Measure the size of a flange

At some point, with all the possibilities of thread form, diameter, and pitch, you need to send it off to SK Grimes or another machinist. You could buy the thread pitch gauges and comparator and thread micrometer (to measure minor diameter) to fully define the thread, but that still won’t help you to find a ring.

• Flanges are integral parts of many engineering and plumbing projects.
• Flange Face Surface Finish
• Pressure Classes of Flanges
• Flanges Manufacturing Process

Place one end of a tape measure on the inside of the flange. The diameter is used to determine what size pipe a flange can be used with, so you must find this information by using the inside of the flange as opposed to the outside.

We have the professional engineers, measurement the size of Pipe flanges.

Stretch your tape measure across the center of the circular shape of the flange until it touches the other side of the unit. Keep this end of the tape measure on the inside of the flange as well. Because the flange is circular in shape, the tape measure must stretch across the exact center of the flange to provide an accurate measurement.

Read your tape measure, in inches. The distance you have found is the diameter of your flange.

Flange materials acc. to ASTM

Dimensions from carbon steel and stainless steel flanges are defined in the ASME B16.5 standard. The material qualities for these flanges are defined in the ASTM standards.

These ASTM standards, define the specific manufacturing process of the material and determine the exact chemical composition of pipes, fittings and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by “Grade”.

For example, a carbon steel flange can be identified with Grade F9 or F11, a stainless-steel flange with Grade F316 or Grade F321 etc..

Below you will find as an example a table with chemical requirements for fittings ASTM A403 Grade WP304, WP304L, WP316L and a table with frequent Grades, arranged on pipe and pipe-components, which belong together as a group.
As you may be have noted, in the table below, ASTM A105 has no Grade. Sometimes ASTM A105N is described;

“N” stands not for Grade, but for normalized. Normalizing is a type of heat treatment, applicable to ferrous metals only. The purpose of normalizing is to remove the internal stresses induced by heat treating, casting, forming etc.

Chemical requirements composition, %

Chemical elements	Grade F304 (A)	Grade F304L (A)	Grade F316L (A-B)
Carbon, max	0.08	0.035	0.035
Manganese, max	2.00	2.00	2.00
Phosphorus, max	0.045	0.045	0.045
Sulfur, max	0.03	0.03	0.03
Silicon, max	1.00	1.00	1.00
Nickel	8-11	8-13	10-15
Chrome	18 – 20	18 – 20	16 – 18
Molybdenum	-	-	2.00-3.00

(A) Carbon 0.040% max. is necessary where many drawing passes are required, as with outside
diameter <0.5 inch (12.7 mm), or nominal wall thickness <0.049 inch (1.2 mm).
(B) On pierced tube, Nickel may be 11 – 16.00%.

ASTM Grades

Material	Fittings	Flanges	Valves	Bolts & Nuts
Carbon Steel	A234 Gr WPA	A105	A216 Gr WCB	A193 Gr B7 A194 Gr 2H
	A234 Gr WPB	A105	A216 Gr WCB
	A234 Gr WPC	A105	A216 Gr WCB
Carbon Steel Alloy High-Temp	A234 Gr WP1	A182 Gr F1	A217 Gr WC1	A193 Gr B7 A194 Gr 2H
	A234 Gr WP11	A182 Gr F11	A217 Gr WC6
	A234 Gr WP12	A182 Gr F12	A217 Gr WC6
	A234 Gr WP22	A182 Gr F22	A217 Gr WC9
	A234 Gr WP5	A182 Gr F5	A217 Gr C5
	A234 Gr WP9	A182 Gr F9	A217 Gr C12
Carbon Steel Alloy Low-Temp	A420 Gr WPL6	A350 Gr LF2	A352 Gr LCB	A320 Gr L7 A194 Gr 7
	A420 Gr WPL3	A350 Gr LF3	A352 Gr LC3
Austenitic Stainless Steel	A403 Gr WP304	A182 Gr F304	A182 Gr F304	A193 Gr B8 A194 Gr 8
	A403 Gr WP316	A182 Gr F316	A182 Gr F316
	A403 Gr WP321	A182 Gr F321	A182 Gr F321
	A403 Gr WP347	A182 Gr F347	A182 Gr F347

ASTM Materials

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FITTINGS

ASTM A234 = This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction.
ASTM A420 = Standard specification for piping fittings of wrought carbon steel and alloy steel for low-temperature service.
ASTM A403 = Standard specification for wrought austenitic stainless steel piping fittings.

