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Reducing Flanges

Managing pipeline transitions can lead to space issues or poor sealing if the flange doesn’t fit both ends properly. Our Reducing Flanges (Weld Neck or Slip-On) solve this by connecting pipes of different sizes with one integrated unit. 

Standard Specification

ASME B16.5, ASME B16.47 (Series A/B), MSS SP-44

Pressure Rating

Class 150 to 2500 (PN10 to PN420) [Based on larger flange size]

Material

Carbon Steel (A105), Stainless Steel (A182 F304/F316), Alloy Steel (A694 F52)

Nominal Size

½”×¼” to 24″×12″ (DN15×DN8 to DN600×DN300) [Max 3:1 size ratio]

Flange Type

Weld Neck (WN) or Slip-On (SO) [No threaded/blind reducing flanges]
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Product Description

These flanges maintain sealing integrity, match the bolt pattern of the larger flange, and reduce fabrication errors. We support up to 3:1 reduction with high weld reliability and bore alignment to meet ASME fit. 

Facing Type

Raised Face (RF) or Ring-Type Joint (RTJ) [Matches larger flange]

Dimensions

Hub length per larger size [Taper angle ≤30° per ASME B16.25]

Bolt Circle Diameter

Matches larger flange size [ASME B16.5 Table 4]

Number & Size of Bolt Holes

Matches larger flange [Holes drilled for smaller pipe clearance]

Surface Finish

125-250 μin RA (RF), 63-125 μin RA (RTJ) [Bore transition smooth-ground]

Corrosion Resistance

Material-matched or dissimilar (with buttering layer)

Temperature Rating

-29°C to +538°C [Limited by base material]

Material Certification

EN 10204 3.1, NACE MR0175 (optional), PED 2014/68/EU

Gasket Compatibility

Matches larger flange [Full-face gaskets required]

Coating/Plating

Internal FBE coating (for CS), Electropolishing (for SS)

Manufacturing Method

Forged (A105/A182) + CNC machining [Bore transition radius ≥5% of diameter difference]

Technical Advantages

Mismatched bolt holes or bore steps can delay installation and risk leakage. Our reducing flanges follow ASME B16.5 dimensions and match the larger flange’s bolt circle for easy fit-up. 
 Each flange is CNC-machined with a smooth ground transition and a bore radius of at least 5 percent of the diameter difference. Material grades and gasket faces match the system’s pressure and temperature needs without rework. 

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Industry Applications

Refinery Pipe Networks

Connects reducers to reactors or separators with proper bolt alignment and thermal tolerance. 

Chemical Plants

Bridges different pipe sizes while withstanding corrosive flow media using SS or alloy grades. 

Power Generation Lines

Handles transitions in steam or feedwater systems with high-pressure Class 1500+ ratings.

Offshore Platforms

Offers NACE-compliant flanges in Duplex or F52 where sour service and compact transitions are critical. 

Skid-Mounted Process Units

Reduces layout space with single-flange pipe step-downs in modular assemblies. 

Water Treatment Systems

Connects varying line sizes with clean weld transitions and optional internal coatings for corrosion protection. 

Reducing Flanges

Solid Transition Without Bolt Misalignment

Switching pipe sizes should not compromise sealing or bolt fit. Our reducing flanges use full-size outer diameters and face thickness to maintain pressure rating integrity. 
 
Our Flanges help reduce layout issues and fit within existing pipe standards without adding stub-ins or couplings. You can rely on these for smoother assembly and fewer installation conflicts. 

reducing flanges

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Having Doubts? Our FAQ

Check all our Frequently Asked Question

Can I use reducing flanges without modifying the smaller pipe side?

Yes, reducing flanges are machined to match the smaller pipe’s outer diameter and wall thickness. This allows direct welding or slip-on fit without sleeve inserts. You avoid extra fittings or reducers.

Do reducing flanges impact gasket compression or sealing?

No, the sealing surface and bolt pattern match the larger flange size. This maintains standard gasket compression and ensures uniform sealing pressure. Only full-face gaskets are used to avoid leakage.

Will there be bolt misalignment due to the different pipe sizes?

No, bolt holes follow the larger flange’s bolt circle dimensions. The holes are drilled with clearance to match smaller pipe centers. This keeps bolting aligned and tight.

What if I need a reducing flange in non-standard sizes?

We support custom machining within the 3:1 size ratio using forged blanks. This covers special transitions not listed in standard charts. Lead times may vary based on material and bore size. 

How do I ensure bore alignment across the weld joint?

We grind the bore transition smoothly to reduce turbulence or flow loss. The taper angle stays within 30 degrees per ASME B16.25. This ensures clean weld prep and smooth internal flow.

Can Frigate supply reducing flanges as per my project drawings and line-class requirements?
  • Yes, Frigate manufactures reducing flanges against approved drawings, line lists, and project specifications. 
  • We match pressure class, facing type, material grade, and dimensional requirements to your application. 
  • Our team reviews bore transition, bolt circle, and weld-end details before production. 
  • This helps buyers reduce fit-up issues and avoid site-level modification. 
What documents does Frigate provide with reducing flange orders?
  • Frigate can supply EN 10204 3.1 material test certificates with the shipment. 
  • We support dimensional inspection reports, heat number traceability, and compliance records as required. 
  • NACE, PED, and project-specific documentation can be included on request. 
  • This makes procurement, QA approval, and site documentation easier to manage. 
Can Frigate handle bulk orders and repeat supply for EPC or OEM projects?
  • Yes, Frigate supports both one-time project quantities and scheduled repeat manufacturing. 
  • We can align production with your BOM, delivery schedule, and inspection plan. 
  • Our manufacturing approach helps maintain consistency across multiple flange sizes and material grades. 
  • This is useful for EPC packages, skid builders, and plant maintenance contracts. 
How does Frigate help reduce procurement and installation risk?
  • Frigate manufactures reducing flanges with controlled machining and dimensional checks before dispatch. 
  • We ensure the larger flange bolt pattern is maintained for easier site assembly. 
  • Our team verifies transition geometry and weld preparation to minimize mismatch risk. 
  • This helps customers reduce rework, shutdown delays, and leakage-related failures. 
Why should I source reducing flanges directly from Frigate as a manufacturer?
  • Frigate is a manufacturer, which gives you better control over specifications, quality, and delivery coordination. 
  • We support custom sizing within the permitted reduction range and application-specific material selection. 
  • Buyers get direct technical support during quotation, drawing review, and production stages. 
  • This shortens communication cycles and improves order accuracy for critical piping systems. 
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LOCATIONS

Registered Office

10-A, First Floor, V.V Complex, Prakash Nagar, Thiruverumbur, Trichy-620013, Tamil Nadu, India.

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9/1, Poonthottam Nagar, Ramanandha Nagar, Saravanampatti, Coimbatore-641035, Tamil Nadu, India. ㅤ

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LOCATIONS

Registered Office

10-A, First Floor, V.V Complex, Prakash Nagar, Thiruverumbur, Trichy-620013, Tamil Nadu, India.

Other Locations

  • Bangalore
  • Chennai
  • Coimbatore
  • Germany
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Become a Supplier

GENERAL ENQUIRIES

  • manufacture@frigate.ai
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Reducing Flanges

Reducing Flanges

Need reliable wires and cables for your next project? Get in touch with us today, and we’ll help you find exactly what you need!

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Reducing Flanges

Reducing Flanges

Need reliable Machining for your next project? Get in touch with us today, and we’ll help you find exactly what you need!

Get Latest Price

Get Price Form