Flanges

Contents [hide]

1 Flange Descriptions

2 Flange Specification

3 Flange Materials

4 Flange Size

5 Flange Facing Types

6 Flange Facing Code, ASME

7 Flange Facing Finish

8 Flange Specification and Identification

9 Flange ANSI B16.5 and B16.47 Class Rating

10 Flange Pressure Classes

11 Flange Maximum Pressure and Temperature Ratings, ANSI B16.5 (in)

12 Flange Dimensional Tolerances, ASME B16.5 (in)

13 Flange Welding Bevel Standard, ANSI B16.5 and B16.47 (in)

Flange Descriptions

Blind Flange - These flanges do not have a bore. It is used to blind off a flange or even a valve.

When used at the end of a pipe or fitting, it provides an easy to open access for further extension

of the pipe. The blind flange and its bolts are stressed more than any other flange.

Lap Joint Flange - This flange is used with a lap joint stub end fitting. It is similar to a slip-on

flange, but with two differences. The radius and the flat face, both allow the flange to secure

against the stub end fitting. This is useful where alignment of bolt holes is difficult, such as with

spools to be attached to flanged nozzles of vessels. A lap joint is used in low pressure

applications and not suitable where high external of heavy loads are present.

Slip-on Flange - Slip-on flanges are designed to slip over the outside of pipe, long-tangent

elbows, reducers, and swages. The flange has poor resistance to shock and vibration. It is easier

to align than welding neck flange. This flange is ideal for low pressure applications since the

strength when under internal pressure is about one third that of a weld neck flange.

Socket Flange - This is similar to a slip-on flange, except they have a bored and counter bore.

The counter bore allows the pipe to fit into the socket/counter bore. The bore of the flange is the

same diameter as the inside of the pipe. These flanges were first designed for small diameter,

high pressure pipe.

Threaded Flange - It is similar to a slip-on Flange, but has internal threads. It is normally used

for low pressure and not used where temperature or stress is very high.

Weld Neck Flange - This flange comes in two types, regular and long. The hub of the weld neck

is designed to reduce the stress at the base of the flange. Regular weld neck flanges are used

with buttweld fittings and long weld neck flanges are usually used with equipment and vessel

nozzles. A long weld neck flange is rarely used with pipe. Both types of flanges are bored to

match the inside diameter of the pipe or fitting to which it will be welded to. They are suitable

where high pressure, extreme temperatures, shear impact and vibratory stresses apply.

Ring Joint Facing Flange - Also known as RTJ Flanges. These are used for a leak-proof

connection in high pressure applications. The flange has a hexagonal groove sealing surface and

is fitted with a ring that is compressed in a groove.

Flange Specification

ASME B16.5 - Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard

ASME B16.47 - Large Diameter Steel Flanges: NPS 26 Through NPS 60 Metric/Inch Standard

(Covers MSS SP-44 and API 605 flanges)

MSS SP-44 - Steel Pipeline Flanges (Covered by ASME B16.47 Series A)

API 605 - Cancelled (Covered by ASME B16.47 Series

API Spec 6A - Specification for Wellhead and Christmas Tree Equipment

ASME B16.5 and ASME B16.47 cover pipe flanges up to NPS 60 (B16.5 from 1/2" to 24" and

B16.47 from 26" to 60"). ANSI B16.47 covers two series of flanges, Series A is equal to MSS SP-

44-44, and Series B is equal to API 605 (API 605 has been canclled).

Flange Materials

Standards usually specify the material from which the flange is produced.

Flange Size

There are available flange sizes and grades for all standard pipe wall thicknesses and pressure

ratings.

Flange Facing Types

One end of the flex joint is a flat face to match the pump face and the other end is raised face to match the flange.

Flat Face (FF) - Typically these flanges are used on pump facings or on fiberglass flanges where

the torque of compressing the gasket will damage the flange body. They are found in 150# and

300# ratings. Their principal use is to make connections with 125# and 250# cast iron flanges,

respectively.

Raised Face (RF) - The raised face is the most common used flange face. It is called raised face

because the gasket is raised 1/16" and 1/4" above the bolt circle face: 1/16" for 300 lb. and less,

1/4" for 400 lb. and more. The flange facings are machine finished to ANSI/ASME B16.5

requirements.