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FLANGES

ASTM A105 = This specification covers standards for forged carbon steel piping components, that is, flanges, fittings, Valves, and similar parts, for use in pressure systems at ambient and higher-temperature service conditions.
ASTM A182 = This specification covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, and Valves and parts for high-temperature service.
ASTM A350 = This specification covers several grades of carbon and low alloy steel forged or ring-rolled flanges, forged fittings and Valves for low-temperature service.

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VALVES

ASTM A216 = This specification covers carbon steel castings for Valves, flanges, fittings, or other pressure-containing parts for high-temperature service and of quality suitable for assembly with other castings or wrought-steel parts by fusion welding.
ASTM A217 = This specification covers steel castings, martensitic stainless steel and alloys steel castings for Valves, flanges, fittings, and other pressure-containing parts intended primarily for high-temperature and corrosive service.
ASTM A352 = This specification covers steel castings for Valves, flanges, fittings, and other pressure-containing parts intended primarily for low-temperature service.
ASTM A182 = This specification covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, and Valves and parts for high-temperature service.

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BOLDS & NUTS

ASTM A193 = This specification covers alloy and stainless steel bolting material for pressure vessels, Valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications.
ASTM A320 = Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for Low-Temperature Service.
ASTM A194 = Standard specification for nuts in many different material types.

Read your tape measure, in inches. The distance you have found is the diameter of your flange.

Pressure Classes of Flanges

Forged steel flanges, according to ASME B16.5, are made in seven primary ratings as 150Lbs, 300Lbs,  400Lbs, 600Lbs, 900Lbs, 1500Lbs, 2500Lbs.

The concept of flange ratings likes clearly. A Class 300 flange can handle more pressure than a Class 150 flange, because a Class 300 flange are constructed with more metal and can withstand more pressure. However, there are a number of factors that can impact the pressure capability of a flange.
The Pressure Class or Rating for flanges will be given in pounds. Different names are used to indicate a Pressure Class.
For example: 150 Lb or 150 Lbs or 150# or Class 150, all are means the same.

Example of Pressure Rating

Flanges can withstand different pressures at different temperatures. As temperature increases, the pressure rating of the flange decreases. For example, a Class 150 flange is rated to approximately 270 PSIG at ambient conditions, 180 PSIG at approximately 400°F, 150 PSIG at approximately 600°F, and 75 PSIG at approximately 800°F.
In other words, when the pressure goes down, the temperature goes up and vice versa. Additional factors are that flanges can be constructed from different materials, such as stainless steel, cast and ductile iron, carbon steel etc.. Each material have different pressure ratings.
Below an example of a flange NPS 12 with the several pressure classes. As you can see, inner diameter and diameter of the raised face at all the same; but outside diameter, bolt circle and diameter of bolt holes become larger in each higher pressure class.
The number and diameters (mm) of the bolt holes are:

• Class 150 – 12 x 25.4, Class 300 – 16 x 28.6
• Class 400 – 16 x 34.9, Class 600 – 20 x 34.9
• Class 900 – 20 x 38.1, Class 1500 – 16 x 54
• Class 2500 – 12 x 73

Pressure-Temperature Ratings Example

Pressure-temperature ratings are maximum allowable working gage pressures in bar units at the temperatures in degrees celsius. For intermediate temperatures, linear interpolation is permitted. Interpolation between class designations is not permitted.
Pressure-temperature ratings apply to flanged joints that conform to the limitations on bolting and on gaskets, which are made up in accordance with good practice for alignment and assembly. Use of these ratings for flanged joints not conforming to these limitations is the responsibility of the user.
The temperature shown for a corresponding pressure rating is the temperature of the pressure-containing shell of the component. In general, this temperature is the same as that of the contained fluid. Use of a pressure rating corresponding to a temperature other than that of the contained fluid is the responsibility of the user, subject to the requirements of applicable codes and regulations. For any temperature below -29°C, the rating shall be no greater than the rating shown for -29°C.
As an example, below you will find two tables with material groups acc. to ASTM, and two other tables
with flange pressure-temperature ratings for those ASTM materials acc. to ASME B16.5.

