268652323-API-510-Study-Material (1)

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INTRODUCTION

API 510 STUDY MATERIAL

HOW TO USE THESE BOOKS

These books can be used in a self-study or instructor led format. There are two volumes, the

Text and the Questions and Answers.

TEXT BOOK

The Text book's table of contents follows the API !" #ody of $nowled%e that was in effect

at the time of its writin%. &ach area can be studied as a stand alone module for those who do

not intend to sit for the API !" exam, but want to obtain a better understandin% on a %iven

ode sub(ect.

The )rocess found to most effective for %eneral use is to study each sub(ect of interest and

com)lete the *ui++es at the end of that module. As re%ards to calculations, after masterin%

the %iven material, refer to the Advanced aterial section to increase the de)th of understandin%. The Advanced aterial covers the calculations re*uired for some actual

circumstances that mi%ht be encountered in the field.

or those intendin% to sit for the API !" examination, some hel)ful su%%estions are

contained in the back of the Text book. These include such thin%s as what )ara%ra)hs to tab

within the A& ode books, and cross over sub(ects from the API to the A& odes. At

this writin% the exam candidate is allowed to use the A& ode books and the API books

on the first )ortion of the test only. /o reference material is allowed for the second half of

the test0

QUESTIONS AND ANSWERS BOOK

The Questi!s "!# A!s$e%s "%e #i&i#e# i!t t$ t'(es)

The first )ortion covers the A& odes, ections 1III 2iv. ! 3nfired Pressure 1essels,

ection I4 5eldin%, and ection 1 /ondestructive Testin%. These *uestions are ty)ical of

)revious /ational #oard Authori+ed Ins)ector exams. These should be used to obtain a feel

for the nature of the A& ode *uestions. They are not for memori+ation.

The second )ortion contains *uestions from the API !" ode and the 6ecommended

Practices, titled 6PI 78 Ins)ection of Pressure 1essels, 6PI 79 Pressure 6elievin% 2evices

and ha)ter II -onditions ausin% 2eterioration of ailures. These *uestions are for memori+ation if the examination will be taken0

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API !" odule

T"*+e , C!te!ts

API ;2&

API 510 C%%si! R"tes "!# I!s(e-ti! I!te%&"+s

co)e 9

Ins)ection Interval !"

6ecords and Test !!

etal loss includin% corrosion avera%in% !

orrosion rates !

6emainin% orrosion Allowance !9

6emainin% ervice

ethods of Ins)ection 8=

6ecords and 6e)orts :9

IRE Ch"(te% 11

overa%e from the API !" #ody of $nowled%e ?:

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ASME Se-ti! 2III Di&) 1

3i!t E,,i-ie!-ies

35-: 5eld ate%ories ?>

35-! 6T &xamination of 5elded @oints >

35-8 )ot &xamination of 5elded @oints =

35- !! 6T and 3T &xaminations 9!

35-!8 aximum Allowable @oint &fficiencies 9=

Pst$e+# He"t T%e"t4e!t

35-?" Procedures for Postweld eat Treatment =:

3-9 6e*uirements for Postweld eat Treatment =?

2esse+s U!#e% I!te%!"+ P%essu%e

3B-87 Thickness of hells 3nder Internal Pressure =9

3B-:8 ormulas and 6ules for 3sin% ormed eads !"7

3B-:? 3nstayed lat eads and overs CircularD !!:

C'+i!#e% U!#e% Ete%!"+ P%essu%e

3B-8> Thickness of hells and Tubes C&xternal PressureD !8"

P%essu%e Testi!

3B-8" 2esi%n Tem)erature !87

3B-88

Mi!i4u4 Re6ui%e4e!ts ,% Att"-h4e!t We+#s "t O(e!i!s

35-!9 5eld i+e 2etermination !?"

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Rei!,%-e4e!t ,% O(e!i!s i! She++s "!# He"#s

3B-:9 ;)enin%s in 1essels !?9

3B-:7 6einforcement of ;)enin%s !?7

3B-?"

Mi!i4u4 Desi! Met"+ Te4(e%"tu%e "!# Ee4(ti!s ,%4 I4("-t Testi!

3B->? har)y Im)act Test 6e*uirements !9!

3-99 aterials !9?

3-97 Im)act Testin% of 5eldin% Procedures !9?

3-9> 2esi%n !9?

P%"-ti-"+ K!$+e#e

3B-77 aterial Identification !7"

3B-=: Ins)ection of aterials !7!

3B- !!9 /ame Plate arkin%s !78

3B-!!= /ame Plates !7?

3B- !8" 2ata 6e)orts !7

Se-ti! IX

We+#i! ! P%essu%e 2esse+s 7Se-ti! IX O&e%&ie$8

Article I Beneral 6e*uirements !79

Article II 5eldin% Procedure Qualifications !77

Article III 5eldin% Performance Qualifications !7=

Article I1 5eldin% 2ata !>!

We+#i! D-u4e!t"ti! Re&ie$

5eldin% Procedure )ecification C5PD !>8

Procedure Qualification 6ecord CPQ6D !>9

Practice 5PEPQ6 reviews !>=

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Se-ti! 2 7NDE Su*se-ti! A8

Article 8 6adio%ra)hy !=

Article 3ltrasonics !=>

Article 9


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API !" odule

P6&36& 1&&< I/P&TI;/ ;2&

;verview

Se-ti! 1

9e!e%"+

S-(e:

The API !" a))lies to )ressure vessels in the )etrochemical and refinin% industries after

they have entered service. The A& ode a))lies to the new construction of vessels.

5hile it a))lies only to new construction it is often the ode to which a vessel is re)aired.

There are other construction odes to which a vessel can be constructed, for instance the

2e)artment of Trans)ortation C2;TD )rovides rules for the construction of and shi))in% of

com)ressed %as cylinders. The ode for the construction of stora%e tanks is API 9: and so

forth.

The API !" exem)ts certain vessels such asF

a. 1essels on moveable structures tank cars. etc..

b. All vessels exem)ted by ection 1III 2I1. ! of the A& ode.

c. 1essels that do not exceed %iven volumes and )ressures.

ection 9 Alternative 6ules for /atural 6esource 1essels.

9+ss"%' , Te%4s:

In this section the terms used in the API !" ode are defined such as Alteration, A&ode, API Authori+ed Ins)ector, onstruction ode, aximum Allowable 5orkin% Pressure,

aximum Allowable hell Thickness and ;n-tream Ins)ections (ust to mention a few.

tudy this section carefully as many *uestions on the &xam often come from here.

Se-ti!

O$!e%;Use% I!s(e-ti! O%"!i


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Se-ti! =

I!s(e-ti! P%"-ti-es

P%e("%"t%' W%>:

;ften *uestions are asked about what must be done before entry into a vessel. drainin%,

cleanin%, )ur%in% and %as testin% also the warnin% of )ersonnel in the area, both inside and

outside the vessel, etc.. heckin% of safety e*ui)ment is necessary as well as ins)ection

tools.

M#es , Dete%i%"ti! "!# ?"i+u%e:

ome of the listed modes of deterioration are fati%ue, cree), brittle fracture, %eneral corrosion

stress corrosion crackin%, hydro%en attack, carburi+ation, %ra)hiti+ation, and erosion. A

%eneral *uestion may be asked such asG list six modes of deterioration or a more s)ecific

*uestion such asG what is cree) de)endent u)on.

C%%si!;R"te Dete%4i!"ti!:

;ne im)ortant as)ect of vessel maintenance and o)eration is the determination of how

fre*uently a vessel needs to be ins)ected. This can be lar%ely driven, by the rate at which a

vessel is corrodin%. There are three methods reco%ni+ed by API !" for this determination.

a. A corrosion rate may be calculated from data collected by the owner or user on vessel

)rovidin% the same or similar service.

b. orrosion rate may be estimated from )ublished data or from the owner user's ex)erience.

c. After !,""" hours of service usin% corrosion tabs or on-stream /2& measurements.

If the estimated rates are in error they must be ad(usted to determine the next ins)ection date.

M"i4u4 A++$"*+e W%>i! P%essu%e Dete%4i!"ti!:

The continued use of a )ressure vessel must be based on calculations usin% the current

edition of the A& ode or the edition the vessel was constructed to. A vessels A5P

may not be raised unless a full reratin% has been )erformed in accordance with section .:.

In corrosive service the wall thickness used in the calculations must be the actual thickness as

determined by the ins)ection. but must not be thicker than ori%inal thickness on the vessel's

ori%inal material test re)ort or anufacturer's 2ata 6e)ort minus twice the estimated

corrosion loss before the next ins)ection.

De,e-t I!s(e-ti!:

areful visual examination is the most im)ortant and most universally acce)ted method of

ins)ection. ;ther methods that may be used to su))lement visual ins)ection are ma%netic

)article, ultrasonics, eddy current, radio%ra)hic, )enetrant and hammer testin% C when the

vessel is not under )ressureD. 1essels shall be checked visually for distortion. Internal

surfaces should be )re)ared by an acce)table method of cleanin%, there is no hard and fast

rule for cleanin%. &xternal surfaces may re*uire the removal of )arts of the insulation in an

area of sus)ected )roblems or to check the effectiveness of the insulatin% system. ometimes

de)osits inside a vessel act to )rotect its metal from attack. It can be necessary to clean

selected areas down to bare metal to ins)ect those areas if )roblems are sus)ected from )ast

ex)erience or if some indication of a )roblem is )resent.



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I!s(e-ti! , P"%ts:

a. The surfaces of shells and heads should be checked for cracks, blisterin%, bul%es, or other

si%ns of deterioration. 5ith )articular attention )aid to knuckle re%ions of heads and su))ort

attachments.

b. Ins)ect welded (oints and their heat affected +ones for cracks or other defects. 6ivets in

vessels shall be ins)ected for %eneral corrosion, shank corrosion. If shank corrosion is

sus)ected hammer testin% or an%le radio%ra)hy can be used.

c. &xamine sealin% surfaces of manways, no++les and other o)enin%s for distortion, cracks

and other defects. Pay close attention to the weldin% used to make these attachments.

