guidelines for piping design

7/29/2019 Guidelines for Piping design

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Piping Design Fundamentals

Thomas XavierSr Mechanical Engineer

December 12, 2007


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Piping Design fundamentals

Introduction

Designation of pipe size and thickness

Piping Components

Piping Material

Piping Codes and Standards

Piping Layout

Piping Design bases


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Introduction


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Introduction

Piping system are like arteries and veins of our

bodies. They carry the life blood of the modern

civilization

In a modern city they transport water, waste water,crude oil, natural gas, chemicals, gases, vapors,

solids from one location to another.

Piping includes pipes, flanges, fittings, bolting,

gaskets, valves, pipe supports, pipe hangers, andother items necessary to prevent over pressurization

and over stressing.

Define Piping : ?


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Introduction

Definition of Piping :

Pipe sections when joined with fittings,

valves, and other mechanical equipment

and properly supported by hangers andsupports are called piping.


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Designation of Pipe size andthickness


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Pipe size

NPS Nominal pipe size, without the inch symbol

DN- Diameter nominal Up to size 12 inch the outside diameter is less than the size designator

(i.e. 2,3,4,6....).

Outside diameter of NPS 14 and larger pipe is the same as the sizedesignator in inches.

The inside diameter will depend upon the pipe wall thickness specifiedby the schedule number


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Pipe wall thickness

Schedule is expressed in numbers(5,5S,10,10S,20,20S,30,30S,40,40S,60,80,80S,100,120,140,160)

The higher the schedule number the thickerthe pipe is.

The outside diam is standardized and theinside diam will change based on the

thickness.

The inside diameter will depend upon the pipewall thickness specified by the schedulenumber


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Piping Components


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Piping components

The term pipingrefers to the overall networkof pipes, fittings, flanges, valves and other

components that comprise a conduit system

used to convey fluids.

Piping componentsplays a important role in

the composition and operation of the system.


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Piping componentsPressure Pipe

Steel and alloy pressure piping available in cast, wrought,seamless and seamwelded forms.

Welded and seamless wrought steel pipe is supplied under

ASME B36.10M. SS pipe is supplied conforming to ASME

B36.19M

Commonly specified pipe materials


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Piping components Pipe fittings

Ductile and cast Iron fittings

Cast Iron threaded fittings

Malleable Iron Threaded fittings

Cast Brass and Cast Bronze threaded fittings

Soldered-joint fittings

Cast Iron Flanged Fittings

Cast and Forged Steel and Nickel Alloy Flanged Fittings

Forged Steel Threaded and Socket Welding fittings

Wrought Steel Butt welded fittings


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Piping components

Cast Steel Flanged fittings


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Piping components Forged Steel Threaded / Socket welded fittings


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Piping components

Wrought-steel welding fittings include elbows,

tees, crosses, reducers, laterals, lap joint stub

ends, caps and saddles.

Wrought steel fittings are made to the

dimensional requirements of ASME B16.9

and ASME B16.28.

Fittings made as per ASME B 16.9 is

available in sizes NPS (DN 15) through

NPS 48 (DN 1200) and as per ASME B 16.28

are available in sizes NPS to NPS 24.

Wrought steel butt welded fittings


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Piping components

Wrought steel butt welded fittings


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Piping componentsWrought steel butt welded fittings


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Piping componentsWrought steel butt welded fittings


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Piping componentsStrainers

Wye strainer

Basket strainer

Conical startupstrainer

Air Release Valve

Air/ Vaccum

Release ValveCombination Valve


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Piping componentsExpansion Joint


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Piping componentsFlanges


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Piping componentsGaskets


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Piping componentsJoining Ductile or Cast Iron Pipe


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Piping componentsJoining Ductile or Cast Iron Pipe


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Piping components - ValvesFunction

Stopping flow Allowing flow

Regulating and controlling flow to

fulfill the objectives of the system

Types of valves

Gate valve

Globe valve

Check valve

Ball valve

Plug valve

Butterfly valve

Diaphragm valve

Pinch valve

Pressure relief valve

Control valve


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Piping componentsValves

Classification of valves based on Mechanical motion Linear motion valves Gate, globe, diaphragm, pinch and lift check valves

Rotary motion valves - Butterfly, ball, plug, eccentric and swing check valves

Classification based on valve size

Pressure Temperature Rating

Cold Working Pressure (CWP)Rating (29o C to 38oC )

NFPA Rating

Classification based on Rating

Smaller valves NPS 2 (DN 65 and smaller

Large valves- NPS 2 (DN 65) and larger


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Piping componentsMajor Valve parts

Body

Bonnet or Cover

Bonnet or Cover Bolting

Disc

Valve Trim The removable and replaceable valve Internal parts that come incontact with flow medium

Valve seats, Disc, Glands, Spacers, Guides, Bushings & Internal springs

Non Pressure Retaining partsValve seats, stem, yoke, packing, gland

bolting,

bushing, hand wheel, and valve actuators


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Piping components - Valves

Rising stemGate Valve NonRisingstem

Gate Valve

Wafer type butterfly valve

Flanged butterfly valve


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Flanged endglobe valve Angle globe valve

with screwed ends Needle valve with

screwed ends


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Lift Check valve Flanged Swing check valve

Folding Disc check valve


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Ball valve

Needle valve

Diaphragm valve


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Flanged Safety Valve

Threaded Safety Valve


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Piping components - Actuators

Function of Actuators

Assist in operating of large valves

Assist the operator in operating the valves against high fluid pressure

To reduce the time required for operation

Valve is required to operated from a remote location

When the valve is to attain a position (open or close) in the event of accident

Types of Actuators

Gear Actuators When rim pull exceeds a given value varying between 50lb (22

kgf) to 250 lb (113 kgf)

Electric Motor actuators Pneumatic Actuator

Hydraulic Actuator

Solenoid Actuator


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Piping components Control ValveDefn : They areconsidered the final control elementin an automated andusually very sophisticated control loop.

