Pipeline_Design.ppt

5/24/2018 Pipeline_Design.ppt

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CHAPTER - 06

PIPELINE DESIGN


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BASIC DESIGN CONSIDERATION

1. SAFETY2. SECURITY OF SUPPLY

3. COST EFFECTIVENESS4. REGULATORY AND LEGAL

COMPLIANCE


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PIPELINE LEGISLATION

1. In the USA, the Department ofTransportation issues a range of

Pipeline Safety Regulations. Theseregulation rely heavily on ASMEB31 Standards.

2. In Indonesia, we should findwhether we have the regulation orjust adopt the ASME B31.


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1. ANSI B31.4 : Liquid PetroleumTransportation

2. ANSI B31.8 : Gas Transmission andDistribution Piping System

3. IGE/TD/1 : For Methane gas only4. BS 8010 ( in 1993)

5. ISO 13623 : International Pipelinestandard, covering oil and gas lines,currently being reviewed by the Pipeline

industry world-wide.

PIPELINE DESIGN CODE


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OIL PIPELINES :

1. No account is taken of populationdensity in the location of the pipelines.

2. There is no specified distance tooccupied buildings.

3. You can generally build an oil pipelinewith a high design factor (0.72) in mostlocation.



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GAS PIPELINES :

1. Account is taken of population

density in the location of thepipelines.2. Minimum distance from occupied

buildings is specified.

3. Design factor is lowered inpopulated areas (0.3 in UK and 0.4in USA)



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C L I EN T P RO J E C TM A N A G E R

C L I E N TP R O J E C T

E N G I N E E R

DE S I G N E R

P RO J E C TENG INE ER

DE S I G N E RP RO J E C TM A N A G E R

D E S I G N E R -Q U A L I T Y

S Y S T E M

D E S I G N E R -Q U A L I T Y

AU D IT O R

DISCIPLINEE N G I N E E R

C A DDESIGN

T E C H N I C A LS P E C I A L I S T

O T H E R S T A F F

QUALITY PLAN


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ROUTEEnvironmental & Safety

Consideration

QUALITY ASSURANCEPlan

SERVICE CONDITIONPressure, etc

DESIGN FACTORLocation and

Pressure

DESIGN CRITERIAPressure, Temp,

Stress, etc

CHOSENDESIGN

MATERIALSMaterial and Wall

thickness

INTERNAL CORROSION

CROSSINGTERMINAL &

STATIONS

TESTING AND

COMMISSIONINGEXTERNAL

CORROSION

DESIGN FLOW-CHART


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TYPICAL ORGANIZATION OFDETAILED DESIGN

PROJECT SPECIALISTS

MATERIALS

CATHODIC PROTECTIONSAFETY

ENVIRONMENT

CIVIL

PIPELINE

AND PIPING

CLIENT PROJECT

MANAGER

PROJECT

MANAGER

PROJECT

ENGINEER

PROCESS

SYSTEM


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STEP-1: SUBSTANCECLASSIFICATION

Assessment of the hazard potential of the substancein the pipeline. This is depend on what code weused. BS 8010 covers most substances, and IGETD/1 Specializes in Natural Gas.1. Category A - Typically water based fluid2. Category B - Flammable and toxic substances which are

liquids at amb. Temp and atmospheric pressure condition.3. Category C - Non Flammable substance s which are gases

at amb. Temp and atmospheric pressure condition.

4. Category D - Flammable and toxic substances which aregases at ambient temp. and atmospheric pressureconditions and are conveyed as gases or liquids, eg.Methane.


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1. Pipelines carrying Category A substances(water) are not limited in this way

2. Pipelines carrying Category B substances

are similarly not limited, but may requirea safety evaluation or extra protection.3. The location of Category C and D

substances pipeline is dependant on thepopulation density along the route. Thisthen dictates that the operating stresslevels and proximity of buildings.

STEP-2: LOCATION CLASSIFICATION

GENERAL


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1. To determine the number of buildingsintended for human occupancy for anonshore pipeline, lay out a zone of 1/4

mile wide along the route of the pipelinewith the pipeline on the center line ofthis zone, and divide the pipeline intorandom sections 1 mile in length.

2. Count the number of building intendedfor human occupancy within each 1 milezone.


GENERAL


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1. Class 1: Areas with a population< 2.5 persons/hectare

2. Class 2: Areas with a population>= 2.5 persons/hectare, andwhich may be heavily developed(shops)

3. Class 3: Central areas of towns,with high population, buildingdensity, etc.


BS 8010


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Location Class 1:is any 1mile section has 10 or fewer

building intended for humanoccupancy, such as waterland, desert, mountains,

grazing land, farmland, andsparsely populated area.


ASME B31.8


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Location Class 2:is any 1 milesection has more than 10 but

fewer than 46 buildingsintended for humanoccupancy, such as fringe

areas around cities and towns,industrial areas, ranch orcountry estates, etc.


ASME B31.8


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Location Class 3:is any 1 milesection has 46 or more buildingsintended for human occupancy,

except when Location Class 4prevails. This class for suburbanhousing development, shopping

centers, residential areas,industrial areas and other notmeeting location class 4requirement.


ASME B31.8


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Location Class 4:includes areaswhere multistory buildings areprevalent, and where traffic is

heavy or dense and where theremaybe numerous other utilitiesunderground. Multistory means

4 or more floors above groundincluding the first or groundfloor.