C%%si! "!# Mi!i4u4 Thi->!ess E&"+u"ti!:

orrosion occurs in two ways, %eneral Ca fairly uniform wastin% away of a surface areaD or

)ittin%Cthe surface may have isolated or numerous )its, or may have a washboard like

a))earance in severe casesD. 3niform wastin% may be difficult to detect visually andultrasonic thickness measurements are normally done for that reason. A )it may be dee)er

than it a))ears and should be investi%ated thorou%hly to determine its de)th. The minimum

actual thickness and maximum corrosion rate may be ad(usted at any ins)ection for any )art

of a vessel. 5hen there is a doubt about the extent of corrosion the followin% should be

considered for ad(ustin% the corrosion rates.

a. /ondestructive examination such as ultrasonics or radio%ra)hy. If after these

examinations considerable uncertainty still exists the drillin% of test holes may be

re*uired.

b. If suitable o)enin%s exist readin%s may be taken throu%h them.

c. The de)th of corrosion can be %au%ed from uncorroded surfaces ad(acent to the area

of interest.

d. or an area of considerable si+e where circumferential stress %overns the least

thickness may alon% the most critical element of the area may be avera%ed over a

len%th not exceedin% the followin%F

!. or vessels with an inside diameter of 9" inches or less one half the vessel

diameter or 8" inches whichever is less.

8. or vessels with an inside diameter %reater than 9" inches one third the vessel

diameter or ?" inches whichever is less.

e. 5idely scattered )its may be i%nored if the followin% are trueF

!. /o )it is %reater than half the vessel wall thickness without addin% corrosion

allowance into the wall thickness.

8. The total area of the )its does not exceed 7 s*uare inches in any > inch diameter

circle.

:. The sum of their dimensions alon% any strai%ht line within the circle does not

exceed 8 inches.

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f. As an alternative to the above the thinnin% com)onents may be evaluated usin% the

rules of ection 1III 2ivision 8 A))endix ? of the A& ode. If this a))roach is

used consultin% with an en%ineer ex)erienced in )ressure vessel desi%n is re*uired.

%. 5hen corrosion is located at a weld with a (oint efficiency less than !." and also in the

area ad(acent to the weld s)ecial consideration must be %iven to the calculations for

minimum thickness. Two sets of calculations must be )erformed to determine the

maximum allowable workin% )ressureG one for the weld usin% its (oint efficiency and

one for the remote area usin% & e*uals !.". or )ur)oses of these calculations the

surface at the weld includes one C!D inch on either side of the weld or twice the

minimum thickness whichever is %reater.

h. 5hen measurin% a elli)soidal or toris)herical head the %overnin% thickness may be as

followsF

!. The thickness of the knuckle re%ion with the head ratin% calculated usin% the

a))ro)riate head formula.

8. The thickness of the central )ortion of the dished re%ion, in which case the dished

re%ion may be considered a s)herical se%ment whose allowable )ressure is

calculated usin% the ode formula for s)herical shells.

The s)herical se%ment of both elli)soidal and toris)herical heads shall be considered to

be in an area located entirely in with a circle whose center coincides with the center of

the head and whose diameter is e*ual to >" )ercent of the shell diameter. The radius of

the dish of toris)herical heads is to be used as the radius of the s)herical se%ment. The

radius of the s)herical se%ment of elli)soidal heads shall be considered to be the

e*uivalent s)herical radius $!2, where 2 is the shell diameter Ce*ual to the ma(or axisDand $I is as %iven in Table !.

Se-ti! @

I!s(e-ti! "!# Testi! % P%essu%e 2esse+s

"!# P%essu%e;Re+ie&i! De&i-es

9e!e%"+:

ection ? re*uires that )ressure vessels be ins)ected at the time of installation unless a

anufacturer's 2ata 6e)ort is available. urther all )ressure vessels must be ins)ected at

fre*uencies )rovided in ection ?. These ins)ections way be internal or external and mayre*uire any number of nondestructive techni*ues.

The ins)ection may be made while the vessel is in o)eration as lon% as all the necessary

information can be )rovided usin% that method.

Ete%!"+ I!s(e-ti!:

The fre*uency for the external ins)ection of above the %round vessels shall be every years

or at the *uarter corrosion rate life whichever is less. This ins)ection should be )erformed

when the vessel is in service if )ossible.

Thin%s to be checked shall include the followin%F

a. &xterior insulation

API !" Pa%e = of :!"


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b. u))orts

c. Allowance for ex)ansion

d. Beneral ali%nment

e. i%ns of leaka%e

#uried vessels shall be monitored to determine their surroundin% environmental condition.

The fre*uency of ins)ection must be based on corrosion rate information obtained on

surroundin% )i)in% or vessels in similar service.

1essels known to have a remainin% life in excess of !" years or have a very ti%ht insulation

systems a%ainst external corrosion do not need to have the insulation removed for ins)ection

however, the insulation should be ins)ected for its condition at least every years.

I!s(e-ti! I!te%&"+s:

The )eriod between internal or on-stream ins)ections shall not exceed !" years or one-half

the estimated remainin% corrosion-rate life whichever is less. In cases where the remainin%

safe o)eratin% life is estimated at less than ? years the ins)ection may be the full remainin%safe o)eratin% life u) to a maximum of 8 years. Internal ins)ection is the )referred method

;n tream may be substituted if all of the followin% are true.

5hen the corrosion rate is known to be less than "."" inch )er year and the estimated

remainin% life is %reater than !" years internal ins)ection of the vessel is unnecessary as lon%

as the vessel remains in the same service, com)lete external ins)ections are formed and all of

the followin% are trueF

The non-corrosive character of the contents have been )roven over a five year )eriod.

/othin% serious is found durin% the externals. The o)eratin% tem)erature of the vessel does

not exceed the lower tem)erature limits for the cree)-ru)ture ran%e of the vessel metal. Thevessel cannot be sub(ect to accidental ex)osure to corrosives. i+e and confi%uration make

internal ins)ection im)ossible. The vessel is not sub(ect to crackin% or hydro%en dama%e.

The vessel is not )late-lined or stri)-lined.

The remainin% life calculation formula is %iven in ection ? and will be demonstrated in a

latter exam)le )roblem alon% with the other formulas re*uired for )ressure vessels in

accordance with API !".

P%essu%e Test:

5henever a )ressure test becomes necessary they are to be conducted in a manner inaccordance with the vessel's construction ode. The followin% concerns should be addressed

when )ressure testin% a vessel.

a. If the test will be hydrostatic the test tem)erature should he above 7"H, but not

%reater than !8"H.

b. Pneumatic tests are )ermitted when hydrostatic testin% is not )ossible. The safety

)recautions of the A& ode shall be used.

c. 5hen the test )ressure will exceed the set )ressure of the lowest relief device, these

devices shall be )rotected by blindin%, removal or clam)s C%a%sD.

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P%essu%e;Re+ie&i! De&i-es:

;ne of the ma(or concerns for )ressure relief devices is their re)air. Pressure relief devices

must be re)aired by *ualified or%ani+ations havin% a fully documented written *uality control

system and re)air trainin% )ro%ram for re)air )ersonnel. /o hard and fast rule is %iven for

the testin% of relief devices the interval between tests is de)endent on the service conditions

of the device. There are minimum of ! items that should be addressed in the written *uality

control documentation. uch as a Title )a%e, 6evision lo%, ontents Pa%e, tatement of

Authority, ;r%ani+ational hart, etc. . Previous &xams have re*uired namin% 9 of these !

items.

Re-%#s:

Pressure vessel owners and users must maintain )ermanent and )ro%ressive records on their

)ressure vessels. Items that should be included are anufacturer's 2ata 6e)orts, vessel

identification numbers, 61 information, results of ins)ection and any re)airs or alterations

)erformed.

Se-ti! 5

Re("i%s A+te%"ti!s "!# Re%"ti! , P%essu%e 2esse+s

9e!e%"+:

ection covers re)airs and alterations to )ressure vessels by weldin% and the re*uirements

that must be met when )erformin% such work. These re)airs and alterations must be

)erformed to the edition of the A& ode that the vessel was built to.

Auth%i


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P%-e#u%e "!# Qu"+i,i-"ti!s:

The re)air or%ani+ations must use *ualified welders and weldin% )rocedures in accordance

with a))licable- re*uirements of ection I4 of the A& ode.

Qu"+i,i-"ti! Re-%#s))

Qualifications 6ecords must be maintained for all weldin% o)erations and must be available

for review by the API Ins)ector )rior to all weldin% o)erations.

He"t T%e"t4e!t;P%ehe"ti!:

Alterations and re)airs can be )erformed on vessels that were ori%inally )ostweld heat

treated by usin% only )reheatin% within s)ecific limitations. Postweld heat treatment in these

cases would not then be re*uired. This alternative a))lies to only P-/os. ! and P-/os. :

materials of the A& ode and should be used only after considerin% the ori%inal intent of

the )ostweld heat treatment. In some services the heat treatment was re*uired due to thecorrosive nature of the contents of the vessel. In such cases this ty)e of )rocedure may not

restore the metallur%ical condition needed to combat corrosion. or this reason consultin%

with an en%ineer ex)erienced with )ressure vessels is re*uired. Two techni*ues for these

ty)es of re)airs or alterations are described in ection .8.: and are very similar to those

found in )ara%ra)h 3-9 of ection 1III 2ivision ! of the A& ode. The ma(or

differences are the minimum )reheat tem)erature and the holdin% time and tem)erature after

the com)letion of the welded re)air or alteration. 2etails and a))licability of these

)rocedures will be discussed in detail durin% the covera%e of )ara%ra)h 3-9 of the

A& ode.

