice

Valves, strainers, instruments on the pipe should be easily accessible.

If needed separate ACCESS PLATFORMSto be provided to facilitate these.

Desired location and orientation of valves / instruments and other pipecomponents are to be checked and maintained, like some valves or strainers

can only be installed in horizontal position.

Specific requirements for instrument installation to be checked, like

temperature gauge can not be installed in pipe which is less than 4 inch in size.

Specific requirements of STRAIGHT LENGTHof pipe for some components to

be maintained, like for flow orifice we need to provide 15 times diameterstraight pipe length at upstream of orifice and 5 times diameter straight at down

stream of orifice.


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Also arrangement is kept in the

pipeline so that liquid can be

drained out if required.

To achieve this a DRAIN

connection with Valveis provided

at the lowest point of the pipeline

For Pipeline which shall carry liquid, we have to make sure that all air is allowed

to vent out of the line when the line is filled with liquid.

To achieve this a VENT connection with Valveis provided at the top most point

of the pipeline.

Let us look

into typicalVent and

Drain

arrangement

in a pipeline

Pipes are also slopped

towards low points.

Pipe line Vents

and Drains


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Let us have a look into a piping model done by PDWB

The Term PDWB stands forPiping Design Work Bench


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This is a PDWB

model of Feedwater line along

with pumps and

other accessories

L t l k i t Pi i I t i D i

L t l k i t Pi i


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Let us look in to a Piping Isometric Drawing

From the Piping 3D Model we create the Piping Isometric drawings.

These piping isometric drawings are used to fabricate and erect the piping

at job site.

Let us look in to a Piping

Isometric Drawing

From the Piping 3D Model

we create the Piping Isometric

drawings.

These isometric drawings

are used to fabricate

and erect the piping

at job site.

This is part

Isometric for DM

water transfersystem

Click to see P&ID


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INSULATION MATERIAL Th i l ti t i l h ld b b d d t f h t


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INSULATION MATERIAL- The insulating material should be bad conductor of heat.

There are two basic categories

1) Fibrous Material, which has large voids full of air between fibers - Cork, Glass Wool,

Mineral Wool, Organic Fibers. Note stagnant air is a bad conductor.

2) Cellular Material, which has closed void cells full or air - Calcium Silicate, Cellular

Glass (Foam Glass), Polyurethane Foam (PUF), Polystyrene (Thermocol), etc.

Some times Cast material like Cement Plaster or Plaster of Paris are also used.

INSULATION CLADDING - Insulation materials are generally soft or fragile. So the

outer surface of insulation are protected with Aluminum sheet or GI sheet

cladding.

Have a look at how

pipes are insulated,

and general

components ofinsulation

Pipe Material Selection - to select appropriate pipe material based on flowing fluid property.


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Pipe Sizing Calculation - to select required pipe diameter based on velocity and pressure drop.

Find out

Flow volume

per second

Check Velocity

Allowable per

second

Calc. flow area

required and

Pipe size

Calc. Press.

Drop for that

Pipe size

Check Press.

Drop meets

Press. Budget

Pipe

Size

OK

YES

Increase

Pipe Size

NO

Find out type

of Fluid

flowing

Check Pipe

life

Expectancy

Select suitable

Material per

practice (Note-1)

Check Mat.

Listed in

Design Code

Pipe

Material

OK

YES

See Note-1

NONote-1 : Material is selected per past experience with cost in

mind and per material listed in design code. If material isnot listed in code we may select next suitable material

listed.

Find out

Fluid Temp.

& Pressure

Pipe Thickness Selection - to select appropriate pipe thickness based on flowing fluid property.

Select Mat.

& Diameteras above

Decide on

Corrosionallowance

Calc. Pipe

Thickness perCode (Note-2)

Check if S&L

PDT matchesrequirement

Selected

S&L PDTfor Project

YES

Create new

PDT for

Project

NONote-2 : S&L has a standardized sets of piping materials suitable for various

fluids and various service conditions, These are call - Piping Design

Table (PDT). If calculated pipe thickness do not match with standard

PDT, Project Specific PDT are created with PDTSsoftware.

Find out

Fluid Temp.& Pressure

Created

new PDT

for Project


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This is an example of

project specific PDT

In Power plant there are some piping which carries steam at high pressure and


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In Power plant there are some piping which carries steam at high pressure and

temperature. And also there are piping which carries water at High pressure.

These pipes carries the main cycle steam and water of the steam power plant.

These pipelines are call the CRITICAL PIPING.

Very special care are taken for design of these piping.

First the pipe material selection for such piping is very important as it has to

withstand the high pressure and may be also high temperature.

As these pipes carry the main system fluid of the power plant, they are given

the right of way, and routed at beginning of the overall plant layout.

Steam pipes run at very high temperature and the hot pipes expand. We have tobuilt in flexibility in the high temperature pipe routing so that the expansion

force is absorbed within the piping.

Also there should be enough flexibility in these pipe routing so that high loads

are not transferred to the nozzles of Turbine or Pumps

There are many recognized international codes which lay down guide lines andmandatory requirements for design of such piping.

The most important codes used by power plant piping engineers are

ASME ANSI B31.1- Power Piping Code & IBR - the Indian Boiler Regulation

Pipe Stress Analysis


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Pipe Stress Analysis

We have already seen that some of the pipes are subjected to high pressure

and high temperature. Also pipes carry the load of the flowing fluid.

