UNI Flanges Descriptions

UNI Flanges are pipeline connection components manufactured according to Italian UNI standards. Their dimensions, bolt patterns, pressure ratings, sealing surfaces, and connection structures are standardized to provide reliable compatibility between pipes, valves, pumps, pressure vessels, and industrial equipment.

Depending on operating pressure, temperature, medium, and installation requirements, UNI Flanges can be manufactured from carbon steel, stainless steel, alloy steel, and duplex stainless steel.

They are available in multiple designs, including Plate, Weld Neck, Blind, Threaded, Loose, and Lap Joint Flanges.

Here is a detailed feature and performance table for UNI Flanges:

Plate Flanges

Our UNI Plate Flanges are manufactured according to Italian UNI dimensional standards and are available in different nominal pressure ratings.

Common standards include:

UNI 2276 – PN6
UNI 2277 – PN10
UNI 2278 – PN16
UNI 6083 – PN25
UNI 6084 – PN40

Plate flanges feature a simple flat circular structure and are welded directly onto the pipe. Their economical design, easy installation, and standardized bolt-hole arrangement make them suitable for water treatment, general industrial pipelines, chemical systems, HVAC systems, and other low- to medium-pressure applications.

Plate Flanges

Slip-On Flanges

Our slip-on flanges are designed to slide easily over the pipe, with the inside diameter slightly larger than the outside diameter of the pipe.

They are normally connected to the pipe by fillet welding on both the inside and outside. Their simple installation and easy alignment make them suitable for general industrial piping systems where installation convenience and economical fabrication are important.

UNI-style slip-on and plate flange solutions can be supplied according to customer dimensions and project requirements.

Slip-On Flanges

Weld Neck Flanges

UNI Weld Neck Flanges feature a long tapered hub extending gradually from the flange body to the pipe connection.

The tapered neck helps transfer stress smoothly from the flange to the pipe, making weld neck flanges particularly suitable for pipelines subject to pressure, temperature fluctuations, vibration, or other demanding operating conditions.

Common UNI weld neck flange standards include:

UNI 2280 – PN6
UNI 2281 – PN10
UNI 2282 – PN16
UNI 2283 – PN25
UNI 2284 – PN40
UNI 2285 – PN64
UNI 2286 – PN100

They are widely used in petrochemical plants, oil and gas pipelines, power plants, pressure vessels, and high-pressure industrial systems.

 

 

 

Weld Neck Flanges

Socket Weld Flanges

A Socket Weld Flange features a recessed socket in which the pipe end is inserted before welding.

The design provides good rigidity, compact dimensions, and reliable sealing performance. Socket weld flanges are generally suitable for smaller-diameter, higher-pressure pipelines.

They are commonly used in petroleum, chemical processing, power generation, pressure vessels, shipbuilding, pharmaceuticals, machinery, and other industrial systems.

Socket Weld Flanges can also be manufactured according to customer drawings and specific project requirements.

Socket Weld Flange

Threaded Flanges

UNI Threaded Flanges have internal threads machined into the flange bore and connect directly to pipes with corresponding external threads.

Threaded connections reduce the need for field welding and are useful in applications where welding is difficult or undesirable.

Common UNI threaded flange standards include UNI 2253 and UNI 2254, with other pressure classes available according to applicable specifications and customer requirements.

They can be supplied in carbon steel, stainless steel, alloy steel, and other materials.

Threaded Flanges

Lap Joint Flanges

UNI Lap Joint and Loose Flanges are designed for use with stub ends or welding collars.

The flange itself can rotate around the pipe, making bolt-hole alignment easier during installation. This design is particularly useful for piping systems that require frequent dismantling, inspection, cleaning, or maintenance.

Common UNI loose flange standards include UNI 6088, UNI 6089, and UNI 6090.

Lap Joint and Loose Flanges are widely used in chemical processing, water treatment, food processing, marine piping, and corrosion-resistant piping systems.

Lap Joint Flanges

Blind Flanges

UNI Blind Flanges are solid circular flanges without a center bore and are designed to close the end of a pipeline, valve, pressure vessel, or equipment nozzle.

Unlike welded pipe caps, blind flanges provide a removable closure, making inspection, maintenance, cleaning, and future pipeline expansion easier.

Common UNI blind flange standards include:

UNI 6091 – PN6
UNI 6092 – PN10
UNI 6093 – PN16
UNI 6094 – PN25
UNI 6095 – PN40
UNI 6096 – PN64
UNI 6097 – PN100

Blind Flanges can be supplied in carbon steel, stainless steel, alloy steel, and duplex stainless steel.

Blind Flanges

Advantages of UNI Flanges

Standardized Dimensions and Interchangeability

UNI Flanges are manufactured according to established Italian dimensional standards, providing consistent outside diameters, bolt-hole arrangements, flange thicknesses, bore dimensions, and sealing surfaces.

This helps simplify pipeline installation, replacement, maintenance, and equipment connection.

Reliable Sealing Performance

UNI Flanges are available with different sealing face designs according to operating and project requirements.

When correctly matched with suitable gaskets, they provide dependable sealing for water, steam, gas, oil, chemicals, and industrial process media.

Wide Pressure Range

UNI Flanges cover a broad range of nominal pressure classes including PN6, PN10, PN16, PN25, PN40, PN64, and PN100.

Different flange designs and material grades can therefore be selected according to operating pressure, temperature, pipeline size, and medium.

Multiple Connection Types

UNI Flanges are available in several configurations, including Plate Flanges, Weld Neck Flanges, Blind Flanges, Threaded Flanges, Loose Flanges, and Lap Joint Flanges.

This allows different connection solutions to be selected according to installation and maintenance requirements.

