inspection_practices_for_piping_system_components.doc

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DRAFT 3

INSPECTION PRACTICES FOR PIPING SYSTEMCOMPONENTS

API RECOMMENDED PRACTICE 574THIRD EDITION, XXX 200X

American Petroleum Institute

This dra! is "r #"$$i!!%% &a''"!i()*+r*"s%s "('-


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RP 574 3rd Edi!i"( Dra! 3

FORE.ORD

This recommended practice is based on the accumulated knowledge and experience of engineers,inspectors, and other personnel in the petroleum and petrochemical industry. It is intended to supplementthe API 5! Piping Inspection "ode.

The information in this recommended practice does not constitute and should not be construed as a codeof rules, regulations, or minimum safe practices. The practices described in this Publication are notintended to supplant other practices that ha#e pro#en satisfactory, nor is this Publication intended todiscourage inno#ation and originality in the inspection of refineries and chemical plants. $sers of thisrecommended practice are reminded that no book or manual is a substitute for the %udgment of aresponsible, &ualified inspector or piping engineer.

API Publications may be used by anyone desiring to do so. '#ery effort has been made by the Instituteto assure the accuracy and reliability of the data contained in them( howe#er, the Institute makes norepresentation, warranty, or guarantee in connection with this Publication and hereby expressly disclaimsany liability or responsibility for loss or damage resulting from its use or for the #iolation of any federal,state, or municipal regulation with which this Publication may conflict.

)uggested re#isions are in#ited and should be submitted to the director of the )tandards *epartment,American Petroleum Institute, +! - )treet, ./., /ashington, *.". !!!5, standards0api.org.

American Petroleum Institute 1 i 1


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CONTENTS

INSPECTION PRACTICES FOR PIPING SYSTEM COMPONENTS--------------------------------------------------------/

API RECOMMENDED PRACTICE 574

THIRD EDITION, XXX 200X----------------------------------------------------------------------------------------------------------------------- /

FORE.ORD------------------------------------------------------------------------------------------------------------------------------------------------ i

S#"*%---------------------------------------------------------------------------------------------------------------------------------------------------------- /

R%%r%(#%s-------------------------------------------------------------------------------------------------------------------------------------------- ----- /

T%r$s, D%i(i!i"(s, A#r"($s, a(d A&&r%ia!i"(s--------------------------------------------------------------------------------3+.+ *efinitions.......................................................................................................................................... 2+. Acronyms and Abbre#iations......................................................................................................... ....3

Pi*i() C"$*"(%(!s---------------------------------------------------------------------------------------------------------------------------------- 1+.2 Piping................................................................................................................................................. 4

+.2.+ eneral........................................................................................................................................4+.2. 6iber 7einforced Plastic Pipe.................................................................................................... +8+.2.2 )mall1bore Pipe......................................................................................................................... ++.2.9 -inings....................................................................................................................................... +

+.9 Tubing.............................................................................................................................................. ++.5 :al#es.............................................................................................................................................. +

+.5.+ eneral...................................................................................................................................... ++.5. ate :al#es............................................................................................................................... +3+.5.2 lobe :al#es............................................................................................................................. +3+.5.9 Plug :al#es.......................................................................................................................... ..... +3+.5.5 ;all :al#es................................................................................................................................. +4+.5.8 *iaphragm :al#es..................................................................................................................... +4+.5. ;utterfly :al#es...................................................................................................................... ... +4

+.5.3 "heck :al#es............................................................................................................................ +4+.5.4 )lide :al#es...............................................................................................................................!

+.8 6ittings.......................................................................................................................................... .. !+.8.+


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+.+5 )pecial @oints................................................................................................................................. 2+.+8 on1metallic Piping @oints.............................................................................................................. 2

+.+8.+ eneral.................................................................................................................................... 2+.+8. ;ell and )pigotTapertaper...................................................................................................... 9+.+8.2 ;utt and /rap......................................................................................................................... 9+.+8.9 6lange16lange.................................................................................................................. ....... 9

R%as"(s "r I(s*%#!i"(--------------------------------------------------------------------------------------------------------------------------- 24+.+ eneral.......................................................................................................................................... 9+.+3 )afety............................................................................................................................................. 9+.+4 7eliability and 'fficient Bperation..................................................................................................5+.! 7egulatory 7e&uirements........................................................................................................... ... 5

I(s*%#!i"( P'a(s-------------------------------------------------------------------------------------------------------------------------------------- 25+.+ eneral.......................................................................................................................................... 5+. *e#eloping an Inspection Plan.......................................................................................................8

+..+ 7isk1;ased Inspection Plans................................................................................................... +.. Inter#al1based Inspection Plans....................................................................................... ....... +..2 "lassifying Piping )er#ice....................................................................................................... 3

+.2 "$I?........................................................................................ ....2+.9.5 )oil1to1Air >)A? Interface........................................................................................................ 29+.9.8 )er#ice1specific and -ocali=ed "orrosion........................................................................... ....25+.9. 'rosion and 'rosion1"orrosion................................................................................................28+.9.3 'n#ironmental "racking.......................................................................................................... 28+.9.4 "orrosion ;eneath -inings and *eposits.................................................................................2+.9.+! 6atigue "racking................................................................................................................... 2+.9.++ "reep "racking...................................................................................................................... 23+.9.+ ;rittle 6racture....................................................................................................................... 23+.9.+2 6ree=e *amage.....................................................................................................................24+.9.+9 "ontact Point "orrosion.........................................................................................................24+.9.+5 on1


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far as accessibility permits. )ome piping is large enough for internal inspection which can only occurwhile the piping is offline.................................................................................................................. .. 92+..9 Ade&uate follow1up inspections should be conducted to determine the causes of defects, suchas leaks, misalignment, #ibration, and swaying, which were detected while the unit was operating..92

+.3 Inspection )cope............................................................................................................................92+.3.+ Piping inspection should be fre&uent enough to assure that all piping has sufficient thickness to pro#ide both pressure containment and mechanical support. 6or pipes undergoing uniformcorrosion, calculating the corrosion rate and remaining life at each "7T?...........................................................................52+.22.2 "aliper Thickness


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+.9+.2 -eak Testing............................................................................................................................ 84+.9 Inspection of ew 6abrication, 7epairs and Alterations.................................................................!

+.9.+ eneral ................................................................................................................................... !+.9.


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FIG9RES

+ 11 "ross )ection of a Typical /edge ate :al#e

11 "ross )ection of a Typical lobe :al#e

2 11 "ross )ections of Typical -ubricated and onlubricated Plug :al#es

9 11 "ross )ection of a Typical ;all :al#e

5 11 "ross )ection of a Typical *iaphragm :al#e

8 11 Typical ;utterfly :al#e

11 "ross )ections of Typical "heck :al#es

3 11 "ross )ection of a Typical )lide :al#e

4 11 6langed1'nd 6ittings and /rought )teel ;utt1/elded 6ittings

+! 11 6orged )teel Threaded and )ocket1/elded 6itt ings

++ 11 "ross )ection of a )ocket1/elded Tee "onnection

+ 11 6lange 6acings "ommonly $sed in 7efinery and chemical plant Piping

+2 11 Types of 6langes

+9 11 "ross )ection of a Typical ;ell1and1)pigot @oint

+5 11 "ross )ections of Typical Packed and )lee#e @oints

+8 11 "ross )ections of Typical Tubing @oints

+ 11 Piping "ircuit 'xample

+3 11 'rosion of Piping

+4 11 "orrosion of Piping

! 11 Internal "orrosion of Piping

+ 11 )e#ere Atmospheric "orrosion of Piping

11 In%ection Point "ircuit

2 11 )oil1to1Air Interface "orrosion

9 11 7adiograph of a "atalytic 7eformer -ine

5 11 7adiograph of "orroded Pipe /hose Internal )urface Is "oated /ith Iron )ulfide )cale

8 11 )ketch and 7adiograph of *ead1end "orrosion

11 $nderground Piping "orrosion ;eneath Poorly Applied Tape /rap

3 D Pipe1to1soil Internal Potential )ur#ey use to Identify Acti#e "orrosion )pots in $nderground Piping

4 11 'xample of Pipe1to1)oil Potential )ur#ey "hart

2! 11 /enner 6our1pin )oil 7esisti#ity Test

2+ 11 )oil ;ar used for )oil 7esisti#ity


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S#"*%

This recommended practice supplements API 5! by pro#iding piping inspectors with information thatcan impro#e skill and increase basic knowledge and practices. This recommended practicedescribespractice describesinspection practices for piping, tubing, #al#es >other than control #al#es?,

and fittings used in petroleum refineries and chemical plants. "ommon piping components, #al#e types,pipe %oining methods, inspection planning processes, inspection inter#als and techni&ues, and types ofrecords are described to aid the inspector in fulfilling their role implementing API 5!. This pu blicationdoes not co#er inspection of specialty items, including instrumentation and control #al#es.

R%%r%(#%s

The following referenced documents are a #aluableaid to the application of this document. 6or datedreferences, the latest edition of the referenced document >including any amendments ?amendments?applies.

