Iso 7005 Pn16

[Orestes Hardy]

AS2129originates from BS10 and has been metricated. In some cases slightly larger bolt holes provide better clearance as metric bolts are specified in lieu of UNC bolts used by BS10. AS4087 is an update of AS2129, however AS2129 is still widely used so it has not been deleted as a standard, however, it now only covers AS table D to H.

AS4087 is the latest standard for BS table D to H, the same drilling is used but the new PN pressure rating system has been adopted. As the new pressure ratings are slightly higher the flange thicknesses have slightly increased. Also the raised face dimensions (although rarely specified, flat face is mostly used) are slightly larger. Table C, J to R, no longer exist, PN16 is the same drilling as Table D, PN21 is the same as Table E, PN35 is the same as Table H.

Although the standards say they are identical, I notice some very minor flange thickness differences between ISO 7005 (AS4331) and EN1092. Refer the Global Supply Line online slide rule above for differences.

Although the standards say they are identical, there are some very minor flange thickness differences between ISO 7005 (AS4331) and EN1092. Refer the Global Supply Line online slide rule above for differences.

ASME (American Society of Mechanical Engineers, of which Australian Pipeline Valve is a member company) is a group of standards, which are in turn covered within the American Standards Institute (ANSI), hence their flanges can be referred to as ANSI or ASME class. Class is also traditionally abbreviated CL or LB (verbally spoken as pound) or cross hash (#) but not psi as this can be misconstrued as the cold working pressure (CWP). Since ANSI 150 for instance has a CWP of 285 psi, so unlike the PN system the class is not related to CWP. AS4331 has adopted ANSI drilling and sizes but uses PN rating classes. Consequently in some sizes flanges are thicker to bring the rating up to the required PN rating.

A Class 300 flange is rated to a higher pressure than a Class 150 flange, because a Class 300 flange is constructed with more metal and therefore can withstand more pressure. However there are a number of factors that can impact the pressure capability of a flange.

Pressure/temperature ratings are maximum allowable working pressures allowed as per ASME B16.5 (published in metric and imperial). For intermediate temperatures, linear interpolation is calculated by manufacturers.

The temperature shown for a corresponding pressure rating is the temperature of the pressure-containing shell of the valve or flange. In general, this temperature is the same as that of the media in line and the external environment, whichever is greatest (but also lowest temperature of each must be factored for low temperature service). For any temperature below -29C, the rating shall be no greater than the rating shown for -29C, depending on materials the rating can be lower.

LB is the origin of the Latin word Libra (weighing scale) a Roman unit of mass similar to a pound, hence this has been adopted as another way of saying Class. Never say PSI as this can be confused with API 6B flanges which are rated by PSI (CWP).

ISO Flanges come in different ISO dimensions. The flanges are sexless and are made under ISO 63 through ISO630 standards. The lip outer diameter, inner diameter and the thicknesses vary for the different standards. The ISO 160 Blank Flange has 153mm lip outer diameter, 149.9mm li inner diameter and the wall thickness is 3.9mm. These flanges come in different pressure classes as well.

The ISO 7005 Pn16 Flange has a pressure number of PN16 where the flanges can range from PN6 through PN64 in pressure numbers. There are also centering ring, K-style and F-style flanges which have different dimensions. The flanges also vary in production type, face type and functional types. The ISO Slip On Flange is a functional type which allows the pipes to slip onto the flange to get to the connection position. There are also socket weld, weld neck and other types of flanges. The flange faces differ as flat face, raised face and ring type joint. The manufacturing of various flanges such as the ISO Kf Vacuum Flange can be threaded, forged, plate or screwed flange type. These different types use different connection methods. The threaded flanges connect with threaded pipe ends. The Iso 6164 Square Flange is a special type that is used in unique applications. The applications include general corrosive applications, water lines, petroleum, oil and gas and in the power generation industries. The ISO 5211 Mounting Flange is a mounting flange that is used as the base for a pipeline to be erected. The materials used for the making of these flanges also vary.

However, the PN flanges from ISO 7005 can be used in where required which is interchangeable with ASME 16.5. For more information on it the following sentence is copied from ISO 7005 Standard which states-

The materials that can be used to manufacture the flanges are given in table-9 of EN-1092 STD. basically all common material like carbon steel, alloy steel, stainless steel and low temp carbon steel are available in European material standards.

PN10, PN16, PN25 and PN40 specify both pressure class in bars of pressure, and metric flange dimensions (such as bolt circle diameter, hole size, bolt size etc) according to international flange standards such as ISO 7005-1 or DIN 2501 that use the metric system of measurements. Flanges produced to ANSI, AWWA, ASA, or old British standards that are dimensioned in inches will not mate up with metric flanges in general. It is good practice when specifying a PN flange standard to indicate the actual working pressure since it is a common occurrence that a specific PN, say PN16, flange drilling is required on a fitting or valve to match adjacent flanges, but the pressure requirement is less than PN16.

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