API 570 Part 2 - Pipe Design

 

API 570 Piping Inspection Code Part 2: Pipe Design

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1

 

Objectives Understand

B31.3’s scope B31.3’s  scope and organization

Know the three needed B31.3 piping Determine the allowable stress “S” “S”  

classes

Determine

the Quality Factor “E” “E”   Calculate pipe thickness Calculate blank (blind) thickness 

Familiarize yourself with basic design issues

O t h e r B 3 1 ’’s  s: B31.1  – P o w e r P i p i n g ( B o i l e r ) B31.4  – P i p e l i n e S y s t e m s f o r L i q u i d s B31.8  – P i p e l i n e Sy Sy s t e m s f o r G a s e s

•

•

•

B31.11  – S l u r r y P i p i n g S y s t e m s B31.2  – F u e l G a s P i p i n g B31.5  – R e f r i g e r a t io io n P i p i n g B31.9  – B u i l d i n g S e r v i c e s

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B31.3 Piping Classes Normal

Normal or Severe

Service

 Majority

of plant Piping

Cycle 150 psig

Severe

Cyclic Service

 High

Stress  Over 7000 stress cycle Category

D

Category D

 Not

damaging humans  Pressure Limit ≤ 150 psig  Temp: -20 thru 366 oF “Duh Utility  Utility Piping” Piping”    “Duh Category

15 psig

M

None Code



Very Toxic

Nonmetallic

Not covered in API 570 exam

0 psig -20oF

High

Pressure

Excess

of Flange Class 2500

-366oF

None Code & Category D Non-Toxic Non-Hazardous Non-Flammable •

•

•

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B31.3 Organization Table

of Content

Chapter

I

 Scope  Definition

Chapter

Appendix App App

A-Z

A: “S” “S” &  & “E” “E”   C: Thermal Growth

Index

II-VI

 Three

Piping Services  Normal Service  Severe Cyclic Service  Category D

Chapter  Three

VII-IX Piping Services



 Nonmetallic M  High Pressure  Category

Note: Two important tools for finding open book info – info  – Table  Table of Contents and the Index! 5/27/2014 5:27:04 AM

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B31.3 Organization Basic Concept 1.

Pipi Piping ng clas classe ses s in in Cha Chapt pter er IIII-VI VI? ? Only Normal Service, Severe Cyclic and Category D. The other three are in Chapter VII-IX  – not  – not covered in API exam.

2.

How How Cha Chapt pter er II II-V -VII orga organi nized zed? ? By sequence of project activity. DESIGN  DESIGN  the pipe… pipe…then BUILD  BUILD  the pipe… pipe…then INSPECT INSPECT   the pipe… pipe …then TEST the TEST the pipe.

3.

How 1: the theIf3code piping piping classes classesa(Severe, (Se vere,class Normal, Normthen al, Cat Crule at D)applies identifi identified ed in into Chapter Chthat apter II-VI? II-VI?class. Rule mentions piping only piping Rule 2: If code does not mention piping classes, then the rule applies to all 3 piping classes (Severe, Normal, Cat D). Eg: 304.1.2 Wall Thickness Calcs (class not mentioned) 341.4 Required Examinations 341.4.2 Category D 341.4.7 Normal Service 341.4.3 Severe Cyclic

4.

All par parag agra raph phs s in in B31 B31.3 .3 are are 3xx 3xx.. The The “3” stands for B31.” B31.”3” 

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The B31.3 Players Owner 

Overall responsibility for compliance with the Code

Designer  Design

complies with Code

Manufacturer  Provides

materials & workmanship that complies with the Code

Owner’s Inspector  Inspector Owner’s  Assure

that the Code requirements for inspection, examination and testing are met (TIE)  Full access to all piping work

Owner

Designer

Manufacturer

Inspector

B31.3 Organization

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Exercise 1 1.

What What are the quali qualific ficati ation on requi requirem rement ents s for NDE NDE personne personnel? l?

2.

What What are the the requir requireme ements nts for the the weld weld metal metal of of tack weld welds? s?

3.

The Owner’s Owner’s Inspector  Inspector must have how many years of related inspection experience?

4.

A hyd hydrot rotest est must must be held held for at at least least ____ ______ __ minu minutes tes..

5.

