90 Deg BW Elbow

In industrial piping systems, elbows, as core components for changing the direction of fluid flow, have their performance and compliance with standards directly impacting the safety and efficiency of the entire system. The ASME B16.9 90 degree butt weld elbow, a classic product conforming to the standards of the American Society of Mechanical Engineers (ASME), is widely used in industries such as petroleum, chemical, and energy due to its precise dimensional control and stable structural performance. It has become an indispensable connecting component in industrial piping engineering.

90 Degree BW Elbow

Appearance

The ASME B16.9 90 degree butt weld elbow is manufactured using processes like hot pushing and cold forming, resulting in a regular 90 degree curved structure. Both ends feature butt welding connection ports, with the inner and outer walls finely machined. The surface roughness meets ASME B16.9 standard requirements, ensuring tight-fitting welds when connected to pipes and reducing the risk of medium leakage. The product's external surface is typically treated based on the service environment, such as hot-dip galvanizing, painting, or passivation. This not only enhances corrosion resistance but also provides a cleaner, more uniform appearance, free from defects like burrs or cracks.

Function of Butt Weld Elbow

In piping systems, the primary function of the ASME B16.9 90 degree elbow is to change the flow direction of the medium, suitable for scenarios where spatial layout requires altering the pipe direction. Specific uses include: Firstly, connecting straight pipe sections with different orientations, such as at equipment inlets/outlets, where pipes pass through walls, or to bypass obstacles, thereby replacing complex piping arrangements and simplifying the system structure. Secondly, optimizing the flow state of the medium; its smooth inner wall design reduces flow resistance, lowers pressure loss, and avoids vortex generation caused by sudden directional changes. It is particularly suitable for conveying media like liquids, gases, or steam that require high flow stability. Thirdly, ensuring system sealing and pressure-bearing capacity; compared to threaded or socket weld connections, the butt welding method offers superior sealing performance and can withstand higher working pressures and temperatures, meeting the safe operation requirements of high-pressure piping systems.

Types of ASME B16.9 90 Degree Elbows

Based on structural parameters and connection requirements, ASME B16.9 90 degree bw elbows are mainly classified into the following two categories to meet the design needs of different piping systems:

Bend Radius: Long Radius (LR) and Short Radius (SR) Elbows

Long Radius Elbow (LR)

The bend radius (R) is equal to 1.5 times the pipe's nominal diameter (DN), i.e., R=1.5DN. Its advantages include lower flow resistance for the medium, reduced pressure loss, and more uniform stress distribution. It can adapt to higher working temperatures and pressures, making it the most commonly used type in industrial piping systems, suitable for most conventional medium transport scenarios like petroleum pipelines and chemical process piping.

Short Radius Elbow (SR)

The bend radius (R) is equal to 1 times the pipe's nominal diameter (DN), i.e., R=1DN. This type is characterized by a smaller volume and reduced space occupation, making it suitable for installation in space-constrained areas like internal equipment piping or piping layouts within cramped machinery rooms. However, due to the smaller curvature radius, flow resistance is relatively higher, and pressure loss is slightly increased. They are generally not suitable for conveying high-pressure, high-velocity media, or media sensitive to flow resistance.

Seamless Elbow and Welded Elbow

Seamless Elbow

Formed from high-quality pipe material through processes like hot pushing or extrusion, the entire fitting has no longitudinal weld seam. It features high strength and good pressure resistance. It is suitable for high-pressure, high-temperature piping systems and those requiring high media purity, such as petroleum refining units and natural gas transmission pipelines. Under high-pressure conditions, the seamless structure effectively avoids potential stress concentration issues at weld seams, ensuring long-term stable operation of the piping system.

Welded Elbow

Formed by hot pressing steel plate followed by welding, or made using welded pipe as raw material through pushing. There is a longitudinal weld seam along the fitting's axis. Compared to seamless elbows, welded elbows have lower production costs and higher production efficiency. They are suitable for medium- and low-pressure piping systems, such as civil building water supply and drainage, and general industrial circulating water pipelines. Through strict welding process control and non-destructive testing, welded elbows can also meet the usage requirements for most conventional operating conditions, offering significant advantages in cost-sensitive projects.

