Dimensions of 180 degree butt weld elbows

　　180 degree butt welded elbows play a crucial role in modern industrial piping systems. They enable a 180-degree reversal of the pipeline's direction, making them an indispensable key pipe fitting.

　　I. What is a 180-degree Butt-Welded Elbow?

　　A 180-degree butt-welded elbow, also known as a "U-bend," is a special pipe fitting that allows for a complete 180-degree reversal of the pipeline's direction. This type of elbow uses a butt-welding connection method, meaning that the two ends of the elbow are connected to the pipeline through welding, forming a high-strength, leak-free piping system. It is particularly suitable for high-pressure, high-temperature, or extremely tight-sealing conditions.

　　II. ASME B16.9 Butt-Welded 180° Elbow Dimensions

　　The dimensions of 180° butt-welded elbows are based on the nominal diameter (DN), covering key indicators such as nominal diameter range, radius of curvature, end wall thickness, and center distance:

　　• Nominal Diameter (DN): The nominal diameter range of ASME B16.9 butt-welded 180° elbows is typically DN15 (1/2 inch) to DN600 (24 inches), adaptable to different piping systems;

　　• Bending Radius (R): Long radius elbows R=1.5DN, short radius elbows R=1DN;

　　• End Wall Thickness (t): The wall thickness must conform to the corresponding pipe wall thickness class in ASME B16.9 standard (such as SCH40, SCH80, SCH160, etc.). For example, the wall thickness of a DN100 SCH40 elbow is 6.02mm, and the wall thickness of an SCH80 elbow is... 8.56mm, ensuring wall thickness matching with pipes of the same grade and guaranteeing weld strength;

　　1. ASME B16.9 standard 180-degree long radius and short radius butt weld elbow dimensional parameters

Nominal Size		Outside Diameter at Bevel	Center to Center		Back to Face
			180°  Returns
DN	NPS	OD	O		K
			LR	SR	LR	SR
15	1/2	21.3	76		48
20	3/4	26.7	76		51
25	1	33.4	76	51	56	41
32	1 1/4	42.2	95	64	70	52
40	1 1/2	48.3	114	76	83	62
50	2	60.3	152	102	106	81
65	2 1/2	73.0	190	127	132	100
80	3	88.9	229	152	159	121
90	3 1/2	101.6	267	178	184	140
100	4	114.3	305	203	210	159
125	5	141.3	381	254	262	197
150	6	168.3	457	305	313	237
200	8	219.1	610	406	414	313
250	10	273.0	762	508	518	391
300	12	323.8	914	609	619	467
350	14	355.6	1067	711	711	533
400	16	406.4	1219	813	813	610
450	18	457.0	1372	914	914	686
500	20	508.0	1524	1016	1016	762
550	22	559.0	1676	1118	1118	838
600	24	610.0	1829	1219	1219	914

　　2. ASME B16.9 Tolerance Range for Butt-Welded Pipe Fittings

Nominal  Size		All Fittings		45°&90° Elbows & Tees, Crosses	3D Radius Elbows	Returns			Caps	Reducers & Lap Joint Stub Ends	Lap Joint  Stub Ends
DN	NPS	OD 3) 4)	ID 3)	A   B   C   M	A   B	O	K	U	E,  E1	H   F	G	R	t
15-65	1/2 -21/2	+1.6 -0.8	± 0.8	± 2	± 3	± 6	± 6	±  1	± 3	± 2	0     -1	0     -1	+1.6 0
80-90	3-31/2	± 1.6	± 1.6	± 2	± 3	± 6	± 6	±  1	± 3	± 2	0     -1	0     -1	+1.6 0
100	4	± 1.6	± 1.6	± 2	± 3	± 6	± 6	±  1	± 3	± 2	0     -1	0     -2	+1.6 0
125-200	5-8	+2.4 -1.6	± 1.6	± 2	± 3	± 6	± 6	±  1	± 6	± 2	0     -1	0     -2	+1.6 0
250-450	10-18	+4.0 -3.2	± 3.2	± 2	± 3	± 10	± 6	± 2	± 6	± 2	0     -2	0     -2	+3.2 0
500-600	20-24	+6.4 -4.8	± 4.8	± 2	± 3	± 10	± 6	± 2	± 6	± 2	0     -2	0     -2	+3.2 0
650-750	26-30	+6.4 -4.8	± 4.8	± 3	± 6	---	---	---	± 10	± 5	---	---	---
800-1200	32-48	+6.4 -4.8	± 4.8	± 5	± 6	---	---	---	± 10	± 5	---	---	---
1300-1500	52-60	+6.4 -4.8	± 4.8	± 5	---	---	---	---	---	---	---	---	---
1600-1700	64-68	+6.4 -4.8	± 4.8	± 5	---	---	---	---	---	---	---	---	---
1800-2000	72-80	+6.4 -4.8	± 4.8	± 5	---	---	---	---	---	---	---	---	---

　　III. Application Scope

　　Petrochemical Industry: Refining units, chemical plant reactor piping, high-pressure steam pipelines, used for changing flow direction and thermal compensation.

　　Power Industry: Power plant boiler systems, turbine piping, especially in areas requiring U-shaped expansion joints.

　　Refrigeration and HVAC: Central air conditioning systems, refrigeration unit piping, used for piping detours in compact spaces.

　　Shipbuilding: Engine piping, ballast systems, adapting to the narrow and complex spatial layout of ship hulls.

　　Food and Pharmaceutical Industry: Sanitary stainless steel piping systems, enabling connections and detours between process equipment.

　　Paper and Textile Industry: Process piping systems, especially in situations where pipe crossings need to be avoided.

　　When selecting 180-degree butt-welded elbows, the design must comprehensively consider the characteristics of the medium, operating pressure and temperature, space constraints, and system pressure drop requirements. Long-radius elbows are more suitable for applications prioritizing energy conservation and reduced wear, while short-radius elbows are suitable for projects with space constraints.