Desc Descri ribe be the the hea heatt tre treat atme ment nt cal calle led d “Normalizing” “Normalizing”  

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Answers 1 1.

What What are the quali qualific ficati ation on requi requirem rement ents s for NDE NDE personne personnel? l? SNT-TC-1A  SNT-TC-1A 

2.

What What are the the requir requireme ements nts for the the weld weld metal metal of of tack weld welds? s? 328.5.1 Made by qualified welder or welding w elding operator  

3.

The Owner’s Owner’s Inspector  Inspector must have how many years of related inspection experience? 10 years  years 

4.

A hy hydr drot otes estt must must be be held held fo forr at lea least st 10 minutes. 10 minutes.

5.

Desc Descri ribe be the the hea heatt tre treat atme ment nt cal calle led d “Normalizing” “Normalizing”   A process in which a ferrous metal is heated to a suitable temperature above the transformation range and subsequently cooled in still air at room r oom temperature.

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Retirement Thickness The Formula

t=

PD 2(SE+PY)

304.1.2

P = design pressure (psig) D = outside diameter (inch) see B16.5 Table S = allowable stress (psi) E = quality factor  Y = coefficient from Table Table 304.1.1  Y produces very minor affect on the calculated thickness. Generally it reduces the retirement thickness by about 1%. The Coefficient Y for our calculations will be 0.4.

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Info Thickness Terms The terms have not been standardized throughout different codes. As a result, the terms used can be very confusing. 1. Retire Retirement ment T Thickne hickness ss (th (this is ter term m is not us used ed in code). The m minimum inimum thick thickness ness allowed. If the component is below this thickness, the component should be repaired or replaced.  In B31.3 this is called “pressure “pressure design  design thickness” thickness”    In API API 570 this is called “required “required  thickness” thickness”    Many call it “minimum  thickness”  or “t-min”  2. Retire Retirement ment th thicknes ickness s plu plus s Corro Corrosion sion A Allowanc llowance. e. Wh When en ord ordering ering new pi pipe, pe, y you ou always need to add the appropriate corrosion allowance. In B31.3 this is called “minimum “minimum required  required thickness” thickness”   

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Strength & Stress Stress   

Measures Strength

Materials fail when “overstressed” “overstressed”   Stress = Load/Area Units: psi (lbs per sq in)

Ultimate

Tensile Strength

 Stress

at which w hich failure occurs  Determined by Tension Test SMTS – Specified  Specified Minimum Tensile Strength  Also called SMTS – Strength – Strength  – the  the ability to withstand an applied load

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Strength Characteristics Elastic   

Properties

Metals stretch when loaded Metals return to original shape when load is removed Stretch is proportional to load. Higher load = more stretch

Plastic

Properties

 High

Stress, metal stretches  If above Yield Stress, it does not return to original shape when load is removed. “Permanent  deformation” deformation”    “Permanent

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Info Definitions  Yield Strength: the stress level where the material behaves beha ves plastically. plastically. No longer in the elastic range. Elastic: the deformation of a metal under a load which causes no permanent deformation. Elastic behavior is considered to be linear (the greater the pull the greater the growth/stretch). Plastic: stressed beyond the elastic limit and results in permanent deformation.

Strength of a plate can very significantly depending on the orientation. The strength is best in the direction of the roll. Transverse to the rolling direction the strength can be reduced by 30%. In the through-thickness direction it can even be less!

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Allowable Stress “S” – refer – refer to B31.3 App A-1 Allowable   

Stress

What the designer is “allowed” “allowed” to  to use in thickness calculation. Based on Code Safety Factor – Factor – B31.1  B31.1 = 3 to 1. S = SMTS/Safety Factor

Stress

vs Temperature

 As

the temperature increases, the strength str ength decreases “S” decreases  decreases  Also “S” Failure

Stress

 Stress

= Load/Area eg 60,000 psi

Allowable

Stress



 S 60,000/3 = SMTS/Safety Factor eg = 20,000 psi

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Exercise 2 1.

What is the the allowab allowable le stress stress for for a A106 A106 Gr B pipe pipe that has has a design design temper temperature ature of 700oF?

2.

What is the the allowab allowable le stress stress for a A671 A671 Gr CC70 CC70 that has has a max operat operating ing tempera temperature ture of of o 400 F?