L-"+ Pst$e+# He"t T%e"t4e!t:

The API !" ode )ermits )ostweld heat treatment to be a))lied locally, this means that the

entire vessel circumference may not be re*uired to be included in the heat treatment. @ust as

in the alternative to )ostweld heat treatment above consideration to a))lyin% this local

treatment must be made with re%ards to service. It does not a))ly to all situations the

followin% four ste)s must be a))lied )rior to usin% this ty)e of heat treatment.

a. The a))lication must be reviewed by a *ualified en%ineer.

b. uitability of this ty)e of )rocedure is reviewed and consideration is %iven to such

thin%s as base metal thickness, hardness, and thermal %radients.

c. A )reheat of :""H or hi%her is maintained durin% weldin%.

d. The distance included in )ostweld heat treatment tem)erature on each side of the

welded area shall be not less than two times the base metal thickness as measured

from the weld. At least two thermocou)les must be used. The sha)e and si+e of the

area will determine the si+e of the thermocou)les re*uired.

e. eat must be a))lied to any no++le or any attachment within the local )ostweld heat

treatment area.

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Re("i%s t St"i!+ess Stee+ We+# O&e%+"' "!# C+"##i!:

Prior to the re)air or re)lacement of corroded or missin% clad material a re)air )rocedure

must written. ome of the concerns that must be addressed are as followsG out %assin% of the

base metals, hardenin% of the base metal durin% re)airs, )reheatin% and inter)ass

tem)eratures and )ostweld heat treatment.

Desi!:

The desi%n of welded (oints included in the API !" are in com)liance with those of the

A& ode. All butt (oints shall be full )enetration and must have com)lete fusion. illet

weld )atches may be allowed as tem)orary re)airs and can be a))lied to the inside or outside

of vessels but re*uire s)ecial considerations. The (urisdiction where the vessel is o)eratin%

may for instance )rohibit their use. Patches to the overlay in vessels must have rounded

cornersG this is also true of flush CinsertD )atches.

M"te%i"+:

All materials for re)airs must conform to the A& ode. arbon or alloy steels with a

carbon content which exceeds ".: )ercent may not be used in welded construction.

I!s(e-ti!:

The acce)tance of welded re)airs or alterations should include /2& that is in a%reement with

the A& odes that a))ly. If the A& ode methods are not )ossible or )ractical,

alternative /2& may be used.

Testi!:

After re)airs a )ressure test must be a))lied if the API Ins)ector believes one is needed.

/ormally )ressure tests are re*uired after an alteration. If (urisdictional a))roval is re*uired

and it has been obtained /2& may be substituted for a )ressure test. If an alteration has been

)erformed a )ressure vessel en%ineer must be consulted )rior to usin% /2& in )lace of

)ressure test.

Re%"ti!:

6eratin% a )ressure vessel by chan%in% its tem)erature ratin%s or its maximum allowable

workin% )ressure may be done only after meetin% the re*uirements of API !" %iven in

ection .:. alculations, com)liance to the current construction code, current ins)ectionrecords indicatin% fitness, )ressure testin% at some time for the )ro)osed reratin% and

a))roval by the API Ins)ector are re*uired. The reratin% is only com)lete when the Ins)ector

has overseen the attachment of an additional name)late with the re*uired information %iven

in ection .:.

API !" Pa%e !: of :!"


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API !" odule

;66;I;/ 6AT& A/2 I/P&TI;/ I/T&61A<

&xam)les

etal loss e*uals the )revious thickness minus the )resent thickness.

P%*+e4 1

2etermine the metal loss for a tower shell course which measured .9"" in durin% its last

internal ins)ection in arch of !=>=. The )resent readin% is .7" arch !==:.

etal loss J Previous thickness minus the )resent thickness.

.9"" Previous

-.7" Present

.":"

AnswerF etal !ess 4i!us the %e6ui%e# thi->!ess)

P%*+e4 =

The tower shell course in Problem K! has a minimum thickness re*uired by ode of.""L.alculate the corrosion allowance. The actual thickness is .7"L as of arch !==:.

.7" in actual thickness

-."" re*uired thickness

."7"L corrosion allowance

6emainin% service life e*uals the corrosion allowance divided by the corrosion rate.

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P%*+e4 @

alculate the remainin% service life of the tower of )roblem K!.

."7" corrosion allowance from Problem K:

.""7 corrosion rate from Problem K8

."7" J =.:: Mrs.

.""7L

Internal ins)ection e*uals half of the remainin% service life, but not %reater than ten C!"D

years.

=.:: Mrs. J ?.9 Mrs.

8

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API !" odule

&TI;/ !, 8, and :

ind the answers to these *uestions by usin% the stated API !" )ara%ra)h at the end of the

*uestion.

Qui+ K!

!. 5hat code covers maintenance ins)ection of )etrochemical industry vesselsN C!. !. !D

8. 2efine A5P accordin% to the API !" ode.C!.8.>D O!==7 :.>

:. 2efine reratin%. C!.8.!?D O!==7 :.!!

?. 5hat is a )ressure vesselNC!.8.!!D ect 1III 3-!CaD O!==9 :.!!

. 3nder what circumstances must an API !" ins)ector be re-certifiedN

CA)). # Para%ra)h #. 9D O!==9 #?.! A)). #

9. In terms of cree), what must be consideredN C:.8D O!==9 .8

7. 5hat is the most valuable method of vessel ins)ectionN C:.D O!==7 .

>. 2escribe the correct way to clean a vessel for ins)ection. C:.D O!==7 .8

=. 5hat metals mi%ht be sub(ect to brittle fracture even at room tem)eratureN C:.8DO!==7 8

!". /ame five methods other than visual that mi%ht be used to ins)ect a vessel.C:.D

!!. 5hen a new ode vessel is installed, must a first internal ins)ection be )erformedNC?.!D

!8. A vessel was last ins)ected internally in @uly of !=>:. 2urin% that ins)ection it was

determined to have a remainin% life of !9 years. 5hat is the latest date of the next

internal ins)ectionN C?.:D O!==7 9.:

Answers on next )a%e.

API !" Pa%e !9 of :!"


17/310

A/5&6 T; Q3I K!

!. answerF API-!"

8. answerF is the maximum %au%e )ressure )ermitted at the to) of a )ressure vessel in

its o)eratin% )osition for a desi%nated tem)erature.

:. answerF A chan%e in either tem)erature ratin% or maximum allowable )ressure of a

vessel or both.

?. answerF A container desi%ned to withstand internal or external )ressure by an exterior

source by the a))lication of heat direct or indirect or both.

. answerF Ins)ector who has not been actively en%a%ed in an API ins)ection within the

)revious : years. 6e-certify by written examination.

9. answerF Time, Tem)erature R tress.

7. answerF areful visual examination

>. answerF wire brushin%, blastin%, chi))in%, %rindin%Cor combinationD

=. answerF At ambient tem)erature, carbon, low alloy, and other erritic teels.

!". answerF !. a%netic Particle 8. 2ye Penetrant :. 6adio%ra)hy ?. 3ltrasonic

Thickness measurement. . etallo%ra)hic &xamination 9. Acoustic &mission

Testin% 7. ammer Test.

!!. answerF /o as lon% as manufacture re)ortC2ataD assures that the vessel is satisfactory

for the intended use is available.

!8. answerF !==!

API !" Pa%e !7 of :!"


18/310

API !" odule

6P 79 I/P&TI;/ ; P6&36& 6&9 the A& ode re*uires that they be stam)ed

with a certified ca)acity.

API !" Pa%e !> of :!"


19/310

S",et' Re+ie, 2"+&es

A safety relief valve is a s)rin%-loaded valve that is ca)able as functionin% as a relief valve in

li*uid service or as safety valve in %as or va)or service. afety relief valves may be of the

conventional, balanced or )ilot o)erated ty)es.

C!&e!ti!"+ SR2

A conventional 61 has its s)rin% housin% vented to the dischar%e side. Its o)enin%

)ressure, closin% )ressure and relievin% ca)acity are directly affected by chan%es in back

)ressure.

onventional 61s are used in flammable, hot and toxic services. 3sually they are )i)ed to

safe remote )oints of dischar%e such as a flare stack. onventional 61s are found in

service for %as, va)or, steam, air or li*uids. onventional 61s are also used in corrosive

service. onventional 61s may not be used in services where any back)ressure is constant

or where any built-u) back)ressure exceeds !"S of its set )ressure. They are not to be used

on steam boilers, su)erheaters or as )ressure control or by)ass valves.

B"+"!-e# S",et' Re+ie, 2"+&es

A balanced 61 has a )ressure-balancin% bellows, )iston or both. This arran%ement is

)rovided to minimi+e the effect of any back)ressure on the o)eration of the balanced 61.

5hether it is )ressure ti%ht downstream de)ends on its desi%n. It may have a liftin% lever as

an o)tion.

#alanced 61s are used in flammable, hot and toxic services. 3sually they are )i)ed to safe

remote )oints of dischar%e such as a flare stack. #alanced 61s are found in service for %as,

va)or, steam, air or li*uids. #alanced 61s are also utili+ed in corrosive service. They arenot to be used on steam boilers, su)erheaters or as )ressure control or by)ass valves.

#ecause balanced-ty)e valves have vented bonnets and the vent may need to )i)ed to a safe

)oint. In the event that a bellows fails in such a valve the fluid will be dischar%ed to the

bonnet and out its vent.

Pi+t;O(e%"te# S",et' Re+ie, 2"+&es

A )ilot o)erated safety relief valve CP;61D is a )ressure relief valve whose main relievin%

valve is controlled by a small s)rin% loaded Cself-actuatedD )ressure relief valve. It is a

control for the lar%er valve and may be mounted with the main valve or remote from the

main valve. The A& ode re*uires that the main valve be ca)able of o)eratin% at the set )ressure and ca)acity even if the smaller fails.

Pilot o)erated relief valves are used under conditions where any of the followin% are trueF a

lar%e relief valve is re*uired, low differential exists between the normal o)eratin% )ressure

and the set )ressure of the valve, very short blown down Ctime between o)enin% and closin%D

is re*uired, back )ressures on the outlet of the valve are very hi%h, )rocess service where

their use is economical, )rocess conditions re*uire sensin% at a remote location.