API )td 5!, Piping Inspection Code, )econd 'dition

API 7P 5+, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry

API 7P 5, Welding Inspection and Metallurgy

API 7P 53 Material erification Program for !e" and Existing Alloy Piping #ystems

API )td 541+A)


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API 7P 421;, Design, Materials, Fa0rication, 1peration, and Inspection +uidelines for Corrosion Controlin 2ydroprocessing Reactor Effluent Air Cooler 4REAC5 #ystems

API 7P 428, Refractory Installation 6uality Control +uidelines ( Inspection and *esting MonolithicRefractory )inings and Materials

API 7P 49+, #teels for 2ydrogen #er%ice at Ele%ated *emperatures and Pressures in PetroleumRefineries and Petrochemical Plants

API 7P 495,A%oiding En%ironmental Crac&ing in Amine 3nits

API Publ. +A, +uidelines for Wor& in Inert Confined #paces in the Petroleum Industry

A)


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A)T< ' +++3, Practice For AE Examination 1f Reinforced *hermosetting Resin Pipe;

A)T< 5, Method for Field Measurement of #oil Resisti%ity 3sing the Wenner Four$Electrode Method


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#"(di!i"( $"(i!"ri() '"#a!i"(sCM;s*esignated areas on piping systems where periodic examinations are conducted. Pre#iously, they werenormally referred to as Gthickness monitoring locationsH >T


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*i*%A pressure1tight cylinder used to con#ey a fluid or to transmit a fluid pressure, ordinarily designatedJpipeJ in applicable material specifications.

BT'


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BT' A rerating may consist of an increase, decrease, or a combination. *erating below original designconditions is a means to pro#ide increased corrosion allowance.

ris6&as%d i(s*%#!i"(R:I

A risk assessment and management process that is focused on inspection planning for loss ofcontainment of pressuri=ed e&uipment in processing facilities, due to material deterioration.

BT' These risks are managed primarily through inspection in order to influence the probability of failure.

s$a'' &"r% *i*i()S:PPipe or pipe components that are less than or e&ual to P) .

s"i'!"air =S i(!%ra#%An area where increased in whichexternal corrosion may can occur on partially buried pipeand whereburied piping begins to extend abo#e ground..

BT' The =one of the corrosion will #ary depending on factors such as moisture, oxygen content of the soil andthe operating temperature. The =one generally is considered to be from +J >2! cm? below to 8J >+5 cm? abo#e thesoil surface. Pipe running parallel with the soil surface that contacts the soil is included.

s*""'sA section of piping encompassed by flanges or other connecting fittings, such as unions.

S!ri* 'i(i())trips of metal plates or sheets that are welded to the inside of the pipe wall.

BT' ormally the strips are of a more corrosion resistant or erosion resistant alloy than the pipe walland pro#ide additional corrosionerosion resistance.

s!r+#!+ra' $i(i$+$ !hi#6(%ss


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!%s!i()Procedures used to determine material hardness, strength, and notch toughness.

'A


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3-2-/0RTradiographic examination techni&ue

3-2-//9Tultrasonic examination techni&ue

3-2-/2.FMTwet fluorescent magnetic particle examination techni&ue

Pi*i() C"$*"(%(!s

/-3 Pi*i()

/-3-/ G%(%ra'

4-/-/-/ Piping can be made from any material that can be rolled and welded, cast, or drawn through diesto form a tubular section. The two most common carbon steel piping materials used in the petrochemicalindustry are A)T< A 52 and A +!8. The industry uses both seamlessand '7/ piping for mostprocessser#icesdepending upon current economics and the potential for accelerated corrosion of the weld seamin the ser#ice. Piping of a nominal si=e larger than +8 in. >9!8 mm? is usually made by rolling plates tosi=e and welding the seams. "entrifugally cast piping can be cast then machined to any desiredthickness. )teel and alloy piping are manufactured to standard dimensions in nominal pipe si=es up to 93in. >++4 mm?.

4-/-/-2 Pipe wall thicknesses are designated as pipe schedules in nominal pipe si=es up to 28 in. >4+9mm?. The traditional thickness designations M standard weight, extra strong, and double extra strong Mdiffer from schedules and are used for nominal pipe si=es up to 93 in. >++4 mm?. In all standard si=es,the outside diameter remains nearly constant regardless of the thickness. 6or nominal pipe si=es e&ual toor less than + in. >2!5 mm?, Tthe si=e refers to the inside diameter of standard weight pipefor nominalpipe si=es e&ual to or less than + in. >2!5 mm?,.or nominal pipe si=es of +9 in. >258 mm? and larger,tThe si=e denotes the actual outside diameterfor nominal pipe si=es e&ual to or greater than +9 in. >258mm?. The pipe diameter is expressed as nominal pipe si=e >P)? which is based on these si=e practices.Table + and Table listslistthe dimensions of ferritic and stainless steel pipe from P) +3 up throughP) 9. )ee A)


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Ta&'% /@N"$i(a' Pi*% Si%s, S#h%d+'%s, .%i)h! C'ass%s, a(d Di$%(si"(s " S!%%' Pi*%

Pi*%Si%

>P)?

A#!+a'O-D-in.

S#h%d+'%.%i)h!C'ass

A**r"i$a!% I-D-

in.

N"$i(a'Thi#6(%ss

in.

+3 !.9!5 9! )T* !.84 !.!83

3! ) !.+5 !.!45

+9 !.59! 9! )T* !.289 !.!33

3! ) !.2! !.++4

23 !.85 9! )T* !.942 !.!4+

3! ) !.92 !.+8

+ !.39! 9! )T* !.8 !.+!4

3! ) !.598 !.+9

+8! !.989 !.+33

111 ) !.5 !.49

29 +.!5! 9! )T* !.39 !.++2

3! ) !.9 !.+59+8! !.8+ !.+4

111 ) !.929 !.2!3

+ +.2+5 9! )T* +.!94 !.+22

3! ) !.45 !.+4

+8! !.3+5 !.5!

111 ) !.544 !.253

+ K +.88! 9! )T* +.23! !.+9!

3! ) +.3 !.+4+

+8! +.+8! !.5!

111 ) !.348 !.23

+ N +.4!! 9! )T* +.8+! !.+95

3! ) +.5!! !.!!

+8! +.223 !.3+

111 ) +.+!! !.9!!

.25 9! )T* .!8 !.+59

3! ) +.424 !.+3

+8! +.83 !.299

111 ) +.5!2 !.928

N .35 9! )T* .984 !.!2

3! ) .22 !.8

+8! .+5 !.25111 ) +.+ !.55

2 2.5!! 9! )T* 2.!83 .+8

3! ) .4!! .2!!

+8! .89 .923

111 ) .2!! .8!!

American Petroleum Institute 1 +! 1


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2 N 9.!!! 9! )T* 2.593 !.8

3! ) 2.289 !.2+3

11 ) .3 !.828

9 9.5!! 9! )T* 9.!8 !.2

3! ) 2.38 !.22

+! 2.89 !.923

+8! 2.923 !.52+

111 ) 2.+5 !.89

5 5.582 9! )T* 5.!9 !.53

3! ) 9.3+2 !.25

+! 9.582 !.5!!

+8! 9.2+2 !.85

111 ) 9.!82 !.5!

8 8.85 9! )T* 8.!85 !.3!

3! ) 5.8+ !.92

+! 5.5!+ !.58

+8! 5.+3 !.+4

111 ) 9.34 !.389

3 3.85 ! 3.+5 !.5!

2! 3.!+ !.

9! )T* .43+ !.2

8! .3+2 !.9!8

3! ) .85 !.5!!

+!! .92 !.549

+! .+3 !.+4

+9! .!!+ !.3+

111 ) 8.35 !.35+8! 8.3+2 !.4!8

+! +!.5 ! +!.5! !.5!

2! +!.+28 !.2!

9! )T* +!.!! !.285

8! ) 4.5! !.5!!

3! 4.58 !.549

+!! 4.2+ !.+4

+! 4.!8 !.399

+9! 3.5! +.!!!

+8! 3.5!! +.+5

American Petroleum Institute 1 ++ 1


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+ +.5! ! +.5! .5!

2! +.!4! !.22!

111 )T* +.!!! !.25

9! ++.423 !.9!8

111 ) ++.5! !.5!!

8! ++.88 !.583! ++.29 !.833

+!! ++.!8 !.399

+! +!.5! +.!!!

+9! +!.5!! +.+5

+8! +!.+8 +.2+

+9 +9.!!! +! +2.5!! !.5!

! +2.28 !.2+

2! )T* +2.5! !.25

9! +2.+9 !.923

111 ) +2.!!! !.5!!

8! +.3+ !.549

3! +.5!! !.5!

+!! +.+9 !.423

+! ++.3+ +.!49

+9! ++.5!! +.+5

+8! ++.+33 +.9!8

+8 +8.!!! +! +5.5!! !.5!

! +5.28 !.2+

2! )T* +5.5! !.25

9! ) +5.!!! !.5!!

8! +9.833 !.8583! +9.2+ !.399

+!! +2.423 +.!2++

+! +2.58 +.+4

+9! +2.+9 +.923

+8! +.3+ +.549

+3 +3.!!! +! +.5!! !.5!

! +.28 !.2+

111 )T* +.5! !.25

2! +.+9 !.923

111 ) +.!!! !.5!!

9! +8.38 !.58

8! +8.5!! !.5!

3! +8.+9 !.423

+!! +5.833 +.+58

+! +5.5! +.25

+9! +9.38 +.58

+8! +9.923 +.3+

American Petroleum Institute 1 + 1


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! !.!!! +! +4.5!! !.5!

! )T* +4.5! !.25

2! ) +4.!!! !.5!!

9! +3.3+ !.549

8! +3.28 !.3+

3! +.423 +.!2++!! +.923 +.3+

+! +.!!! +.5!!

+9! +8.5!! +.5!

+8! +8.!8 +.484

.!!! +! +.5!! !.5!

