Stub end

Stub end

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.

  • They are also called Lap Joints and Vanstone Flared Laps.
  • Lap Joint Flanges - available in a range of sizes to pair with stub end fittings for easy dismantling
  • Stainless stub end such as Stainless Steel ASTM A403, 304L, 316L, 317
  • Carbon steel Stub end is tested and verified for durability, accuracy and precision
  • Pipe collars are made from plates, with dimensions and tolerances in accordance with EN 1092-1 (Din 2642) or for lap joint flanges according to Asme B16.5.
Stub end
Nominal Pipe Size 1/2 up to 2.1/2 3 to 3.1/2 4 5 to 8 10 to 18 20 to 24
Outside Diameter at Welding End (OD) 0.8 0.8 0.8 + 1.6
- 0.8
+ 2.29
- 0.76
+ 3.05
- 0.76
Overall Length (F) 1.6 1.6 1.6 1.6 2 2
Outside Diameter of Lap (G) + 0
- 0.76
+ 0
- 0.76
+ 0
- 0.76
+ 0
- 0.76
+ 0
- 1.6
+ 0
- 1.6
Thickness of Lap (T) + 1.52
- 0
+ 1.52
- 0
+ 1.52
- 0
+ 1.52
- 0
+ 1.52
- 0
+ 1.52
- 0
Fillet Radius of Lap (R) + 0
- 0.76
+ 0
- 0.76
+ 0
- 1.6
+ 0
- 1.6
+ 0
- 1.6
+ 0
- 1.6
Wall Thickness (t) Not less than 87.5% of Nominal Wall Thickness

Dimensional tolerances are in millimeters unless otherwise indicated.

Stub ends dimensions

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

Nominal Pipe Size Outside Diameter
at Bevel
Length Radius of Fillet Diameter of Lap
A B
NPS D L R G
1/2
3/4
1
21.3
26.7
33.4
51
51
51
3.0
3.0
3.0
0.8
0.8
0.8
35
43
51
11/4
11/2
2
42.2
48.3
60.3
51
51
64
5.0
6.0
8.0
0.8
0.8
0.8
64
73
92
21/2
3
31/2
73.0
88.9
101.6
64
64
76
8.0
10.0
10.0
0.8
0.8
0.8
106
127
140
4
5
6
114.3
141.3
168.3
76
76
89
11.0
11.0
13.0
0.8
1.6
1.6
157
185
218

8
10
12

219.1
273.0
323.8
102
127
152
13.0
13.0
13.0
1.6
1.6
1.6
270
324
381
14
16
18
355.6
406.4
457.0
152
152
152
13.0
13.0
13.0
1.6
1.6
1.6
413
470
533
20
22
24
508.0
559.0
610.0
152
152
152
13.0
13.0
13.0
1.6
--
1.6
584
641
692

The Stub End is available with us in different specifications, which find applications in a piping system to allow quick disconnection of the particular section involved.

Stub End is the fitting that be used in place of welded flanges where rotating back up flanges are desired.

MSS Type A stub ends are the industry norm and are utilized with standard flat face lap joint flanges. The lap thickness of the stub end typically meets the thickness of the schedule pipe it accompanies, and the exterior of the base has a curved machine radius for the lap joint flange to mate flush over the stub end. There are many instances in which lead time is critical and of more importance than adherence to existing ANSI / ASME flange specifications, and as such our customers will often choose to purchase a slip on flange and have the face machined to meet the radius requirement of the corresponding stub end piece.

Stainless steel stub end
ROC R16.9 2 1/2" SCH 40S
A403 WPS304L
DIMENSIONAL TOLERANCES OF STUB ENDS MSS SP-43

The MSS standard is the regular length stub end and the most commonly used in the flange industry.

Lap Joint Flanges

Lap Joint Flanges (LJ Flanges) are used on piping fitted with lapped pipe or with lap joint stub ends the combined initial cost of the two items being approximately one-third higher than that of comparable welding neck flanges.

Lap joint flange
Standards, Dimensions & Weight

Standards: ANSI, MSS, API, AWWA, DIN, JIS, BS and GB.

Stubend geometry

The Stub End, which essentially a short length of pipe, which has one end that is flared outwards and the other end prepared to be welded to pipe of the same Nominal Pipe Size (NPS), material and of a similar wall thickness. The Lap Joint Flange, which is a ring backing Flange and it is very similar in geometry to the Slip-on Flange.