ASTM Group 2-1.1 Materials

Nominal Designation	Forgings	Castings	Plates
C-Si	A105(1)	A216  r.WCB(1)	A515 Gr.70(1)
C-Mn-Si	A350 Gr.LF2(1)	-	A516 Gr.70(1),(2)
C-Mn-Si-V	A350 Gr.LF6 Cl 1(3)	-	A537 Cl.1(4)
3½Ni	A350 Gr.LF3	-	-

NOTES:

(1) Upon prolonged exposure to temperatures above 425°C, the carbide phase of steel may be converted to graphite. Permissible but not recommended for prolonged use above 425°C.
(2) Do not use over 455°C.
(3) Do not use over 260°C.
(4) Do not use over 370°C.

ASTM Group 2-2.3 Materials

Nominal Designation	Forgings	Castings	Plates
16Cr-12Ni-2Mo	A182 Gr.F316L	-	A240 Gr.316L
18Cr-13Ni-3Mo	A182 Gr.F317L	-	-
18Cr-8Ni	A182 Gr.F304L(1)	-	A240 Gr.304L(1)

 (1) Do not use over 425°C.

Pressure-Temperature Ratings for ASTM Group 2-1.1 Materials

Working pressure by Classes, BAR

Temp.°C	150	300	400	600	900	1500	2500
-29 to 38	19.6	51.1	68.1	102.1	153.2	255.3	425.5
50	19.2	50.1	66.8	100.2	150.4	250.6	417.7
100	17.7	46.6	62.1	93.2	139.8	233	388.3
150	15.8	45.1	60.1	90.2	135.2	225.4	375.6
200	13.8	43.8	58.4	87.6	131.4	219	365
250	12.1	41.9	55.9	83.9	125.8	209.7	349.5
300	10.2	39.8	53.1	79.6	119.5	199.1	331.8
325	9.3	38.7	51.6	77.4	116.1	193.6	322.6
350	8.4	37.6	50.1	75.1	112.7	187.8	313
375	7.4	36.4	48.5	72.7	109.1	181.8	303.1
400	6.5	34.7	46.3	69.4	104.2	173.6	289.3
425	5.5	28.8	38.4	57.5	86.3	143.8	239.7
450	4.6	23	30.7	46	69	115	191.7
475	3.7	17.4	23.2	34.9	52.3	87.2	145.3
500	2.8	11.8	15.7	23.5	35.3	58.8	97.9
538	1.4	5.9	7.9	11.8	17.7	29.5	49.2

Pressure-Temperature Ratings for ASTM Group 2-2.3 Materials

Working pressure by Classes, BAR

Temp.°C	150	300	400	600	900	1500	2500
-29 to 38	15.9	41.4	55.2	82.7	124.1	206.8	344.7
50	15.3	40	53.4	80	120.1	200.1	333.5
100	13.3	34.8	46.4	69.6	104.4	173.9	289.9
150	12	31.4	41.9	62.8	94.2	157	261.6
200	11.2	29.2	38.9	58.3	87.5	145.8	243
250	10.5	27.5	36.6	54.9	82.4	137.3	228.9
300	10	26.1	34.8	52.1	78.2	130.3	217.2
325	9.3	25.5	34	51	76.4	127.4	212.3
350	8.4	25.1	33.4	50.1	75.2	125.4	208.9
375	7.4	24.8	33	49.5	74.3	123.8	206.3
400	6.5	24.3	32.4	48.6	72.9	121.5	202.5
425	5.5	23.9	31.8	47.7	71.6	119.3	198.8
450	4.6	23.4	31.2	46.8	70.2	117.1	195.1