Aside from the control valve, the loop consists of a transmitter, that

measures the variables (pressure, flow, level or temperature) and a

controller (computer)

Components of a Control Valves Valve body (reciprocating or rotating stem)

Actuating device (spring diaphragm type)

Valve positioner (convert signal to air signal to control position)

Airset or regulator (to supply air pressure to the positioner)


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Piping Materials


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Piping materialsFactors to be considered for selecting materials Code Requirements

Must be suitable for the flow medium

Must be suitable for meeting the temperature and pressure safely during thedesign life.

Operating environmental conditions

Cost

Availability

Carbon and low alloy steel come closest to being the idealconstruction material. Due to the fact that the majority of pipingapplication employ iron based metals, these will be onlyemphasized in this presentation.


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Piping materials

Properties of Metal

Chemical Properties

Mechanical Properties

Physical Properties

Other Properties


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Piping materialsChemical Properties of metal

Chemical properties are the dictated by the various elemental constituency of thesolid. This is usually measured by the relative atomic weight percent of thevarious elements within the material

Steel always contain Carbon, manganese, phosphorous, sulfur and silicon invarying amounts.

Hydrogen, oxygen and nitrogen enter as gases during manufacturing.

To make steel nickel, copper, molybdenum, chromium, tin, antimony etc areadded. Each of this addition causes a specific effect on the steel.


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Piping materials

Physical Properties of metal Density.

Thermal Conductivity

Thermal Expansion

Specific Heat

Mechanical Properties of metal

Modulus of Elasticity (Youngs Modulus).

Yield Strength

Ultimate Tensile Strength

Elongation and Reduction of Area

Hardness

Toughness

Fatigue resistance

Elevated Temperature Tensile and Creep strength


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What is the difference between Codes and Standards?


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What is the difference between Codes and Standards?


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Code ASME B31: Code for Pressure Piping ASME B31.1, 31.2, 31.3, 31.4, 31.5, 31.8, 31.9 & 31.11

ASME performance test codes

NFPA Codes

International Plumbing Codes Uniform Plumbing Codes

Local authority codes etc.


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Standards American National Standard Institiute (ANSI) American Society for Testiing and Materials (ASTM)

American Gas Association

American Petroleum Institute (API)

American Water Works Association (AWWA) American Welding Society (AWS)

Air Conditioning and Refrigeration Institute

American Society of Heating and Refrigerating and Air-conditioning Engineers(ASHRA)

Institute of Electrical Engineers (IEEE)

Instrument Society of America

National Fire Protection Association (NFPA) Publications

Indian (IS), British, German (DIN), Japanese (JIS), ISO standards etc.


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Piping Layout


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Piping layoutconsiderationORHierarchyofReferenceDesignInformation System P&ID

P&ID implementation and Physicalization

Piping specification

Equipment Outlines

GA or Equipment layout drawings

Collection of as built drawings

Piping layout considerations and planning studies for improved pipingeconomics

Interference

Piping flexibility

Valve location

Drain location, Instrument location etc.

PipingLayout


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Example : Piping ofcentrifugal pump

Piping of centrifugal pumps, particularly the suction piping, can seriously affect theoperating efficiency and life expectancy of the pump. Problems like vibration, erosioncavitation out of balance conditions etc.

Suction and discharge must be independently supported. Designer can consider use ofexpansion joints on either suction or discharge if required.

Suction piping should not contain vertical loops or air pockets

When reduction is required at pump suction use eccentric reducer flat side up. Provide at least 3 to 4 diameter of straight pipe between pump suction and first elbow for

horizontal suction.

Only long radius elbow to be used at or adjacent to any pump suction connection.

When pump flanges are cast iron flat faced, the mating flanges must also be flat faced andthe joint made up with full face gaskets.

Piping Layout


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Example : Modern Piping Layout

Piping Layout


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Piping Design bases


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Factors to be considered for Design

Physical attributes Size, layout, dimensional limits, dimensional standards, specialdesign practices for configuration control ( weld joints, slope, plugging etc.)

Loading and Service conditions Loading conditions Dead weights, pressure changes, temperature changes, Snow

loads, ice loads, wind loads, Earthquake loads

Service conditions Combination of loads occurring simultaneously ( Water hammer,Relief valve discharge loads, Acoustically induced vibration loads

Environmental Factors

Corrosion/ erosion

Flow assisted corrosion

Material related considerations

Pressure integrity Leak tight condition in piping systems

Piping Design BasesDefn. : Design bases are the physical attributes, loading, service conditions,environmental factors and materials related factors which must be considered in the

detailed design of a piping system to ensure its pressure integrity over its design life


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Sizing of a Piping system Fluid flow design Reasonable design velocities for Water flowing through pipes

The detailed fluid flow design of a piping system requires the consideration of a numberfluid parameters including flow rate, viscosity, density and pipe wall frictional drag

Piping Design Bases - Sizing


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Sizing of a Piping system Pressure Integrity Design

Determination of Pipe wall thickness :

1. From minimum inside diameter select the Outside diameter from standards.

2. Based on fluid service suitable piping material required to be found (strengthallowances, corrosion, erosion allowances, joining)

3. As per code calculate the required minimum wall thickness.

4. Select an appropriate nominal wall thickness from standard (i.e. schedule)

5. Confirm the standard manufacturing tolerance will not reduce the nominal wallthickness

6. Confirm that the inside diam of the pipe is compatible with the minimum inside

diameter requirements obtained from the fluid flow evaluation.

Piping Design Bases - Sizing


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Questions ???


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Thank You

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