Ring Type Joint (RTJ) (Class 300 and larger) - This flange is normally used for high pressure

gas pipe work. Ring type gaskets must be used on this type of flange.

Tongue and Groove (T&G)

Small Tongue and Groove

Large Tongue and Groove

Small Male and Female

Large Male and Female

Flange Facing Code, ASME

ASME B16.5 requires that for flanges and flanged fittings the surface is to have a specific roughness. A

concentric or spiral serrated finish with 30 to 55 groves per inch and a surface roughness between 125

and 500 microinches. This allows different surface grades to be used with various types of gaskets to

ensure a tight flange surface. These are some of the common finishes used on raised faces and flat

faces.

Flange Facing Finish

The flange face finish is determined by the standard used and measured as an Arithmetical Average

Roughness Height (AARH). An example would be ANSI B16.5 which specifies face finishes within a

range 125AARH - 500AARH (3.2 Ra to 12.5 Ra).

Cold Water - It has a mirror like finish. This is made with a wide tool at a high speed which

gives a finished surface much like a ground surface. When a surface has this type of finish it is

normally used metal to metal, not with a gasket. It is seldom used in the oil, chemical or related

industries.

Concentric Serrated - A 90 degree inclined angle tool is used to make the grove. It makes a

grove 1/64" deep and 1/32" apart in a concentric circle.

Smooth - This can be made with several different types of tool shapes. No tool markings will

appear to the naked eye on the surface. The roughness of the finish is from 125-250 microinch.

Spiral Serrated - This is similar to a stock finish but the difference between them is the way the

grove is made. A 90 degree inclined angle tool is used to make the grove. It makes a grove

1/64" deep and the feed is 1/32".

Stock - The surface is created by a continuous spiral groove. The roughness of the finish is from

125 to 500 microinches and is cut with a tool with an approximately 0.06 inches or larger radius.

Flange Specification and Identification

All flanges should be stamped for identification on the outside diameter of the base for east

identification with:

Flange Stamping

Manufacturer's name.

Nominal pipe size (NPS).

Pressure rating (150 lb., 300 lb., etc.)

Face designation - the machined gasket surface.

Bore - the nominal pipe size (NPS).

Material designation

Ring gasket number - used for ring joint flange.

Heat number of code - the batch number used when forged and tested

Normally, a flange should be hard stamped but in some cases the stamping may not be legible or

completely visible for observation. In that case it may have to be visually observed and physically

measured. Check the number of bolts and bolt size, measure the flange and pipe size. Then compare

these measurements with flange data.

Flange ANSI B16.5 and B16.47 Class Rating

Flange

Type

ANSI

B16.5

1/2"-24"

ANSI

B16.47

Series A

(MSS SP-44)

26"-60"

ASME

B16.47

Series B

(API 605)

26"-60"

Blind 150-2500 300-900 300-900

Lap Joint 150-2500 - -

Slip-On 150-2500 - -

Socket 150-2500 - -

Threaded 150-2500 - -

Weld Neck 150-2500 150-900 75-900

Flat/Raised Facing As Above As Above As Above

Ring Joint Facing 150-2500 300-900 300-900

Other Facings 150-2500 - -

Flange Pressure Classes

Flanges are normally manufactured in seven basic ratings: 150 Lb, 300 Lb, 400 Lb, 600 Lb, 900 Lb,

1500 Lb and 2500 Lb. The ratings can be expressed in different ways but mean the same thing - 150

Lb, 150 Lbs, 150# or Class 150.

Each class of flange can handle more pressure than the previous class because of its construction. The

higher the class is, the thicker the metal is. Thus a higher pressure can be handled. There a numerous

factors that can affect the pressure capability of a flange, such as the type of metal that is used. But

basically when pressure goes down, the temperature goes up and vise versa.

Flange Maximum Pressure and Temperature Ratings, ANSI B16.5 (in)

This table is in accordance with ANSI B16.5 maximum allowable non-shock pressure (psig) and

temperature ratings for steel pipe flanges and flanged fittings.

