Upload
girish-babu
View
230
Download
0
Embed Size (px)
Citation preview
8/2/2019 Piping Basics 1
1/29
8/2/2019 Piping Basics 1
2/29
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.
Piping FundamentalsFor Fresher Engineers
8/2/2019 Piping Basics 1
3/29
In any plant various fluids flow through pipesfrom one end to other.
Now let us start with a plant where we see threetanks.
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 thefluids from Tank-1 to Tank-2 and Tank-3
LET US BRING THE PIPES.
8/2/2019 Piping Basics 1
4/29
We have just brought the pipes, now weneed to solve some more problems.
Pipes are all straight pieces.
We need somebranch
connections
We need some bendconnections
To solve theseproblems we need thepipe components,which are called
PIPE FITTINGS
8/2/2019 Piping Basics 1
5/29
These are the pipe fittings,
There are various types of fittings for variouspurposes, some common types are -
Elbows/Bends, Tees/Branches,Reducers/Expanders, Couplings, Olets, etc.
Anyway, the pipes andfittings 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.
8/2/2019 Piping Basics 1
6/29
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-1to other tanks.
We need some arrangement to stop theflow if needed
To control the flow in a pipe line weneed to fit a special component.
That is called - VALVE
8/2/2019 Piping Basics 1
7/29
There are many types of valves, categorizedbased on their construction and functionality,
Those are - Gate, Globe, Check, Butterfly, etc.
Other than valves another importantline component of pipe line is a filter,
which cleans out derbies from theflowing fluid. This is called a
STRAINER
8/2/2019 Piping Basics 1
8/29
Here we see a more or less functional pipingsystem, with valves and strainer installed.
Let us now investigate some aspects of pipeflexibility.
If this tank nozzleexpands, whenthe tank is hot.
In such case we need to fit a flexiblepipe component at that location,
which is called an EXPANSIONJOINT
8/2/2019 Piping Basics 1
9/29
When some fluid is flowing in a pipe we mayalso like know the parameters like, pressure,temperature, flow rate etc. of the fluid.
To know these information we need
to install INSTRUMENTS in thepipeline.
8/2/2019 Piping Basics 1
10/29
There are various types instruments to measure variousparameters. Also there are specific criteria for installationof various pipe line instruments.
Next we shall lookinto how to
SUPPORT thepipe/and its
components.
8/2/2019 Piping Basics 1
11/29
Here are some of the pipe supporting arrangements.There can be numerous variants. All depend onpiping designers preference and judgement.
Let us see some OTHER types of supports
8/2/2019 Piping Basics 1
12/29
8/2/2019 Piping Basics 1
13/29
8/2/2019 Piping Basics 1
14/29
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 SPP&IDsoftware.
By this time you have already come to know that while we prepare P&IDs inSPP&ID, we enter all the pipe lines system information in the drawing.
So the SPP&ID 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 SPP&ID
8/2/2019 Piping Basics 1
15/29
8/2/2019 Piping Basics 1
16/29
This is screen picture of P&ID made by SPP&ID
If we click on any line it will show the Data embedded.
8/2/2019 Piping Basics 1
17/29
After the P&ID is ready we start the layout work.
Here we carryout pipe routing / layout in Virtual 3D environment.
Preferable
Not Preferable
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 minimumchange in direction.
Should not hinder any normal passage way. Also should not encroach any
equipment maintenance space.
8/2/2019 Piping Basics 1
18/29
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 pipecomponents are to be checked and maintained, like some valves or strainerscan only be installed in horizontal position.
Specific requirements for instrument installation to be checked, liketemperature 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 tobe maintained, like for flow orifice we need to provide 15 times diameterstraight pipe length at upstream of orifice and 5 times diameter straight at downstream of orifice.
Example of Straight length requirement for Flow Orifice
8/2/2019 Piping Basics 1
19/29
Also arrangement is kept in thepipeline so that liquid can bedrained out if required.