Broad Material Selection

UNI Flanges can be manufactured from carbon steel, stainless steel, alloy steel, duplex stainless steel, and other special materials.

Suitable materials can be selected for applications involving corrosion, high temperature, pressure, seawater, chemicals, or other demanding operating environments.

Applications

Oil and Gas Industry

UNI Flanges are used in oil and gas pipelines, processing equipment, storage systems, valve connections, pump systems, and auxiliary piping.

Different materials and pressure ratings can be selected according to pipeline temperature, operating pressure, and transported medium.

Water Treatment Systems

Municipal water supply, wastewater treatment plants, pumping stations, irrigation systems, and industrial water networks can use UNI Flanges because of their standardized dimensions and convenient installation.

Chemical Processing

Chemical plants use UNI Flanges for process pipelines, reactors, storage tanks, heat exchangers, pumps, valves, and equipment connections.

Stainless steel, alloy steel, and duplex stainless steel materials can be selected for corrosive process environments.

Power Generation

UNI Flanges can be used in cooling water, steam, condensate, auxiliary piping, fuel systems, and other connections in power generation facilities.

Different pressure ratings are available for demanding operating conditions.

Marine and Shipbuilding

UNI Flanges are suitable for seawater systems, cooling systems, fuel lines, drainage systems, and general utility piping used in ships and marine equipment.

Corrosion-resistant materials are available for demanding marine environments.

Industrial Manufacturing

UNI Flanges are also widely used in machinery manufacturing, HVAC systems, food processing equipment, pressure vessels, pumps, valves, heat exchangers, and general industrial pipelines.

Why Choose Us

UNI Standards Manufacturing Capability

We manufacture UNI Flanges according to applicable Italian UNI dimensional requirements and customer technical specifications.

products can also be supplied according to EN, DIN, ASME/ANSI, JIS, BS, GOST, and other international standards for different projects and markets.

Comprehensive Production Capabilities

Our integrated manufacturing facilities cover raw material inspection, cutting, forging, heat treatment, machining, drilling, surface finishing, testing, marking, and packaging.

This allows consistent quality control throughout the complete production process.

Extensive Size and Pressure Range

We can supply UNI Flanges in a wide range of nominal diameters and pressure classes for different pipeline and equipment requirements.

Both standard products and customized flanges can be manufactured according to customer drawings and technical specifications.

Multiple Material Options

Available materials include carbon steel, stainless steel, alloy steel, duplex stainless steel, and other special grades.

Material certificates can be provided according to customer and project requirements.

Quality Assurance

Our UNI Flanges undergo dimensional inspection, visual inspection, material verification, and physical and chemical testing when required.

Additional inspections such as ultrasonic testing, magnetic particle testing, PMI, hardness testing, and third-party inspection can also be provided according to customer specifications.

International Supply Experience

With extensive experience supplying international industrial markets, we understand different dimensional standards, documentation requirements, inspection procedures, packaging requirements, and project specifications.

COMPANY PROFILE

Shanxi HongKai Forging Co., Ltd. is located in Dingxiang County, Shanxi Province, China, an area well known for flange forging and industrial manufacturing.

With extensive experience in the flange and forging industry, the company has integrated manufacturing capabilities covering forging, heat treatment, machining, physical and chemical testing, surface treatment, packaging, and shipment.

Our production facilities and quality control system allow us to manufacture standard and customized flanges for customers in different industries and international markets.

Our flange products can be manufactured according to major international standards including ASME/ANSI, EN, DIN, UNI, JIS, GOST, BS, and customer-specific drawings.

We provide carbon steel flanges, stainless steel flanges, alloy steel flanges, duplex stainless steel flanges, and customized forged products for industrial piping systems.

 

 

 

 

 

 

FAQ

Q: What are UNI Flanges?

A: UNI Flanges are pipe connection components manufactured according to Italian UNI dimensional standards. They are used for connecting pipes, valves, pumps, pressure vessels, and other industrial equipment.

Q: What are the common UNI flange standards?

A: Common UNI flange standards include UNI 2276, UNI 2277, UNI 2278, UNI 6083, and UNI 6084 for plate flanges; UNI 2280 through UNI 2286 for weld neck flanges; UNI 6088 through UNI 6090 for loose flanges; and UNI 6091 through UNI 6097 for blind flanges.

Q: What pressure ratings are available for UNI Flanges?

A: Common nominal pressure ratings include PN6, PN10, PN16, PN25, PN40, PN64, and PN100. Available pressure ratings depend on flange type, size, material, and applicable UNI specification.

Q: What types of UNI Flanges can you manufacture?

A: We can manufacture Plate Flanges, Weld Neck Flanges, Blind Flanges, Threaded Flanges, Loose Flanges, Lap Joint Flanges, and other customized flange configurations according to customer requirements.

Q: What materials are available for UNI Flanges?

A: Common materials include carbon steel, stainless steel, alloy steel, and duplex stainless steel. Special material grades can also be supplied according to drawings, specifications, and operating conditions.

Q: What is the difference between UNI Flanges and EN Flanges?

A: UNI refers to Italian national standards, while EN refers to European standards. Many traditional UNI flange dimensions have corresponding or successor dimensions within EN 1092-1. UNI designations are still widely used in purchasing, replacement projects, maintenance, and international industrial markets.

Q: Can UNI Flanges be customized?

A: Yes. We can manufacture UNI Flanges according to customer drawings and technical requirements, including customized dimensions, materials, pressure ratings, sealing faces, drilling patterns, surface treatments, markings, and inspection requirements.

Contact Us

Ready to discuss your UNI Flanges requirements?

Contact our technical team at kevin.zhao@hkflange.com for technical support, product selection, customized manufacturing, and competitive quotations.

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