! )T* +.5! !.25

2! ) +.!!! !.5!!

8! !.5! !.35

3! +4.5! +.+5

+!! +4.5! +.25

+! +3.5! +.85

+9! +3.5! +.35

+8! +.5! .+5

9 9.!!! +! 2.5!! !.5!

! )T* 2.5! !.25

111 ) 2.!!! !.5!!

2! .38 !.58

9! .89 !.833

8! .!8 !.484

3! +.58 +.+4

+!! !.423 +.52++! !.28 +.3+

+9! +4.38 .!8

+8! +4.2+ .299

American Petroleum Institute 1 +2 1


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Ta&'% 2@N"$i(a' Pi*% Si%s, S#h%d+'%s, a(d Di$%(si"(s " S!ai('%ss S!%%' Pi*%

Pi*% Si%

>P)?

A#!+a' O-D-

in.

N"$i(a' .a'' Thi#6(%ss

S#h- 5S S#h- /0S S#h- 40S S#h- ?0S

+3 .9!5 111 !.!94 !.!83 !.!48

+9 .59! 111 !.!85 !.!33 !.++423 .85 111 !.!85 !.!4+ !.+8

+ .39! !.!85 !.!32 !.+!4 !.+9

29 +.!5! !.!85 !.!32 !.++2 !.+59

+ +.2+5 !.!85 !.+!4 !.+22 !.+4

+ +9 +.88! !.!85 !.+!4 !.!2+9! !.+4+

+ + +.4!! !.!85 !.+!4 !.+8+95 !.!!

.25 !.!85 !.+!4 !.8+59 !.+3

+ .35 !.!32 !.+! !.!2 !.8

2 2.5!! !.!32 !.+! !.+8 !.2!!2 + 9.!!! !.!32 !.+! !.8 !.2+3

9 9.5!! !.!32 !.+! !.2 !.22

5 5.582 !.+!4 !.+29 !.53 !.25

8 8.85 !.+!4 !.+29 !.3! !.92

3 3.85 !.+!4 !.+93 !.2 !.5!!

+! +!.5! !.+29 !.+85 !.285 !.5!!

+ +.5! !.+58 !.+3! !.25 !.5!!

+9 +9.!! !.+58 !.+33 111 111

+8 +8.!! !.+85 !.+33 111 111+3 +3.!! !.+85 !.+33 111 111

! !.!! !.+33 !.+3 111 111

.!! !.+33 !.+3 111 111

9 9.!! !.+3 !.5! 111 111

4-/-/-3 Allowable tolerances in pipe diameter differ from one piping material to another. Table 2 lists theacceptable tolerances for diameter and thickness of most A)T< ferritic pipe standards. The actualthickness of seamless piping may can #ary from its nominal thickness by a manufacturing tolerance ofas much as +.5 O. The under tolerance for welded piping is !.!+ in. >!.5 mm?. "ast piping has athickness tolerance of ++8 in. >+.8 mm? and 1! in. >! mm?, as specified in A)T< A 52!. "onsult the

A)T< or the e&ui#alent A)


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Ta&'% 3 B P%r$issi&'% T"'%ra(#%s i( Dia$%!%r a(d Thi#6(%ss "r F%rri!i# Pi*%

ASTMMa!%ria'S!a(dard

A##%*!a&'% Dia$%!%r T"'%ra(#%s a A##%*!a&'% Thi#6(%ss T"'%ra(#%s b

A 52Q P) + N +89 in. 1+2 in.

1+.5 O

R P) + N S + OR P) +3 Q P) + N +89 in. 1+2 in.

A +!8 R P) + N Q P) 9 +2 in. 1+2 in.

A 2+ R P) 9 Q P) 3 ++8 in. 1+2 in.

A 52! R P) 3 Q P) +3 22 in. 1+2 in.

A 2+ R P) +3 Q P) 8 +3 in. 1+2 in.

A 4! R P) 8 Q P) 29 52 in. 1+2 in.

R P) 29 Q P) 93 2+8 in. 1+2 in.

A +29 "ircumference S !.5 O of specified diameter. Acceptable tolerance of plate standard.

A +25 + O of nominal 1+.5 O

A 253 S !.5 O 1!.!+ in.

A 9!4/all Q !.+33 in. thickness S !.! O

1!.!+3 in./all R !.+33 in. thickness S !.9! O

A 95+ M +3 in.( 1!

A 95Q 9 in. I.*. +2 in.

O with +3 in. max.( 1!R 9 in. I.*. ++8 in.

A 59

R P) +3 Q + N +89 in. 1+2 in.

1+.5 O

R P) + + Q 9 +2 in. 1+2 in.

R P) 9 Q 3 ++8 in. 1+2 in.

R P) 3 Q +3 22 in. 1+2 in.

R P) +3 +3 in. 1+2 in.

A 53 )ee A)T< A 53, Table 9.

A 88! M

Ten percent greater than the specifiedminimum wall thickness.

ero less than the specified minimumwall thickness.

A 8+ !.5 O of specified diameter. !.!+ in. less than the specifiedthickness.A 8, A 84+ S !.5 O of specified diameter.

A 3+2

R P) + +9 S !.!+! in.

U1!.+ O for wall Q !.+33 in.

S !.!2! in. for wall thickness R !.+33 in.

R P) + N Q P) 8 S !.!! in.

R P) 3 Q P) +3 S !.!2! in.

R P) ! Q P) 9 S !.!9! in.

P) 2! S !.!5! in.

A 3+9 )ee A)T< A 3+9, Table +.

a Tolerance on nominal diameter unless otherwise specified.

b Tolerance on nominal wall thickness unless otherwise specified.



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/-3-2 Fi&%r R%i("r#%d P'as!i# Pi*%

4-/-2-/ on metallic materials ha#e gained significant use in piping systems in the hydrocarbon industry.They ha#e significant ad#antages in many ways o#er the more familiarcommonmetallic materials,thatengineers and inspectors are familiar with howe#er they do but they also ha#e uni&ue construction anddeterioration mechanisms that if inade&uately addressed can lead to premature failuresif not addressedade&uately.

4-/-2-2 The term non metallics has a broad range definition so for the purposes ofbut in this sectionrefers we will restrict oursel#esto the fiber reinforced plastic groups encompassed by the genericacronyms 67P and 7P. The extruded, generally homogenous non1metallics,such as high and low1density polyethylene are excluded.

4-/-2-3 Typical ser#ice applications of 67P piping include( ser#ice water, process water, coolingmedium, potable water, sewagegray water >non ha=ardous waste, non ha=ardous drains, non ha=ardous#ents, chemicals, firewater ring mains, firewater deluge systems, produced and ballast water.

4-/-2-4 *esign of these piping systems is largely dependent on the application.


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structure are specified and the pipe is manufactured to a specification and to a specified le#el of &ualityand tolerances.

4-/-2-1 The 67P inspector should #erify by documentation and inspection that the piping system hasbeen built with the proper materials, &uality, hardness and thickness as re&uested in the pipespecification. A final inspection should be performed at the %ob site to insure that the pipe has not

experienced any mechanical damage during shipment.

/-3-3 S$a''&"r% Pi*%

)mall1bore piping, can be used as primary process piping or as nipples, secondary, and auxiliary piping.ipples are normally 8 in. >+5 mm? or less in length and are most often used in #ents at piping highpoints and drains at piping low points and used to connect secondaryauxiliary piping. )econdary pipingis normally isolated from the main process lines by closed #al#es and can be used for such functions assample taps. Auxiliary piping is normally open to ser#ice and used for flush lines, instrument piping,analy=er piping, lubrication, and seal oil piping for rotating e&uipment.

/-3-4 ;i(i()s

Internal linings can be incorporated into piping design to reduce corrosion, erosion, product

contamination, and pipe metal temperatures. The linings can generally be characteri=ed as metallic andnon1metallic. 2. mm? less than theactual outside diameter.? Tubing is usually made in small diameters and is mainly used for heatexchangers, instrument piping, lubricating oil ser#ices, steam tracing, and similar ser#ices.

/-5 a'%s

/-5-/ G%(%ra'

The basic types of #al#es are gate, globe, plug, ball, diaphragm, butterfly, check, and slide #al#es.:al#es are made in standard pipe si=es, materials, body thickness, and pressure ratings that permit themto be used in any pressure1temperature ser#ice in accordance with A)


25/87


socket welding, or be#eled for butt1welding. Although many #al#es are manually operated, they can bee&uipped with electric motors and gear operators or other power operators to accommodate a large si=eor inaccessible location or to permit actuation by instruments. ;ody thicknesses and other design dataare gi#en in API 549, API 544, API 8!!, API 8!, API 8!2, API 8!3, API 8!4, and A)5+ mm? usually ha#e portopenings that are approximately the same si=e as the #al#e end openings which is called a full1ported#al#e. 6igure + shows a cross section of a full1ported wedge gate #al#e.

7educed port gate #al#es ha#e port openings that are smaller than the end openings. 7educed port#al#es should not be used as block #al#es associated with pressure relief de#ices or in erosi#eapplications, such as slurries, or lines that are to be JpiggedJ.