ASME B31.8


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It is of interest to note that a study of fires following a gas pipelinefailure showed a clear trend between burn radius and pressure, butno correlation with a pipe diameter.The study plotted the radius of the burn area around a pipelineagainst the pipeline pressure, and concluded that an upper bound:

Upper Bound Burn Radius for A Gas PipelinePressure Radius

260 psi 92 ft (28.1 m)

987 psi 610 ft (186 m)This table gives a simple Rule of Thumb for safe distance (ignoring

wind speeds, terrain, etc), for example, a pipeline at a pressure 1000psi would cause burn damage up to a distance of ~ 200 m either side

of corridor, if it failed and the gas ignited.

BURN RADIUS WHEN PIPELINE FAIL


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TABLE: LOCATION CLASS vsDESIGN FACTOR

THIS TABLE BELOW IS FROM ASME B31.8 WITH ADDITIONAL INFORMATION INPUTFROM BS 8010

LOCATION CLASS LOCATION CLASS LOCATION CLASS LOCATION CLASS

ASME B31.8 BS 8010 B31.8 (MAX) BS 8010 (MAX)

1. DIVISION 1 1 0.8 0.72

1. DIVISION 2 1 0.72 0.72

2 1 0.6 0.72

3 2 0.5 0.3 to 0.72*1

4 3 0.4 0.3*2

TABLE 1 LOCATION CLASS:

*1VARIANCE TO BE JUSTIFIED BY SAFETY EVALUATION

*2 MAXIMUM PRESSURE LIMITED TO 7 BARG.


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The Distance between a normallyoccupiedbuilding and a pipeline is given in BS8010 as:

Category A Substances: Nostipulated requirement.

Category B Substances: the designedmust take account of access duringconstruction, maintenancerequirements, access for emergencyservices, etc., before specifying aproximity.

STEP-3: DISTANCE TO OCCUPIEDBUILDING


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Category C and D Substances (excludingMethane): For pipelines with a designfactor not exceeding 0.72 the minimum

distance is:= Q [ D^2/32000+D/160+11]*[p/32+1.4]

where D = Outside pipe diameter (mm),P is max. operating pressure (bar)

Q is substance:ex. Ammonia, Q = 2.5, NGL, Q =

1.25

STEP-3: DISTANCE TO OCCUPIEDBUILDING


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We want to ensure that our pipeline does not fail due to:

BURST STRUCTURAL COLLAPS

FATIGUE FRACTURE We do not want our pipeline to become unserviceable

due to:

OVALISATION

DISPLACEMENTS Therefore we control our stresses below a DESIGN

LEVEL or DESIGN FACTOR. This factors vary incodes.

DESIGN CRITERIA


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1. It is important to understand the originsand meaning of these Design factors:

2. First, the design factor is a simpleengineering way of ensuring that your

working stresses in your pipeline are wellbelow the yield or ultimate tensile strength ofthe pipeline material.

3. The Design Factor depend on the Location

Class.4. The Design Factors vary in the CODES.5. The Design factor is HOOP STRESS over SMYS

DESIGN FACTOR


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DESIGN FACTOR - ASME B31.8

1. Class 1 Div.1 : 0.802. Class 1 Div.2, 0 - 10 buildings : 0.723. Class 2 11 - 45 buildings : 0.60

4. Class 3 46+ dwellings : 0.505. Class 4 Multistory buildings : 0.406. Originally, a corridor width of 0.5 mile

wide (now 0.25), with the pipeline at

the center, was used to determine thepopulation density at risk.


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1. Most of pipelines around the world have amaximum design factor of 0.72, althoughthere are some pipelines operating athigher factors.

2. This 0.72 design factor originates in NorthAmerica, from the American PipelineStandard ASME B31. A 72 % SMYS designstress is additionally based on

conservative assumptions, e.g. minimumwall thickness.

THE 0.72 DESIGN FACTOR


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1. The 72 % SMYS limit originates from1930s in the USA, and was based on themill testing of pipelines.

2. The mill test was typically 90% SMYS.Operators agreed that a 1.25 safetyfactor on this was reasonable, thereforethe 72% SMYS limit was created and

appeared in the American Code ASMEB31.8 in the 1960s. It has no structuralsignificance, and is an historical limit.



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1. The 0.72 design factor was based on theuse of a safety margin of 1.25 on ahydrotest to 90% SMYS.

2. Using the same logic (I.e. safety factor

1.25) pipelines hydrotested to 100% SMYSwould be able to operate at 80% SMYS. Inthe 1980s, the ASME B31.8 committeeconsidered > 72 % SMYS pipelines, and

1990 addenda to 1989 ASME B31.8 Editionincluded provisions for the operation ofpipelines up to 80% SMYS.



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1. However, US Department ofTransportation Regulations usuallyrestrict the maximum design factor in

oil and gas lines to 72 % SMYS.2. This restriction was problematic for

some lines in the USA, that wereoperating at above 72%, and in some

cases 80% SMYS when it came intoforce.



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The use of a design factor of 0.72 will ensurereasonable safety factor ( see figure nextpage).

For example, a pre-service hydrotest to 100%

SMYS means that a 72% SMYS pipeline has asafety factor of 100/72 on pressure.

This safety factor is needed to account for : uncertainties in pipe supplies (e.g. wall

thickness)

Uncertainties in pressure (e.g.overpressures)

Most important - the inevitabledeterioration of the pipeline with time.

INHERENT SAFETY FACTOR


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SAFETY MARGIN IN APIPELINE

0.72

1

1.3

DESIGN HYDROTEST FAILURE

DESIGN FACTOR

Safety factorbased on failure

Safetyfactor basedon hydrotest


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1. PROTECTION2. CROSSING

3. DESIGN TEMPERATURE4. CORROSION ALLOWANCE5. VALVE SPACING

6. OVER PRESSURE7. FATIGUE

OTHER CONSIDERATIONS


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Pipelines can be protected to reduce therisk of pipeline damage.