Stub ends are mechanical joints that comprises of two components.

This type of flanged connection was also referred to as “Van Stone” or “Vanstone flare laps”, however this is an historic terminology and very rarely used technically or commercially.

N.D. Out diamater Hight(F) 翻边直径G 倒角半径R
NPS DN OD Mss ANSI Nominal&max Nominal&min A Max B Max
1/2 15 21.3 50.8 76.2 35 34 3 0.8
3/4 20 26.7 50.8 76.2 43 42 3 0.8
1 25 33.4 50.8 101.6 51 50 3 0.8
11/4 32 42.4 50.8 101.6 64 63 4.8 0.8
11/2 40 48.3 50.8 101.6 73 72 6.4 0.8
2 50 60.3 63.5 152.4 92 91 7.9 0.8
21/2 65 73 63.5 152.4 105 104 7.9 0.8
3 80 88.9 63.5 152.4 127 126 9.6 0.8
31/2 90 101.6 76.2 152.4 140 139 9.6 0.8
4 100 114.3 76.2 152.4 157 156 11.2 0.8
5 125 141.3 76.2 203.2 186 185 11.2 1.6
6 150 168.3 88.9 203.2 216 215 12.7 1.6
8 200 219.1 101.6 203.2 270 269 12.7 1.6
10 250 273.1 127 254 324 322 12.7 1.6
12 300 323.9 152.4 254 381 379 12.7 1.6
14 350 355.6 152.4 304.8 413 411 12.7 1.6
16 400 406.4 152.4 304.8 470 468 12.7 1.6
18 450 457.2 152.4 304.8 533 531 12.7 1.6
20 500 508 152.4 304.8 584 582 12.7 1.6
22 550 559 152.4 304.8 641 639 12.7 1.6
24 600 610 152.4 304.8 692 690 12.7 1.6
STUB ENDS TYPICAL APPLICATIONS

The combination of stub ends and backing flanges is an alternative way to join pipes compared to the use of standard flanges.

90° Lateral Wye R500 DN150 Export to Pilipinas with lap-joint flanges

This solution is used in these typical scenarios:

TYPES OF STUB ENDS

Stub ends are manufactured in three different types and two standard length.

Type “A”: this type is produced and machined to fit lap joint flanges.The mating surfaces of the stub end and the lap joint flange have a matching profile and surface. The lap thickness of type A stub ends is > = the minimum wall thickness of the connected pipe. The outside the stub end and the lap joint flange have a matching profile and surface. The lap thickness of type A stub ends is > = the minimum wall thickness of the connected pipe. The outside corner of type A has a radius to accommodate the lap join flange, whereas the inside corner is squared.

Type “B”: this type of stub ends is suited for standard slip-on flanges acting as lap-joint flanges. The lap thickness of type B stub ends is >= the minimum WT of the connecting pipe. The lap of these type of stub ends has generally a serrated face. To ensure tight joints, chamfers on the ID side of the flange are required.

Type “C”: this last type can be used both with lap joint and slip-on backing flanges and are fabricated out of pipes. The lap of C-type stub ends is flared over and the lap thickness is 75% of the connecting pipe WT. Type C has a short fillet outer radius able to host any back up flange.

Type “CS”: this type is similar to “C” with the difference that the lap face has concentric serrations machined during the manufacturing process.

Short pattern (MSS) and long pattern stub ends (ASA)
Short / long pattern stub ends (ASA/MSS)

Short pattern (MSS) and long pattern stub ends (ASA)

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)

Stub ends dimensions and weight

Dimensions and manufacturing tolerances are covered in ASME B16.9 - Butt Weld Fittings and MSS-SP-43 (JIS B2312, JIS B2313 may also apply).

Stub End come in three standard lengths, MSS SP43 or ANSI B16.9 short and long pattern. Short pattern stub ends are mostly used for flanges from class 300 to class 600 and above. Besides these standard types, End-Users and contractors can require stub ends with non-standard lengths to suit specific project’s requirement. This will of course come at an additional cost.