Fi)+r% / B Cr"ss S%#!i"( " a T*i#a' .%d)% Ga!% a'%

/-5-3 G'"&% a'%s

A globe #al#e, which is commonly used to regulate fluid flow, consists of a #al#e body that contains acircular disc that mo#es parallel to the disc axis and contacts the seat. The stream flows upwardgenerally, except for #acuum ser#ice or when re&uired by system design >e.g. fail closed?, through theseat area against the disc, and then changes direction to flow through the body to the outlet disc. Theseating surface may can be flat or tapered. 6or fine1throttling ser#ice, a #ery steep tapered seat may canbe used( this particular type of globe #al#e is referred to as a needle #al#e. A globe #al#e is commonlyconstructed with its inlet and outlet in line and with its port opening at right angles to the inlet and outlet.6igure illustrates a cross section of a globe #al#e.

Fi)+r% 2 B Cr"ss S%#!i"( " a T*i#a' G'"&% a'%

/-5-4 P'+) a'%s

A plug #al#e consists of a tapered or cylindrical plug fitted snugly into a correspondingly shaped seat inthe #al#e body. Plug #al#es usually function as block #al#es to close off flow. /hen the #al#e is open,an opening in the plug is in line with the flow openings in the #al#e body. The #al#e is closed by turningthe plug one1&uarter turn so that its opening is at right angles to the openings in the #al#e body. Plug#al#es may can be operated by a gear1operated de#ice or by turning a wrench on the stem. Plug #al#es

are either lubricated or nonlubricated( 6igure 2 illustrates both types. -ubricated plug #al#es use agrease1like lubricant that is pumped into the #al#e through groo#es in the body and plug surfaces topro#ide sealing for the #al#e and promote ease of operation. onlubricated plug #al#es on the otherhand use as sealing elements metal seats or non1metallic slee#es, seats, or complete or partial linings orcoatings.



26/87


Fi)+r% 3 B Cr"ss S%#!i"(s " T*i#a' ;+&ri#a!%d a(d N"('+&ri#a!%d P'+) a'%s

/-5-5 :a'' a'%s

A ball #al#e is another one1&uarter turn #al#e similar to a plug #al#e except that the plug in a ball #al#e

is spherical instead of tapered or cylindrical. ;all #al#es usually function as block #al#es to close off flow.They are well suited for conditions that re&uire &uick onoff or bubble tight ser#ice. A ball #al#e istypically e&uipped with an elastomeric seating material that pro#ides good shutoff characteristics(howe#er, all1metal, high1pressure ball #al#es are a#ailable. 6igure 9 illustrates a ball #al#e.

Fi)+r% 4 B Cr"ss S%#!i"( " a T*i#a' :a'' a'%

/-5- Dia*hra)$ a'%s

A diaphragm #al#e is a packless #al#e that contains a diaphragm made of a flexible material thatfunctions as both a closure and a seal. /hen the #al#e spindle is screwed down, it forces the flexiblediaphragm against a seat, or dam, in the #al#e body and blocks the flow of fluid. These #al#es are notused extensi#ely in the petrochemical industry but they do ha#e application in corrosi#e ser#ices belowapproximately 5!L6 >++L"? where a leak tight #al#e is needed. 6igure 5 illustrates a diaphragm #al#e.

Fi)+r% 5 B Cr"ss S%#!i"( " a T*i#a' Dia*hra)$ a'%

/-5-7 :+!!%r' a'%s

A butterfly #al#e consists of a disc mounted on a stem in the flow path within the #al#e body. The body isusually flanged and of the lug or wafer type. A one1&uarter turn of the stem changes the #al#e from fullyclosed to completely open. ;utterfly #al#es are most often used in low1pressure ser#ice for coarse flowcontrol. They are a#ailable in a #ariety of seating materials and configurations for tight shutoff in low andhigh1pressure ser#ices. -arge butterfly #al#es are generally mechanically operated. The mechanicalfeature is intended to pre#ent them from slamming shut in ser#ice. 6igure 8 illustrates the type ofbutterfly #al#e usually specified for water ser#ice.

Fi)+r% B T*i#a' :+!!%r' a'%

/-5-? Ch%#6 a'%s

A check #al#e is used to automatically pre#ent back flow. The most common types of check #al#es areswing, lift1piston, ball, and spring1loaded wafer check #al#es. 6igure illustrates cross sections of eachtype of #al#e( these #iews portray typical methods of pre#enting back flow.



27/87


Fi)+r% 7 B Cr"ss S%#!i"(s " T*i#a' Ch%#6 a'%s

/-5-1 S'id% a'%s

The slide #al#e is a speciali=ed gate #al#e generally used in erosi#e or high1temperature ser#ice. It

consists of a flat plate that slides against a seat. The slide #al#e uses a fixed orifice and one or two solidslides that mo#e in guides, creating a #ariable orifice that make the #al#e suitable for throttling orblocking. )lide #al#es do not make a gas tight shutoff. Bne popular application of this type of #al#e iscontrolling fluidi=ed catalyst flow in 6"" units. Internal surfaces of these #al#es that are exposed to highwear from the catalyst are normally co#ered with erosion resistant refractory. 6igure 3 illustrates a slide#al#e.

Fi)+r% ? B Cr"ss S%#!i"( " a T*i#a' S'id% a'%

/- Fi!!i()s

/--/ M%!a''i# Fi!!i()s

6ittings are used to connect pipe sections and change the direction of flow, or allow the flow to bedi#erted or added to. 6ittings can be cast, forged, drawn from seamless or welded pipe, or formed andwelded. 6ittings may can be obtained with their ends flanged, recessed for socket welding, be#eled forbutt welding, or threaded for threaded connections. 6ittings are made in many shapes, such as wyes,tees, elbows, crosses, laterals, and reducers. 6igure 4 illustrates types of flanged and butt1weldedfittings. 6igure +! illustrates types of threaded and socket1welded fittings.

/--2 FRP Fi!!i()s

67P fittings are manufactured by different processes. In%ection molding, filament winding and contactmolding are the most common techni&ues. The same criteria used to accept the pipe should be appliedto fittings. In particular, contact molded fitt ings should be inspected to insure that they are manufacturedto the same specification as the pipe. "ontact molded fittings fabrication is critical because the layers ofreinforcement must be o#erlapped to make sure that the strength of the layers is not compromised. Bnepiece contact molded fittings are the preferred method but many items such as Tees and branchconnections are often manufactured using two pieces of pipe. The Inspector must check to make surethat the reinforcement on those pieces and the gap between them is within the tolerance specified. Theexposed cut edges must be protected accordingly.

67P 6langes are manufactured using the same methods as the fittings. "ontact molded flanges shouldbe inspected for dimensions, drawback and face flatness. The layers of reinforcement should extendonto the pipe in order to create the proper bond and hub reinforcement.


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Fi)+r% /0 B F"r)%d S!%%' Thr%ad%d a(d S"#6%!.%'d%d Fi!!i()s

/-7 F'a()%s

/-7-/ M%!a''i# F'a()%s

A)see 5.9?Threaded %oints that are located ad%acent to rotating e&uipment or otherspecific sources of high #ibration can be especially susceptible to failure due to fatigue. )pecialconsideration should be gi#en to these situations.

American Petroleum Institute 1 + 1


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/-// .%'d%d "i(!s

/-//-/ G%(%ra'

/elded %oints ha#e for the most part replaced threaded and flanged %oints except in small bore pipingwhere some users still rely on threaded %oints and in cases where piping is connected to e&uipment whichre&uires periodic maintenance. @oints are either butt1welded >in #arious si=es of pipe? or socket1welded>typically P) and smaller?.

/-//-2 :+!!8%'d%d "i(!s

;utt1welded connections are the most commonly found in the petrochemical industry. The ends of thepipe, fitting, or #al#e are prepared and aligned with ade&uate root opening in accordance with A)concentric or spiral? to smooth>depending on the type of gasket, gasket material, and ser#ice conditions?, or groo#es maycanbe cut forseating metal1ring gaskets. 6igure + illustrates common flange facings for #arious gaskets. Thecommon types of flanges are welding neck, slip1on welding, threaded, blind, lap %oint, and socket welded.'ach type is illustrated in 6igure +2. The flanges of cast fittings or #al#es are usually integral with thefitting or the #al#e body.

Fi)+r% /2 B F'a()% Fa#i()s C"$$"(' +s%d i( R%i(%r a(d Ch%$i#a' P'a(! Pi*i()

American Petroleum Institute 1 1


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Fi)+r% /3 B T*%s " F'a()%s

/-/3 Cas! Ir"( Pi*% "i(!s

"ast iron pipe %oints can be of the flanged, packed, slee#e, hub1and1spigot1end or hub1and1plain1end, or

bell1and1spigot1end or bell1and1plain1end type. Push1on %oints with rubber or synthetic ring gaskets area#ailable. "lamped %oints are also used. Threaded %oints are seldom used for cast iron. The hub1and1plain1end %oint is shown in 6igure +9. 6igure +5 illustrates cross sections of a bell1type mechanical %oint, aslee#e connection, and a typical proprietary connection >see 5.?. These types of %oints are seldom usedin process piping ser#ice.

Fi)+r% /4 B Cr"ss S%#!i"( " a T*i#a' :%''a(dS*i)"! "i(!

Fi)+r% /5 B Cr"ss S%#!i"(s " T*i#a' Pa#6%d a(d S'%%% "i(!s

/-/4 T+&i() "i(!s

Tubing can be %oined by welding, soldering, or bra=ing or by using flared or compression fittings. 6igure+8 illustrates flared and compression %oints.

Fi)+r% / B Cr"ss S%#!i"(s " T*i#a' T+&i() "i(!s

/-/5 S*%#ia' "i(!s

Proprietary %oints are a#ailable that incorporate uni&ue gaskets, clamps, and bolting arrangements.These designs offer ad#antages o#er con#entional %oints in certain ser#ices. These ad#antages o#ercon#entional flanges can includeF

a? higher pressure and temperature ratings(

b? smaller dimensions(

c? easier installation 1 axial and angular alignment re&uirements are less stringent(

d? greater force and moment toleration.