P;61s are not suited for service with dirty, viscous CthickD fluids or fluids that mi%ht

)olymeri+e ChardenD in the valve. Any of these conditions mi%ht )lu% the small o)enin%s of

the )ilot system. If the o)eratin% tem)eratures mi%ht exceed the safe limit of the dia)hra%ms

or seals or if the o)eratin% fluids mi%ht chemically attack these soft )arts of the valve.

API !" Pa%e != of :!"


20/310

P%essu%e "!#% 2"-uu4 2e!t 2"+&es

Pressure andEor vacuum vent valves are used for the )rotection of stora%e tanks and are

cate%ori+ed into three kindsG wei%ht loaded, )ilot o)erated or s)rin% and wei%ht loaded.

These valves )rotect a%ainst an excessive differential in the outside )ressure Catmos)hericD

and the inside )ressure or vacuum. If while drawin% down Cdrainin%D a stora%e tank where to

develo) a vacuum the tank mi%ht be crushed by atmos)heric )ressure. In the case where

internal )ressure where to exceed desi%n )ressure the tank mi%ht bul%e or ru)ture. In cases

where the tank mi%ht o)erate alternatin% between )ressure and vacuum a breather ty)e valve

is used, this valve will both vent %as )ressure and break any vacuum, which mi%ht develo)

durin% o)erations of the stora%e tank.

Ru(tu%e Dis>s

A ru)ture disk C62D is a thin )late Cusually in the sha)e of a bul%eD that may be made of

various metals or of combinations or metals in thin layers. 62s may also be made of )lastic-

metal combinations or coated metals. /on-metallic 62s are manufactured from im)ervious

%ra)hite Cusually flatD and other non-metallic materials. The ru)ture disks are held betweens)ecially made flan%es and desi%ned to ru)ture at )redetermined )ressure and are of course

not ca)able of reclosin%. ost ru)ture disks are desi%ned to have the inside of the bul%e

facin% )ressure althou%h some are made to have the outside of the bul%e facin% )ressure,

these are called reverse bucklin% 62s They may be used to )rotect a%ainst excessive internal

)ressure. If the service involves a vacuum, the ru)ture disk normally will use a vacuum

su))ort. A ru)ture disk in this service is desi%ned to )rotect a%ainst an excessive internal

)ressure should it occur due to a failure of the system. &ach ty)e of 62 has s)ecial

considerations based on its desi%n. A 62 can be used alone or in combination with a

)ressure relief valve.

/ormal uses of 62s include all of the followin%G )rotections for the u)stream side of P61sa%ainst corrosion, )rotect 61s a%ainst )lu%%in% or clo%%in%, in )lace of P61s if nonreclosin%

is )ermitted, as additional backu) over )ressure )rotection, in outlets of vent )i)in% to

)rotect the P61 from corrosion and to minimi+e leaka%e of a P61.

)ecial handlin% for, stora%e, a))lications and the installation of 62s is re*uired and the

manufacturer's recommendations directions should be followed. A s)ecial consideration in

the A& ode is the relievin% ca)acity ratin% of the safety relief valve if the 62 is installed

between the 61 and the vessel.

or bul%ed metal ru)ture disks with the )ressure ex)osed to the inside of the bul%e and for

flat 62s the o)eratin% )ressure is usually limited to a ran%e of from 9S to >S or thedesi%n ru)ture )ressure. The )ercenta%e used de)ends on the ty)e of )ressure service the

ru)ture disk is in. The lower 9S is normally used when the service involves )ulsatin%

)ressure or wide swin%s in )ressure. The reasons for these limits include cree) of the ru)ture

disk material that can result in sudden ru)ture at normal o)eratin% )ressures. This can occur

ra)idly if o)eratin% tem)eratures are hi%h. or these and other reasons the service life of a

62 is about one year. They are easily dama%ed by the handlin% involved in their removal

and are best re)laced durin% any maintenance activities.

API !" Pa%e 8" of :!"


21/310

2"%i"ti!s $ith Resi+ie!t 2"+&e Se"ts

5hen ti%hter sealin% of P61s is desired the valves are manufactured with " rin%s in the

seatin% )arts. The valves are similar to P61s with metal to metal seatin% only but with soft

)arts to increase the seal ti%htness a%ainst leakin%. The a))lications for these ty)es of valves

are numerous but fall into the followin% cate%oriesG corrosive service,

toxicEflammableEex)ensive )roducts, o)eratin% )ressure very close to the set )ressure, in

vibratin% minor )ressure sur%es, hard forei%n )articles in fluid and in )ulsatin% )ressure or

vibratin% service.

are should taken when choosin% the material that the soft )arts, such as ;-6in%s, are made

from. They must resist the chemicals and )ressures they are ex)osed to in the intended

service. om)arable service should serve as a %uide when choosin% materials, failin% this

information the valve manufacturers can be consulted.

Re"s!s ,% I!s(e-ti!s

If a )ressure relief valve fails to o)en over)ressure could occur and cause serious dama%eand even loss of life. Protection of )ersonnel and e*ui)ment may finally de)end on the

)ro)er functionin% of the safety relief device. or these reasons the %eneral condition of the

devices and the fre*uency of ins)ection must be established.

C"uses , I4(%(e% Pe%,%4"!-e

The )rimary causes of failure or im)ro)er )erformance fall into cate%ories as listed in 6P

79. They can be classified as followsG corrosion, dama%ed seatin% surfaces, failed s)rin%s,

im)ro)er settin%Ead(ustment, )lu%%in%Estickin%, wron% materials for the service, installation

in the wron% service or location. 6ou%h handlin% durin% service and shi))in% or installation.

Im)ro)er hydrostatic tests of dischar%e )i)in% can cause dama%e to s)rin%s or to bellows of balanced relief valves.

?%e6ue!-' "!# Ti4e , I!s(e-ti!

2efinite time intervals are re*uired for the ins)ection, testin% and re)air of relief devices.

ome services re*uire more fre*uent ins)ection than others but the basic fre*uency must be

based on safety not economics. API !" establishes the maximum fre*uency to be !" years

but actual service may re*uire a shorter interval between ins)ections. The ideal time for

ins)ection is durin% a scheduled shut down of o)erations.

API !" Pa%e 8! of :!"


22/310

API !" odule

6P 79 &TI;/ ! A/2 8

ind the answers to these *uestions by usin% the stated API 79 )ara%ra)h at the end of the

*uestion.

Qui+ K8

!. ow often should a safety relief valve be testedN C?.D

8. A vessel made of P-! material one inch thick is bein% re)aired by weldin%. The vessel

was ori%inally )ostweld heat-treated. Is there any method to avoid P5T of the re)airN

C.8.:D

:. 5hy are relief devices installed on )ressure vesselsN C6P 79 8!.D

?. ow many ty)es of )ressure relief valves are thereN C6P 79 8.8.!.! ection 1III 3B-

!89D

. Mou notice that a )ressure relief device has a closed bonnet. 5hat ty)e of valve is itN

C8.8.!.:.!D

9. 5hile reviewin% maintenance records you notice that bul%ed ru)ture disks in a unit are

three years old. Is this okayN C8.8.:.:D

7. A )ilot o)erated safety valve has been installed in heavy crude service. Is this

okayN C8.8.!..:D

!. 2urin% sEds or !" years. C.!.!D

8. yes

:. to )rotect )ersonnel and )lant e*ui)ment.

?. safety valve, relief valve, safety relief valve, )ilot o)erated safety relief valve.

. relief valve.

9. no ! year

7. no

API !" Pa%e 88 of :!"


23/310

API !" odule

6P 79 &TI;/ :, ?, , 9, 7, and >


*uestion.

Qui+ K:

!. 2escribe a sho) ins)ection of a relief device. C:.8D

8. /ame three causes of im)ro)er )erformance of a )ressure relievin% device. CTitles of

ection ? )ara%ra)hsD

:. The s)rin% of a relief valve broke. 5hat )robably caused it to breakN C?.:D

?. The valve sho) is settin% safety relief valves usin% water is this acce)tableN C?.?D

. Mou are ask to set a schedule for the ins)ection of relief devicesG what will determine

the time between the settin% of valvesN C.!.! the max. is !" years )er API !"D

9. Mou notice workers o)enin% 61. dischar%e lines to the atmos)here. 5hat )recautions

should be takenN C9.!.!D

7. 5hat should the o)eratin% history of a )ressure valve includeN C9.!.:D

>. Mou are asked to visually ins)ect an 61 before it is taken to the sho). 5hat is the

)ur)ose of this and why is it im)ortantN C7.!.!D

=. 5hat is the )ur)ose of a )ressureEvacuum vent valve on an atmos)heric tankN C7.:.8D

!". 5hy are records ke)t for )ressure relievin% devicesN C>.!D

Answers Qui+K:

!. heck )o) )ressures, extend check for external conditions, and conform to s)ecifications.

8. orrosion, dama%e seat surfaces, and im)ro)er len%th of )i)in%N C?.8D

:. urface corrosion, stress corrosion.

?. /o.

. Performance of the devices in the )articular service.

9. Precautions should be taken to )revent the release of hydrocarbons, hydro%en sulfide 7.

C8D, or other ha+ardous materials in the systems and to )revent the i%nition of iron

sulfides in the )i)in%.

>. Avera%e o)eration conditions, the number and severity of u)sets and their effect on the

valve, the extent of any leaka%e while in service and other evidence of malfunctionin%.

=. To hole the de)osits of corrosion the corrosion )roducts and its im)ortance because theymay be loose and dro) out durin% trans)ortation R sho) fabrication.

!". To vent air and va)or in tanks when fillin% and to admit air when air drawn down.

API !" Pa%e 8: of :!"


24/310

API !" odule

API 6P 78 I/P&TI;/ ; P6& 36& 1&&


25/310

Se-ti! =

C!st%u-ti! St"!#"%#s

The first unfired )ressure vessels were constructed to the desi%n of the user or manufacturer.