3.

What What is SMTS SMTS of A106 106 Gr C pip pipe? e?

4.

In the the stress stress tabl tables es what what do do single single bars bars repres represent ent? ?

5.

In the the stress stress tabl tables es what what do do doubl double e bars bars repre represen sent? t?

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Answers 2 1.

What is the the allowab allowable le stress stress for for a A106 A106 Gr B pipe pipe that has has a design design temper temperature ature of 700oF? 16500 psi

2.

What is the the allowab allowable le stress stress for a A671 A671 Gr CC70 CC70 that has has a max operat operating ing tempera temperature ture of of o 400 F? 21700 psi

3.

What What is SMTS SMTS of A106 106 Gr C pip pipe? e? 70000 psi

4.

In the the stress stress tabl tables es what what do do single single bars bars repres represent ent? ? Affected by reference note

5.

In the the stress stress tabl tables es what what do do doubl double e bars bars repre represen sent? t? Prohibited by reference note

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Stress on Welds Stress   

on Cylinder affected by

Pressure Thickness Diameter Pressure in a cylinder always creates both circ and long stress

 Circ

stress on cylinder are generally twice as high as the longitudinal stress. So long welds are usually more critical than circ weld!

Circ Weld

Long Weld

Circumferential (Hoop) Stress will affects Long Weld Longitudinal Stress will affects Circ Weld

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Quality Factor “E”  “E”  What 

is “E” “E”  

Additional “safety “safety  factor” factor”    For long weld or castings

Determine

“E” 

 If

given a pipe description – description – Table  Table 302.3.4 spec – Table  Table A-1A & 1B  If given Material spec – Factors  Seamless

Pipe  E = 1.0, no long welds  Rolled & Welded Pipe  Type of weld  Amount of NDE (RT)  Cast Pipe  Material  Casting Method

Note: In ASME Section VIII, “E” “E” is  is called “Joint “Joint  Efficiency” Efficiency”.. Same concept, just different term.

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Exercise 3 1.

What is “E” “E” for  for A333 ERW pipe?

2.

What What is the quali quality ty factor factor for A53 A53 Typ Type e S?

3.

What is “E” “E”   for a pipe with a long weld that is double-butt-welded using Electric Fusion process?

4.

Determine Determine the retirement retirement thickn thickness ess of seaml seamless ess 14 NPS NPS pipe. pipe. Design Design pressure pressure is is 500 psig psig and allowable stress is 15,000 psi at design temperature. Y = 0.4

5.

Determine Determine the the minimum minimum allowe allowed d thicknes thickness s for an 8 NPS NPS pipe. pipe. The pipe pipe is A53 A53 Gr B Type Type E o (ERW). Design pressure is 400 psig and design temperature is 700 F.

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19

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Answers 3 1.

What is “E” “E” for  for A333 ERW pipe?

0.85

2.

What What is the quali quality ty factor factor for A53 A53 Typ Type e S?

3.

What is “E” “E”   for a pipe with a long weld that is double-butt-welded using Electric Fusion process? 0.85

4.

Determine Determine the retirement retirement thickn thickness ess of seaml seamless ess 14 NPS NPS pipe. pipe. Design Design pressure pressure is is 500 psig psig and

1.00

0.230” ”  allowable stress is 15,000 psi at design temperature. Y = 0.4 t = 0.230 5.

Determine Determine the the minimum minimum allowe allowed d thicknes thickness s for an 8 NPS NPS pipe. pipe. The pipe pipe is A53 A53 Gr B Type Type E o t = 0.122” (ERW). Design pressure is 400 psig and design temperature is 700 F. 0.122” 

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Pipe – Pipe  – Ordered  Ordered Thickness Rolled

and Welded

Calculate tmin Add Corrosion Allowance  Select nominal thickness 



Seamless

tw/CA = tmin + CA tnom ≥ tw/CA

Pipe

 Calculate tmin  Corrosio n  Add Corrosion

Allowance  Adjust for mill tolerance  Select nominal thickness

tw/CA = tmin + CA tadj ≥ tw/CA /0.875 tnom ≥ tadj 

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Exercise 4 1.

