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What are Stub Ends

What are Stub Ends?

Stub Ends are pipe 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 up flange 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. 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

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.

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Dimensions of lap joint stub ends ASME B16.9

NPS OD of Barrel Long Pattern Short Pattern Radius of  Diameter of
Max Min Length, F  Length, F Fillet, R Lap, G
1/2 22.8 20.5 76 51 3 35
3/4 28.1 25.9 76 51 3 43
1 35 32.6 102 51 3 51
1 ¼ 43.6 41.4 102 51 5 64
1 ½ 49.9 47.5 102 51 6 73
2 62.4 59.5 152 64 8 92
2 ½ 75.3 72.2 152 64 8 105
3 91.3 88.1 152 64 10 127
3 ½ 104 100.8 152 76 10 140
4 116.7 113.5 152 76 11 157
5 144.3 140.5 203 76 11 186
6 171.3 167.5 203 89 13 216
8 222.1 218.3 203 102 13 270
10 277.2 272.3 254 127 13 324
12 328 323.1 254 152 13 381
14 359.9 354.8 305 152 13 413
16 411 405.6 305 152 13 470
18 462 456 305 152 13 533
20 514 507 305 152 13 584
22 565 558 305 152 13 641
24 616 609 305 152 13 692
Notes:
1) Gasket face finish shall be in accordance with ASME B16.5 for raised face flanges.
2) The lap thickness T shall not be less than nominal pipe wall thickness.
3) When short pattern stub ends are used with larger flanges in Classes 300 and 600,with most sizes in Classes 900 and higher,and when long pattern stub ends are used with larger flanges in Classes 1500 and 2500,it may necessary to increase the length of the stub ends in order to avoid covering the weld with the flange.Such increases in length shall be a matter of agreement between the manufacturer and purchaser.
4) When special facings such as tongue and groove,male and female,etc.,are employed,additional lap thickness must be provided and such additional thickness shall be in addition to (not included in) the basic length F.

Lap Joints are consisted of three series.

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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 typically manufactured by two methods, Type A & Type B and are available in two standard lengths , long (ANSI) or short (MSS) pattern.

Features of stub end

  • 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
  • GB12459, GB13401
  • JIS2313

Specifications of stub end

  • Grades: ASME / ASTM SA / A234
  • Material:
  • Stainless Steel,316/316L Stainless Steel, 304/304L Stainless Steel and Chrome-moly
  • Carbon steel

Technical Specifications of stub end

  • 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

20171231091330 17019 - What are Stub Ends

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:

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 of stub end

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.

Study on improvement of hole turning forming process of superalloy components

Superalloys have excellent high-temperature strength, good oxidation resistance, thermal corrosion resistance, good fatigue performance, fracture toughness and other comprehensive properties. They are mainly used to manufacture high-temperature components of aviation and ships and energy conversion devices such as aerospace vehicles and rocket engines.
The hole turning structure is a hole with a vertical flange perpendicular to the plate surface, which can reduce the weight and increase the stiffness of the structure. However, due to the high deformation resistance of superalloys, forming is very difficult, as shown in the attached table. For the components with a certain height, the traditional forming method is to adopt the rigid punch and die structure, and the die manufacturing precision is high; For high hole turning components, the method of drawing → punching bottom hole → hole turning is adopted, which requires multiple sets of high-precision matching forming tooling and multiple complex forming processes, resulting in the processing difficulty and manufacturing cost of Superalloy hole turning components. The superalloy has excellent high temperature strength, good oxidation resistance, hot corrosion resistance and good fatigue performance It is mainly used to manufacture high-temperature components of aviation and ships and energy conversion devices such as aerospace vehicles and rocket engines.
The hole turning structure is a hole with a vertical flange perpendicular to the plate surface, which can reduce the weight and increase the stiffness of the structure. However, due to the high deformation resistance of superalloys, forming is very difficult, as shown in the attached table. For the components with a certain height, the traditional forming method is to adopt the rigid punch and die structure, and the die manufacturing precision is high; For high turn over components, the method of drawing → punching bottom hole → turn over is adopted, which requires multiple sets of high-precision matching forming tooling and multiple complex forming processes, resulting in the processing difficulty, manufacturing cost and tensile stress of Superalloy turn over components, resulting in tensile deformation along the tangential direction until the inner diameter D reaches the diameter d after turn over.