This was true until about !=:" after that time the APIEA& ode or the American ociety

of echanical &n%ineers ode CA&D was used. In !=9 the APIEA& ode was

discontinued and the A& ode was ado)ted as the standard for the construction )ressure

vessels within its sco)e. ection 1II 2ivisions ! and 8 of the A& ode are the unfired

)ressure vessel odes. ection 1II 2ivision ! is the ode the vast ma(ority of vessels are

built toG ection 1II 2ivision 8 used for vessels in hi%h )ressure service or where lower

factors of safety are desired. 2ivision 8 has more restrictions on construction, materials,

ins)ection and nondestructive examination than 2ivision !. These restrictions usually result

in a vessel that would be thinner than that re*uired by 2ivision ! and the resultin% cost

savin%s could be si%nificant is some instances.

eat exchan%ers are built usin% both the A& ode and the tandards of Tubular

&xchan%er anufacturers Association CT&AD.

Se-ti! @

M"i!te!"!-e I!s(e-ti!

The basic rule for the maintenance of a vessel in service is to maintain it to the ori%inal

desi%n and the edition of the ode it was constructed under. If the vessel is re-rated this is

may done usin% the ori%inal or latest edition of the ode. This im)lies that )ersons

res)onsible should be familiar with the ori%inal construction edition of the ode and the

latest edition of the ode if a vessel has been re-rated. In addition )ersonnel res)onsible for

these vessels must be familiar with any nations state, county or city re%ulations. The A&

has minimum re*uirements for construction, ins)ection and testin% of )ressure vessels that

will be stam)ed with the ode ymbol however (urisdictions may have more restrictivere*uirements. om)liance with A& ode may not be enou%h to satisfy a (urisdiction's

re*uirement.

Se-ti! 5

Re"s!s ,% I!s(e-ti!

The main reason for ins)ection is to determine the )hysical condition of a vessel. 5ith this

information the causes and rate of deterioration can be established and safe o)erations

between shutdowns can be determined. orrectin% conditions causin% deterioration and

)lannin% for re)airs and re)lacement of e*ui)ment can also be done usin% the ins)ection

information. cheduled shutdowns and internal ins)ections can )revent emer%encyshutdowns and vessel failures. Periodic ins)ection allows the for the formin% of a well

)lanned maintenance )ro%ram by usin% data such as corrosion rates to determine re)lacement

and re)air needs. &xternal visual ins)ections alon% with the thorou%h use of various

nondestructive examination techni*ues can reveal leaks, cracks, local thinnin% and unusual

conditions.



26/310

Se-ti! /

C"uses , Dete%i%"ti!

The causes of deterioration are many but fall into several %eneral cate%ories as followsF

inor%anic and or%anic com)ounds. steam or contaminated water, atmos)heric corrosion.

These ty)es of corrosive a%ents fall into the class of chemical and electrochemical attack.

Attack is also )ossible from erosion and, or im)in%ement. The attack could come from any

combination of the above exam)les.

orrosion is the )rime cause of wear in )ressure vessels. The most common internal

corrodents are sulfur and chloride com)ounds. austic, inor%anic acids, or%anic acids and

low ) water can also cause corrosive attack in vessels.

&rosion is the wearin% away of a surface that is bein% hit by solid )articles or dro)s of li*uid.

It is similar to sandblastin% and is usually found where chan%es in direction or hi%h-s)eed

flow is )resent. It occurs in such )laces as inlet no++les and the vessel wall o))osite the

no++le. ;utlet no++les are likely s)ots when fast flowin% )roducts are in use. In some

instances corrosion and erosion are found to%ether.

etallur%ical and )hysical chan%es can occur when a vessel material is ex)osed to fluids the

vessel contains. &levated o)eratin% tem)eratures also contribute to these )roblems. The

chan%es that take )lace may be severe enou%h to result in crackin%, %ra)hiti+ation, hydro%en

attack, carbide )reci)itation, inter%rannular corrosion, embrittlement and other chan%es.

echanical forces such as thermal shock, cyclic tem)erature chan%es Chi%h to low tem)s on

a fre*uent basisD, vibrations, )ressure sur%es, and external loads can cause sudden failures.

racks, bul%es and torn internal com)onents are often a result of mechanical forces.

aulty materials can build in failure into a )ressure vessel or one of its com)onents. #admaterials can result in leaka%e, blocka%e, cracks and even s)eed u) corrosion in some. The

selection of an im)ro)er material for new construction of or for a re)air to a vessel will often

result in the same ty)e of failures as will )ro)er materials that have manufacturin% or

fabrication defects.

aulty fabrication includes )oor weldin%, im)ro)er or lack of heat treatment, tolerances

outside those )ermitted by odes and im)ro)er installation of internal e*ui)ment such as

trays and the like. Any of these ty)es of faulty fabrications may result in failures due to

cracks or hi%h stress concentrations, etc., in vessels.

Se-ti! .

?%e6ue!-' "!# Ti4e , I!s(e-ti!

any thin%s determine the fre*uency of ins)ection for )ressure vessels. hief amon% the

reasons is corrosion rates that are determined by the service environment. 3nless there are

insurance or le%al reasons, the re*uency of ins)ection should be based n information from

the first ins)ection )erformed, usin% either on stream or internal methods.

/ormally ins)ection )lannin% will allow for the next ins)ection to occur when at least half

the ori%inal corrosion allowance remains. ;ther factors such as a need for fre*uent cleanin%

may )rovide an o))ortunity to shorten the ins)ection fre*uency. If the )rocess fluids or

o)eratin% conditions chan%e, shorter ins)ection fre*uencies may be needed to determine what

effects the new conditions may have had.

API !" Pa%e 89 of :!"


27/310

;))ortunities for ins)ections will re*uire the in)ut of all %rou)s involvedG )rocess,

mechanical and ins)ection )ersonnel. The o))ortunity may have to be made if any laws

re*uire a fre*uency or the insurance com)any has a re*uirement for it in the )olicy written on

the e*ui)ment. A convenient time for ins)ections, of course, is any time e*ui)ment is

removed from service for cleanin%. Also if a vessel or exchan%er was removed for

o)erational reasons, an ins)ection mi%ht then become needed to insure the inte%rity of the

e*ui)ment before returnin% it to service.

Another consideration for the ins)ection of vessels is the review of the in service o)erational

records to look for )ressure dro)s and out of the ordinary conditions that mi%ht indicate a

)roblem.

Se-ti!

Meth#s , I!s(e-ti! "!# Li4its

To )erform a )ro)er ins)ection it is im)ortant to know the history of the vessels to be

ins)ected. $nowin% what re)airs have been re*uired in the )ast and ins)ectin% the re)air

after it has been in service may hel) to develo) better re)air methods. It may also hel) to

locate similar )roblems. In every case, careful visual ins)ection is a re*uirement. $nowin%the service conditions of a vessel allows the concentration of efforts in areas known to have

)roblems in a )articular service.

afety )recautions before enterin% a vessel are of the utmost im)ortance. 1essels have small

o)enin%s and often many internal obstructions that make %ettin% out of one *uickly nearly

im)ossible. The bottom line isF make sure it is safe to enter a vessel. uch thin%s as isolation

of lines by blindin%, )ur%in% and cleanin% alon% with %as testin% )rior to entry cannot be

overlooked. In some cases )rotective clothin% and air su))ly systems are called for if entry

is desired before cleanin% to look at the vessel's existin% conditions for indications of

)roblems. Always inform )ersonnel inside and outside a vessel that ins)ection )ersonnel are

enterin% the vessel.


28/310

oncrete su))orts are ins)ected with same concerns as concrete foundations. lose attention

to any seals and the )ossibility of tra))in% moisture because of faulty seals should be

investi%ated.

teel su))orts should be examined for corrosion, distortior? and crackin%. If corrosion is

severe, actual measurements of the remainin% thickness should be )erformed and a corrosion

rate established (ust as in a vessel. 5ire brushin%, )ickin% and ta))in% with a hammer is

fre*uently used ins)ection techni*ues. ost of the time corrosion can be slowed or

)revented by )ro)er. )aintin% alone. ometimes )rotective barriers such as %alvani+in% are

re*uired. As )art of steel su))ort ins)ection, vessel lu%s should be examined usin% the same

methods of wire brushin%, etc., described above. 5elds used to attach lu%s can develo)

cracks and some cracks can then run into the vessel's walls. If a vessel's steel su))orts are

'insulated and an indication of leaka%e is )resent, the insulation must be removed to

determine if corrosion under insulation has occurred.

Buy wires are cables that stretch from different )oints of a vessel to the %round where they

are anchored to under%round concrete )iers CdeadmenD. Ins)ection of these %uy wires must

include checkin% the connections for ti%htness and the cables for the correct tensions. Theconnections consist of turnbuckles used for ti%htenin% and 3 bolt cli)s for securin%. An

connectors must be checked for )ro)er installation and the )resence of corrosion- The cable

must be checked for corrosion and for broken strands.

/o++les and ad(acent areas are sub(ect to distortion if the vessel foundation has moved due to

settlin%. &xcessive thermal ex)ansion, internal ex)losions, earth*uakes, and fires can cause

dama%e to )i)in% connections. lan%e faces should be checked for s*uareness to reveal any

distortion, If evidence of distortion is found cracks should be ins)ected for, usin% non-

destructive examination. All ins)ections should be external and internal whenever )ossible.

1isible %asket seatin% surfaces must be ins)ected for distortion and cuts in the metal seatin%

surfaces. 5all thickness readin%s must also be taken on no++les and internal or externalcorrosion monitored.

Broundin% connections must be ins)ected for )ro)er electrical contact. The cable

connections should be ti%ht and )ro)erly connected to the e*ui)ment and the %roundin%

system. All %roundin% systems should be checked for continuity Cno breaksD and resistance

to electrical flow, ontinuity checks are usually made usin% electrical test

e*ui)ment such as an ;hm meter. lie resistance readin%s are recommended to be between

and 8 ;hms.

