ASME B16.28 Buttwelding Short Radius Elbows And Returns Dimension

ASME B16.28 standard specifies requirements for wrought steel buttwelding, including pressure ratings equivalent to seamless pipes of the same material, overall dimensions for nominal pipe sizes (NPS) from 1 to 24, testing procedures for proof and nondestructive electric tests, tolerances for dimensions and alignments, and markings for identification such as manufacturer, size, material, and rating.

This blog outlines the ASME B16.28 standard for short radius buttweld fittings, detailing their functions, dimensional forms for 90 degree elbows and 180 degree returns, and tolerances.

90 Degree Short Radius Elbow

The 90 degree short radius elbow is used in piping systems to change flow direction by 90 degrees in compact spaces, with a centerline radius equal to the nominal pipe size, ideal for applications requiring minimal space and reduced pressure drop.

ASME B16.28 90 Degree Short Radius Elbows Dimension (inches)

Nominal pipe size	Outside diameter at bevel D	Center-to-end A
1	1.32	1.00
1	1.66	1.25
1 1/4	1.90	1.50
2	2.38	2.00
2 1/2	2.88	2.50
3	3.50	3.00
3 1/2	4.00	3.50
4	4.50	4.00
5	5.56	5.00
6	6.62	6.00
8	8.62	8.00
10	10.75	10.00
12	12.75	12.00
14	14.00	14.00
16	16.00	16.00
18	18.00	18.00
20	20.00	20.00
22	22.00	22.00
24	24.00	24.00

180 Degree Short Radius Returns

The 180 degree short radius return is designed to reverse flow direction by 180 degrees in tight configurations, commonly used in heat exchangers, boilers, or piping loops where space is limited, maintaining a radius equal to the nominal pipe size.

ASME B16.28 180 Degree Short Radius Returns (inches)

	180 deg RET	URNS
Nominal pipe size	Outside diameter at bevel D	Center-to-end A	Back-to-face K
1	1.32	2.00	1.62
1 1/4	1.66	2.50	2.06
1 1/2	1.90	3.00	2.44
2	2.38	4.00	3.19
2 1/2	2.88	5.00	3.94
3	3.50	6.00	4.75
3 1/4	4.00	7.00	5.50
4	4.50	8.00	6.25
5	5.56	10.00	7.75
6	6.62	12.00	9.31
8	8.62	16.00	12.31
10	10.75	20.00	15.38
12	12.75	24.00	18.38
14	14.00	28.00	21.00
16	16.00	32.00	24.00
18	18.00	36.00	27.00
20	20.00	40.00	30.00
22	22.00	44.00	33.00
24	24.00	48.00	36.00

GENERAL NOTES:

(a) Dimension A is equal to one-half of dimension O.

ASME B16.28 Tolerances Form

Tolerances ensure manufacturing precision for fit and performance; they apply to outside/inside diameters, wall thickness, angles, center-to-end/center-to-center/back-to-face dimensions, and end alignments, with values equal plus/minus unless noted.

Tolerance Table

Nominal Pipe Size	All Fittings					90 deg Elbows	180 deg Returns
	Outside Diameter at Bevel [Notes(1),(2)]	Inside  Diameter at   End [Notes(1),(3),(4)]	Wall Thickness [Note(3)]	Angu Off Angle 0	larity Off Plane P	Center-to- End Dimension A	Center-to- Center Dimension 0	Back-to- Face Dimension K	Alignments of Ends U
1/2 to   2 1/2   3 to 3 1/2 4 5 to 8 10 to 12 14 to 16 18 20 to 24	+0.06 -0.03 0.06 0.06 +0.09 -0.06 +0.16 -0.12 +0.16 -0.12 +0.16 -0.12 +0.25 -0.19	0.03 0.06 0.06 0.06 0.12 0.12 0.12 0.19	Not less than 87.5% of  nom- inal thick- ness marked on fitting	0.03 0.03 0.03 0.06 0.09 0.09 0.12 0.12	0.06 0.06 0.06 0.12 0.19 0.25 0.38 0.38	0.06 0.06 0.06 0.06 0.09 0.09 0.09 0.09	0.25 0.25 0.25 0.25 0.38 0.38 0.38 0.38	0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25	0.03 0.03 0.03 0.03 0.06 0.06 0.06 0.06

GENERAL  NOTE:Dimensions  are  in  inches.Tolerances  are  equal  plus  and  minus  except  as  noted.

NOTES:

(1)Out-of-round  is  the  sum  of absolute  values  of  plus  and  minus  tolerance.

(2)This tolerance may be exceeded in localized areas of formed fitings where increased wall thickness is required to meet design requrements   of   para.2.1.

(3)The  inside  diameter  and  the  nominal  wall thicknesses  at  ends  are to  be  specified  by  the  purchaser.Wall  thickness  tolerance applies  throughout  the  fitting.

(4)Unless otherwise specified by the purchaser,these tolerances apply to the nominal inside diameter,which equals the difference between the  nominal  outside  diameter  and  twice  the  nominal  wall  thickness.

Dimensions Of Short Radius Elbows

Short radius elbows under ASME B16.28 have a centerline radius equal to the NPS, ensuring compact turns; refer to the table in Heading 2 for 90 degree elbow dimensions, which align with standard requirements for NPS 1 to 24.

Nominal Pipe Size	Outside Diameter at Bevel D			Center-to-End A 90 deg Elbows
	Min.	Nom.	Max.	Min.	Nom.	Max.
1	32	33	34	23	25	27
1 1/4	41	42	43	30	32	34
1 1/2	47	48	49	36	38	40
2	59	60	61	49	51	53
2 1/2	72	73	74	62	64	66
3	88	89	90	74	76	78
3 1/2	101	102	103	87	89	91
4	113	114	116	100	102	104
5	140	141	144	125	127	129
6	167	168	171	150	152	154
8	217	219	221	201	203	205
10	270	273	277	252	254	256
12	321	324	328	302	305	308
14	353	356	360	353	356	359
16	403	406	410	403	406	409
18	454	457	461	454	457	460
20	503	508	514	505	508	511
22	554	559	565	556	559	562
24	605	610	616	607	610	613

Summary

This document summarizes ASME B16.28's key aspects for short radius buttweld elbows and returns, including their functions in piping, dimensional tables for 90-degree and 180-degree fittings, and tolerances.

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