Piping Fundamentals - For Fresh Engineers

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Piping Fundamentals For Fresher Engineers
Piping System - What is that? Concept Layout
Development Piping Components their access
requirement. Straight length requirements. Ori
entation of various tapings, components,
etc. Piping Drains Vents Insulation. Mater
ial Sizing Critical piping system
consideration. Pipe Stress Analysis. Pipe
Supports
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Piping Fundamentals For Fresher Engineers
Let us first Discuss about WHAT IS PIPE! It is a
Tubular item made of metal, plastic, glass etc.
meant for conveying Liquid, Gas or any thing that
flows. It is a very important component for any
industrial plant. And its engineering plays a
major part in overall engineering of a Plant. In
next few pages we shall try to familiarize about
pipe and its components.
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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.
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.
We now have to complete the end connections.
These, in piping term, we call TERMINAL
CONNECTIONS.
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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 we need 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 the flowing 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.
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
INSTRUMENTS in the pipeline.
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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 SUPPORT the
pipe/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 OTHER types 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 and Instrumentation Drawing, in
  short PID. For PID generation we use SPPID
  software.
• By this time you have already come to know that
  while we prepare PIDs in SPPID, we enter all
  the pipe lines system information in the drawing.
• So the SPPID drawing is an Intelligent drawing
  which under its surface carries all the
  information about a pipe like, Pipe size, Flowing
  Fluid, etc.
• Let us see a PID prepared in SPPID

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This is screen picture of PID made by SPPID If
we click on any line it will show the Data
embedded.
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After the PID is ready we start the layout work.
Here we carryout pipe routing / layout in
Virtual 3D environment.
We use PDS 3D software 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.

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• While carrying out pipe routing we also need to
  consider the following
• Valves, strainers, instruments on the pipe should
  be easily accessible.
• If needed separate ACCESS PLATFORMS to be
  provided to facilitate these.
• Desired location and orientation of valves /
  instruments and other pipe components 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 LENGTH of pipe
  for some components to be maintained, like for
  flow orifice we need to provide 15 times diameter
  straight pipe length at upstream of orifice and 5
  times diameter straight at down stream of orifice.

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• 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 Valve is
  provided at the top most point of the pipeline.

• Also arrangement is kept in the pipeline so that
  liquid can be drained out if required.
• To achieve this a DRAIN connection with Valve is
  provided at the lowest point of the pipeline
• Pipes are also slopped towards low points.

Let us look into typical Vent and Drain
arrangement in a pipeline
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This is a 3D model of Feed water line along with
pumps and other accessories
Let us have a look into a piping model done by
PDS 3D
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• INSULATION - When hot fluid flows through pipe
  then generally pipe is insulated.
• There are two primary reasons for insulating the
  pipe carrying hot fluid.
• Containing the heat inside the pipe. Insulation
  preserves the heat of the fluid. It is called Hot
  Insulation
• Personnel safety, so that people do not get burn
  injury by touching hot surface of pipe. It is
  called Personnel Protection Insulation

INSULATION

• Cold pipes are also insulated
• Cold or chilled fluid carrying pipes are
  insulated to prevent heating of cold fluid from
  outside. It is called Cold Insulation.
• Some times cold pipes are insulated to prevent
  condensation of atmospheric water vapor on pipe
  surface. It is called Anti-Sweat Insulation.

• Other types of Insulation
• When gas flows through pipes at high velocity, it
  creates noise. In such cases pipes are insulated
  to reduce noise. It is called Acoustic
  Insulation.
• Some times pipe and its content are heated from
  outside, by heat tracing element. In that case
  pipe along with heat tracing element are
  insulated to conserve the heat of the tracer. It
  is called Heat Tracing Insulation.

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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 of insulation
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Piping Calculations
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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.

CRITICAL PIPING

• Steam pipes run at very high temperature and the
  hot pipes expand. We have to built 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 and mandatory
  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

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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 various loading 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.

PIPE STRESS ANALYSIS

• 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.

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PIPE STRESS ANALYSIS

• 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 analysis software
• 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.

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Types of Pipe Supports

• 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 of restrain 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.

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Some Special Considerations for Piping

• 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 than1 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 pipe
  carrying 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 Protection of 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 below freezing.
• 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.

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We have come to the End of Session. Hope you have
gathered the fundamentals on the subject of
Piping