/-/ N"($%!a''i# Pi*i() "i(!s

/-/-/ G%(%ra'

There are se#eral methods of %oining 67P pipe and fittings. @oints in non1metallic piping are often ofse#eral different designs depending upon the manufacturer of the pipe. )ome common %oint designs in67P pipe systems include a bell and spigot, butt and wrap, tapertaper and flange1flange.

American Petroleum Institute 1 2 1


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/-/-2 :%'' a(d S*i)"!including flatness and wa#iness according to the specification? is re&uired in order to pre#ent damage atthe specifedspecifiedtor&ue #alues. 6ull face gaskets are re&uired for bolting full face flanges. 6langesbolting to raise face connections must be e#aluated indi#idually for re&uired tor&ue #alues and propergasket re&uirements.

R%as"(s "r I(s*%#!i"(

/-/7 G%(%ra'

The primary purposesof inspection areis to perform acti#ities using appropriate techni&ues necessarytoidentify acti#e deterioration mechanisms and to specify repair, replacement, or future inspections foraffected piping. These purposesThisre&uiresde#eloping information about the physical condition of thepiping, the causes of itsany deterioration, and itstherate of deterioration. ;y de#eloping a database ofinspection history, the user maycan predict and recommend future repairs and replacements, and actaccordingly, to pre#ent or retard further deterioration and most importantly, pre#ent loss of containment.ThisThese actionsshould result in increased operating safety, reduced maintenance costs, and morereliable and efficient operations. API 5! pro#ides the basic re&uirements for such an inspectionprogram. This recommended practice supplements API 5! by pro#iding piping inspectors withinformation that can impro#e skill and increase basic knowledge and practices.

/-/? Sa%!

A leak or failure in a piping system maycan be only a minor incon#enience, or it maycanbecome apotential source of fire or explosion depending on the temperature, pressure, contents, and location ofthe piping. Piping in a petrochemical plant maycan carry flammable fluids, acids, alkalis, and otherharmful chemicals that would make leaks dangerous to personnel. Bther piping maycancarry processstreams that contain toxic by1products generated during processing. -eaks in these kinds of lines cancreate dangerous en#ironmental conditions. Ade&uate inspection is a prere&uisite for maintaining thistype of piping in a safe, operable condition. In addition, federal regulations such as B)CAWs 4"67+4+!.++4 has mandated that e&uipment, including piping, which carries significant &uantities ofha=ardous chemicals be inspected according to accepted codes and standards which includes API 5!.



32/87


-eakage maycan occur at flanged %oints in piping systems especially in critical high temperatureser#ices, during start1ups or shutdowns, and sometimes after the e&uipment has reached operatingtemperature. )pecial attention should be gi#en to assure plant personnel are aware of these ha=ards andbe prepared to act in case leakage does occur.

/-/1 R%'ia&i'i! a(d Ei#i%(! O*%ra!i"(

Thorough inspection and analysis and the use of detailed historical records of piping systems areessential to the attainment of acceptable reliability, efficient operation, and optimum on1stream ser#ice.Piping replacement schedules can be de#eloped to coincide with planned maintenance turnaroundschedules through methodical forecasting of piping ser#ice li fe.

/-20 R%)+'a!"r R%+ir%$%(!s

7egulatory re&uirements usually co#er only those conditions that affect safety and en#ironmentalconcerns. Inspection groups in the Petrochemical industry familiar with the industryWs problems ofteninspect for other conditions that ad#ersely affect plant operation.

API 5! was de#eloped to pro#ide an industry standard for the inspection of in1ser#ice process piping. Ithas been adopted by a number of regulatory and %urisdictional authorities. In addition, in some areas

other re&uirements ha#e been specified for the inspection of piping. 'ach plant should be familiar withthe local re&uirements for process piping inspection.

I(s*%#!i"( P'a(s

/-2/ G%(%ra'

An inspection plan is often de#eloped and implemented for piping systems within the scope API 5!.Bther piping systems may also be included in the inspection program and accordingly ha#e an inspectionplan.

An inspection plan should contain the inspection tasks, scope of inspection, and schedule re&uired to

monitor damage mechanisms and assure the mechanical integrity of the piping components in thesystem. The plan will typically

a? define the type>s? of inspection needed, e.g. external,

b? identify the next inspection inter#al and date for each inspection type,

c? describe the inspection and *' techni&ues,

d? describe the extent and locations of inspection and *',

e? describe any surface cleaning re&uirements needed for inspection and examinations,

f? describe the re&uirements of any needed pressure or tightness test, e.g. type of test, test pressure,and duration, and

g? describe any re&uired repairs.

Bther common details in an inspection plan includeF

describing the types of damage mechanisms anticipated or experienced in the e&uipment(



33/87


defining the location of the damage(

defining any special access re&uirements.

Inspection plans for piping maycan be maintained in spreadsheets, hard copy files and proprietaryinspection software databases. Proprietary software, typically used by inspection groups, often assists in

inspection data analysis and record keeping.

/-22 D%%'"*i() a( I(s*%#!i"( P'a(

An inspection plan is often de#eloped through the collaborati#e work of the inspector, piping engineer,corrosion specialist and operating personnel. They should consider se#eral pieces of information such asoperating temperature ranges, operating pressure ranges, process fluid corrosi#e contaminant le#els,piping material of construction, piping system configuration, process stream mixing andinspectionmaintenance history. In addition, other information sources can be consulted including APIand A"' publications to obtain industry experience with similar systems. All of this informationpro#ides a basis for defining the types of damage and locations for its occurrence. Xnowledge of thecapabilities and limitations of *' techni&ues allows the proper choice of examination techni&ue>s? toidentify particular damage mechanism in specific locations. Bn1going communication with operatingpersonnel when process changes andor upsets occur that could affect damage mechanisms and ratesare critical to keeping an inspection plan updated.

6or piping systems, inspection plans should address the followingF

a? condition monitoring locations >"


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Inspection plans may be based upon #arious criteria but should include a risk assessment or fixedinter#als as defined in API 5!.

/-22-/ Ris6:as%d I(s*%#!i"( P'a(s

7-2-/-/ Inspection plans based upon an assessment of the likelihood of failure and the conse&uence offailure of a piping system or circuit is 7;I. 7;I may be used to determine inspection inter#als and thetype and extent of future inspectionexaminations. API 7P 53! details the systematic e#aluation of boththe likelihood of failure and conse&uence of failure for establishing 7;I plans. API Publication 53+ detailsan 7;I methodology that has all of the key elements defined in API 7P 53!.

7-2-/-2 Identifying and e#aluating potential damage mechanisms, current piping condition and theeffecti#eness of the past inspections are important steps in assessing the likelihood of a piping failure.The likelihood assessment should consider all forms of degradation that could reasonably be expected toaffect piping circuits in any particular ser#ice. 'xamples of those degradation mechanisms includeFinternal or external metal loss from an identified form of corrosion >locali=ed or general?, all forms ofcracking including hydrogen assisted and stress corrosion cracking >from the inside or outside surfacesof piping?, and any other forms of metallurgical, corrosion, or mechanical degradation, such as fatigue,embrittlement, creep, etc. )ee API 7P 5+ for details of common degradation mechanisms.

7-2-/-3 Identifying and e#aluating the process fluid>s?, potential in%uries, en#ironmental damage, unitpiping and e&uipment damage and unit loss of production are important aspects in assessing theconse&uences associated with a failure of piping.

7-2-/-4 Any 7;I assessment should be thoroughly documented in accordance with API 7P 53!definingall the factors contributing to both the probability and conse&uence of a failure of the piping system.

7-2-/-5 After an 7;I assessment is conducted, the results may be used to establish the inspection planand better define the followingF

a? the most appropriate inspection and *' methods, tools, and techni&ues(

b? the extent of *' >e.g. percentage of piping to examine?(

c? the inter#al for internal, external, and on1stream inspections(

d? the need for pressure testing after damage has occurred or after repairsalterations ha#e beencompleted(

e? the pre#ention and mitigation steps to reduce the probability and conse&uence of a piping failure.>e.g. repairs, process changes, inhibitors, etc.?

/-22-2 I(!%ra'&as%d I(s*%#!i"( P'a(s

Inspection plans which are based upon the specific inspection inter#als for the #arious types of pipinginspection and of specific types of damage are considered inter#al1based. The types of inspection where

maximum inter#als are defined in API 5! includeF external #isual, "$I, thickness measurement,in%ection point, soil1to1air interface, small bore piping, auxiliary piping and threaded connections.

The inter#al for inspections is based upon a number of factors including the corrosion rate and remaininglife calculations, piping ser#ice classification, applicable %urisdictional re&uirements and the %udgment ofthe inspector, the piping engineer, or a corrosion specialist. The go#erning factor in the inspection planfor many piping circuits is the piping ser#ice classification.

American Petroleum Institute 1 1


35/87


/-22-3 C'assii() Pi*i() S%ri#%

According to API 5!, all process piping shall be classified according togi#en aconse&uence of failureclassification. Piping classes #ary from "lass +, high conse&uence, to "lass 2, low conse&uence. Addingmore "


36/87


b? process fluid and its phase >e.g. gas, li&uid, two1phase, solid?(

c? flow #elocity(

d? temperature(

e? pressure(

f? changes in temperature, #elocity, pressure, direction, phase, metallurgy, or pipe cross1section

g? in%ection of water or chemicals(

h? process fluid contaminants(

i? mixing of two or more streams(

%? piping external conditions including coatingpainting, insulation, and soil conditions as applicable(

k? stagnant flow areas >e.g. deadlegs?.