ASME B16.25 END WELDING BEVE
ASME B16.25 END WELDING BEVEL
Ends/Face lap finishing

ASME B16.25 END WELDING BEVEL as right

The following types of ends may be ordered:

  • Beveled Ends (generally ASME B16.25)
  • Squared Ends
  • Flanged Ends
  • Victaulic Grooves
  • Threaded Ends (Male Only)

Material for Stub Ends

Stub Ends are available in numerous ASTM and other international recognized materials, to match pipe specifications, as low alloy, stainless steel, austenitic-ferritic, high alloy steels (nickel alloy such as Inconel, Incoloy 800, Monel, Hastelloy C276), non-ferrous materials (copper, cupronickel 90 /10 and cupronickel 70 / 30) and titanium / zirconium / tantalum.

Material Grade UNS Equivalent
A234 WPB Carbon Steel B K03006
A403 Stainless Steel 304/304L S30403
304H S30409
316/316L S31603
316H S31609
317L S31703
904L N08904
309S/H S30908
310S S31008
321 S32100
6XN N08367
20CB N08020
347 S34709
254SMO S31254
A815 Duplex /Super Duplex 2205 S31803/S32205
Zeron 100 S32760
2507 S32750
410 S41000
A366 Nickel Alloys HC22 N06022
HB-3 N10675
HG3 N06985
HX N06002
HC2000 N06200
HC276 N10276
NCI N06600
NC N04400
N N02200
NL N02201
NCMC N06625
NICMC N08825
NIC10 N08810
NIC11 N08811

Lap-joint flanges are most commonly available in carbon steel and low temperature carbon steel, because it is a lower cost than the Stub End that will be wetted by the service and it must be of a suitable grade of steel. If orientation and alignment of bolt holes is the only issue, then for standardization, then the Stub End and the Lap Joint Flange can be of the same material.

The most common material grade for stub end is the ASTM A403 / ASME SA403 (stainless steel stub ends). With reference to EU materials, the most common grades are DIN 1.4301, DIN1.4306, DIN 1.4401, DIN 1.4404.

Stub Ends assembly

Stub ends and lap joint flanges can be assembled following this process:

It can also be mated to a fabricated plate Flange with compatible, bolting dimensions.

Why use Stub Ends?
Lap Joint Stub End

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.
Commercial benefits

Commercial advantages are that the Stub End, will be wetted and it must be made of a grade of material that meets the process design and service conditions of the pipeline. However, the Lap Flange is un-wetted and it can be made of a lower grade of material as long as it meets
the mechanical strength requirements of the piping systems.

This means that instead of:

Duplex Stub End and a Duplex Lap Joint, you could have Duplex Stub End and Carbon Steel Lap Flange.

Or you could have Stainless Stub End and Carbon Steel Lap Flange. There are other bimetallic combinations that result in a flange assembly that is commercially cheaper.

During recent years the price differential between Duplex/Stainless Steel and Carbon Steel has narrowed and this practice on large Projects has become less common, however a cost difference always exists (the higher the NPS and the length of the pipeline / piping system, the higher the saving). On the other hand, the warehousing cost of one single component, i.e. a Weld Neck Flange, requires less shelf space than the cost of warehousing a Lap Joint and a Stub End. End Users and Contractors shall determine the actual convenience of using stub ends, considering all these factors and generally the commercial advantage is still valid and it may suit certain situation, especially in “brownfield” modifications.

Installation benefits

The “loose” Flange concept of a Lap Joint, is very beneficial during field installation of piping systems. If two spools are to be mated up in the field, having one Flange that can be rotated is very advantageous when aligning the bolt holes, prior to the introduction of the Stub bolt and the accompanying nuts. The facility of easier orientation and alignment of bolt holes, is of particular use it there is a spool that
has to be removed frequently, if positive isolation is a process requirement.

Stub Ends limitations

A Lap Joint consists of two independent components that are not integrated with a weld and like for like in size/pressure class/material it lacks the mechanical strength and capabilities to withstand fatigue, like a one piece Weld Neck Flange or a welded together Slip On or Socket Weld Flanges. In cyclic services, collars EN 1092-1 type 35 PN 16-25-40 are used instead of stub ends (especially to close pumps and compressors). If carefully consideration is given to Process Design condition, the service and the final application, then a Lap Joint Flange mechanical connection are a valid and cheaper method for installing piping systems compared to the use of standard flanges.

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:

How to order a Stub Ends

The following information shall be provided to order a stub end:

Stub end finish

Stub ends can be ordered with different ends finishing:

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

Common type of Butt weld pipe fittings

A common example using welded pipe fitting is a pipe reduced by concentric reducer, welded to a weld neck flange and connected to an equipment. Figure below represent complete collection of butt welded pipe fitting




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