Design of Piping System
Piping System Design - 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
Critical piping system consideration.
Pipe Stress Analysis.
Pipe Supports
Pipe Fabrication
Piping Fundamentals –
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 it’s engineering plays a major part in overall
engineering of a Plant.
In next few pages we shall try to familiarize about pipe
and it’s components.
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.
To solve these
problems we need the
pipe components,
which are called
We have just brought the pipes, now we
need to solve some more problems.
Pipes are all straight pieces.
PIPE FITTINGS
We need some
branch
connections
We need some bend
connections
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 with
the Tank nozzles.
We now have to complete the
end connections.
These, in piping term, we call
TERMINAL CONNECTIONS.
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
These are flanged joints
This is a welded joint
To control the flow in a pipe line we
need to fit a special component.
That is called - VALVE
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
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
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.
Next we shall look
into how to
SUPPORT the
pipe/and it’s
components.
There are various types instruments to measure various
parameters. Also there are specific criteria for installation
of various pipe line instruments.
Here are some of the pipe supporting arrangements.
There can be numerous variants. All depend on
piping designer’s preference and judgement.
Let us see some OTHER types of supports
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 P&ID. For P&ID generation we use SPP&ID
software.
By this time you have already come to know that while we prepare P&IDs in
SPP&ID, we enter all the pipe lines system information in the drawing.
So the SPP&ID drawing is an Intelligent drawing which under it’s surface carries all
the information about a pipe like, Pipe size, Flowing Fluid, etc.
Let us see a P&ID prepared in SPP&ID
This is screen picture of P&ID made by SPP&ID
If we click on any line it will show the Data embedded.
After the P&ID 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.
Not Preferable
Preferable
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.
Example of Straight length requirement for Flow Orifice
 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
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
INSULATION - When hot or Cold fluid flows through pipe then generally pipe is
insulated “Hot” or “Cold” insulation respectively.
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
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 it’s 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.
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, Stainless Steel or GI
sheet cladding.
Have a look at how
pipes are insulated,
and general
components of
insulation
Pipe Material Selection - to select appropriate pipe material based on flowing fluid property.
Find out type
of Fluid
flowing
Find out
Fluid Temp.
& Pressure
Check Pipe
life
Expectancy
Select suitable
Material per
practice (Note-1)
Check Mat.
Listed in
Design Code
YES
Pipe
Material
OK
NO
Note-1 : Material is selected per past experience with cost in
mind and per material listed in design code. If material is
not listed in code we may select next suitable material
listed.
See Note1
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
YES
Pipe
Size
OK
NO
Increase
Pipe Size
Pipe Thickness Selection - to select appropriate pipe thickness based on flowing fluid property.
Select Mat.
& Diameter
as above
Find out
Fluid Temp.
& Pressure
Decide on
Corrosion
allowance
Calc. Pipe
Thickness per
Code
 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 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
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.
 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
Inputs
Tools we use
 Geometric layout of Pipe
 PIPSYS - is an integrated pipe stress
analysis module of PLADES 2000
 Pipe supporting configuration
 Pipe Diameter and Thickness
 Pressure inside Pipe
 CEASER - Commercial Piping analysis
software
 Cold and Hot temperatures of Pipe
 There are many other commercial software
available
 Weight of Pipe and insulation
Outputs
 Weight of carrying Fluid
 Stress of the pipe at various loading
conditions
 Pipe material Property (Young’s Modulus,
Thermal Expansion Coefficient)
 Load at various supports and restrains.
 Thrust on pipe due to blowing wind.
 Movement of pipe at support locations
 Thrust on pipe due to earthquake
 Pipe terminal point loading.
 Load of Snow on pipe
Codes and Standards
 Any transient loading like Steam Hammer
load
 Any other load on the piping
 In general Power Plant Piping have to
comply stipulations of ASME ANSI B31.1
 In India Power cycle Piping to comply IBR
code requirements.