7-3-2-/ "omplex process units or piping systems are di#ided into piping circuits to manage thenecessary inspections, calculations, and recordkeeping. /hen establishing the boundary of a particularpiping circuit, the inspector may also si=e it to pro#ide a practical package for recordkeeping andperforming field inspection. ;y identifying like en#ironments and damage mechanisms as circuits, thespread of calculated corrosion rates of the "


37/87


inspector needs to determine ifscaffolding, portable manlifts, or other methods towillpro#ide ade&uateaccess.

/-24 I(s*%#!i"( "r S*%#ii# Da$a)% M%#ha(is$s

Bil refinery and chemical plant piping can be sub%ect to internal and external damage mechanisms. ThispPiping carries a range of fluidsthat. These fluidscan be highly corrosi#e, erosi#e, proneand pronetostress corrosion cracking or sub%ect to material degradation in ser#ice. In addition, both abo#eground andburied piping is sub%ect to external corrosion. The inspector should be familiar with the potential damagemechanisms for each piping system. API 7P 5+, *amage "$I?(

e? soil1to1air interfaces(

f? ser#ice specific and locali=ed corrosion(

g? erosion and corrosionerosion(

h? en#ironmental cracking(

i? corrosion beneath linings and deposits(

%? fatigue cracking(

k? creep cracking(

l? brittle fracture(

m? free=e damage(

n? contact point corrosionat support points(

o? dew point corrosion.

American Petroleum Institute 1 2! 1


38/87


Fi)+r% /? B Er"si"( " Pi*i()

Fi)+r% /1 B C"rr"si"( " Pi*i()

Fi)+r% 20 B I(!%r(a' C"rr"si"( " Pi*i()

Fi)+r% 2/ B S%%r% A!$"s*h%ri# C"rr"si"( " Pi*i()

/-24-/ I(%#!i"( P"i(!s

In%ection points are sometimes sub%ect to accelerated or locali=ed corrosion from normal or abnormal operatingconditions. In%ection points may be treated as separate inspection circuits, and these areas need to be inspectedthoroughly on a regular schedule. 'xamples of in%ection points are chlorine in reformers, water wash in o#erheadsystems, polysulfide in%ection in catalytic cracking wet gas, anti1foam in%ections, corrosion inhibitors, andneutrali=ers.

/hen designating an in%ection point circuit for the purposes of inspection, the recommended upstreamlimit of the in%ection point circuit is a minimum of + in. >2!! mm? or three pipe diameters upstream ofthe in%ection point whiche#er is greater. The recommended downstream limit of the in%ection point circuitis the second change in flow1direction past the in%ection point, or 5 ft >.8 m? beyond the first change inflow direction whiche#er is less. In some cases, it may be more appropriate to extend this circuit to thenext piece of pressure e&uipment, as shown in 6igure .

The placement of "


39/87


Fi)+r% 22 B I(%#!i"( P"i(! Cir#+i!

/-24-2 Pr"#%ss Mi P"i(!s

Process mixing tees are pipe components that combine two process streams of differing composition,temperature or other parameter that could cause damage. e.g. thermal fatigue?. )ome examplesincludeF

a? mixing of a chloride1containing stream from a catalytic reformer >e.g. naphtha? with a wethydrocarbon stream from elsewhere(

b? mixing a low temperature, high sulfur1containing hydrocarbon stream with a high temperature streamis an issue when bulk fluid temperature is increased where high temperature sulfidation becomesacti#e(

c? mixing hydrogen into a hydrocarbon stream where the stream temperatures are significantlydifferent.

The inspector, unit process engineer and corrosion engineer will typically re#iew process flow diagramsto identify susceptible process mixing tees and define the extent of the mix point circuit.


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This section pro#ides guidelines for identifying potential "$I areas for inspection. The extent of a "$Iinspection program may #ary depending on the local climate. +5L"?( cui is particularly aggressi#e where operating temperatures causefre&uent or continuous condensation and re1e#aporation of atmospheric moisture(

f? carbon steel piping systems which normally operate in ser#ice abo#e 25!L6 >+5L"?, but are inintermittent ser#ice(

g? dead1legs and attachments that protrude from insulated piping and operate at a different temperaturethan the operating temperature of the acti#e line(

h? austenitic stainless steel piping systems operating between +9!L6 +!L6 >8!L"? and 9!!L6 >!5L"?>susceptible to chloride stress corrosion cracking?(

i? #ibrating piping systems that ha#e a tendency to inflict damage to insulation %acketing pro#iding apath for water ingress(

%? steam traced piping systems that maycan experience tracing leaks, especially at tubing fittingsbeneath the insulation(

k? piping systems with deteriorated insulation, coatings, andor wrappings( bulges or staining of theinsulation or %acketing system or missing bands >bulges maycanindicate corrosion product build up?(

l? piping systems susceptible to physical damage of the coating or insulation, thereby exposing thepiping to the en#ironment.

/-24-4-2 T*i#a' ;"#a!i"(s "( Pi*i() Cir#+i!s S+s#%*!i&'% !" C9I

The abo#e noted areas of piping systems maycanha#e specific locations within them that are moresusceptible to "$I. These areas includeF

a? all penetrations or breaches in the insulation %acketing systems, such as

deadlegs >#ents, drains, etc.?,

pipe hangers and other supports,

#al#es and fittings >irregular insulation surfaces?,



41/87


bolt1on pipe shoes, and

steam and electric tracer tubing penetrations(

b? termination of insulation at flanges and other piping components(

c? damaged or missing insulation %acketing(

d? insulation %acketing seams located on the top of hori=ontal piping or improperly lapped or sealedinsulation %acketing(

e? termination of insulation in a #ertical pipe(

f? caulking which has hardened, separated, or is missing(

g? low points in piping systems that ha#e a known breach in the insulation system including low pointsin long unsupported piping runs(

h? carbon or low1alloy steel flanges, bolting, and other components under insulation in high1alloy pipingsystems.

Particular attention should be gi#en to locations where insulation plugs ha#e been remo#ed to permitpiping thickness measurements on insulated piping. These plugs should be promptly replaced andsealed. )e#eral types of remo#able plugs are commercially a#ailable that permit inspection andidentification of inspection points for future reference.

/-24-5 S"i'!"Air =S I(!%ra#%

Inspection at grade should include checking for coating damage, bare pipe, and pit depth measurements.If significant corrosion is noted, thickness measurements and exca#ation may be re&uired to assesswhether the corrosion is locali=ed to the )A interface or maycanbe more per#asi#e to the buriedsystem. Thickness readings at )A interfaces maycanexpose the metal and accelerate corrosion, ifcoatings and wrappings are not properly restored. 6igure 2 is an example of corrosion at a soil1to1air

interface although it had been wrapped with tape. If the buried piping has satisfactory cathodic protectionas determined by monitoring in accordance with API 5!, exca#ation is re&uired only if there is e#idenceof coating or wrapping damage. If the buried piping is uncoated at grade, consideration should be gi#ento exca#ating 8 in. >+5!mm? to + in. >2!!mm? deep to assess the potential for hidden damage.

Alternately, speciali=ed ultrasonic techni&ues such as guided wa#e can be used to screen areas for moredetailed e#aluation.

At concrete1to1air and asphalt1to1air interfaces for buried piping without cathodic protection, the Inspectorshould look for e#idence that the caulking or seal at the interface has deteriorated and allowed moistureingress. If such a condition exists on piping systems o#er ten years old, it may be necessary to inspectfor corrosion beneath the surface before resealing the %oint.

)ee API 5+ for additional information on corrosion at )A interfaces.

Fi)+r% 23 B S"i'!"Air I(!%ra#% C"rr"si"(



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/-24- S%ri#%s*%#ii# a(d ;"#a'i%d C"rr"si"(

7-4--/ An effecti#e inspection program includes the following three elements, thatelements that helpidentify the potential for ser#ice1specific and locali=ed corrosion and select appropriate "e.g. A)T< A 52 and API 5-? can corrode at higher rates than silicon1killedsteel pipe >e.g., A)T< A +!8? in high temperature sulfidic en#ironments.

k? under1deposit corrosion in slurries, crystalli=ing solutions, or coke producing fluids(

l? chloride carryo#er in catalytic reformer units particularly where it mixes with other wet streams(

m? welded areas sub%ect to preferential attack(

n? Jhot spotJ corrosion on piping with external heat tracing(

BT' In ser#ices,which become much more corrosi#e to the piping with increased temperature >e.g., sour water,caustic in carbon steel? corrosion or )"" can de#elop at hot spots that de#elop under low flow conditions.

o? steam systems sub%ect to Jwire cuttingJ, graphiti=ation, or where condensation occurs.



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/-24-7 Er"si"( a(d Er"si"(C"rr"si"(

'rosion can be defined as the remo#al of surface material by the action of numerous indi#idual impactsof solid or li&uid particles, or ca#itation. It can be characteri=ed by groo#es, rounded holes, wa#es, and#alleys in a directional pattern. 'rosion is usually in areas of turbulent flow such as at changes ofdirection in a piping system or downstream of control #al#es where #apori=ation maycantake place.'rosion damage is usually increased in streams with large &uantities of solid or li&uid particles and high#elocities. A combination of corrosion and erosion >erosion1corrosion? results in significantly greatermetal loss than can be expected from corrosion or erosion alone.

