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Stub Ends for Flanged Joints

What is a stub end and why should it be used? Stub ends are buttweld fittings that can be used (in combination with a lap joint flange) alternatively to welding neck flanges to make flanged connections. The use of stub ends has two advantages: it can reduce the total cost of flanged joints for piping systems in high material grades (as the lap joint flange does not need to be of the same material of the pipe and the stub end but can be a lower grade); it speeds up the installation process, as the lap joint flange can be rotated to facilitate the alignment of the bolt holes. Stub ends are available in short and long pattern (ASA and MSS stub ends), in sizes up to 80 inches.

STUB END APPLICATION

A stud end and a lap joint flange can be used together as an alternative way to make a flanged connection than welding neck flanges.

The two devices to be combined, in this case, are:

  • The stub end, which is essentially a piece of pipe, with one end flared outwards and the other prepared to be welded to a pipe of the same bore size (NPS = nominal pipe size), material and wall thickness. The most widely used fabrication tool for stub ends is the flaring machine, which is able to flare the end of the pipe and then cuts it to length.
  • A Lap Joint Flange, which is used to actually bolt the two lengths of pipe together.

flanged joint with stub end

 BENEFITS OF LAP JOINT STUB ENDS

The use of stub ends has these two advantages:

Reduces the overall cost of the flanged joint

Generally, the lap joint flange is of a lower grade than the material of the stub end and the pipework, thus saving the total weight of high-grade material used for the flanged joint.

Example:

For an SS316 pipe, instead of using a full 316 welding neck flange, a combination of an SS316 stub end and a carbon steel lap joint flange would do the same exact job, but the total weight of SS316 material would be lower, and the cost as well.

Essentially, stub ends allow to minimize the weight of high-grade material in stainless, duplex, and nickel alloy piping, saving costs. Of course, the bigger the diameter and the class of the flanges, the higher the saving!

Facilitates the installation of the flange

The lap joint flange can be rotated on the pipe and simplify the alignment of the bolt holes of the mating flanges

It shall be noted that stud ends are becoming popular also in high-pressure applications (whereas they were used for low-pressure applications only in the past).

Stub end with lap joint flange

STUB END TYPES

Stub ends are available in three different types, named “Type A”, “Type B” and “Type C”:

  • The first type (A) is manufactured and machined to match standard lap joint backing flange (the two products have to be used in combination). The mating surfaces have an identical profile to permit a smooth loading of the flare face
  • Stub ends type B are have to be used with standard slip-on flanges
  • Type C stub ends can be used either with lap joint or slip-on flanges and are manufactured from pipes

Stub end types

SHORT/LONG PATTERN STUB ENDS (ASA/MSS)

Stub ends are available in two different patterns:

  • the short pattern, called MSS-A stub ends
  • the long pattern, called ASA-A stub ends (or ANSI length stub end)
Short and long pattern stub ends
Short pattern (MSS) and long pattern stub ends (ASA)

STUB END FINISH

Stub ends can be ordered with different ends finishing:

  • Beveled Ends
  • Squared Ends
  • Flanged Ends
  • Grooved Ends
  • Threaded Ends (Male Only)

STUB END MATERIALS

ASTMGradeUNS Equivalent
A234 WPB Carbon SteelBK03006
A403 Stainless Steel304/304LS30403
304HS30409
316/316LS31603
316HS31609
317LS31703
904LN08904
309S/HS30908
310SS31008
321S32100
6XNN08367
20CBN08020
347S34709
254SMOS31254
A815 Duplex /Super Duplex2205S31803/S32205
Zeron 100S32760
2507S32750
410S41000
A366 Nickel AlloysHC22N06022
HB-3N10675
HG3N06985
HXN06002
HC2000N06200
HC276N10276
NCIN06600
NCN04400
NN02200
NLN02201
NCMCN06625
NICMCN08825
NIC10N08810
NIC11N08811

STUB ENDS DIMENSIONS

The chart shows the MSS and ANSI stub end dimensions in inches.

