ISO 27509-2020 pdf free download.Petroleum and natural gas industries – Compact flanged connections with IX seal ring.
This document specifies detailed manufacturing requirements for circular steel and nickel alloy compact flanged connections and associated seal rings, for designated pressures and temperatures in class designations CL 150 (PN 20) to CL 1500 (PN 260) for nominal sizes from DN 15 (NPS ½) to DN 1200 (NPS 48), and for CL 2500 (PN 420) for nominal sizes from DN 15 (NPS ½) to DN 600 (NPS 24).
NOTE NPS is expressed in accordance with ASME B36.IOM and ASME B36.19M.
This document is applicable to welding neck flanges, blind flanges, paddle spacers and spacer blinds (paddle blanks), valve/equipment integral flanges, orifice spacers, reducing threaded flanges and rigid interfaces for use in process piping for the petroleum, petrochemical and natural gas industries.
This document is applicable within a temperature range from —196 °C to +250 °C. This document is not applicable for external pressure.
2 Normative references
The following documents are referred to in the text in such a way that some or aI 01 their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
Iso 2768-1, General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
ISO 4287, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Terms, definitions and surface texture parameters
ISO 4288, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Rules and procedures for the assessment of surface texture
ISO 5167-1, Measurement of fluid flow by means of pressure differential devices inserted in circular crosssection conduits running full — Part 1: General principles and requirements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
– ISO Online browsing platform: available at
– IEC Electropedia: available at
5 Design
5.1 General
CFCs shall:
a) be designed for face-to-face make-up for transfer of the bolt loading through the flange faces;
b) be designed so that a static mode is maintained in the bolted joint up to 1,5 times the specified pressure/temperature rating, see 2. Static mode is maintained as long as the difference between maximum and minimum nominal stress sustained by the bolts in the joint does not exceed 5 % of the minimum values specified in Table 3:
c) be standardized to cover as a minimum the same pressure temperature class designations and sizes as can be found in ASME B16.5 with equal or better performance;
d) be standardized to fit with commonly used standards by the valve industry [e.g. ASME B16.34, Iso 14313 and EN 12516 (all parts)], and other valve standards which make reference to these standards for pressure design;
e) conform with the applicable requirements in the piping or pressure vessel code agreed between the supplier and the purchaser.
The weakest part of flanged connections in accordance with this document regarding fatigue failure is always located somewhere in the transition from flange to pipe or flange to nozzle neck of an equipment or valve. The bolted joint itself is never subjected to fatigue load if considerations to cycling temperatures are taken when selecting bolt material, see Z3.
Supplier specific CFCs may refer to this document when additional requirements to the minimum requirements specified in this document are agreed between purchaser and supplier. The intension is to allow alternative and additional designs to the products in this document without compromising any of the listed items a), b) and e) in this subclause as well as the requirements of &1 and .
5.2 Design principles
Figure 1 shows the design principles of compact flanges and its seal system in accordance with this document.
The flange face includes a slightly convex bevel with the highest point, called the heel, adjacent to the bore and a small outer wedge around the outer diameter of the flange. The assembly is made up by tightening/tensioning the flange bolting which pulls the two connector halves together. The bevel angles have been standardized for different and relevant adjoining pipe wall thicknesses for each welding neck flange of a given size and pressure class.
For the IX seal ring, axial forces are exerted on the taper of the metal seal ring and translated into a radial sealing force. Furthermore, with increased pre-load, the bevel is closed and face to face contact is achieved at the outer wedge while most of the bolt pre-load is transferred as compressive forces between the flange faces at the heel, as illustrated in Figure 1. The arrows in the figure indicate the applied forces/pressure and the contact forces after make-up and during normal operation.ISO 27509 pdf free download.