Types of protection are:

Adding Concrete Protective Coating. Encasing with Steel Pipe of LargerDiameter

Steel mesh or slab coverings or

surrounds Lowering the line to a greater depth Increasing the Wall Thickness

1. PIPELINES PROTECTION


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1. Depth of Cover is also an effective method ofprotection. IGE TD/1 requires a minimum depth ofcover 1.1 m, whereas BS 8010 requires minimum of900 mm for pipelines in agricultural areas. Researchwork showed that the likelihood of damage is

reduces by a factor of 10 as the depth of cover isincreased from 1.1 m to 2.2 m.

2. Increased Pipe Wall Thickness offers protectionagainst damage. For example very few (5%) ofexcavating machinery used in suburban areas will beable to penetrate 11.9 mm wall.

3. Pipelines protected by sleeves are no longer populardue to difficulty in maintenance, and the possibilityof corrosion and difficulty of finding it.

1. PIPELINES PROTECTION


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1. When a pipeline crosses, or is crossed by, a road thenit may be subject to additional forces. The design ofcrossings must take into account the daily andseasonal traffic densities and the risk of interference

in this type of area.2. Road crossing must be installed by open cut, boring

or tunneling methods. Boring is the most popular asit is cheap and mechanized. Tunneling is expensiveand mainly manual, but may be necessary in e.g.

hard rock. Open cuts are used on little used roads forconvenience and low cost.3. The major pipeline codes used in UK (BS 8010 Part

2.8, IGE TD1 contain these requirement.

2. ROAD CROSSING


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2. RAILWAY CROSSING

1. Rail Crossings can be designed in thesame way as road crossings, althoughthe distance from the top of the

sleeve/pipe to the rail surface is usuallydeeper than required for roads (in BS8010 the distance increases from 1.2 m(road) to between 1.4 and 1.8 m.

2. River or estuary crossings are usuallydesigned as submarine pipelines.


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1. Pipeline design must take into account thetemperature of the environment and theproduct.

2. The temperature will effect both operationand material properties.

3. BS 8010 does not limit on designtemperature, but IGE TD/1 recognizes thatmost buried pipelines in the UK will operate

at 5 Deg. C and therefore require the pipematerial to be tested for adequate toughnessproperties at 0 Deg. C.

3. DESIGN TEMPERATURE


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1. If a pipeline is carrying a non-corrosivesubstance, an internal corrosion allowance isnot needed.

2. Similarly, if both an anti-corrosion coatingsystem and a cathodic protection system areinstalled , no external corrosion allowance isneeded.

3. Where internal or external corrosion is

expected, a study must be conducted tocalculate the necessary corrosion allowance,which is then added to the design thickness.

4. CORROSION ALLOWANCE


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1. It is common sense to place isolating valves at thebeginning and end of a pipeline, and at intervalsbetween these two valves to limit the extent ofpossible leak, and to assist in maintenance.

2. Similarly, valves need to be easily accessible, but

away from normally buildings and be protectedfrom vandalism.

3. The spacing of valves is usually linked to ClassLocation, in pipeline codes. This suggest that thespacing is based on environ mental and safety

criteria, that minimizes damage and injuries.4. In BS 8010, valves must be no more than 16 km

apart for Category B substances.5. Category C and D, are about 16 km

5. VALVE SPACING


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1. Changes in flow, or the sudden closure ofthe valve, will cause pressure surges.

2. Pipeline must be protected from thesesurges (by, for example, a relief valve).

3. This surges are inevitable. Most designcodes allow them to exceed the designpressure, providing they are controlled.

4. Most codes allow 10% overpressures.

5. BS 8010 limit to 10 % of the internaldesign pressure.

6. But duration limited to 5 hours at any one

time or 20 hours per day.

6. OVERPRESSURES


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6. OVER PRESSURES (contd)

FAILURE STRESS OF DEFECT FREE PIPELINE SAFETY MARGIN

ON FAILURE

1 SMYS OF PIPELINE

SAFETY MARGIN

HYDROTEST PRESSURE SAFETY MARGIN ON SMYS

ON HYDROTEST

0.8 ALLOWANCE

FOR SURGES

0.6

0.4

0.2

PIPELINEHOOPSTRE

SS(%S

MYS)

PIPELINE OPERATION (TIME)

ALLOWANCE FOR SURGE

DESIGN PRESSURE


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1. Pipeline pressures are rarely constant2. In oil lines, they can varying as different batches are

sent down the pipeline.3. In gas lines, the pressure can vary due to customer

demand.4. Pressure cycling in pipeline can cause minor defects

to grow to a critical size, and cause failure. Thesedefects may have survived the pre-servicehydrotest.

5. BS 8010 and IGE TD/1 have guidance on fatigue. Alimit of 15000 cycles of maximum daily variation inhoop stress of 125 N/mm2 is quoted. Smaller andlarger stress ranges are allowed longer fatigue livesthan 15,000.

7. FATIGUE CONSIDERATION


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TRANSMISSION PIPELINES ARE TESTED BEFORE GOINGINTO SERVICE, BY PRESSURIZING THEM WITH WATER.

NATURAL GAS, OR AIR, IS NOT USED AT HIGH PRESSUREBECAUSE THE ENERGY CONTENT OF A PNEUMATIC TEST

IS MANY TIMES GREATER THAN THAT OF HYDRAULICTEST. HYDROSTATIC TESTING OF PIPELINES STARTED IN

1950s in USA for CHECKING FOR LEAKS PROVING THE STRENGTH OF THE PIPELINE

REMOVING DEFECT ON CERTAIN SIZE BLUNTING DEFECTS THAT SURVIVE REDUCING RESIDUAL STRESS WARM PRESTRESSES DEFECT THAT SURVIVE.