Types of Pipe Supports
In the beginning of this discussion we
talked about various types of pipe
supports. Here is some elaboration
Constant Load Spring
 There are three general types
 Rigid type (no flexibility in the
direction of restrain)
Variable Spring
 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.
Rigid Support
 Dynamic Support (Degree of
restrain depends on acceleration
of load)
Rigid Hanger
 Spring type (Allows pipe
movement in direction of
loading)
Dynamic Support,
Snubber
Rigid Support
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.
SPOOL
An assembly of fittings, flanges and pipe that may be
pre-fabricated.
It does not include:
• Bolts
• Gaskets
• Valves
• Instruments
Spool size is limited by transportation
Piping Fabrication
Drawing/Documents for Pipe Work
PURPOSE
THE MAIN PURPOSE OF A DRAWING
IS TO COMMUNICATE INFORMATION
IN A SIMPLE AND EXPLICIT WAY
STAGES OF DRAWINGS
 Issued for information
IFI
 Issued for review
IFR
 Issued for approval
IFA
 Issued for construction
IFC
 Issued for as built
IFAB
DRAWINGS/DOCUMENTS FOR PIPE WORK
 Overall Plot Plan
 Key Plan
 Schematic diagrams
 Flow diagrams
(Process or service)
 Isometric drawings
 Line identification
 Process and Instrumentation
Diagrams (PID)
•
Isometric sketches (ISOS)/spool drawings
•
Cutting Plan
•
Field routing drawings for small bore piping
•
General Arrangement drawings
•
Test Packs
•
As built drawings
•
Process Flow Diagram (Optional)
….contd
•
Pipe Supports Schedule
•
Project Specifications for Fabrication, Welding and
Erection
•
Project Quality Plan (PQP)/Quality Inspection Plans
(QIPs)
•
Material Specifications
•
Stress Relieving Standards
OVERALL PLOT PLAN
INFORMATION ON AN OVERALL PLOT
PLAN
• Battery limit of overall Plot of the Project
• Location of Project Site with reference to any other
known/established facilities
• Plant North, actual north, wind direction.
This information help in erecting the plant
equipment
• General grade level with reference to a known level
for example mean sea level
INFORMATION ON AN OVERALL
PLOT PLAN
• Layout of various units/sections of a project
indicating roads and other facilities within the site
• It also gives the layout of plant equipment within
various units/section of Plant
• It also gives equipment list in various units of the
Project, their elevation
KEY PLAN
INFORMATION ON A KEY PLAN
In addition to the information given in Plot
Plan, Key Plan gives:
• Plant area/classification
• Drawings classification for each
area/block
SCHEMATIC DIAGRAM
Shows
 Path of flow by single lines
 Process equipment shown by simple
figures (rectangle, circle. square etc.)
 Process notes included
Diagram is not to scale
but
Relationships between equipment, piping, process is shown
FLOW DIAGRAM
Un scaled drawing
 Describing the process
(flow sheet)
 State materials to be conveyed
 Specify their flow rates and information
like temperature, pressure etc.
ISOMETRIC DRAWINGS
ISOMETRIC DRAWINGS
• The purpose of an isometric drawing is to show a
three-dimensional picture in one drawing
• It resembles a picture without the artistic details
• The isometric drawing combines the floor plan
and the elevation
• It clearly shows the details and the relationship of
the pipes in a piping installation
• The isometric drawing follows certain rules or
conventions to show three dimensions on a flat
surface
ORTHOGRAPHIC AND ISOMETRIC DRAWINGS
INFORMATION ON AN ISOMETRIC
DRAWING
• ISO Number & Revision
• Orientation – Reference to Project Site – (North).
• Coordinates of Key Reference Items
• Elevation of Piping Sections and their angle with
reference to horizontal (H) and vertical (V).
• Pipe Supports No., type, elevation (T.O.S).