Auxiliary e*ui)ment such as %au%e corrections, si%ht %lasses, and safety valves may be

visually ins)ected while the vessel is still in service. Ins)ection while a vessel is 'm serviceallows the )resence of excessive vibrations to be detected and noted. If excessive vibrations

exist, en%ineerin% CGan determine if any additional measures are re*uired to )revent fati%ue

failures.

Protective coatin%s and insulation should be ins)ected for their condition- 6ust s)ots or

blisterin% are common )roblems associated with )aint and are easily found by visual

ins)ection. cra)in% away a loose coatin% film will often reveal corrosion )its. These )its

should be measured for de)th and a))ro)riate action taken. Insulation can usually be

effectively visually ins)ected. If an area of insulation is sus)ected, sam)les may be cut out

and examined for its condition. Insulation su))ortin% cli)s, an%les, bands, and wires should

be examined.

API !" Pa%e 8> of :!"


29/310

&xternal surface corrosion a))ears in forms other than rust. austic embrittlement, hydro%en

blisterin% and soil corrosion are also found on the external surfaces of e*ui)ment. Area of a

vessel that need s)ecial attention often de)ends on its contents. 5hen caustic is stored or

used in a vessel, the areas around connections for internal heaters should be checked for

caustic embrittlement. In caustic service, de)osits of white salts often are indications of leaks

thou%h cracks. ydro%en blisterin% is normally found on the inside of vessels, but can

a))ear on the outside if a void in the vessels material is close to the outer surface. 3nless

readily visible, leaks in a vessel are best detected by )ressure testin%. racks in vessels are

normally associated with weldin% and can he found usin% close visual ins)ection. In some

services nondestructive tests to check for cracks is (ustified and should be )erformed. ;ther

concerns when )erformin% external ins)ection are bul%es, %ou%es, and blisterin%. ot s)ots

when found in service should be monitored and thorou%hly evaluated by an en%ineer

ex)erienced in )ressure vessels.

Internal ins)ections should be )re)ared for by assemblin% all necessary ins)ection e*ui)ment

such as tools, ladders, and li%hts.

urface )re)aration will de)end on the ty)e of )roblems that a vessel may have in a

%iven service. ;rdinarily the cleanliness re*uired by o)erations is all that is needed for manyins)ections. If better cleanin% is re*uired, the ins)ector can scra)e or wire brush a small

area. If serious conditions are sus)ected, water washin% and solvent cleanin% may not be

enou%h to reveal )roblems. In these instances, )ower wire brushin%, abrasive %rit blastin%,

etc., may be re*uired.

Preliminary visual ins)ection should be )receded by a review of re)orts of )revious

ins)ections. Preliminary ins)ection usually involves seekin% out known )roblem areas based

on ins)ection ex)erience and service. any vessels are sub(ect to a s)ecific ty)e of attack

such as crackin% in areas such as u))er shell and heads. Preliminary ins)ection may reveal a

need for additional cleanin% for a )ro)er detailed ins)ection.

2etailed internal ins)ections should start at one end of a vessel and )ro%ress to the other end.

A systematic a))roach such as an item check list will hel) to )revent overlookin% hidden but

im)ortant areas. All )arts of vessel should be ins)ected for corrosion. hydro%en blisterin%,

deformation, and crackin%. In areas where metal loss is serious, detailed thickness readin%s

should be taken and recorded. If only %eneral metal loss is )resent, one thickness readin% on

each head and shell may be enou%h.


30/310

/o++les should be checked for corrosion and their welds for crackin% at the time of the

vessels internal ins)ection. /ormally ultrasonic thickness readin%s will reveal any loss of

metal in no++les and other o)enin%s in a vessel. Internal e*ui)ment such as trays and their

su))orts are visually ins)ected accom)anied by li%ht ta))in% with a hammer to ex)ose thin

areas or loose attachments. onditions of trays must be determined to check for excessive

leaka%e caused by )oor %asket surfaces or holes from corrosion. &xcessive leaka%e can

cause o)erational )roblems and may lead to )oor )erformance of a vessel or unscheduled

shut downs.

Ins)ection of metallic linin%s must determine if the linin% has been sub(ected to service

corrosive attack, that linin%s are )ro)erly installed, and that no cracks or holes are )resent in

the linin%. ost )roblems with linin%s are found by careful visual ins)ections. Ta))in% the

linin% li%htly with a hammer can reveal loose linin% or corrosion. 5elds around no++les

deserve s)ecial attention due to cracks or holes that are often found in these areas. If the

surfaces of the linin% are smooth, thickness measurements usin% ultrasonic techni*ues may

be )erformed. If re*uired, small sections of linin% can be cut out and measured for thickness.

A very useful method of trackin% the corrosion rate of linin%s, is by the weldin% of small tabs

at ri%ht an%les to the linin% when the linin% is first installed. These tabs are made of the samematerial and thickness as the linin% and can be easily measured at the time of installation and

at the next ins)ection to determine the rate of corrosion takin% )lace in the vessel.

6emember that both sides of the tab are ex)osed to the corrosion and the linin%'s loss must be

determined by dividin% the tab's loss by two. A bul%e in a liner can be caused by a leak in the

liner )ermittin% a )ressure or a )roduct build ti) between the liner and the )rotected base

metal.

/onmetallic liners are made of many different materials such as %lass, )lastic, rubber.

ceramic, concrete, refractory, and carbon block or brick liners. The )rimary )ur)ose when

ins)ectin% these ty)es of linin%s is to insure that no breaks in the linin% are )resent. These

breaks are referred to as holidays. #ul%in%, breakin%, and chi))in% are all si%ns that a break

is )resent in the linin%. The s)ark tester method if very effective in findin% breaks in suchnonmetallic linin%s as )lastic, rubber, %lass, and )aint. The device uses a hi%h volta%e with a

low current to find o)enin%s in linin%s. The electrical circuit is %rounded to the shell and the

)ositive lead is attached to a brush. As the brush is swe)t over the linin%, if a break is

)resent, electricity is conducted and an alarm is sounded. A little warnin%F this is obviously

not a device to be used in a flammable or ex)losive atmos)here nor should the device have

such a hi%h volta%e value that it can )enetrate throu%h a sound linin%. The s)ark tester is not

useful for brick concrete, tile, or refractory linin%s. 6emember linin%s can be dama%ed

durin% a careless ins)ectionG often (ust by dro))in% a tool.

oncrete and refractory linin%s often s)all Cflake awayD or crack. This dama%e is readily

detected durin% a visual ins)ection. inor cracks may take some %entle scra)in% to find. If bul%in% is obvious cracks may also be )resent. If any break is )resent, fluid has )robably

leaked in between the linin% and the outer shell and may have caused corrosion.


31/310

In thickness measurements usin% radio%ra)hs, the )lacement of a device such as ste) %a%e Ca

device of a known material and thicknessD in the radio%ra)hic ima%e is com)ared to the

ima%e of the )i)in% or vessel wall and the thickness determined by measurement.

orrosion buttons are made of a material that are not ex)ected to corrode in a %iven service

and then installed in )airs at s)ecific locations in the vessel. easurements are taken by

)lacin% a strai%ht ed%e across the two buttons and then %au%in% the de)th with a steel rule or

some other measurin% device. 5hen corroded surfaces are very rou%h, test holes throu%h the

vessel may be used to measure the wall thickness. A variation on test holes is de)th drillin%.

In this techni*ue, small holes are drilled to a known de)th Cnot all the way throu%hD in the

new vessel wall, then )lu%%ed with corrosion resistant )lu%s to )rotect the bottom of the hole

from corrosion. 2urin% internal ins)ections the )lu%s are removed and de)th readin%s are

taken. Any wall loss that has occurred is detected by the hole de)th becomin% more shallow

than the ori%inal readin%.

)ecial methods of detectin% mechanical chan%es include nondestructive techni*ues, acid

etchin% small areas to find cracks, and sam)le removal. Acid etchin% re*uires abrasivecleanin% and the a))lication of an a))ro)riate Cfor the metalD chemical usually acid. The

etchin% a))roach allows fine cracks to stand out in contrast to the base metal. am)le

involves the removal by mechanical cuttin% out a small )ortion of the area of interest and

then analy+in% it under a microsco)e. ;ften the filin%s created durin% the removal can be

cleaned and then sub(ected to a chemical analysis. A weld re)air to the site of sam)le

removal will be re*uired and should be made as carefully as any welded re)air.

etallur%ical chan%e tests can be made usin% many of the same techni*ues described in

mechanical chan%es. Additional tests include hardness chemical s)ot, and ma%netic tests.

Portable harness testers such as the #rinell will detect )oor heat treatment, carburi+ation and

other )roblems that involve a chan%e in hardness. hemical tests to a small )ortion of ametal will reveal the ty)e of metal to determine if the wron% metal has been installed

)ossibly durin% a )ervious re)air. a%netic tests are used to determine if a material such as

austenetic stainless steelG normally not ma%netic, have become carburi+ed, which will allow

the austenetic stainless to become attracted to a ma%net.

Testi!

ammer testin% used durin% visual ins)ection will reveal conditions such asG thin sections.

ti%htness of bolts and rivets, cracks in linin%s, lack of bond in refractory and concrete linin%s.

The hammer is also used to remove scale for s)ot ins)ection. ammer testin% is an art

learned from ex)erience and caution is warranted whenever usin% this method. It is notsmart to hammer on anythin% under )ressure and hammerin% on some )i)in% systems can

dislod%e scale or debris and )lu% u) a )ortion of the system such as a catalyst bed.