HYDROSTATIC TESTING


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HISTORICALLY, PIPELINES, PRESSURE VESSEL, PIPINGHAVE BEEN TESTED FROM 1.1 TO 1.5 TIMES THEDESIGN PRESSURE.

THE CONCEPT OF AHIGH LEVEL TEST, OR TEST TOYIELD WAS INTRODUCED INTO THE UK AND USA IN

1967, WHEN IT WAS RECOGNIZED THAT TESTING TO80% OR 90% SMYS WOULD NOT REVEAL DEFECTSTHAT MAY CAUSE FAILURE DURING OPERATION.

WHERE THE PIPELINE CROSSES RIVERS, ROADS,RAILWAYS AND OTHER ACCESS ROUTES, THE THICKERWALL SECTIONS HERE MAY NEED TO BE TESTED

SEPARATELY. THIS MAY BE DONE BEFORECONSTRUCTION OR SEGREGATED FROM THE MAINLINE AND TESTED IN ISOLATION.

HYDROSTATIC TESTING


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BS 8010 GIVES THE FOLLOWING TESTREQUIREMENTS :

THE HYDROTEST SHOULD BE THE LOWER OF 150 %THE MAXIMUM OPERATING PRESSURE, OR THATPRESSURE THAT WILL INDUCE A HOOP STRESS OF

90% SMYS. CATEGORY C SUBSTANCE PIPELINES DESIGNED TO

OPERATE AT DESIGN FACTOR OF NOT MORE THAN0.3 CAN BE PNEUMATICALLY TESTED AT AMBIENTTEMPERATURE. THE MAXIMUM DESIGN FACTOR FOR

PNEUMATIC TEST MUST NOT EXCEED 0.375, NOT BELESS THAN 1.25 TIMES THE MAXIMUM OPERATINGPRESSURE.

HIGH LEVEL TESTING CAN BE CARRIED OUT, ANDTHE TEST PRESSURE SHOULD BE 114% (SEAM

WELDED PIPE) AND 102% SEAMLESS SMYS.

HYDROSTATIC TESTING


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SMALL LEAKS CAN BE OFTEN DIFFICULT TODETECT. A SMALL CHANGE IN WATER/PIPETEMPERATURE MAY GIVE THE APPEARANCE OFA LEAK. STANDARD RULE OF THUMB USE THETEMPERATURE MEASUREMENT TOCOMPENSATE FOR THIS EFFECT. THE PIPELINETEST TEMPERATURE MAY BE AFFECTED BYALTITUDE, RIVER CROSSINGS, EXPOSEDVERSUS BURIED, WATER TEMPERATURE

GRADIENT ETC. AIR, EITHER TRAPPED ORENTRAINED, WILL ALSO AFFECT THE PRESSUREVOLUME RECORDING.

HYDROSTATIC TESTING


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IF THE DECREASE IN PRESSURE VOLUME ISNOT ATTRIBUTABLE TO THE EFFECT DESCRIBEDABOUT IT MAY BE NECESSARY TO RE-TESTSHORTER SECTIONS OF THE PIPELINE TOESTABLISH AND LOCATE A LEAK.

AFTER TESTING IS USUAL TO EXPEL THE WATERUSING COMPRESSED AIR OR IN THE CASE OFLIQUID LINES, THE PRODUCT THATWILLNORMALLY FLOW. FURTHER DRYING, MAINLY

FOR GAS PIPELINE, IS ACHIEVED VIA THE USEOF PURPOSE-BUILT PIGS, HEATED AIR,VACUUM, INERT GAS, OR LIQUID CHEMICALSCAVENGERS RUN AS SLUGS.

HYDROSTATIC TESTING


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COMPARISON OF ENERGY LEVELS :PNEUMATIC vs HYDRAULIC TESTING

where: Vessel Details & Assumption:

*P = Pressure in Vessel (Mpa) *P = Test Pressure = 48 Mpa

*V = Vessel Volume (m 3) *Internal Diameter = 1700 mm

*Po = Ambient Pressure (=0.1 Mpa) *Thickness = 149 mm

*e = Poisson's ratio (=0.229) *Length = 16700 mm

*K = Internal Diameter/External *V = 37.91 m 3

*E = Young Modulus (=210 x 10^3Mpa) *Assume strain energy content in both*Mb = Bulk Modulus of Water (=2.05 x 10^3 Mpa) cases is same.

*U = U = (P^2.V.(3(1-2e)+2K^2(1+e)))/(2.E(K^2-1)) *Perfect gas laws apply.

25 x 108

TOTAL ENERGY =

W + U

PNEUMATICTESTING

HYDRAULIC

TESTING

Wa = P. V log P/Pa 1.12 x 1012

4.9 x 106 2300 : 1 1.12 x 10

12

Ww = Vo (P-Po)/2Mb 21.3 x 106 4.9 x 106 4.1 : 1

ENERGY CONTENTof Air, Wa, orWater, Ww(JOULES)

W (JOULES)

STRAIN ENERGYIN WALLS, U

(JOULES)W:U

RATIO OF ENERGIES, PNEUMATIC TO HYDROLIC =450 : 1


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PIPE TESTING : SAFETY MARGIN

0.72

1

1.3

0

0.2

0.4

0.6

0.8

1

1.2

1.4

DESIGN HYDROTEST FAILURE

DESIGN

FACTOR


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The tensile properties of line pipe material are measuredas the Yield Strength and the Ultimate Tensile Strength.

