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.

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.

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.

• 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.

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

1. Technical Drawing

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

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

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

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

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.

Why use Stub Ends?

Commercial benefits

This means that instead of:

• Duplex Stub End and a duplex lap joint flange, 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.

Installation benefits

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.

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.

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.

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.)

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