Pressure andEor vacuum tests are )er-formed when a vessel is first built and then a))lied after

enterin% service if any serious )roblem has been disclosed, which brin%s into *uestion the

inte%rity of the vessel. After ma(or re)air work, a )ressure test is normally re*uired. ome

(urisdictions and com)any's )olicies re*uire tests on a time basis even if no re)air work has

been done. These ty)es of tests often involve raisin% the internal )ressure above normal

o)eratin% )ressure and the )ossibility of dama%e to the vessel from the test exists. Pressure

tests should a))lied carefully by *ualified )ersonnel usin% calibrated %a%es with )ositive

control of the test e*ui)ment. The ob(ect is to reveal any )roblems, not to create one. ost

of the time these tests use water or some other fluid ChydrostaticD )ermitted by the odes.

2urin% hydrostatic testin% of a vessel )ressure dro), leaks and deformation Cbul%in%D in the

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32/310

vessel may be revealed. If the vessel's su))orts can not hold the wei%ht of the fluid or the

vessel cannot tolerate contamination by the testin% fluid, a %as test C)neumaticD may be used.

Pneumatic testin%, by its nature, can be more dan%erous than hydrostatic testin%. aution is

always advisable durin% a )neumatic test, and it is normally the last choice of ty)es. The

reason for this is that %as that has been com)ressed has a %reat deal of stored ener%y, and if

failure occurs, it will likely be ex)losive. ave you ever blown out a car tireN 2urin% a

)neumatic test, a soa) solution is often a))lied to weld seams and fittin%s and then, lookin%

for bubbles, leaks can be revealed. Another method, sound detection, uses s)ecial listenin%

devices to bear and locate the leaks. Another sound based device is Acoustic &missions. As

a vessel is )ressuri+ed, it emits sounds from any flaws )resent in the metal. #y usin% several

listenin% devices attached to different )arts of the vessel, the location of a serious flaw is

found by usin% trian%ulation. ome vacuum vessels can be tested with internal )ressure

rather than a vacuum. If a vacuum vessel can be )ressure tested, it is the )referred method

because it is easier to detect leaks with internal )ressure.

1acuum tests are conducted by creatin% a vacuum inside the vessel and observin% the

vacuum %a%e for any loss of vacuum that mi%ht occur. If the vacuum remains unchan%ed the

assum)tion is made that no leak exists.

Testin% tem)erature can be very im)ortant with some )ressure vessel materials due to the

brittle characteristics of these metals at low tem)eratures. The A& recommends that the

test tem)erature be at least :"H above the minimum desi%n metal tem)erature to )revent the

risk of brittle fracture. A brittle fracture can be com)ared to %lass breakin% and shatterin%.

or that reason every effort must be made to )revent it. In combination with a )neumatic test

and its stored ener%yG a brittle failure would be a devastatin% bomb. or all materials the

%eneral recommendation for test tem)erature is 7"H minimum and !8"H maximum for

safety when conductin% a )ressure test, no unnecessary )ersonnel should be allowed in the

area until the test is com)lete. Pneumatic tests must follow a )rocedure described in the

A& ode that raises the )ressure in small ste)s with short sto)s at each ste).

Pressure testin% of exchan%es can be )erformed when they are first shut down and before

bundle removal in order detect any leaks that mi%ht have been )resent durin% recent service.

If leaks are detected durin% the initial test, )artial disassembly can be )erformed and the test

)ressure rea))lied to locate the source of the leaks. eat exchan%ers may also be

disassembled and cleaned, ins)ected, re)aired if needed, then reassembled and tested. If a

leak is detected in the exchan%er after re-assembly, disassembly will a%ain be re*uired to

re)air the leak. The method of testin% an exchan%er will de)end on its desi%n. ome can be

tested with their channel covers removed if of the fixed tube sheet desi%n with the )ressure

a))lied to the shell side. If a tube in the bundle is discovered to be leakin% at other than the

tube sheet roll, it may be )lu%%ed with a ta)ered )lu% which effectively removes that tubefrom service. If the leak is located where the tube is rolled Cex)andedD into the tube sheet, an

attem)t to re-roll the tube is usually made and the test )ressure rea))lied. ;ften tube bundles

are tested out of their shells if of the floatin% head desi%n.


33/310

above what are re*uired by the odes they were built to. &xtra thickness can be re*uired by

the desi%n as sacrificial metal Ccorrosion allowanceD in the vessel )arts.

&xtra thickness can be due to the nominal )late thickness as o))osed to the actual thickness

re*uired by calculation, i.e., the shell has a re*uired thickness of .?: and .""L )late is

used because .?: is not manufactured. ;wners, 3sers or odes may re*uire that the metal

cannot be less than a certain thickness in a )articular service. ometimes a reduction in

)ressure or tem)erature for a vessel will allow its continued service with thinner metal.

ethods of re)air to vessels should be reviewed to insure that they com)ly with any odes

or standards that may a))ly. everal (urisdictions reco%ni+e the minimum re)air techni*ues

of the API. ;ther (urisdictions re*uire that the re)airs be made to the /ational #oard of

#oiler and Pressure 1essel Ins)ectors C/##P1ID, /ational #oard Ins)ection ode-8:

C/#ID and that the re)air concern holds a valid 6 C6e)airD tam) from the /##P1I. In

addition to usin% a concern holdin% the 6 tam) an /##P1I 6e)air form 6! may also be

re*uired. In some instances, Insurance arriers will re*uire that the /#I be followed and

that an /#I Authori+ed Ins)ector in their em)loy a))roves the re)air. 6e)airs made to

vessels by weldin% will re*uire visual ins)ection as a minimum and may also involve various

nondestructive examinations C/2&D methods based on the severity of the re)air and theori%inal /2& used in the construction ode. 3nless the Ins)ector can acce)t a sound

technical ar%ument a%ainst re*uirin% a )ressure test after a ma(or re)air, one should be

a))lied. If the re)air to a vessel involves cracks s)ecial )re)aration of re)air area is re*uired.

The ma(or concern in crack re)airs is the com)lete removal of the crack. racks may be

removed by chi))in%, flame, arc, or mechanical %ou%in%. Any crack removal techni*ue that

uses hi%h heat in)ut to the affected area can cause the crack to %row, so caution must be used

with those techni*ues. In cases where many cracks are )resent it is normally better to re)lace

the entire section of the material. hallow cracks may be removed by %rindin% usin% a

blendin% method if the final thickness does not fall below the minimum re*uired.

Ins)ection records and re)orts are im)ortant and are re*uired by most odes and

(urisdictions such as the tate, API, and the /##P1I /#-8:. These re)orts are of threety)esF #asic 2ata, ield /otes, and ontinuous ile. The basic data includes ori%inal

manufacturer's drawin%s and data re)orts as well as desi%n information. ield notes are notes

about and measurements of the e*ui)ment and may be written or entered into a com)uter

data base. 3sually field notes are in the form of rou%h records ins)ections and re)airs

re*uired. ontinuous files include all information about a vessel's o)eratin% history, )revious

ins)ection re)orts, corrosion rate tables Cif anyD and records of re)airs and re)lacements.

o)ies of re)orts containin% the location, extent, and reasons for any re)airs should be sent

to all mana%ement %rou)s such as &n%ineerin%, ;)erations, and aintenance de)artments.

eat &xchan%ers are used to transfer heat from one %as or li*uid to another %as or li*uid

without the two fluids mixin%. eat exchan%ers fall into classesF condensers and coolers. Acondenser has the effect of chan%in% a %as fluid to a li*uid or )artial li*uid fluid and

ordinarily use water as the coolant. oolers lower the tem)erature of a fluid and may use

water or another )rocess fluid of a lower tem)erature as the coolant. ometimes air is used

to lower the tem)erature of a fluid. The e*ui)ment is then referred to as an air cooler.

Into a tube sheet by rollin% Cex)andin%D them into the tube sheet holes. In heat exchan%ers,

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34/310

after rollin% tubes, the ends are sometimes welded to the tube sheet for sealin% )ur)oses. In

some cases the tubes are inserted into the tube sheet and )ackin% rin%s are installed to seal

the area around the tube ends. The method of construction used is de)endent on the service

intended for the exchan%er. There are four basic desi%n ty)es of shell and tube heat

exchan%ers. They areF ;ne ixed Tube heet with a loatin% ead Cthe most commonD, Two

ixed Tube heets, ;ne ixed Tube heet with 3-Tubes, and 2ouble Tube heet Cused when

even the sli%htest leak cannot be allowedD.

6eboilers and &va)orators )erform the o))osite function of the condenser or cooler. They do

what their names im)lyF boil and eva)orate. In %eneral they use steam or a hotter fluid from

a )rocess to boil or eva)orate another fluid. The 6eboiler is normally used to boost heat back

u) to a desired level at some intermediate ste) of a )rocess stream.

ome ;ther ty)es of heat exchan%ers includeF &x)osed #undle, tora%e Tank eaters, Pi)e

oils Ceither sin%le or double )i)eD, #ox-Ty)e eater oils, and Plate-Ty)e.

Ins)ection of &xchan%er #undles should start with the establishment of any %eneral corrosion

)atterns. Ins)ectin% an exchan%er bundle when it is first removed can reveal the ty)eCsD andlocations of corrosion and de)osits. 1isual ins)ection techni*ues include li%ht scra)in% and

hammerin% testin% with a very li%ht ball )een hammer C? to > o+D to locate corrosion and

thinnin%. The inside of the tubes may be )artially ins)ected usin% boresco)es, fiber o)tics,

and s)eciali+ed )robes. ince only the outside of tubes in the outer )ortion of a bundle can

be seen, inner tubes must be ins)ected usin% /2& techni*ues such as &ddy urrent or

3ltrasonics. In some instances a tube may selected for removal and s)littin% for ins)ection.

The results of this destructive examination can then be used to determine the )robable

%eneral condition of the remainin% tubes. ;ther )ortions of the exchan%er such as the tube

sheets, baffles, im)in%ement )lates, floatin% head, and channel covers will re*uire visual

ins)ection and may re*uire measurin% to determine their conditions.

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35/310

API 6P 78 &TI;/ !, 8, :, ?, and 9


*uestion.