The Pipe Manufacturer ensures the strength of our pipe isabove certain specified minimum levels.

These specified minimum levels are: SMYS : SPECIFIED MINIMUM YIELD STRENGTH is the

minimum yield strength prescribed by thespecification under which pipe is purchased from themanufacturer.

SMTS : SPECIFIED MINIMUM TENSILE STRENGTH isthe minimum tensile strength prescribed by the

specification under which pipe is purchased from themanufacturer. Our actual Yield Strength and Tensile Strength are

above those specified.

MATERIAL PROPERTIES


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1. Coefficient of Thermal Expansion: The LinearCoefficient of Thermal Expansion for CARBON and LOW

ALLOY HIGH TENSILE STEEL may be taken as:

6.5 x 10-6in./in./oF ---- for T


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Ensuring a Design Stress is BelowCritical Material Properties

800

700

600

500

YIELD STRENGTH

400

300

200

100

0

0 2 4 6 8 10 12

WE DESIGN OUR STRUCTURES IN THIS REGION, BUT THE FAIL IN

THIS REGION, AT MUCH HIGHER STRESSES AND STRAINS.

ULTIMATE TENSILE STRENGTH

FAILURE

STRAIN, %

STRESS, /mm^2

YIELDSTRAIN


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DESIGN STRESSES

STRAIN, %

STRESS,

%S

MYS

PIPE

BULGING

LIMIT

PIPEBURST

LIMIT

STRAIN

BASED

DESIGN

PIPE

CIRCULARIT

YLIMIT

PIPE IS NOT

SERVICEABLE

PIPE IS NOT

SAVE

DESIGN

LIMIT

HYDROTEST

LIMIT

NONLINIER

ELASTIC

LIMIT


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1.TRENCH CONDITION: Calledalso as BURIED PIPELINE . Thisconsist of excavating a ditch andplacing a pipe within the trench.

2.EMBANKMENT CONDITION: thisconsist of laying the pipe on the

natural ground and building anembankment over the pipe.

PIPELINE INSTALLATION


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RESTRAINED LINES : This is forportion of the piping systemthat called as Buried Pipeline.

UN-RESTRAINED LINES: This isthe portion of pipeline which isaboveground and right before

the pipeline going into thetrench.

PIPELINE AS A SYSTEM


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1. THE CALCULATION WILL BE DEPENDON WHAT TYPE OF PORTION OFPIPELINE TO BE CALCULATED SINCE

THERE ARE FUNDAMENTALDIFFERENCES IN LOADINGCONDITIONS.

2. THIS IS WILL AFFECT TO DIFFERENT

LIMITS ON ALLOWABLELONGITUDINAL EXPANSION STRESS.

PIPELINE AS A SYSTEM


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THE NET LONGITUDINALCOMPRESSIVE STRESS DUE TO THECOMBINED EFFECTS OF

TEMPERATURE RISE AND FLUIDPRESSURE:

RESTRAINED LINES

SL= E (T2- T1) - uSh


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STRESS DUE TO EXPANSION :

UN-RESTRAINED LINES

SE= Sb2+ 4 St

2

ZWhere :

SE= Stress due to expansion, Psi.Sb= Equivalent Bending Stress (in-Lb)

St = Torsional moment, in-LbZ = Section Modulus of pipe, in3


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1. NOMINAL WALL THICKNESS = tntn = t + A

where :

tn=nominal wall thickness satisfyingrequirements of pressure and

allowances

t = pressure design wall thickness ascalculated in inches (mm) in accordance

with para. 404.1.2 at next page.A= sum of allowance for threading, grooving,

corrosion, increased wallthickness.

NOMINAL WALL THICKNESS, tnASME B31.4


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t = PiD / 2 Swhere :

t = Internal Pressure Design Wall ThicknessPi = Internal Design Pressure, Psi.D = Outside Diameter of Pipe, inch.S = Applicable Allowable Stress Value, Psi in

accordance with para. 402.3.1 a, b, c or d.

INTERNAL DESIGN PRESSURE WALL

THICKNESS, t (ASME B31.4)


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NOMINAL WALL THICKNESS, t FOR AGIVEN DESIGN PRESSURE or THE DESIGNPRESSURE FOR STEEL GAS PIPING SYSTEM:

P = 2S t F E T

D

NOMINAL WALL THICKNESS, tASME B31.8


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where :P = DESIGN PRESSURE, PSIGS = SMYS, PSID = NOMINAL OUTSIDE DIAMETER, IN.

t = NOMINAL WALL THICKNESS,INF = DESIGN FACTORE = LONGITUDINAL JOINT FACTOR

T = TEMPERATURE DERATING FACTOR

NOMINAL WALL THICKNESS, tASME B31.8


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1. PRIMARY STRESSEScaused by SUSTAINED

LOAD, such as pressure,weight.

2. SECONDARY STRESSES

caused by THERMALEXPANSION.

BASIC CONCEPT OF STRESS


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I. NORMAL STRESSLONGITUDINAL STRESS

CAUSED BY INTERNAL FORCESDUE TO INTERNAL PRESSUREBENDING STRESS

HOOP STRESSRADIAL STRESS

II. SHEAR STRESS

PRIMARY STRESSES


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NORMAL STRESSESARE THOSE ACTINGIN A DIRECTION NORMAL TO THEFACE OF THE CRYSTAL STRUCTURE

OF THE MATERIAL AND MAY BEEITHER TENSILE OR COMPRESSIVEIN NATURE. THIS MAY BE APPLIEDIN MORE THAN ONE DIRECTION ANDMAY DEVELOP FROM A NUMBER OFDIFFERENT TYPES OF LOADS.