Based on American Society of Mechanical Engineers - ASME B16.5

ANSI Class 150 300 400 600 900 1500 2500

Temperature oF Maximum Allowable Non-Shock Pressure PSIG

-20 to 100 285 740 990 1480 2220 3705 6170

200 260 675 900 1350 2025 3375 5625

300 230 655 875 1315 1970 3280 5470

400 200 635 845 1270 1900 3170 5280

500 170 600 800 1200 1795 2995 4990

600 140 550 730 1095 1640 2735 4560

650 125 535 715 1075 1610 2685 4475

700 110 535 710 1065 1600 2665 4440

750 95 505 670 1010 1510 2520 4200

800 80 410 550 825 1235 2060 3430

850 65 270 355 535 805 1340 2230

900 50 170 230 345 515 860 1430

950 35 105 140 205 310 515 860

1000 20 50 70 105 155 260 430

Flange Dimensional Tolerances, ASME B16.5 (in)

Weld Neck Flange

Dimension Flange Tolerance

A Outside Diameter When O.D. is 24" or less: 1/16" (1.6mm)

When O.D. is over 24": 1/8" (3.2mm)

D Inside Diameter

10" and smaller: 1/32" (0.8mm)

12" thru 18": +1/8" (3.2mm)

20" and larger: -1/16" (1.6mm)

B Diameter of contact face

1/16" raised face: 1/32" (0.8mm)

1/4" Raised Face, Tongue & Groove (male &

female): 1/64" (0.4mm)

J Diameter of hub at base

When hub base is 24" or smaller: 1/16"

(1.6mm)

When hub base is over 24": 1/8" (3.2mm)

H Diameter of hub at point of

welding

5" and smaller: +3/32" (2.4mm), -1/32"

(0.8mm)

6" and larger: +5/32" (4.0mm), -1/32 (0.8mm)

P Drilling Bolt circle: 1/16" (1.6mm)

Bolt hole spacing: 1/32" (0.8mm)

Eccentricity of bolt circle with

respect to facing

2 1/2" and smaller 1/32" (0.8mm) max.

3" and larger 1/16" (1.6mm) max.

C Thickness 18" and smaller: 1/8" (3.2mm), -0"

20" and larger: 3/16" (4.8mm), -0"

K Length of hub 10" and smaller: 1/16" (1.6mm)

12" and larger: 1/8" (3.2mm)

Blind Flange, Lap Joint Flange, Slip-on Flange,Socket Flange, Threaded

Flange

Dimension Flange Tolerance

A Outside Diameter When O.D. is 24" or less: 1/16" (1.6mm)

When O.D. is over 24": 1/8" (3.2mm)

D Inside Diameter

Threaded: within limits of boring gauge

Lap Joint, Slip-on, Socket

10" and smaller: 1/32" (0.8mm), 0"

12" and larger: -1/16" (1.6mm), 0"

B Diameter of contact

face

1/16" raised face: 1/32" (0.8mm)

1/4" Raised Face, Tongue & Groove (male & female):

1/64" (0.4mm)

E, F, S Diameter of bore

Threaded (S): within limits of boring gauge

Lap Joint (F), Slip-on (E), Socket (E)

10" and smaller: 1/32" (0.8mm), 0"

12" and larger: -1/16" (1.6mm), 0"

P Drilling

Bolt circle: 1/16" (1.6mm)

Bolt hole spacing: 1/32" (0.8mm)

Eccentricity of bolt circle with respect to facing

2 1/2" and smaller 1/32" (0.8mm) max.

3" and larger 1/16" (1.6mm) max.

C Thickness 18" and smaller: 1/8" (3.2mm), -0"

20" and larger: 3/16" (4.8mm), -0"

L, M Length of hub 18" and smaller: 1/8" (3.2mm), 1/32" (0.8mm)

20" and larger: 3/16" (4.8mm), 1/16" (1.6mm)

Flange Welding Bevel Standard, ANSI B16.5 and B16.47 (in)

J = Diameter of hub at base

H = Outside Diameter of flange and mating pipe

D = Inside Diameter of flange

t = Wall thickness of flange hub at bevel

For bevel wall thickness (t) from 0.19 in. (3/16") to 0.88 in. (7/8") inclusive.

For bevel wall thickness (t) greater than 0.88 in (7/8").

Data shown on this page was either gathered and verified using data available in the public domain or

has been calculated by the staff at Piping-Designer.com. It is up to the end user to verify data prior to

use for any project. This page may not be reproduced without the explicit written permission of Piping-

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