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Fig.1 hole size
(2) Limit factor of hole turning forming. In the process of hole turning forming, the diameter D of prefabricated hole will gradually become d during the deformation process, resulting in the maximum deformation, and the thickness thinning is the most serious. Therefore, whether the edge is broken during hole turning is the main parameter to judge whether the hole turning forming can proceed smoothly. Maximum deformation range (also known as hole turning coefficient K) is related to many factors, but the maximum elongation can be used in actual production operation δ Approximate estimate the limit hole turning coefficient, and preliminarily judge whether it will be changed by the deformation degree of prefabricated holes
In case of crack defect, the formula is as follows: kmax = 1 / (1 + δ) ≤ D / D (1) in the process of hole turning (see Fig. 2), the material deformation zone mainly elongates and thins in the tangential direction, but the radial deformation is small. Therefore, the diameter of prefabricated hole can be approximately determined by simple bending method according to the principle of constant neutral layer length. The formula is as follows: D = D-2 (h-0.43r-0.72t) (2)
In the formula:

  • D is the diameter of prefabricated hole;
  • D is the diameter of neutral layer on the vertical side after hole turning;
  • H is the height after turning the hole;
  • R is the fillet radius;
  • T is the thickness of the material, in mm.

20211223122037 15729 - What are Stub Ends

Fig.2 hole turning process dimensions
(3) Flexible punch die structure. Polyurethane rubber is used as the die structure matching the flexible punch with the rigid die. When the polyurethane rubber is under pressure in the closed container frame, it has the property of hydrostatic pressure and the pressure in all directions is the same. Therefore, compared with the traditional structure, it has the following advantages:

  • ① As long as the rigid die is manufactured, the die structure is particularly simple, the structural form is simplified and the die cost is reduced.
  • ② Avoid die clearance lapping due to high requirements for rigid punch and die clearance.
  • ③ The edge part of polyurethane rubber and rigid die exerts pressure on the blank in the process of hole turning, which naturally forms a blank holder, which can play an anti wrinkle role. ④ In the process of hole turning, polyurethane rubber naturally forms an arc punch, which is more favorable for hole turning than flat bottom punch.
  • ⑤ The edge of the formed part is flat and the wall thickness is uniform.
  • ⑥ The forming force can be reduced by 25% ~ 43% by turning the preformed hole, so the turning forming force can be reduced to a great extent.
  • ⑦ The process flow is greatly simplified and the production efficiency is improved.

(4) The principle of determining the size of the hole turning structure. The hole turning height is the main performance index of the part. The formula of the limit hole turning height can be derived from formula (1) and formula (2): Hmax = 0.5d (1-k) + 0.43r + 0.72t (3)
By formula (3) It can be seen that when the superalloy material is certain, that is, K is a constant value, the limit turning height increases with the increase of fillet radius R and material thickness T. when the turning fillet radius R is certain, the limit turning height increases with the increase of neutral layer diameter D of vertical edge after turning. Therefore, the material thickness, fillet radius and neutral layer of vertical edge after turning shall be reasonably selected in part design The layer diameter size can form a higher turning height to meet the use requirements.
2. Hole turning forming test of superalloy components
High temperature alloy materials are generally used as exhaust system parts of helicopter engines. GH3030 cold rolling solid solution is used in a certain type of machine- δ 1.0-gjb1952a superalloy material, and the part structure is shown in Figure 3. Add process allowance to the notch of the part, that is, the hole turning component. The theoretical analysis and forming test of the parts are carried out according to the above forming scheme.

20211223122208 23877 - What are Stub Ends
Figure.3 part structure
The hole turning height of the part is h = 20mm, the fillet radius is r = 4mm, and the diameter of the neutral layer on the vertical side after the hole turning is approximately estimated based on the center line of the material thickness, d = 212.6mm, According to formula (2), the diameter of prefabricated hole d = 177.48mm (1) The hole turning coefficient k = 0.84 ≥ 0.78, which is greater than the limit hole turning coefficient, can be formed by this method. The rigid die is designed and manufactured according to the hole turning size, and 77000t rubber bag press is selected for hole turning forming. Although the hole turning height is high, the direct hole turning forming is realized by using flexible punch die, and the processed parts have good surface quality, high dimensional accuracy and real experiment It proves the feasibility and effectiveness of the theoretical analysis.

Source: China Stub Ends Manufacturer – Yaang Pipe Industry Co., Limited (www.epowermetals.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@epowermetals.com

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