I. NORMAL STRESSES


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LONGITUDINAL STRESS (SL) is the normalstress acting parallel to the longitudinalaxis of the pipe, caused by an internal

force axially within the pipe :SL= Fax /Am --- PSI

Where:Fax = Internal axial force , lb.

Am = Metal cross-sectional area of pipe,in2.

1. LONGITUDINAL STRESSESCAUSED BY INTERNAL FORCES


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LONGITUDINAL STRESS (SL) due to internalpressure:

SL

= Pi

Do

/4 t --- PSIWhere:

Pi = Internal Pressure, Psi.Do = Outside Diameter, in.

t = Design Pressure Wall Thickness, in.

1. LONGITUDINAL STRESSESDUE TO INTERNAL PRESSURE


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BENDING STRESS (SL) is anothercomponent of normal stress:

SL

= Mb

c/ I --- PSIWhere:

Mb = Bending Moment acting on cross- section, in-lb.

C = distance of point of interest from

neutral axis of cross-section, in.I = Moment of Inertia of cross-section,

in4

1. LONGITUDINAL STRESSESBENDING STRESS

SUM OF LONGITUDINAL


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SL= Fax/Am+ P do/4t + Mb/ Z

SUM OF LONGITUDINALSTRESSES


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HOOP STRESS (SH ): is the stress in a pipeof wall thickness t actingcircumferentially in a plane perpendicularto the longitudinal axis of the pipe.

Barlows Formula:

SH= Pi Do/2t --- PSI

2. HOOP STRESSES


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RADIAL STRESS ( SR) : (Psi)SR= P (ri

2-ri2ro

2/r2)/(r02-ri

2)

Where:P = Internal Pressure, PSIri = Internal Radius, inro = Outside Radius, in

3. RADIAL STRESSES


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SHEAR STRESS (t max) are applied in adirectional parallel to the face of the plane ofthe crystal structure of the material, andtends to cause adjacent planes of the crystalto slip against each other:

tmax= V Q/Am--- PSIWhere:

V = Shear Force, lb.

Q = Shear Form Factor, 1.333 for solidcircular section.

Am= Metal cross-sectional of pipe, in2

II. SHEAR STRESSES


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SHEAR STRESS (t max) may also be causedby torsional loads:

tmax=

Mt/2 Z --- PSI

II. SHEAR STRESSES


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tmax=V Q /Am +, Mt/2 ZPSI

SUM OF SHEAR STRESSES

SECONDARY STRESS DUE TO


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SE= Sb2+ 4 St

2

ZWhere :

SE= Stress due to expansion, Psi.Sb= Equivalent Bending Stress (in-Lb)St = Torsional moment, in-LbZ = Section Modulus of pipe, in3

SECONDARY STRESS: DUE TOTHERMAL EXPANSION

SECONDARY STRESS DUE TO


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SB= (iiMi)2+ (ioMo)

2Z

ST= MT/2Z

SECONDARY STRESS: DUE TOTHERMAL EXPANSION


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SE= Stress due to expansion. Sb= Equivalent Bending Stress, Psi. St = Torsional Stress, Psi. Mi = Bending Moment in-plane of member, in-

lb. Mo= Bending Moment out of plane, in-lb. Mt = Torsional Moment ii = SIF under bending in-plane of member i

o = SIF under bending out-plane of member

Z = Section Modulus of pipe, in3

DEFINITION


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THE ALLOWABLE STRESS VALUE, S

FOR NEW PIPE OF KNOWN SPECIFICATION

S = 0.72 x E x SMYS ( psi)where:0.72 = Design Factor based on nominal

Wall Thick.E = Weld Joint Factor.SMYS = Specified Minimum Yield

Strength


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FOR NEW PIPE OF UNKNOWN SPECIFICATION

S = 0.72 x E x MYS ( psi)where:

MYS = Minimum Yield Strength of the

Pipe { 24,000 PSI or determinedIn accordance ANSI B31.4 , para437.6.6 and 437.6.7.

Allowable Stress Value in Shear < 45%SMYS

Allowable Stress value in Bearing < 90%SMYS


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The Allowable Stress Value S to beused to calculate for pipe which hasbeen cold worked in order to meet

SMYS and is subsequently heated to600 F (300 C) or higher (weldingexcepted) shall be:

75 % of The Applicable Stress

Value, S.

THE ALLOWABLE EXPANSION


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THE ALLOWABLE EXPANSIONSTRESS

1.RESTRAINED LINES:

< 90% of SMYS2.UN-RESTRAINED:

SA< 72% SMYS

SUMMARY OF LONGITUDINAL


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SUMMARY OF LONGITUDINALSTRESSES

SUM OF THE LONGITUDINALSTRESSES DUE TOPRESSURE, WEIGHT ANDOTHER SUSTAINEDEXTERNAL LOADING :

< 75% SA< 75% x 72% SMYS

< 54% SMYS

SUMMARY OF CIRCUMFERENTIAL


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SUMMARY OF CIRCUMFERENTIALSTRESSES

SUM OF THE CIRCUMFERENTIALSTRESSES DUE TO INTERNAL DESIGNPRESSURE AND EXTERNAL LOAD IN PIPEINSTALLED UNDER RAILROADS OR

HIGHWAYS WITHOUT USE OF CASING :

< 0.72 x E x SMYS

LIMIT OF CALCULATED STRESS


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OPERATION: The SUM of Longitudinal Stresses

produced by Pressure, Live and DeadLoad and by occasional load, such as

Wind, earthquake: < 80% SMYS TEST: Stress due to test condition are not

subjected to the above limitation. It

is not necessary to consider otheroccasional load, such as wind &earthquake.

