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The ASME Pressure Vessel Joint Efficiencies article provides you withinformation about pressure vessel joint efficiency requirements and theirconnection with radioraphy testin!

"ou may #now Pressure Vessel Joint Efficiencies are lin#ed to the radioraphytestin rades and there is a concession for full radioraphy testin as per the$%&''(a) (*) (b) clause which it is a little bit confusin!

This article provides you the ASME pressure vessel joint efficienciesrequirements and uidelines for the above clause!

+ased on the ASME ,ode requirement- manufacturers have to mar# the type of.T i!e! .T'- .T/- .T0 and .T1 in the pressure vessel name plate and state thesame in Pressure Vessel 2ata .eport!

%e have seen many professionals- from inspectors to quality control enineers

who are confused between .T' and .T/- specifically when they see ASMEPressure Vessel Joint Efficiencies for both .T' and .T/ is the same and equalto '(E3')!

They say both .T' and .T/ are cateori4ed in the 56ull .adioraphy7 part in$%&'' clause !!!

So why are some joints in .T/ radioraphed in spots8

%e are ma#in spot radioraphy- but it is cateori4ed in full radioraphy999

So in this :ASME Pressure Vessel Joint Efficiencies: article we want to answerthis question in very simple way- but before this- we need review joint cateoriesand summari4e them as below;

Category A:

All lonitudinal welds in shell and no44les

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All welds in heads-

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Item :All butt welds in an unfired steam boiler with desin pressure C *D psi($%&''(a))!

Item !:All cateory A and 2 butt welds in vessel when 56ull .adioraphy7optionally selected from table $%&'/(column (a) in this table is selected) and

cateories + and , which intersect ,ateory A shall meet the spot radioraphyrequirement ($%&''(a) (*) (b))!

The point is this; items '- / and 0 are similar- but item 1 is completely different! Fnitems '- / and 0 it is mandated by code to do full radioraphy in all butt welds invessel so it means it is mandatory for desiner to select column (a) in $%&'/table!

+ut in item 1- there is no mandatin rule! A manufacturer with its own decisionhas chosen to use column (a) in table $%&'/ for full radioraphy!

So here there is a concession or bonus to manufacturers for cateories + and ,!

What is concept "ehind this concession or "onus in pressure #essel $%test?

Ff you review item '- / and 0 one more time- you will see that the pressure vessel.T tests are related to the type of welds and services!

"ou can see the pressure vessels in these items are critical from a safety point ofview- one contains a lethal substance- the other one has a hih thic#ness- whichimplicates hih pressure- and the last one is an unfired steam boiler! +ut item 1

has no criticality li#e the other items have!

+ut you should note all 1 items have been cateori4ed in full radioraphyclause( $&''(a))- so to differentiate item '- / and 0 from item 1- the .T symbolsare used in ,ode ($G&''H)!

$% 1:Ftems '- / and 0- (E3')- All butt welds&full lenth radioraphy

$% 2:Ftem 1 (E3')- ,ateory A and 2 butt welds full lenth radioraphy andcateory + and , butt welds spot .adioraphy

$% :(E3D!I*)- Spot radioraphy butt welds

$% !:(E3D!)- Partial >o radioraphy

"ou need to consider the hemispherical head joint to shell as cateory A- butellipsoidal and torispherical head joint to shell as cateory +

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2o you #now why8 %hy ASME considered the strinent rule for pressure vessel.T test in hemispherical head joint8

Ft is because this joint is more critical- because the thic#ness obtained from theformula for hemispherical head appro@imately would be half of the shell

thic#ness

Ft means if the shell thic#ness is ' inch- the hemispherical head thic#ness wouldbe D!* inch!

6or more detail- you may review the Pressure Vessel

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The concept is to define the different types and then introduce some restrictionfor usin them!

6or e@ample- a Type ' weld is defined as a full penetration weld- typically doublewelded and Type / is welds with bac#in strips!

So when you o to service restriction for a vessel containin a lethal substance-you see there is a restriction there that says all cateory A joints shall be weldType ' and ,ateory + and , shall be type ' or type /!

"ou should ta#e this point in to account- which is this; the same joint cateorywith different weld types have different joint efficiencies!

&ummary of weld types:

%ype 1:6ull penetration welds (Typically 2ouble welded)

%ype 2:%elds with bac#in strip

%ype :Sinle welded partial penetration welds

%ype !- . and /:Various =ap welds (rarely used)