An 8 NPS NPS A-10 A-106 6 Gr B pipe pipe has a calcu calculat lated ed tmin of 0.182” 0.182”. The specified corrosion allowance is 0.125” 0.125 ”. What pipe schedule should be ordered?

2.

A 4 NPS piping piping system system has a design design pressure pressure of 800 800 psig psig at at 600oF. Pipe material is A-106 Gr C. Specified corrosion allowance is 0.125” 0.125”. What pipe schedule should be ordered?

3.

A “rolled “rolled   and welded” welded”   12 NPS pipe has a renewal thickness of 0.218” 0.218 ”  and a corrosion allowance of 0.100” 0.100”. What pipe schedule should be ordered?

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Answers 4 1.

An 8 NPS NPS A-10 A-106 6 Gr B pipe pipe has a calcu calculat lated ed tmin of 0.182” 0.182”. The specified corrosion allowance is 0.125” 0.125 ”. What pipe schedule should be ordered?

8” Sch 60

2.

A 4 NPS piping piping system system has a design design pressure pressure of 800 800 psig psig at at 600oF. Pipe material is A-106 Gr C. Specified corrosion allowance is 0.125” 0.125”. What pipe schedule should be ordered? 4” Sch 80

3.

A “rolled “rolled   and welded” welded”   12 NPS pipe has a renewal thickness of 0.218 0.218” ”  and a corrosion allowance of 0.100” 0.100”. What pipe schedule should be ordered? 12” Sch 30 12”

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Pipe – Pipe  – Structural  Structural Minimum The

calculated tmin is based only on pressure loadings

Other  

loadings must be considered during design

Dead Loads: weight of pipe & insulation  Live Loads: weight of process, personnel, ice/snow 

Specified

structural minimums are not listed in the codes.

 Usually  Usually

provided by Owner a list or chart  Increases with line size Real

Steps to Order Pipe

 Calculate tmin  Compare to structural tmin and

pick larger value

 Add corrosion allowance  Adjust for mill tolerance  Pick

appropriate pipe schedule

Note: Other names for Structural Minimum is Arbitrary Minimum Thickness or Mechanical Minimum Thickness

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Blanks (Blind) - Thickness Pressure-rated  Flat

blinds are thick

is the worse w orse shape for pressure containment

Formula –  – Retirement  Retirement Formula

Thickness 

 dg =

inside diameter of gasket  E = 1.0 if no weld  

If

need to order plate:  Add Corrosion Allowance  Select tnom   tnom ≥ tmin + CA

t 



d  g 

3 P  16 SE 

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Exercise 5 1.

Determine Determine the retirem retirement ent thickne thickness ss of a blank blank installe installed d in a 6 NPS line. line. Design Design pressure pressure is 300 psig with a design temperature of 900 oF. The blank is made from stainless steel material A240 Gr 316L. The gasket ID is 6.620” 6.620 ”.

2.

Determine Determine the the nominal nominal plate plate thickne thickness ss to order order for a blind. blind. The The design design pressure pressure is 325 psig psig at o 400 F. The material is A516 Gr 70 (Carbon Steel). The gasket ID is 8.625” 8.625 ”. The specified corrosion allowance is 0.200” 0.200”.

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Answers 5 1.

Determine Determine the retirem retirement ent thickne thickness ss of a blank blank installe installed d in a 6 NPS line. line. Design Design pressure pressure is 300 psig with a design temperature of 900 oF. The blank is made from stainless steel material A240 Gr 316L. The gasket ID is 6.620” 6.620 ”. tmin = 0.4571” 0.4571” 

2.

Determine Determine the the nominal nominal plate plate thickne thickness ss to order order for a blind. blind. The The design design pressure pressure is 325 psig psig at o 400 F. The material is A516 Gr 70 (Carbon Steel). The gasket ID is 8.625” 8.625 ”. The specified corrosion allowance is 0.200” 0.200”. tmin = 0.4571” 0.4571”  tw/CA = 0.4571 + 0.2 = 0.6571” 0.6571 ”  tnom ≥ 0.6571  0.6571” ”  Order round up to 1/16. Therefore need to order 0.688” 0.688 ”. 

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Fluid Service - Limits Pipe

Materials (305)

D – All  All listed materials  Cat D – Service – All  All listed  Normal Service –  Severe

Miter

materials except those limited to Cat D.