LIMIT OF CALCULATED STRESSdue to Occasional Load

DESIGN STRESS:


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DESIGN STRESS:DUE TO EXTERNAL LOAD

Most of pipelines are installed atunderground or also known as BURIEDPIPE.

The pipeline is influenced by environmentalconditions.

There are a number of problems associatedwith this phenomena.

External Load, Bursting Pressure, Thermal

Expansion, Anchor Forces and the PipeBowing Out of the Ground are few of theproblems which should be anticipateddepend on soil condition.


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DESIGN CONSIDERATION

FILL LOADS LIVE LOADS DEGREE OF PROJECTION PRESSURE, VACUUM, WATER HAMMER AND

EXTERNAL LOAD STRESSES IN COMBINATION. DIAMETRAL DEFLECTION BEDDING CONDITIONS SOIL WASHOUT (especially when on pile caps) DEGREE OF SOIL COMPACTION

MOISTURE CONTENT OF SOIL SETTLEMENT

GROUP OF PIPE BASED ON


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GROUP OF PIPE BASED ONDIAMETRICAL RIGIDITY

1. RIGID: Pipe that can not be distorted morethan 0.1 percent without causing damage.

2. SEMI RIGID: Pipe that may be distortedbetween 0.1 percent and 3.0 percent

without causing damage. Most steel pipewill fall into the semi rigid class, since theymay not be distorted greater than 2 % dueto limits of field joints, lining and coating

properties, internal cleaning device.3. FLEXIBLE: Pipe that may be distortedgreater than 3 % without causing damage.


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FILL LOAD

1. In the case where the soil prism directly overor adjacent to the pipe SETTLES MORE than thewalls of the trench, PART of the FILL LOAD willbe transferred to the walls (trench condition).

2. Where the Soil Prism directly over the pipeSETTLES LESS than the soil on either side, THEPIPE will CARRY the weight of the soil directlyover it plus some of soil weight on either side.

3. In the case where the soil prism directly over

the pipe SETTLES the SAME amount as the soileither side, the LOAD on the PIPE is essentiallythe WEIGHT of the SOIL directly OVER thepipe.


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FILL LOADS

THE MARSTON FORMULA FOR RIGID AND SEMIRIGID PIPE:

W(ct) = C w B2 (compressible fill)

Where: W(ct)

= Fill Load on the pipe (lbs/ft)w = Unit weight of trench fill material(lbs/ft3 )C = Calculation coefficient determined from

H/B and the table in attachment.B = Width of trench at the top of pipe (ft)

H = Height of fill above the top of pipe (ft)


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FILL LOADS

1. FLEXIBLE PIPE:

W(cm) = C w BD

Where: W(cm) = Fill Load on the pipe (lbs/ft)

w = Unit weight of trench fill material(lbs/ft3 )C = Calculation coefficient determined

from H/B and the table inattachment.

B = Width of trench at the top of pipe (ft)D = Outside diameter of pipe (ft)

UNIT WEIGHT OF FILL


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UNIT WEIGHT OF FILLMATERIAL

FILL MATERIAL w ( lbs/ft3 )

LOAM OR SANDY LOAM 110

SAND 115

GRAVEL 125

SANDY, GRAVELLY, AND ORDINARY CLAY (maximum) 120

SATURATED CLAY 130


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LIVE LOAD

1. The piping may be exposed to liveloads such as TRUCKS, TRAINS, ANDCONSTRUCTING EQUIPMENT.

2. Live loads presented as an effectivesoil pressure acting on the pipe at adepth measured to the top of the

pipe.


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LIVE LOAD

1. Loading from H20 trucks and E72locomotives, which would be minimumand maximum live load values, can bedetermined from attachment

drawings.2. The loads are described in unit of

vertical pressure and are to beconverted to pounds per lineal foot, to

combine with the loads as determinedin Fill Loads On Buried Pipe.


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LIVE LOAD

FOR LOADING OTHER THAN H20 ORE72, EQUIVALENT VERTICAL EARTHPRESSURE MAY BE FOUND BY MEANSOF BOUSSINESQ AND NEWMARK

ANALYSIS:

QC (b)P (11) =

H2

C(b) is the Boussinesq coefficient.Q is the acting live loads.

DIAMETRICAL DEFLECTION


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DIAMETRICAL DEFLECTION(OVALIZATION)

DH

d

d = diametrical deflection

B = width of trench

D = OD pipe

H = height of fill above pipe

DETERMINING


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GDIAMETRICAL DEFLECTION

using SPANGLER FORMULA

f k w(x) r(m)3

d =Ei + 0.061 E r(m)3

ALLOWABLE DIAMETRICAL


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ALLOWABLE DIAMETRICALDEFLECTION

1. IS BASED ON THE AWWA(AMERICAN WATER WORKASSOCIATION) PUBLICATION NO.

M11, STEEL PIPE DESIGN ANDINSTALLATION.2. THE ALLOWABLE DEFLECTION IS

GIVEN AS A PERCENTAGE OF

DIAMETER.



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1. FOR CEMENT MORTAR ORCOATED PIPE, THE

ALLOWABLE IN ON THE ORDER

OF 2 PERCENT.2. FOR COAL TAR EBAMEL LINED

OR COATED PIPE : 3 - 5 %

3. PIPES WITH MECHANICALJOINTS ARE LIMITED TO 2 %



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1. FLEXIBLE PIPE : Up to 20%2. FOR HYDROCARBON SERVICE

THAT SUBJECT TO INTERNAL

CLEANING, THE ALLOWABLEDIAMETERICAL DEFLECTION ISLIMITED TO 2 % TO ALLOWSUFFICIENT CLEARANCE FORTHE CLEANING DEVICE (PIG) TOTRAVEL THROUGH THE PIPE.


