MeasuringAPITubing&CasingCouplingswith

PlugGages

PMCLoneStarTechnicalBriefDoc.103Rev.B

DavidR.MaischDirectorofEngineering&IndustrialAffairs

PMCLoneStarJuly19,2011

Itiscommontofindtwogagedesignsthroughouttheindustry.Oneisknownas

“ShoulderDesign”,andoneisknownas“RemovableKeysDesign”.Bothdesigns

havetheirbenefits,andbothgetthejobdone,whichoneyouuseispurelyamatter

ofpreference.BothdesignsprovideBasic,MinimumandMaximumscribelinesfor

visualverificationofstandoff,physicalmeasurementsmayalsobetakenwhen

necessary.APISpecification5Bstatesthattherequiredstandoffbetweena

tubing/casingpluggageandacouplingis:

8TPI=A±1P

10TPI=A±1‐1/2P

APISpecification5Bdefines“A”bythenumberofturns.Sinceeachturnis1P,we

canbreak“A”downtoadecimalvaluethatismoreusefulwhengaging.For

example,a4”‐8ExternalUpsetTubinghasan“A”valueof2Turns.Sinceeachturn

is1P,and1Pfor8TPIis0.125”(1/8),thedecimalequivalentof“A“is2x0.125”=

0.250”.Sincethishasatoleranceof±1P,weknowthatthestandofffora4”‐8

ExternalUpsetTubingis0.250”±0.125”

Whengagingtubingandcasingcouplings,thepluggageshouldscrewintothe

couplinguntilhandtight,atthatpointthefaceofthecouplingmustfallinbetween

theMinimumandMaximumscribelinesinordertopassasagoodpart.Ifrequired,

adirectmeasurementcanalsobetaken.Usingthe“ShoulderDesign”plug,the

standoffcanbemeasuredbetweenthefaceofthecouplingandtheshoulder,this

dimensionshouldbe“A”withatoleranceof±1P(8TPI)or±1‐1/2P(10TPI).Using

the“RemovableKeysDesign”,thestandoffcanbemeasuredfromthebackfaceof

thepluggagetothefaceofthecoupling.Whenusingthismethod,itisimportantto

notethedimensionscribedontothebackfaceofthepluggage“Distancefromback

facetoV.P.”.Therequiredstandofffromthebackfaceofthepluggagetothefaceof

thecouplingshouldbe“A”+“DistancefromBackFacetoV.P.”withatoleranceof

±1P(8TPI)or±1‐1/2P(10TPI).

PMC Lone Star

Technical Brief

Non‐Upset Tubing  External‐Upset Tubing 

Size  Threads  Standoff  Standoff  Size  Threads  Standoff  Standoff 

Designation  per in.  Turns  Decimal  Designation  per in.  Turns  Decimal 

D  TPI  A (Turns)  A (Decimal)  D  TPI  A (Turns)  A (Decimal) 

1.050  10  2  0.2000  1.050  10  2  0.2000 

1.315  10  2  0.2000  1.315  10  2  0.2000 

1.660  10  2  0.2000  1.660  10  2  0.2000 

1.900  10  2  0.2000  1.900  10  2  0.2000 

2‐3/8  10  2  0.2000  2‐3/8  8  2  0.2500 

2‐7/8  10  2  0.2000  2‐7/8  8  2  0.2500 

3‐1/2  10  2  0.2000  3‐1/2  8  2  0.2500 

4  8  2  0.2500  4  8  2  0.2500 

4‐1/2  8  2  0.2500  4‐1/2  8  2  0.2500 

Casing 

Size  Threads  Standoff  Standoff 

Designation  per in.  Turns  Decimal 

D  TPI  A (Turns)  A (Decimal) 

4‐1/2  8  3  0.3750 

5  8  3  0.3750 

5‐1/2  8  3  0.3750 

6‐5/8  8  3  0.3750 

7  8  3  0.3750 

7‐5/8  8  3.5  0.4375 

8‐5/8  8  3.5  0.4375 

9‐5/8  8  3.5  0.4375 

10‐3/4  8  3.5  0.4375 

11‐3/4  8  3.5  0.4375 

13‐3/8  8  3.5  0.4375 

16  8  3.5  0.4375 

18‐5/8  8  3.5  0.4375 

20  8  3.5  0.4375 

PMC Lone Star

Technical Brief

PMC Lone Star

Technical Brief

PMC Lone Star

Technical Brief

PMC Lone Star

Technical Brief