This type of corrosion occurs at high #elocity and high turbulence areas. 'xamples of places to inspectincludeF

a? downstream of control #al#es, especially where flashing or ca#itation is occurring(

b? downstream of orifices(

c? downstream of pump discharges(

d? at any point of flow direction change, such as the outside radii of elbows(

e? downstream of piping configurations >welds, thermowells, flanges, etc.? that produce turbulenceparticularly in #elocity sensiti#e systems, such as ammonium hydrosulfide and sulfuric acid systems.

Areas suspected to ha#e locali=ed erosion1corrosion should be inspected using appropriate *'methods that will yield thickness data o#er a wide area, such as ultrasonic scanning and profileradiography..

)ee API 5+ for additional information on erosion and erosion1corrosion.

/-24-? E(ir"($%(!a' Cra#6i()

7-4-?-/ Piping system materials of construction are normally selected to resist the #arious forms of

stress corrosion cracking. )ome piping systems maycanbe susceptible to en#ironmental cracking due toupset process conditions, "$I, unanticipated condensation, or exposure to wet hydrogen sulfide orcarbonates. 'xamples of this include the following.

a? "hloride stress corrosion cracking of austenitic stainless steels resulting from moisture and chloridesunder insulation, under deposits, under gaskets, or in cre#ices.

b? Polythionic acid stress corrosion cracking of sensiti=ed austenitic alloy steels resulting from exposureto sulfidemoisture condensationoxygen.

c? "austic stress corrosion cracking >sometimes known as caustic embrittlement?.

d? Amine stress corrosion cracking in non1stress relie#ed piping systems.

e? "arbonate stress corrosion cracking in alkaline systems.

f? /et hydrogen sulfide stress cracking and hydrogen blistering in systems containing sour water.

g? Cydrogen blistering and hydrogen induced cracking >CI"? damage. This has not been as serious of aproblem for piping as it has been for pressure #essels. It is listed here because it is considered to been#ironmental cracking and maycan occur in piping although it has not been extensi#e. Bneexception where this type of damage has been a problem is longitudinally welded pipe fabricatedfrom plate materials.



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)ee API 5+ for additional details on en#ironmental cracking mechanisms.

7-4-?-2 /hen the Inspector suspects or is ad#ised that specific circuits may be susceptible toen#ironmental cracking, heshe should schedule supplemental inspections. )uch inspections can takethe form of surface *' >PT or /6


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7-4-/0-2 6atigue cracking can typically be first detected at points of high stress intensificationsuch as branch connections. -ocations where metals ha#ing different coefficients of thermal expansionare %oined by welding maycanbe susceptible to thermal fatigue. Preferred *' methods of detectingfatigue cracking include li&uid penetrant examinationtesting, magnetic particle examinationtesting, andangle beam ultrasonic examinationtesting when inspecting from the B* for I* cracking. )uggestedlocations for $T on elbows would include the 2 and 4 o[clock positions. Acoustic emission also may beused to detect the presence of cracks that are acti#ated by test pressures or stresses generated duringthe test. )ee API 5!, )ection 8.8.2, for fatigue considerations relati#e to threaded connections.

7-4-/0-3 It is important for the owner1user and the Inspector to understand that fatigue cra cking islikely to cause piping failure before detection with any *' methods. Bf the fatigue cycles re&uired toproduce failure, the #ast ma%ority are re&uired to initiate cracking and relati#ely few cycles are re&uired topropagate the crack to failure. As such, proper design and installation to pre#ent fatigue cracking areimportant.

)ee API 5+, for additional information on thermal fatigue, mechanical fatigue, and #ibration1inducedfatigue.

/-24-// Cr%%* Cra#6i()

7-4-//-/ "reep is dependent on time, temperature, and stress. "reep cracking maycane#entuallyoccur at design conditions since some piping code allowable stresses are in the creep range. "racking isaccelerated by creepfatigue interaction when operating conditions in the creep range are cyclic.Particular attention should be gi#en to areas of high stress concentration. If excessi#e temperatures areencountered, mechanical property and microstructural changes in metals maycanalso take place, whichmaycanpermanently weaken e&uipment. An example of where creep cracking has been experienced inthe industry is in + K"r steels abo#e 4!!L6 >93L"?.

7-4-//-2 *' methods of detecting creep cracking include li&uid penetrant, magnetic particle,ultrasonic, radiography, eddy current and A"6i.e.strapping pipe diameter? are other common practices for detection. *T #olumetric examinationmethods including profile radiography and ultrasonic techni&ues can be used for detection of creepcracking.

Acoustic emission examination maycanbe utili=ed to identify acti#e creep cracking. The examinationcan be conducted whilst piping is in or out of operation. /hen the examination is conducted maycanbea function of crack orientation. Any piping examined out of operation re&uires a pressure stimulus toacti#ate any damage present.

)ee API 5+ for additional information on creep and stress rupture.

/-24-/2 :ri!!'% Fra#!+r%

7-4-/2-/ "arbon, low1alloy, and other ferritic steels maycanbe susceptible to brittle failure at orbelow ambient temperatures. In some cases, the refrigerating effect of #apori=ing li&uids such asammonia or " or "2 hydrocarbons maycanchill the piping and promote brittle fracture in material that

may not otherwise fail. ;rittle fracture usually is not a concern with relati#ely thin wall piping. that is, the first hydrotest oro#erload? unless critical defects are introduced in ser#ice. The potential for a brittle failure should beconsidered when pressure testing or more carefully e#aluated when pressure testing e&uipmentpneumatically or when adding any other additional loads. )pecial attention should be gi#en to low1alloysteels >especially K "r1+


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7-4-/2-2 A through wall crack resulting from brittle fracture and causing a leak maycan bedetected with helium leak detection. Alternati#ely, acti#e cracking as a result of brittle fracture maycanbe detected and possibly located with acoustic emission examination.

)ee API 5+ for additional information on brittle fracture. API 7P 54, )ection 2 pro#ides procedures forthe assessment of e&uipment for resistance to brittle fracture.

/-24-/3 Fr%%% Da$a)%

7-4-/3-/ At subfree=ing temperatures, water and a&ueous solutions handled in piping systemsmaycan free=e and cause failure because of the expansion of these materials. After unexpectedlyse#ere free=ing weather, it is important to #isually check for free=e damage to exposed pipingcomponents before the system thaws. If rupture has occurred, leakage maycanbe temporarily pre#entedby the fro=en fluid. -ow points, drip legs, and deadlegs of piping systems containing water should becarefully examined for damage.

7-4-/3-2 To pre#ent free=e damage, precautions need to be taken to drain, purge, or heat tracesystems where moisture could collect and unexpectedly free=e during se#ere or sudden subfree=ingtemperature excursions. Bne of the most critical locations for these precautions is the top of the seat ofrelief #al#es and pilot1operated relief #al#es, when moisture could be present. Tail pipes on relief #al#esthat discharge to the atmosphere should always ha#e ade&uate drainage or heat tracing.

/-24-/4 C"(!a#! P"i(! C"rr"si"(

-ocali=ed corrosion at pipe support contact points is the result of cre#ice corrosion due to deposits thatcontain corrosi#e species, water and oxygen typical of an externally corrosi#e en#ironment.


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of time. ;reakdown can be accelerated by exposure tosome chemicals, especially strong alkalines.

*eformation "hange in dimensions due to long term exposure to stressDoften described as creep.

PitPinhole )mall craters in the surface of the laminate from incomplete

resin fill.

)oftening 7eduction in hardness associated with moisture ingresswhen resin has excessi#e #oids.

"reep Permanent deflection of the material under long term stressand temperature. "reep properties are dependent on theresin properties.

)tar "ra=e )harp impact to the external surface.

;listers Permeation of the ser#ice fluid into the laminate >commonin C"l ser#ice?

-iner "racking


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/-2 O('i(% I(s*%#!i"(

/-2-/ T%#h(i#a' R%as"( s "r I(s*%#!i() O('i(% 8hi'% Pi*i() is i( O*%ra!i"(

/-2-/-/ "ertain kinds of external inspections must be done while piping is operating. :ibrationand swaying is e#ident with process flow through the pipe. Proper position and function of supports,hangers, and anchors is most apparent while piping is in operation at temperature. The inspector shouldlook for distortion, settlement or foundation mo#ement which could indicate improper design orfabrication. Pipe rollers and slide plates should be checked to ensure that they operate freely.

/-2-/-2 -eakage is often more ob#ious during operation. Inspectors should look for signs of leakageboth coming from each pipe and onto each pipe. The leakage from a pipe can indicate a hole in the pipe,and leakage onto a pipe can indicate a leak from an unobser#ed source >e.g. beneath insulation?.

/-2-/-3 Thermal imaging inspections may be performed for #arious reasons but. must be done underoperating conditions. Thermal images can show pluggage andor maldistribution of flow that can affectcorrosion mechanisms. Thermal imaging can also show wet insulation that can lead to "$I. Thermalimaging can show breakdown of internal insulating refractory which can lead to high temperaturecorrosion of the pipe wall. Thermal imaging may show malfunctions of heat tracing which could allowunexpected damage mechanisms to operate. 6or instance, tracing that is too hot may cause caustic

stress corrosion cracking of carbon steel carrying caustic solutions, and tracing that is too cold may allowdew point corrosion.

/-2-/-4 7adiography can be as effecti#e during operation as when the piping is offline. Bnlineradiography could detect fouling that might be washed out of piping during unit entry preparation.