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BEDDING CONDITION

1. Class A : Flat Bottom trench with little or noattention paid to tamping.

2. Class B : Flat Bottom trench with backfillplaced in lifts and well tamped.

3. Class C : Pipe Supported on block withbackfill not tamped.4. Class D : Pipe Supported on blocks with

backfill tamped.5. Class E : Bottom of trench conforms to

bottom of pipe for about 90 degrees backfillnot tamped.

6. Class F : Same as Class E, with backfilltamped.

BREAKING LOAD


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BREAKING LOAD

where:

W(br) =

t (min) =

D (o) = Outside Diameter of Pipe (in.)

R (m) = Modulus of Rupture of pipe material (lbs/in2)

0.0795 =

Ring Test Crushing Load (Breaking Load)

Pipe Wall thickness less corrosion allowance

tolerance (in)

W(br) =t (min )2 R (m)

0.0795 (D(o) + t(min))

RING TEST EQUIVALENT


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RING TEST EQUIVALENT(internal pressure)

2.5 W(e)W (r) = Lbs/ft)

b3where, W(e) is Earth Load (Lbs/ft)

b3 is Ratio to 3-edge bearing (load

factor)

RING TEST EQUIVALENT


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RING TEST EQUIVALENT(external loads from earth & truck super load)

2.5 W(e) + W(t)

W (r) = lbs/ft

b3where, W(e) is Earth Load (Lbs/ft)

b3 is Ratio to 3-edge bearing (load

factor)W(t) is Truck Super Load

BURSTING PRESSURE


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BURSTING PRESSURE

2 St (min)

P (B) = Psi

(D(o) - 2t (min))

DEFINITIONS


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DEFINITIONS

D(o) : Outside diameter of pipe (in)d : Diametrical deflection of pipe

due to external loading (in.)r (m) : Mean Radius of Pipe (in.)

E : Young Modulus (Lb/in2)t (min): Pipe Wall (minus MT & CA)t : Nominal Wall Thickness (in)i : Moment of Inertia of section of pipe

per linear foot of pipe (in3)C : Calculation coefficient

DEFINITIONS


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DEFINITIONS

W : Unit weight of fill material (lbs/ft3)W(x) : Total external load on pipe (lb/in)W(f) : Fill Load on Pipe (lb/in)P(11) : Live Loads on Pipe (lb/ft2)

t (min): Pipe Wall (minus MT & CA)f : Deflection lag factor; for initial

deflection, use f=1.0.k : Bedding constant.E : Soil Modulus (psi)q : Angle of Bedding.

LONGITUDINAL STRESS


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LONGITUDINAL STRESSdue to sustained loading

1. Sum Longitudinal Stress = TotalMaximum Bending Stress due toDEAD LOAD and the Stress

developed due Internal Pressure.2. In situation of Live Load may

present problems, the moment

due to the LIVE LOADS areadditive to the loads due topressure and DEAD LOAD.

STEP OF CALCULATION


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STEP OF CALCULATION

1. DETERMINE BENDING MOMENTDUE TO DEAD WEIGHT.

2. DETERMINE BENDING STRESS IN

PIPE DUE TO LIVE LOADS.3. DETERMINE COMBINEDLONGITUDINAL STRESS IN PIPEWALL.

4. DETERMINE ALLOWABLE STRESSLEVEL.

THERMAL EXPANSION OF


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THERMAL EXPANSION OFBURIED PIPE

1. THE RESISTANCE TO THERMAL EXPANSIONOFFERED BY THE SOIL DEPENDS ON THECONTACT MADE BETWEEN PIPE AND SOIL.

2. THIS FRICTIONAL RESISTANCE DEPENDS ON

: THE SURFACE ROUGHNESS OF THEPIPE.

THE TYPE OF SOIL THE CONDITION OF SOIL

3. VALUES FOR COEFFICIENT OF FRICTIONVARY BETWEEN 0.1 TO 0.8.

4. AVERAGE VALUES MAY BE ASSUMED TO BEABOUT 0.4 AND 0.5



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AS THE SOIL AROUND THE PIPE IS IN A STATEOF COMPRESSION, THE SOIL TENDS TO EXERT APRESSURE ON THE WALL OF THE PIPE.

THIS PRESSURE WILL REFER TO PASSIVEPRESSURE.

VALUES OF PASSIVE PRESSURE HAVE BEENFOUND BY KARL TERZAGHI TO VARY FROM 0.2TO 0.8 TIMES THE WEIGHT OF SOIL ABOVE THECENTER LINE OF THE PIPE.

ON CONSERVATIVE SIDE, THE LIGHTER LOAD

MUST BE IMPLIED, AND PP OF 0.2 WILL BEUTILIZED FOR DETERMINING SOIL RESISTANCETO THERMAL EXPANSION.



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BECAUSE BURIED PIPE IS IN INTIMATECONTACT WITH THE SOIL IT IS PLACED IN, THEBEHAVIOR OF THE PIPE DURING THERMALEXPANSION IS DIRECTLY DEPENDENT ON THEPROPERTIES OF THE SOIL

THESE SOIL PROPERTIES AND THEIRINTERACTION WITH THE PIPE ARE DIFFICULT

AND EXPENSIVE TO ASSESS, SUBJECT TOCONTROVERSY AND IN SOME INSTANCEPOORLY UNDERSTOOD AT THIS TIME.

FOR THIS REASON ENGINEERING JUDGEMENTMUST BE USED WHEN EVALUATING THE SOILCONDITIONS AND THEIR AFFECT ON THE

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