Cyclic – short Cyclic –  short list

Ends (306.3)

Flanges

(308.2)

 Slip-on

limits Cyclic – Weld  Weld Neck  Severe Cyclic – Bolting  Low

Socket

(309.2) strength – Only strength –  Only for Class 150 & 300 flanges

Welds (311.2.4) in crevice corrosion corr osion or erosion services

 Avoid  Avoid

 Severe

cyclic ≤ 2 NPS

Threaded

Joints (314)

 Avoid  Avoid

in crevice corrosion corr osion or erosion services  Avoid in cyclic loadings  Severe

cyclic – not cyclic –  not allowed except non-load items like thermowelds

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Info Definitions  Listed  Miter:

Materials: Mater ials: Materials listed in the Appendix A stress chart Elbow fabricated from pipe using pie shaped sections. Often used on large diameter pipe.  Straight Thread: Non-tapered threads. Used in threaded pipe unions.

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Pipe Flexibility A piping system will grow or shrink when w hen the temperature changes

 FxL  F xL G

  

Notice “F” @ 70oF. The chart is based on the pipe being installed at 70oF.

100

G = Growth in inches F = factor from B31.3 Table C-1 L = length of pipe in feet

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Exercise 6 1.

Dete Determ rmin ine e the the to tota tall gro growth wth of 800 800’’ carbon steel line. The line operates at 400oF.

2.

Dete Determ rmin ine e gro growt wth h of a 400 400’’ SS line that operates at 700 oF.

3.

A 12” diameter carbon steel tube is welded to a 12” 12 ” SS tube. The tube operates at 800 oF. a. How much much does does the diamet diameter er of of the the CS tube tube grow? grow? b. How much much does does the the diam diamete eterr of the the SS SS tube tube grow? grow? c. Descri Describe be the the con condit dition ion of this this diss dissimi imilar lar weld weld

Watch out: Negative temps – temps – this  this is how much cold pipe shrinks. Don’t use Don’t  use Table C-3

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Answers 6 1.

Dete Determ rmin ine e the the to tota tall gro growth wth of 800 800’’ carbon steel line. The line operates at 400oF.

2.

Dete Determ rmin ine e gro growt wth h of a 400 400’’ SS line that operates at 700 oF.

3.

A 12” diameter carbon steel tube is welded to a 12” 12 ” SS tube. The tube operates at 800 oF. G = 0.067” a. How much much does does the diamet diameter er of of the the CS tube tube grow? grow? 0.067”  b. How much much does does the the diam diamete eterr of the the SS SS tube tube grow? grow? 0.088”  G = 0.088” c. Descri Describe be the the con condit dition ion of this this diss dissimi imilar lar weld weld Highly stress – stress – thermal  thermal fatigue  fatigue 

G = 21.6 21.6” ” 

30”  G = 30”

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Pipe Flexibility Ways s Way

to increase flexibility

 Make changes in  Expansion loops

direction

 Suitable

anchors and guides  Expansion joints

Watch h Watc

out for branch connections

Stresses

relax over time

Components  Anchors

and Guides

 Hangars  Sliding

Supports (shoes)



 Spring Supports (Constant and Variable) to check cables and pulleys especially on large lines.

 Counterweights  Counterweights –  – important  important

Definitions Anchors : Prevents movement in all 3 directions (“x”, (“x”,  “y”, “y”,  “z”) “z”)   Guides : Prevents movement in 1 or 2 directions. Allows movement in only 1 or 2 directions.

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Pressure Protection Most

piping is protected by relief devices that are designed to protect

other equipment (eg vessels) Full

area stop valves (block valves) can be used on inlet and outlet of relief device

Fabrication  Per

Set

of Devices

ASME Sect. VIII Div. 1

Pressure

 Per

ASME Sect. VIII Div. 1  Thermal relief valves can be set at 120% of Design Pressure Thermal relief valves are typically needed on long runs of pipe that can be blocked in (typically found in a tank Heatbuilds from the sun warms the lines.AAs the product temperature increases, the farm). pressure in “blocked “blocked-in” in”    lines. small thermal relief valve usually with ½ NPS connections is installed to protect the pipe. Normally the thermal relief outlet just bypasses one of the closed valves.