An effecti#e, piping inspection program should include obtaining as many of the re&uired wall1thicknessmeasurements as possible >maintaining the re&uired accuracy? while piping is on stream. ;oth ambient1and high1temperature ultrasonic thickness measurements may be taken. /all1thickness radiographs canbe taken independently on most piping, including insulated piping through undisturbed insulation.7adiographs can also be used to identify corroded areas where ultrasonic thickness monitoring should beestablished, identify external corrosion under insulation >"$I?, and locate areas where internal depositsha#e accumulated.

?-2-2 The appropriate *' techni&ue should be utili=ed for monitoring systems that are typicallysusceptible to types of degradation other than or in addition to loss of wall thickness, i.e. systemssusceptible to stress cracking.

?-2-3 Cistorical records of piping should be studied to determine inspection locations, which sectionswill be approaching retirement thickness, and to establish a replacement schedule .

?-2-4 Bn1stream inspection can reduce downtime by the following means.

'xtending process runs by assuring piping conditions are suitable for continued operation.

a. Permitting fabrication of replacement piping before a shutdown.

b. 'liminating unnecessary work and reducing shutdown personnel re&uirements( for example,personnel who are otherwise used to remo#e insulation and break flanges for inspection during theturnaround can be made a#ailable for other work.

c. Aiding maintenance planning to reduce surges in workload, thus stabili=ing personnel re&uirements.

?-2-5


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continuously. /hene#er a leak occurs, operators should notify an inspector who can determine itsseriousness and recommend the proper correcti#e action. )ee 4.2 on in#estigation of leaks.

?-2- Pipe supports may be inspected for distortion and damage, settlement or mo#ement of thefoundation, and the condition of foundation bolts. Pipe anchors may be inspected to determine theircondition and ade&uacy. Piping should be inspected for swaying or #ibration. Pipe rollers and slide plates

should be inspected to ensure that they operate freely.

?-2-7 Piping, supports, and spring hangers should be inspected for external corrosion and correctlocation or position. $ltrasonic -amb wa#e techni&ues may be used to assess the piping wall loss due tolocali=ed, external corrosion at the supports or hangers. An inspection should also be made for li&uidspills that can cause external corrosion of piping.



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/-2-2 Pra#!i#a' R%as"(s "r I(s*%#!i() O('i(%

/-2-2-/ Bn1stream inspection can incr e ase unit run lengths by gi#ing assurance that piping is fit forcontinued ser#ice.

/-2-2-2 /hen piping must be replaced, on1stream inspection allows an inspector to define the extentof replacement necessary and ha#e replacement piping fabricated before the shutdown.

/-2-2-3 $nits are often crowded during a shutdown, and on1stream piping inspection can increasethe safety and efficiency of shutdown operations by reducing the number of people who need to be in theunit during that time.

/-2-2-4 Bn1stream inspection can reduce surges in work load and thus stabili=e personnelre&uirements.

/-27 O'i(% I(s*%#!i"( 8hi'% Pi*i() is' ("! i( O*%ra!i"(

/-27-/ A common limitation to online inspection is temperature. The e&uipment used in some kinds oftechni&ues cannot operate at temperatures much abo#e ambient. In addition, the radiant heat from somepiping can be too great for technicians to make measurements safely. In both of these instances, piping

inspection may need to be done when the piping is not in operation.

/-27-2 )igns of wet insulation should be noted when piping is offline. /ater dripping onto insulationmay not show dampness during operation because heat from the pipe causes surface water toe#aporate, but water deeper in the insulation can still cause "$I. If dampness is noted during ashutdown, the damp piping should be considered for "$I inspection. I

/-27-3 nspections that cannot be made while piping is operating should be made when the system isshut down. In addition, w/hen piping is opened for any reason, it should be inspected internally as far asaccessibility permits. )ome piping is large enough for internal inspection which can only occur while thepiping is offline.

/-27-4 Ade&uate follow1up inspections should be conducted to determine the causes of defects, such as

leaks, misalignment, #ibration, and swaying, which were detected while the unit was operating.

/-2? I(s*%#!i"( S#"*%

/-2?-/ Piping inspection should be fre&uent enough to assure that all piping has sufficient thickness topro#ide both pressure containment and mechanical support. 6or pipes undergoing uniform corrosion,calculating the corrosion rate and remaining life at each "


51/87


be utili=ed for each inspection. Procedures for the separation of piping, installation of blinds, and leaktesting should be an integral part of safety practices. In general, the section of piping to be openedshould be isolated from all sources of harmful li&uids, gases, or #apors and purged to remo#e all oil andtoxic or flammable gases and #apors.

1-/-2 Cammer testing of pressured piping might cause failure and allow the contents of the piping to

be released. Precautions should be taken before any hammer testing of in1ser#ice piping >see API +1A?.

1-/-3 7adiography must be performed in accordance with the applicable re&uirements of the site and%urisdiction due to potential radiation exposure.

4.+.9 "aution should be taken when attempting to remo#e scale and deposits from the externalsurfaces of in1ser#ice piping especially when operating at high pressure or temperature withha=ardousflammable process fluids. -oss of containment incidents ha#e occurred when deposits wereremo#ed while inspecting for "$I, support point corrosion, cooling water drift corrosion, etc. that wereco#ering through1wall corrosion damage. The owneruser may consider the following to mitigate the riskof a through1wall e#entF

a? $se of profile radiography or $T *' to inspect under deposits and determine the amount of

corrosion damage, before disturbing the deposits.

b? *e#elop an emergency response plan in the e#ent that a through wall leak de#elops. This planshould include pro#isions to isolate the affected area, temporary repair pro#isions, and any additionalpersonal protecti#e e&uipment re&uirements.

/-30 Pr%*ara!"r ."r6

1-2-/ All possible preparatory work should be done before the scheduled start of inspection. )caffoldsshould be erected, insulation remo#ed, and surface preparation completed where re&uired. ;uried pipingshould be exca#ated at the points to be inspected. '&uipment re&uired for personal safety should be

checked to determine its a#ailability and condition. Any necessary warning signs should be obtained inad#ance, and barricades should be erected around all exca#ations. The appropriate signs and barricadesas re&uired by the site and %urisdiction must be in place before radiography is performed.

1-2-2 The tools needed for inspection should be checked for a#ailability, proper working condition,calibration and accuracy. The following tools and instruments are often used in inspection of pipingF

a. A"6< crack detection e&uipment(

b. a lloy analy=er >nuclear source for material identification?(

c. borescope and


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i. hammer(

%. I* and B* transfer calipers(

k. infrared pyrometer and camera(

l. knife(

m. leak detector >sonic( gas test( or soap solution?(

n. li&uid1penetrant e&uipment(

o. magnet(

p. magnetic1particle e&uipment(

&. magnifying glass(

r. material identification kit(

s. microwa#e inspection e&uipment

t. mirror(

u. notebook or sketches(

#. paint(

w. pit1depth gauge(

x. portable hardness tester(

y. radiographic e&uipment(

=. remote tele#ision camera >for internal inspection?(

aa. scraper(

bb. steel rule(

cc. thickness or hook gauge(

dd. ultrasonic e&uipment(

ee. wire brush.

1-2-3 In addition to the list abo#e, gritblasting or comparable e&uipment may be re&uired to remo#epaint and other protecti#e coatings, dirt, or corrosion products so that the surface is properly prepared forthe inspection techni&ue e.g. inspection for cracks with


53/87


procedure to be followed during a piping leak in#estigation. as soon as possible to &uickly understand itscause and nature. Prior to in#estigating any leak, A further precaution is to hold a safety re#iew beforeany leak in#estigation. The re#iew would consider the state of a piping system in terms of pressure,temperature, remaining in#entory of process fluids, potential damage mechanisms and similar factors.The safety re#iew team would define a Ghot =oneH around the leak site and establish personal protecti#ee&uipment re&uirements for entry, decontamination re&uirements upon exit and other re&uirementsnecessary to protect personnel and the en#ironment. The safety re#iew team must be careful makingassumptions about the leak[s cause. Incidents ha#e occurred where in#estigati#e personnel assumedthey knew the cause of a small leak on an operating line and were caught unprepared when the leaksuddenly became &uite large.should be performed to identify the ha=ards and re&uired personalprotecti#e e&uipment re&uired to in#estigate the leak. The ha=ards and le#el of protection should beappropriate for the state of the piping system such as whether the system is operating, depressured, ordein#entoried. 6urther consideration should be gi#en to the ha=ards associated with the leak such astoxicity and fluid temperature. Bne should a#oid assuming they understand the cause of the leak whichcould lead to unsafe in#estigations. Incidents ha#e occurred where in#estigati#e personnel assumed theyknew the cause of a small leak on an operating line and were caught unprepared when the leak suddenlybecame &uite large. )ites ha#e created safety procedures for the in#estigation of piping system leaks. Asa minimum, these procedures should be followed when an inspector is re&uested to in#estigate a leak.

I(s*%#!i"( Pr"#%d+r%s a(d Pra#!i#%s

/-32 E!%r(a' is+a' I(s*%#!i"(

/-32-/ G%(%ra'

'xternal #isual inspections are performed to determine the external condition of piping, insulationsystem, paintingcoating systems, and associated hardware, and to check for signs of misalignment,#ibration, and leakage.API 5!,Appendix * A contains a sample checklist.

/-32-2 ;%a6s

/0-/-2-/ -eaks can be safety or fire ha=ards.( Tthey can cau

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