How to get high quality Stub Ends?

What are Stub Ends?

Stub Ends are fittings used in place of welded flanges where rotating back up flanges are desired. They are also called Lap Joints and Vanstone Flared Laps. A rotating back upflange seats itself against the back surface of the Stub End. When bolts are added, the clamping action of the bolts presses the rotating back up flange against the back of the Stub End.

When bolts are added, the clamping action of the bolts presses the rotating back up flange against the back of the Stub End. The gasket surface of the Stub End then presses against a gasket and another gasket surface providing joints like standard flange joints. The seal is made by the gasket surface of the stub end alone, the flange only provides the clamping pressure on the joint.

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Stub Ends MSS SP-43

Stub Ends also named Lap Joints and vanstone flared laps, it is used in place of welded flanges where rotating back up flanges are desired.

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
  • Minimum lap thickness shall not be less than nominal wall thickness.
  • Contact faces of stub ends shall have a concentric serration or spiral according to the purchaser’s requirements.
  • These lengths and radius apply for schedule 40s or thinner stainless steel pipes.
  • Radius of fillet B is only effective to MSS SP-43 lap joint stub ends.
Lap Joints are consisted of three series.

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  • Type A & B Stub Ends are made similar to forging pipe fittings such as elbows and tees.
  • Type C Stub Ends are made by customized dimensions.

Yaang.com offer stub ends at highly competitive prices.

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Lap Joint Stub End – The ‘mated’ pair to a Lap Joint Flange. Stub Ends are Fittings used in place of welded flanges where rotating back up flanges are desired. Stub Ends are typically manufactured by two methods, Type A & Type B and are available in two standard lengths , long (ANSI) or short (MSS) pattern.

Features:
  • Thermal stability
  • High mechanical strength
  • Long functional life
Manufacturing standards of stub end:
  • ASTM ASME A/SA 403
  • MSS SP43 & SP75 ANSI B16. 9
  • ANSI B16. 28 ASTM A815 ASTM B363 B366
  • DIN2605 DIN2615 DIN2616 DIN2617
  • GB12459GB13401
  • JIS2313
Specifications:
  • Grades: ASME / ASTM SA / A234
  • Material:
  • Stainless Steel,316/316L Stainless Steel, 304/304L Stainless Steel and Chrome-moly
  • Carbon steel
Technical Specifications:
  • Thicknesses are based on ASME B16.48 specifications or the products can be manufactured to customer specifications.
  • Standard surface finish is 125-250 RMS serrated finish.
  • Other finishes available upon request.
  • c/w a standard shop primer on carbon steel products for rust inhibitor purposes.
  • Size: Available in all sizes and thickness

Nominal Diameter

Outside Diameter

      Length(F)

Diameter of Lap Nominal&Maximum
(R)
DN
NPS
OD
LP
SP
G
A
Max
B
Max

15

1/2
21.3
76
51
35

3

0.75

20

3/4
26.7
76
51

43

3

0.75

25

1
33.4
102
51

51

3

0.75

32

1.1/4
42.4
102
51

64

5

0.75

40

1.1/2
48.3
102
51

73

6

0.75

50

2
60.3
152
64

92

8

0.75

65

2.1/2
73.0
152
64

105

8

0.75

80

3
88.9
152
64

127

10

0.75

90

3.1/2
101.6
152
76

140

10

0.75

100

4
114.3
152
76

157

11

0.75

125

5
141.3
203
76

186

11

1.5

150

6
168.3
203
89

216

13

1.5

200

8
219.1
203
102

270

13

1.5

250

10
273.1
254
127

324

13

1.5

300

12
323.9
254
152

381

13

1.5

350

14
355.6
305
152

413

13

1.5

400

16
406.4
305
152

470

13

1.5

450

18
457.2
305
152

533

13

1.5

500

20
508
305
152

584

13

1.5

550

22
559
305
152

641

13

1.5

600

24

610

305

152

692

13

1.5

MSS SP 43 Stub Ends and Caps

1. Technical Drawing

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The typical drawing of lap joint stub ends and caps manufactured to MSS SP 43.

Note: The MSS SP 43 stub end is short pattern. It can be used with lap joint flanges or slip on flanges, depending on which the radius of fillet may differ.

2. Dimensions of MSS SP 43 Stub Ends and Caps

*All dimensions are in inch unit. T: the lap thickness, shall not be less than nominal pipe wall thickness.

*E: cap length; F: stub end length; G: diameter of lap.

*A: radius of fillet if used with lap joint flange; B: radius of fillet if used with slip on flange.

3. Tolerances of Lap Joint Stub Ends & Caps

NPS Fillet of Radius of Lap Outside Diameter of Lap
1/2~1-1/2 +0.00
-0.03
+0.00
-0.03
2~3-1/2 +0.00
-0.03
+0.00
-0.03
4 +0.00
-0.03
+0.00
-0.03
5~8 +0.00
-0.06
+0.00
-0.03
10~18 +0.00
-0.06
+0.00
-0.06
20~24 +0.00
-0.06
+0.00
-0.06

*All dimensions are in inch unit. Tolerances for lap joint stub ends.

NPS 1/2~1-1/2 2~3-1/2 4 5~8 10~18 20~24
Tolerance of Overall Length ± 0.12 ± 0.12 ± 0.12 ± 0.25 ± 0.25 ± 0.25

*All dimensions are in inch unit. Tolerances for caps.

Ends/Face lap finishing

The following types of ends may be ordered:

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

ASME B16.25 END WELDING BEVEL

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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.

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:

  • The Lap Flange is slipped over and onto the Stub end Flange.
  • The Stub End Flange is then welded onto a pipe spool, using an approved Welding. Procedure Specification (WPS), by a qualified Welder. The Lap Joint Flange, backing Flange, can revolve around the Stub End, which is now attached to the piping spool.
  • The bolt holes of the Lap Joint Flange can now be orientated and aligned with the bolt holes of a mating Flange of the same ASME designate rating and NPS.

The Lap Joint Flange can be mated to any Flange covered in ASME B16.5, Weld Neck, Slip On, Threaded, Socket Weld, another Lap Joint Flange. It can also be mated to a fabricated plate Flange with compatible, bolting dimensions.

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Why use Stub Ends?

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 Joint Flange.
  • Or you could have Stainless Steel Stub End and Carbon Steel Lap Joint 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.

How to order a Stub End?

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

  • NPS
  • Schedule
  • Length (according to norms MSS SP43 / ASME B16.9 / custom)
  • Specs and material grade
  • Ends finish
  • Execution: seamless / welded (wx)

Usage:

Petroleum, Chemical, Power, Gas, Metallurgy, Ship-building, Construction, ect.

Using stub ends allows sections of the line to be opened for cleaning, inspection, or quick replacement etc, without the need to re-weld.

Source: China Stub Ends Manufacturer – Yaang pipe fitting Industry Co., Limited (www.ugsteelmill.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@ugsteelmill.com

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References:

  • https://www.nuovarid.com/index.php/products/stub-ends-pipelines
  • https://www.yaang.com/what-is-lap-joint-stub-end.html

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