Dimensions and Weight 

The ASME B16.9 standard strictly defines the dimensions and weights of 90-degree welding elbows to ensure product universality and interchangeability. The following are explanations of the core parameters:

Dimension of ASME B16.9 90 Degree Elbow

Dimension parameters are based on the nominal diameter (DN), covering key indicators such as the nominal diameter range, curvature radius, end wall thickness, and center-to-end distance:

Nominal Diameter (DN): The nominal diameter range for ASME B16.9 90-degree welding elbows typically spans from DN15 (1/2 inch) to DN2000 (80 inches), adapting to piping systems of different specifications.

Bend Radius (R): For Long Radius elbows, R=1.5DN; for Short Radius elbows, R=1DN.

End Wall Thickness (t): The wall thickness must conform to the corresponding pipe wall thickness schedule (e.g., SCH40, SCH80, SCH160, etc.) specified in the ASME B16.9 standard. For example, the wall thickness for a DN100 SCH40 elbow is 6.02mm, and for a SCH80 elbow, it is 8.56mm, ensuring matching wall thickness with pipes of the same schedule and guaranteeing weld strength.

Nominal size		Outside Diameter at Bevel	Center to End
			90°   Elbows
DN	NPS	OD	A
			LR	SR
15	1/2	21.3	38	-
20	3/4	26.7	38	-
25	1	33.4	38	25
32	1 1/4	42.2	48	32
40	1 1/2	48.3	57	38
50	2	60.3	76	51
65	2 1/2	73.0	95	64
80	3	88.9	114	76
90	3 1/2	101.6	133	89
100	4	114.3	152	102
125	5	141.3	190	127
150	6	168.3	229	152
200	8	219.1	305	203
250	10	273.0	381	254
300	12	323.8	457	305
350	14	355.6	533	356
400	16	406.4	610	406
450	18	457.0	686	457
500	20	508.0	762	508
550	22	559.0	838	559
600	24	610.0	914	610
650	26	660.0	991	660
700	28	711.0	1067	711
750	30	762.0	1143	762
800	32	813.0	1219	813
850	34	864.0	1295	864
900	36	914.0	1372	914
950	38	965.0	1448	965
1000	40	1016.0	1524	1016
1050	42	1067.0	1600	1067
1100	44	1118.0	1676	1118
1150	46	1168.0	1753	1168
1200	48	1219.0	1829	1219

How to Calculate the Weight of BW Elbow?

The weight of an elbow is directly related to its nominal diameter, wall thickness schedule, and bend radius. The theoretical weight calculation formula for a 90-degree butt weld elbow is: (D - t) × t × 0.0387 × R / 1000 (Where t = wall thickness in mm; D = outer diameter in mm; R = bend radius in mm).

Reference weights for products of different specifications are also provided, for example:

DN50 SCH40 Long Radius elbow (OD 60.3mm, wall thickness 3.91mm), theoretical weight approximately 0.71kg.

DN100 SCH80 Long Radius elbow (OD 114.3mm, wall thickness 8.56mm), theoretical weight approximately 5.86kg.

DN80 SCH40 Short Radius elbow (OD 88.9mm, wall thickness 5.49mm), theoretical weight approximately 2.2kg.

Actual weight may slightly deviate due to material density (e.g., carbon steel vs. stainless steel), minor variations in manufacturing processes, but must be controlled within the tolerance range allowed by the standard.

Application

With performance and stable quality in compliance with ASME B16.9 standards, the application range of 90 degree butt welded elbows covers multiple industrial fields, mainly including:

Petroleum and Chemical Industry

Energy and Power Sector

Municipal Engineering

Machinery Manufacturing

Food and Pharmaceutical Industry

With its standardized structure, diverse type selection, and wide compatibility, the ASME B16.9 90-degree welding elbow serves as a core component for achieving right-angle direction changes in industrial piping systems, providing reliable assurance for the safe operation of pipelines across different sectors.