Qui< @

!. /ame three sha)es of )ressure vessels. C8.!D

8. 2escribe multilayer construction of a )ressure vessel. C8.8D

:. 5hen carbon steel will not resist corrosive fluids, what method of construction is

normally used for such a vesselN C8.:D

?. /ame four ty)es of internals found in )ressure vessels. C8.?D

. Prior to !=:", what s)ecifications were unfired )ressure vessels built to in refineriesN

C:."D

9. 5hy is it im)ortant to have access to )revious editions of the A& odesN C?."D

7. /ame three ty)es of information %ained from the ins)ection of a )ressure vessel.C. !D

>.


36/310

API PP 78 &TI;/ >.! to >.?.?


*uestion.

Qui< 5

!. 5hat should an ins)ector be aware of before startin% the ins)ection of a )ressure

vesselN C>.!D

8. areful visual is im)ortant to determine what other ty)es of ins)ections mi%ht be

re*uired. /ame three other ty)es of ins)ection. C>.!D

:. #efore an ins)ection starts in a vessel, who else besides the safety man should be

informedN C>.8.!D

?. /ame five tools an ins)ector should have to )erform an ins)ection. C>.8.8D

. .:.8,.:,.?,.,.9,.7,.>,.=,.!",.!!,.!8,.!:D

9. Abrasive %rit blastin%, )ower wire brushin% etc., are usually re*uired under what

conditionsN C>.?.8D

7. If a vessel has had )revious internal ins)ections, what should be done )rior to your

ins)ectionN C>.?.:D

>. 5here will most of cracks found in a )ressure vessel be foundN C>.?.:D

=. 5hy is a systematic )rocedure im)ortant when ins)ectin% a )ressure vesselN C>.?.?D

!". 3nder what o)eratin% conditions should weld seams in a )ressure vessel be %iven s)ecial

attentionN C>.?.?D

Answers to Qui+ K

!. Pressure R tem)erature conditions under which the vessel has been o)erational since last

ins)ection contents R function of vessel serves in the )rocess.

8. a%netic )article-wet or dry, dye )enetrant, ultrasonic shear wave

:. All )ersons workin% around the outside. The vessel that )eo)le will be workin% inside

the vessel.?. lashli%ht, scra)er, )lastic ba%s, R hammer

. . 5elded seams and ad(acent areas, shar) chan%e in sha)e, no++les, R baffles.

=. To avoid overlookin% but obscure im)ortant items

!". 5hen the service of vessel is Amine, 5et ydro%en ulfide, austic Ammonia, yclic,

i%h Tem)erature or other services that may )romote cracks.

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API !" Pa%e :9 of :!"


37/310

API 6P 78 &TI;/ >.?. to >..8


*uestion.

Qui< /

!. 5hen examinin% linin%s, name the three most im)ortant conditions to check. C>.?.D

8. 2escribe the s)ark tester method of ins)ectin% nonmetallic linin%s. C>.?.9D

:. ow may loose non-metallic fittin%s be found usin% a hammerN C> ?.9D

?. 5here a corroded surface is very rou%h, what may be done to measure thicknessN

C>.?.7D

. ow may cracks be made to stand out from the surroundin% areas bein% ins)ectedN

C>.?.>D

9. 5ho should make the decision to tre)an metal from a vessel for metallur%ical

evaluationN C>.?.>D

7. ow may carburi+ed austenetic stainless steel sometimes be detectedN C>.?.=D

>. 5hat functions may an ins)ector's hammer serveN C>..!D,,

=. 5hen testin% a vessel )neumatically what should be on hand to aid in the visual

examinationN C>..8D

!". If it is )ossible to use internal )ressure to test a vacuum vessel, what advanta%e does

that method offerN C>..8D

Answers to Qui+ K

!. /o corrosion, linin% )ro)erly installed, no holes or cracks exist.

8. A hi%h volta%e low current electrodeCbrush ty)eD is )assed over the linin%, the other

end is attached to the end of the vessel. &lectric arc will )ass between electrode and

the hole in the linin%

:. A li%ht ta))in% on linin% will make lessor evident with sound R feel.

?. 2rill test hole to determine thickness.

. &tchin% method CacidD

9. #y someone who knows how to analy+e the )roblems related to the re)air of sam)le

house.

7. a%netic Test

>. u))lement visual ins)ection e.%. thin walls in vessel, loose bolts R nuts, rivets,

cracks in metallic linin%s, lack of bond in concrete to remove scale.

=. oa) solution, ultrasonic sound tester or both.

!".


38/310

API 6P 78 &TI;/ >..: to !".8


*uestion.

Qui+ K7

!. 5hy is it desirable to leak test an exchan%er before disassemblyN C>..:D

8. If a %iven exchan%er be%ins leakin% for the first time in its service life, what should be

doneN C>..:D

:. #efore retirin% a vessel, what should be consultedN C>.9D

?. #efore takin% credit for excess thickness found in a vessel when doin% calculations for

retirement or reratin%, what must also be consideredN C>.9D

. 5hat documents should be consulted )rior to any re)airN C=D

9. 5hen shall a )ressure test be a))liedN C=D

7. 5hy should care be taken when arc %ou%in% a crack before a welded re)airN C=D

>. 5hat must an ins)ector consider when recommendin% the fillin% of )its with an

e)oxyN C=D

=. 5hat does the continuous file containN C!".8D

!". 5ho should receive co)ies of all ins)ection re)ortsN C!".8D

A/5&6 T; Q3I K7!. A leak may be detected by observin% R )oint such as a disconnected no++le or an o)en

bleeder.

8. Ins)ection should be )erformed to determine the nature of deterioration

:. The code edition of that code it is rated under and whether any re%ularities of and

allowable re)airs must be determined.

?. afety, Tem)erature R Pressure

. A))licable code R standards under which it is to be rated should be studied to assure

methods of re)air will not violate a))ro)riate re*uirements

9. or al ma(or re)airs

7. #ecause the heat will cause cracks to len%then or

>. That the )its are not lar%e enou%h or close enou%h to%ether to re)resent a %eneralthinnin% of the com)onent.

=. All information on the vessel o)eratin% history descri)tion and measurement from

)revious ins)ections, corrosion rate tablesCif anyD and records of re)air R re)lacement.

!!. ;)erations, aintenance R &n%ineerin%

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39/310

API 6P 78 APP&/2I4 A


*uestion.

Qui+ K>

!. &x)lain the difference between condensers, coolers and air coolers. CA. !D

8 how by sketch what is meant by ;ne ixed Tube heet with loatin% ead, Two

ixed Tube heets, ;ne ixed Tube heet with 3 Tubes. CA.8.8, 8.:, 8.?D

:. 5hen are 2ouble Tube heet &xchan%ers usedN CA.8.D

?. /ame two ty)es of water heaters. CA.8.7D

. 5hat )rinci)le of coolin% is used with ex)osed tube bundlesN CA.:.8, :.:D

9. /ame two ty)es of Air-ooled &xchan%ers. CA.D

7. 2escribe the construction of 2ouble-Pi)e coils. CA.9.8D

>. 5here are lat-Ty)e eater oils foundN CA.9.:.?D

=. 5hy is it im)ortant to ins)ect exchan%er bundles when they are first )ulled from a

shellN CA.=. !D

!". /ame the likely locations for corrosion in exchan%ers. CA.=.8D

A/5&6 T; Q3IK>

!. ondensers transfer heat by va)ors to another fluid

oolers cools hot by a lower tem)erature

Air-coolers air is used to reduce tem)erature of fluid by air.

8.

:. 5here minute leaks from one fluid to another cannot be tolerated

?. a.D fixed tube sheet ty)e b.D u-tube ty)e

. 5ater flows or s)rayed on bundles

9. 2raft coolers-on to) or below tube bank, forced draft coolers-below tube bank

7. They are in sha)e and of small diameter with minimum wall thickness

>. #ottom of stora%e tank =. #ecause the color ty)e location of scales and a. hel) to )in)oint corrosion )roblems

!". The outside surface of tubes o))osite shell inlet no++les, ad(acent to the baffles are tube

sheets

API !" ;23


40/310

API APT&6 II

;/2ITI;/ A3I/B 2&T&6I;TATI;/ ;6 AI


41/310

already )resent in the crude oil that is bein% refined. hemicals commonly added in refinin%

)rocesses are ulfuric Acid and ydro%en luoride, Phenol Phos)horic Acid, austic

Csodium hydroxideD, ercury, Ammonia, hlorine, and Aluminum.

Alkylation 3nits utili+e either ulfuric Acid or ydrofluoric Acid as a catalyst. ulfuric Acid

is the least corrosive of the two chemicals and corrosion occurrin% in e*ui)ment usin%

ulfuric Acid may be very erratic attackin% )articular )oints in the )rocess stream ulfuric

acid is %enerally less corrosive at hi%h concentrations of >S or more. ydrofluoric Acid is

very corrosive to steel unless it is ke)t at concentrations above 9S ydro%en luoride.

Phenol Ccarbolic acidD is used in the manufacture of lubricatin% oils and aromatic

hydrocarbons. At tem)eratures below ?""H and without water )resent, carbon steel is

usually not severely corroded by Phenol. Above ?""H, carbon steel may corrode ra)idly m

Phenol service.

Phos)horic Acid is used as a catalyst in )olymeri+ation units either in li*uid or de)osited as

)entoxide on clay )ellets. 3nless water concentrations are above a certain level, corrosion is

rare from Phos)horic Acid. 5hen water is )resent in the re*uired concentrations, Phos)horicAcid will attack carbon steel very a%%ressively. Penetration of UL carbon steel in > hours can

occur.

austic is used )rimarily for neutrali+ation of acids and %rease manufacture. austic can be

used and stored in carbon steel vessels and is %enerally not corrosive as lon% as the vessel has

been stress relieved and tem)eratures are ke)t at a safe level. At tem)eratures above 8""H,

it will cause %eneral corrosion in carbon steel.

ercury is found in instrumentation and can enter vessel by misha). If the mercury enters it

will cause stress corrosion attack in co)

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268652323-API-510-Study-Material (1)