• Reference to other ISOs and GA drawing.
…..contd.
INFORMATION ON AN ISOMETRIC
DRAWING
• MTOs
• Piping class and line number
• Test pressure
• Test media
• Line to be heat traced or not
• P&ID reference
…..contd.
INFORMATION ON AN ISOMETRIC
DRAWING
• Insulation requirement
• In line instruments & valve numbers, size, type
• Painting requirement
• Weld positions (spool b/d to mark FW&SW)
• Welding specifications
• Operating & design temperature & pressure
ISOMETRIC DRAWINGS
LINE IDENTIFICATION
INFORMATION ON A LINE IDENTIFICATION
DIAGRAM
• Size
• Plant number/area
• Fluid – piping service
• Material class
• Coating/Insulation category
• Line sequence number
EXAMPLE OF AN ISOMETRIC
DRAWING NUMBER
Fluid
Plant/Area
Material
ISO
Specification Number
74 / BZ / 6 / 412 / 23-2 -A
Nominal Pipe Size
Line Number
Spool
Number
PROCESS AND
INSTRUMENT DIAGRAM
(P&ID)
Types of Process Diagrams
• Process diagrams can be broken down into two major categories:
1. process flow diagrams (PFDs) and
2. process and instrument drawings (P&IDs)
sometimes called piping and instrumentation drawings.
Process Flow Diagrams (PFDs)
• A flow diagram is a simple illustration to
describe the primary flow path through a
unit.
• A process flow diagram provides a quick
snapshot of the operating unit.
Process Flow Diagram (PFD)
Interpretation of Process Flow Diagram
• Previous Figure is a PFD that shows the basic relationships
and flow paths found in a process unit. It is easier to
understand a simple flow diagram if it is broken down into
sections: feed, preheating, the process, and the final products.
This simple left-to-right approach identify
• where the process starts and where it will eventually end. The
feed section includes the feed tanks, mixers, piping, and
valves.
Contd…
• In the second step, the process flow is gradually
heated for processing. This section includes heat
exchangers and furnaces. In the third section, the
process is included.Typical examples found in the
process section could include distillation
columns or reactors. The process area is a complex
collection of equipment that works together to
produce products that will be sent to the final
section.
Process And Instrument Drawings
(P&IDs)
• A process and instrument drawing is more complex. The
P&ID includes a graphic representation of the equipment,
piping, and instrumentation. Modern process control can be
clearly inserted into the drawing to provide a process
technician with a complete picture of electronic and
instrument systems. Process operators can look at their
process and see how the engineering department has
automated the unit. Pressure, temperature, flow, and level
control loops are all included on the unit P&ID.
Process and Instrument Diagram (P&ID)
Interpretation of P&IDs
• In order to read a P&ID, one needs an understanding of the
equipment, instrumentation, and technology. The next step in
using a P&ID is to memorize your plant’s process symbol
list. This information can be found on the process legend.
Process and instrument drawings have a variety of elements,
including flow diagrams, equipment locations, elevation
plans, electrical layouts, loop diagrams, title blocks and
legends, and foundation drawings. The entire P&ID
provides a three-dimensional look at the various operating
units in a plant.
Process Legends
INFORMATION ON P&ID
• Process flow – direction of flow
• Line numbers, Their terminal points including
equipment connections
• Identification of Field Instruments
• In line instruments/vendor items
• Simple Depiction of Control Strategy
• Design/Operating parameters
SYMBOLS
For example, when two steel plates are joined together into a T shape,
welding may be done on either side of the stem of the T.
The weld symbol distinguishes between the two sides of a joint by using
the arrow and the spaces above and below the reference line.
The side of the joint to which the arrow points is known as the arrow side,
and its weld is made according to the instructions given below the reference line.
The other side of the joint is known as the other side, and its weld is made
according to the instructions given above the reference line.
The below=arrow and above=other rules apply regardless of the arrow's
direction.