We need to check and confirm the pipe is not going to fail with these loading.

This process of checking the stress developed in the piping due to variousloading is called Pipe Stress Analysis/Flexibility analysis.

In the process of Analysis we apply various postulated loading on the pipe and

find out the stress resulted from these loading.

Then we check with governing codes if those stresses generated are

acceptable or not. We check support load & movement for various loading condition.

We also check out the terminal point loading generated from pipe to the

equipment connected to the pipe. This loading are to be within acceptable

limits of the equipment suggested by the vendors.

We also find out the pipe growth due to change in temperature and need to

keep the movement of pipe within acceptable limits.

Pipe Stress Analysis is an Interactive and Iterative process.Each step is

checked

If a check fails we have to go back, modify the layout and restart the analysis.

PIPE STRESS ANALYSIS


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S SS S S

Inputs

Geometric layout of Pipe

Pipe supporting configuration

Pipe Diameter and Thickness

Pressure inside Pipe

Cold and Hot temperatures of Pipe

Weight of Pipe and insulation

Weight of carrying Fluid

Pipe material Property (Youngs Modulus,

Thermal Expansion Coefficient)

Thrust on pipe due to blowing wind.

Thrust on pipe due to earthquake

Load of Snow on pipe

Any transient loading like Steam Hammer

load

Any other load on the piping

Tools we use

PIPSYS - is an integrated pipe stress

analysis module of PLADES 2000

CEASER - Commercial Piping analysissoftware

There are many other commercial software

available

Outputs

Stress of the pipe at various loading

conditions

Load at various supports and restrains.

Movement of pipe at support locations

Pipe terminal point loading.

Codes and Standards In general Power Plant Piping have to

comply stipulations of ASME ANSI B31.1

In India Power cycle Piping to comply IBR

code requirements.

PIPSYS - the analysis module of PLADES 2000


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y

It is a very powerful and flexible,

integrated stress analysis

module of PLADES 2000.

We work in PIPSYS in closeinteraction with PDWB piping

Models.

Here are some of the Screen

views

Opening screen - It has a Nick

name - The Blue Screen

Geometry Plot screen - It

shows the model geometry

Types of Pipe Supports


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yp p pp

In the beginning of this discussion we

talked about various types of pipe

supports. Here is some elaboration

There are three general types

Rigid type (no flexibility in the

direction of restrain)

Spring type (Allows pipe

movement in direction of

loading)

Dynamic Support (Degree ofrestrain depends on acceleration

of load)

There are two types of spring

support

Variable load type, here support

load changes as the pipe moves.

Constant load support, the load

remains constant within some

range of movement.

Constant Load Spring

Variable Spring

RigidHanger

RigidSupport

Dynamic Support,

Snubber

Rigid Support

Some Typical Pipe Support Drawings


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y g

Here is some typical Pipe support drawings showing some typical vendor supplied

component numbers.(See Support Catalogues in G drive g:\snl\techdocs)

Some Pipe Support Hardware DetaIs


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Here is some typical Pipe support hardware Pictorial views

Some Special Considerations for Piping


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When pipes are routed UNDER GROUND(Buried) following points to be kept in mind:

Minimum pipe size to be routed under ground shall be not less than 1 inch.

Avoid flange joint in U/G piping.

Keep in mind if pipe leaks U/G, it will be difficult to detect, so avoid U/G routing of pipecarrying hazardous fluid.

Pipe to be laid below Frost Zone at areas where ambient temperature goes below freezing.

U/G, Buried piping should be properly protected from corrosion.

Pipe may be properly wrapped and coated to prevent corrosion.

Or U/G piping be protected by using Cathodic protection.

Freeze Protectionof outdoor Piping:

In the areas where the ambient temperature goes below freezing there is a possibility that

the liquid content of pipe may freeze while the plant is under shut down.

For similar case pipes are wrapped with heat tracing elements to maintain the content

temperature above freezing (around 4 deg. C) even when the ambient temp. is belowfreezing.

Electric Heat tracing is done by wrapping electric coil around pipe, which turns on as the

ambient temperature goes down. Pipes are insulated over the heat tracing coils.

Heat tracing can also be done by winding Steam tubes around main pipes.

Piping Designers Input Output


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INPUTS TO PIPING DESIGNER

From Process

What Fluid

From Where to Where.

Pressure, Temp. and Flow rate.

Type of Flow control.

From Project

What Project Specific

Requirements.

Any existing facility or U/G work

From MechanicalEquipment Locations and

terminal parameters

From Civil

Locations of foundations and

structures

From C&I

Types of control and instrument

installation, tapping requirements

From Electrical

Locations of electrical equipment,

cable tray and bus ducts

OUTPUT OF PIPING DESIGNER

To Process

Final Pipe Size and Pressure

class

Piping system Material

To Project

Plant Interface drawing

Interface with existing facility

To Mechanical

Pipe layout both A/G and U/G

Equipment terminal LoadingTo Civil

Locations of Pipe supports

Pipe support loading to

foundations and structures

Wall Penetrations

To C&ILocations instruments, control

valves on piping isometrics

To Electrical

Pipe layouts both A/G and U/G to

match cable, duct bank routing


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Congratulations

!!!

We have come to the

End of Session for Piping

Hope you have gathered enough knowledge

to talk intelligently

on the subject of piping

and also start work on piping

Date post:	04-Jun-2018
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