ASME B16.5 Threaded Flange Dimension | Material

An ASME B16.5 threaded flange is designed with internal tapered threads that connect to externally threaded pipes, providing a reliable non-welded joint for systems where welding is impractical or prohibited. This flange type is widely used in petrochemical, chemical, and utility pipelines that require safe and removable connections.

How Threaded Flanges Work and When They Are Used

Threaded flanges screw directly onto the pipe end, forming a sealed connection without welding heat. They are ideal for flammable or explosive environments, temporary systems, and piping that may need frequent maintenance.

Threaded Types: NPT vs BSPT

•NPT (National Pipe Thread, tapered) — Most common in American systems

•BSPT (British Standard Pipe Taper) — Common in Asia, Middle East, Europe

Pressure Ratings: Class 150–2500

Threaded flanges follow the ASME B16.5 pressure–temperature rating tables. Higher classes allow higher allowable working pressures.

Typical Allowable Pressures at 38°C

Pressure Class	Allowable Pressure (approx.)
Class 150	285 psi
Class 300	740 psi
Class 600	1480 psi
Class 900	2220 psi
Class 1500	3705 psi
Class 2500	6200 psi

Class 150 Threaded Flange Dimension

Nominal Pipe Size		A	C	D	E	F	G	H	I	J
inch	mm	mm	mm	mm	mm	mm	mm	Holes	mm	mm
1/2	21.30	88.90	11.20	15.70	15.70	30.20	35.10	4	15.70	60.45
3/4	26.70	98.60	12.70	15.70	15.70	38.10	42.90	4	15.70	69.85
1	33.40	108.0	14.20	17.50	17.50	49.30	50.80	4	15.70	79.25
11/4	42.20	117.3	15.70	20.60	20.60	58.70	63.50	4	15.70	88.90
11/2	48.30	127.0	17.50	22.40	22.30	65.00	73.15	4	15.70	98.60
2	60.30	152.4	19.10	25.40	25.40	77.70	91.90	4	19.10	120.7
21/2	73.00	177.8	22.40	28.40	28.40	90.40	104.6	4	19.10	139.7
3	88.90	190.5	23.90	30.20	30.20	108.0	127	4	19.10	152.4
31/2	101.60	215.9	23.90	31.75	31.75	122.2	139.7	8	19.10	177.8
4	114.30	228.6	23.90	33.30	33.30	134.9	157.2	8	19.10	190.5
5	141.30	254.0	23.90	36.60	36.60	163.6	185.7	8	22.40	215.9
6	168.30	279.4	25.40	39.60	39.60	192.0	215.9	8	22.40	241.3
8	219.10	342.9	28.40	44.50	44.50	246.1	269.7	8	22.40	298.5
10	273.00	406.4	30.20	49.30	49.30	304.8	323.9	12	25.40	362.0
12	323.80	482.6	31.75	55.60	55.60	365.3	381.0	12	25.40	431.8
14	355.60	533.4	35.10	57.15	57.15	400.1	412.7	12	28.40	476.3
16	406.40	596.9	36.60	63.50	63.50	457.2	469.9	16	28.40	539.8
18	457.20	635	39.60	68.30	68.30	505.0	533.4	16	31.75	577.9
20	508.00	698.5	42.90	73.15	73.15	558.8	584.2	20	31.75	635.0
24	609.60	812.8	47.80	82.60	82.60	663.4	692.2	20	35.10	749.3

If you’d like to see dimensions for other grades, click the link below.

Class 300 Threaded Flange Dimension

Class 400 Threaded Flange Dimension

Class 600 Threaded Flange Dimension

Class 900 Threaded Flange Dimension

Class 1500 Threaded Flange Dimension

Class 2500 Threaded Flange Dimension

Threaded Flange Material Options

ASTM A105/A105N for carbon steel

ASTM A182 F304/304L,F316/F316L,F904L for stainless steel

ASTM A350 LF2,LF3 for low tempreture steel

ASTM A694 F42,F46,F52,F56,F65,F70 for pipe line steel

ASTM A182 F5,F9,F11,F12,F22,F91,F92 for alloy steel

Advantages Compared with Weld Neck and Slip On Flanges

•No welding, reducing heat-affected zones

•Faster and easier installation

•Lower labor and equipment costs

•Easy disassembly for maintenance

•Suitable for low- to medium-pressure applications

Threaded Flange Selection Guide

•Determine operating pressure and temperature.

•Choose pressure class based on pressure-temperature rating.

•Select material according to corrosion, mechanical, and temperature requirements.

•Match thread type (NPT/BSPT) to pipe.

•Verify dimensions and tolerances per ASME B16.5 tables.

•Consider maintenance and installation environment for optimal performance.

Conclusion

ASME B16.5 threaded flange provides a reliable, removable, and economical connection for low- to medium-pressure piping systems. Correct selection of pressure class, material, and thread type ensures safety, leak-tight performance, and long-term durability in diverse industrial environments

FAQ

How do threaded flanges connect pipes?

Threaded flanges connect pipes by matching their internal tapered threads to the pipe’s external threads; as the flange is screwed on, the taper creates a tight mechanical seal, often enhanced with a gasket between mating flanges, providing a reliable, leak-resistant, non-welded connection suitable for low- to medium-pressure pipelines.