MSS Stub EndANSI Stub EndPipe ODPipe WTLap ODRadiusFlange thk
NPSSchMinNomMaxMinNomMaxMinNomMaxMinNomMaxMinMax Min Nom Min Max
1/2″05S1.94022.0602.9403.003.0600.8090.840.896.057.065.0731.3501.3803/321/8.065.127
10S.073.083.093.083.145
40S.095.109.123.109.171
80S.129.147.165.147.209
3/4″05S1.94022.0602.9403.003.0601.0191.051.106.057.065.0731.6601.6903/321/8.065.127
10S.073.083.093.083.145
40S.099.113.127.113.175
80S.135.154.173.154.216
105S1.94022.0603.9404.004.0601.2841.3151.376.057.065.0731.7002.0003/321/8.065.127
10S.095.109.123.109.171
40S.116.133.150.133.195
80S.157.179.201.179.241
1 1/405S1.94022.0603.9404.004.0601.6291.661.716.057.065.0732.4702.5005/323/16.065.127
10S.095.109.123.109.171
40S.123.140.158.140.202
80S.167.191.215.191.253
1 1/205S1.94022.0603.9404.004.0601.8691.91.965.057.065.0732.8502.8807/321/4.065.127
10S.095.109.123.109.171
40S.127.145.163.145.207
80S.175.200.225.200.262
205S2.4402.52.5605.9406.006.0602.3442.3752.456.057.065.0733.5903.6209/325/16.065.127
10S.095.109.123.109.171
40S.135.154.173.154.216
80S.191.218.245.218.280
2 1/205S2.4402.52.5605.9406.006.0602.8442.8752.966.073.083.0933.9004.1209/325/16.083.145
10S.105.120.135.120.182
40S.178.203.228.203.265
80S.242.276.311.276.338
305S2.4402.52.5605.9406.006.0603.4693.53.596.073.083.0934.9705.00011/323/8.083.145
10S.105.120.135.120.182
40S.189.216.243.216.278
80S.263.300.338.300.362
3 1/205S2.94033.0605.9406.006.0603.96944.096.073.083.0935.4705.50011/323/8.083.145
10S.105.120.135.120.182
40S.198.226.254.226.238
80S.278.318.358.318.380
405S2.94033.0605.9406.006.0604.4694.54.593.073.083.0936.1606.1903/87/16.083.145
10S.105.120.135.120.182
40S.207.237.267.237.299
80S.295.337.379.337.399
505S2.94033.0607.9408.008.0605.5325.5635.683.095.109.1237.2807.3103/87/16.109.171
10S.117.134.151.134.196
40S.226.258.29.258.320
80S.328.375.422.375.437
605S3.4403.53.5607.9408.008.0606.5946.6256.743.095.109.1238.4708.5007/161/2.109.171
10S.117.134.151.134.196
40S.245.280.315.280.342
80S.378.432.486.432.494
805S3.94044.0607.9408.008.0608.5948.6258.743.095.109.12310.59010.6207/161/2.109.171
10S.130.148.167.148.210
40S.282.322.362.322.384
80S.438.500.563.500.562
1005S4.91055.0909.91010.0010.09010.71910.7510.913.117.134.15112.69012.7507/161/2.134.196
10S.144.165.186.165.227
40S.319.365.411.365.427
80S.438.500.563.500.562
1205S5.91066.0909.91010.0010.09012.71912.7512.913.137.156.17614.94015.0007/161/2.156.218
10S.158.180.203.180.242
40S.328.375.422.375.437
80S.438.500.563.500.562
1405S5.91066.09011.91012.0012.09013.9691414.170.137.156.17616.19016.2507/161/2.156.218
10S.165.188.212.188.250
40S.328.375.422.375.437
80S.438.500.563.500.562
1605S5.91066.09011.91012.0012.09015.9691616.180.144.165.17618.44018.5007/161/2.165.227
10S.165.188.212.188.250
40S.328.375.422.375.437
80S.438.500.563.500.562
1805S5.91066.09011.91012.0012.09017.9691818.190.144.165.17620.94021.0007/161/2.165.227
10S.165.188.212.188.250
40S.328.375.422.375.437
80S.438.500.563.500.562
2005S5.91066.09011.91012.0012.09019.9692020.240.165.188.21222.94023.0007/161/2.188.250
10S.191.218.245.218.280
40S.328.375.422.375.437
80S.438.500.563.500.562
2405S5.81066.19011.91012.0012.09023.9692424.240.191.218.24527.19027.2507/161/2.218.280
10S.219.250.281.250.312
40S.328.375.422.375.437
80S.438.500.563.500.562
2605S5.81066.19011.81012.0012.19025.9692626.24029.19029.2507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
2805S5.81066.19011.81012.0012.19027.9692828.24031.69031.7507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
3005S5.81066.19011.81012.0012.19029.9693030.24033.69033.7507/161/2
10S.273.312.351.312.374
40S.328.375.422.375.437
80S.438.500.563.500.562
3205S5.81066.19011.81012.0012.19031.9693232.24035.94036.0007/161/2
10S
40S.328.375.422.375.422
80S.438.500.563.500.563
3405S5.81066.19011.81012.0012.19033.9693434.24037.94038.0007/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
3605S5.81066.19011.81012.0012.19035.9693636.24040.19040.2507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
3805S5.81066.19011.81012.0012.19037.9693838.24042.69042.7507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
4005S5.81066.18611.81012.0012.19039.9694040.24044.69044.7507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
4205S5.81066.18611.81012.0012.19041.9694242.24046.94047.0007/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
4405S5.81066.18611.81012.0012.19043.9694444.24049.19019.2507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
4605S5.81066.19011.81012.0012.19045.9694646.24051.19051.2507/161/2
10S
40S.328.375.422.375.437
80S.438.563.500.562
4805S5.81066.19011.81012.0012.19047.9694848.24053.19053.2507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
5005S5.81066.19011.81012.0012.19049.9695050.24055.19055.2507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
5205S5.81066.19011.81012.0012.19051.9695252.24057.19057.2507/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562
5405S5.81066.19011.81012.0012.19053.9695454.24059.44059.5007/161/2
10S
40S.328.375.422.375.437
80S.438.563.500.562
6005S5.81066.19011.81012.0012.19059.9696060.24065.44065.5007/161/2
10S
40S.328.375.422.375.437
80S.438.500.563.500.562

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