Flanged joints are a critical element of any piping system. They provide the ability to break a connection, ensure tightness, allow repair, and make it possible to service equipment without cutting into the pipeline itself.
In oil & gas, chemical, petrochemical, power, and marine infrastructure, flanges operate in conditions where an error in standard, material, or pressure class can cause a leak and shut down a section of the line. That is why projects with international requirements specify ASME B16.5 and ASME B16.47.
SalesSolution, a Russia-based Engineering & Supply Company, manufactures and supplies pipeline components for industrial facilities, including pipes, flanges, fittings, forgings, fasteners, and gaskets, built to ASME standards.
ASME B16.5 vs. B16.47: the engineering difference
ASME B16.5 covers small- and medium-diameter flanges, typically up to DN 600 (NPS 24), across a wide range of flange types, including weld neck, slip-on, blind, socket weld, and threaded designs.
ASME B16.47 applies to large-diameter flanges, DN 600 and above. This standard is more common in cross-country pipelines, refining units, and power systems, where high reliability is required at large diameters and pressures.
Both standards share the same pressure-class logic (Class 150, 300, 600, 900, 1500, 2500), though dimensions and tolerances differ by series and application.
When selecting a standard, an engineer considers NPS, the process media, design temperature, pressure, load from the connected pipeline, installation requirements, and the availability of compatible gaskets and fasteners.
ASME pressure classes: how flange strength is determined
An ASME pressure class is not a fixed pressure rating for all conditions. It expresses how allowable pressure depends on temperature and material. The same Class 300 rating will carry different allowable parameters at elevated temperature for ASTM A105 versus ASTM A182 F316.
As temperature rises, a material’s strength properties decline. A flange that is perfectly suited at moderate temperature can become unsuitable for hot steam, high-temperature gas, or a process media with sharp temperature swings.
Class 150 and Class 300 are used in standard process systems where media conditions do not call for an extra margin. Class 600 and above are used in high-pressure lines, steam systems, gas media, and critical assemblies where the load on the flanged joint increases.
Joint strength is not determined by the flange alone. It is also shaped by stud and nut material, gasket type, surface finish, bolt torque, pipe alignment, and the absence of excess installation stress.
Flange materials: ASTM A105, A182, and A350 LF2
Flange material selection directly affects operating performance, corrosion resistance, and the applicable temperature range.
ASTM A105 is widely used under standard operating conditions and performs well for oil, gas, and water service where no aggressive chemical components are present.
For more demanding conditions, stainless steel ASTM A182, including grades F304 and F316, is used. These materials offer enhanced corrosion resistance and are applied in the chemical industry, seawater, and aggressive media.
ASTM A350 LF2 is selected for low-temperature service. The material retains impact toughness at sub-zero temperatures and is used on gas, cryogenic, and cold-climate projects, where the risk of brittle fracture becomes the governing constraint.
SalesSolution supplies materials across this flange range to ASME, ASTM, EN, DIN, and GOST standards, from carbon steel A105 through corrosion-resistant steels, Duplex, Super Duplex, and nickel alloys. The specific grade is always determined not only by the media, but by the calculated pressure and temperature parameters.
Flange types: design features and applications
Flanges vary by design and method of connection to the pipe.
Weld neck flanges are the most common, providing even stress distribution and used in high-pressure systems. Slip-on flanges are used in less demanding systems where ease of installation matters.
Blind flanges are used to seal off a pipeline or reserve a future connection point. Socket weld and threaded flanges are used on small-diameter piping, where compactness and simple assembly matter most.
Every flange type carries its own limits on pressure, temperature, diameter, and service media. In practice, the choice of design has to be verified by calculation and by the requirements of the governing standard.
Prior to 2022, SalesSolution worked with EPC contractors including Saipem, Toyo Engineering, Maire Tecnimont and The Linde Group. For industrial systems on this scale, supplying flanges is not just about dimensional compliance; it also requires confirmed material, pressure class, and a complete documentation package.
Sealing surfaces: RF, FF, and RTJ
Flanged-joint tightness depends on the sealing surface, which determines how the gasket takes compression and how bolt load transfers to the contact zone.
Raised Face (RF) is the most common design: the gasket sits on a raised surface, delivering adequate contact pressure for most industrial systems.
Flat Face (FF) is used in low-pressure systems and joints involving brittle components. The flat surface helps distribute load and reduces the risk of damaging the mating part.
Ring Type Joint (RTJ) is used for high pressure and temperature. A metal ring seats in the flange groove and provides sealing under significant loads; this design requires precise surface finishing and a compatible ring material.
Flanged joints in high-pressure piping
In high-pressure systems, flanged joints carry significant loads, including internal pressure, thermal expansion, and vibration.
An engineer verifies the compatibility of the flange, pipe, fitting, gasket, and fasteners. A mismatch in materials, pressure classes, sealing-surface types, or bolt-circle dimensions can cause a leak even where the flange itself formally fits the specification.
SalesSolution supplies flanges to ASME B16.5 and B16.47 from carbon steel A105, alloy grades F11 and F22, stainless F304 and F316, through Duplex S31803 and nickel alloys including Hastelloy C-276 and Inconel 625, covering the full material range required across oil & gas and petrochemical service conditions.
Material compatibility across piping system components
A flange has to be compatible with the pipe, fitting, gasket, studs, nuts, and process media. Incompatibility often surfaces not immediately, but after thermal cycling, bolt loading, corrosion, or a change in operating regime.
ASTM A105 paired with ASTM A106 pipe is the standard combination for carbon-steel systems. For low temperatures, A350 LF2 is paired with materials rated for cold-temperature toughness. For aggressive media, stainless steels, Duplex, Super Duplex, and nickel alloys are used.
Fasteners also have to match the load and temperature. If a flange is rated for a high class but the studs or nuts are selected without accounting for material and temperature, the joint cannot hold the design bolt load.
Manufacturing considerations and quality control
Manufacturing flanges to ASME standards requires strict adherence to process technology.
Non-destructive testing is applied per project and standard requirements, helping detect internal defects, laminations, cracks, and surface flaws that could affect flange performance under pressure.
Flanges built to ASME B16.5 and ASME B16.47 remain a foundational element of piping systems, and their use ensures standardization and equipment compatibility across industries. As a Russia-based Engineering & Supply Company, SalesSolution supports that standardization end to end, from material certification through manufacturing and documentation for every flange it ships.