To achieve this a DRAINconnection with Valve is provided
at the lowest point of the pipeline Pipes are also slopped towards low
points.
For Pipeline which shall carry liquid, we have to make sure that all air is allowedto 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 pointof the pipeline.
Let us look
into typicalVent andDrainarrangementin a pipeline
8/2/2019 Piping Basics 1
20/29
Let us have a look into a piping model done by PDS 3D
This is a 3D model
of Feed water linealong with pumps
and otheraccessories
8/2/2019 Piping Basics 1
21/29
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
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 toconserve the heat of the tracer. It is called Heat Tracing Insulation.
8/2/2019 Piping Basics 1
22/29
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, CellularGlass (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 theouter surface of insulation are protected with Aluminum sheet or GI sheetcladding.
Have a look at howpipes are insulated,and general
components ofinsulation
Pipe Material Selection - to select appropriate pipe material based on flowing fluid property.
8/2/2019 Piping Basics 1
23/29
Pipe Sizing Calculation - to select required pipe diameter based on velocity and pressure drop.
Find outFlow volumeper second
Check VelocityAllowable per
second
Calc. flow arearequired and
Pipe size
Calc. Press.Drop for that
Pipe size
Check Press.Drop meets
Press. Budget
PipeSizeOK
YES
IncreasePipe Size
NO
Pipe Material Selection to select appropriate pipe material based on flowing fluid property.
Find out typeof Fluidflowing
Check Pipelife
Expectancy
Select suitableMaterial per
practice (Note-1)
Check Mat.Listed in
Design Code
PipeMaterial
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 materiallisted.
Find outFluid 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
Find out
Fluid Temp.& Pressure
8/2/2019 Piping Basics 1
24/29
In Power plant there are some piping which carries steam at high pressure andtemperature. 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 towithstand the high pressure and may be also high temperature.
As these pipes carry the main system fluid of the power plant, they are giventhe 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 expansionforce is absorbed within the piping.
Also there should be enough flexibility in these pipe routing so that high loadsare 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
8/2/2019 Piping Basics 1
25/29
Pipe Stress Analysis
We have already seen that some of the pipes are subjected to high pressureand 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 andfind 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 theequipment connected to the pipe. This loading are to be within acceptablelimits of the equipment suggested by the vendors.
We also find out the pipe growth due to change in temperature and need tokeep the movement of pipe within acceptable limits.
Pipe Stress Analysis is an Interactive and Iterative process. Each step ischecked
If a check fails we have to go back, modify the layout and restart the analysis.
PIPE STRESS ANALYSIS
8/2/2019 Piping Basics 1
26/29
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 Hammerload
Any other load on the piping
Tools we use
PIPSYS - is an integrated pipe stressanalysis module of PLADES 2000
CEASER - Commercial Piping analysissoftware
There are many other commercial softwareavailable
Outputs
Stress of the pipe at various loadingconditions
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.
Types of Pipe Supports
8/2/2019 Piping Basics 1
27/29
Types of Pipe Supports
In the beginning of this discussion wetalked about various types of pipe
supports. Here is some elaboration
There are three general types
Rigid type (no flexibility in thedirection of restrain)
Spring type (Allows pipemovement in direction ofloading)
Dynamic Support (Degree ofrestrain depends on accelerationof load)
There are two types of springsupport
Variable load type, here support
load changes as the pipe moves.
Constant load support, the loadremains constant within somerange of movement.
Constant Load Spring
Variable Spring
Rigid
Hanger
Rigid
Support
Dynamic Support,Snubber
Rigid Support
Some Special Considerations for Piping
8/2/2019 Piping Basics 1
28/29
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 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 Protection of outdoor Piping:
In the areas where the ambient temperature goes below freezing there is a possibility thatthe 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 theambient temperature goes down. Pipes are insulated over the heat tracing coils.
Heat tracing can also be done by winding Steam tubes around main pipes.
8/2/2019 Piping Basics 1
29/29
We have come to the End of Session.
Hope you have gathered the fundamentals
on the subject of Piping