Description

API 6A Wellhead Flange Manufacturer for Wellhead Equipment, Christmas Tree & Frac Tree Connections

SGPE manufactures API 6A Wellhead Flanges for drilling wellheads, completion systems, surface Christmas trees, frac trees, flowheads, production manifolds, well-testing packages and high-pressure oilfield connections.

The available range includes API 6B flanges, API 6BX flanges, Double Studded Adapter Flanges, DSAF flanges, blind flanges, test flanges, crossover flanges, threaded flange adapters, flanged weld neck adapters and drawing-based wellhead connectors.

Selected configurations cover nominal sizes from 1-13/16 inches to 21-1/4 inches. Working-pressure classes include 2,000 psi, 3,000 psi, 5,000 psi, 10,000 psi, 15,000 psi and selected 20,000 psi applications.

A wellhead flange cannot be selected from nominal size and pressure rating alone. The mating equipment, API 6B or API 6BX connection, RTJ groove, bolt pattern, through bore, body thickness, material class, temperature class, PSL, bolting and available stack height must all match the actual project.

Reviewing the complete interface before production helps prevent connection problems during wellhead assembly, Christmas tree installation, BOP stack-up, hydraulic fracturing, surface well testing, workover and well-intervention operations.

API 6A Wellhead Flange at a Glance

Technical Item	Typical Available Range or Option
Main products	API 6B, API 6BX, DSA, DSAF, blind, test, crossover, threaded and weld neck adapters
Nominal size	1-13/16 inches to 21-1/4 inches in selected configurations
Working pressure	2,000, 3,000, 5,000, 10,000, 15,000 and selected 20,000 psi
Sealing system	Ring Type Joint connection
RTJ gasket	Type R, RX or BX, as applicable
Typical body materials	Forged AISI 4130, AISI 4140 or project-approved material
Corrosion-resistant options	Stainless steel, duplex, CRA cladding, 316L or Alloy 625 overlay
Sour service	Available for approved H₂S-containing environments
Supply format	Individual flange or complete package with studs, nuts and RTJ gasket
Customization	Connection combination, bore, thickness, ports, material, overlay and coating
Documentation	MTR, dimensional report, NDE records, applicable test report and COC

Need a Custom or Replacement API 6A Flange?

Send the available flange size, pressure rating, RTJ ring number, equipment drawing, flange marking, nameplate or photographs.

When part of the technical information is unavailable, the existing data can be reviewed first. Our engineering team will identify the dimensions that still need to be measured or confirmed before manufacturing.

This service supports urgent replacement wellhead flanges, obsolete equipment, custom DSA flange projects, API 6B-to-6BX adapter flanges and modified crossover connections.

What Is an API 6A Wellhead Flange?

An API 6A Wellhead Flange forms a pressure-containing connection between surface wellhead, Christmas tree and flow-control equipment.

A standard flange may connect a casing head to a casing spool, a casing spool to a tubing head or a tubing head to a tree adapter. Other arrangements connect master valves, tree crosses, flowheads, frac trees, pressure-test equipment and production manifolds.

Adapter and crossover flanges allow equipment with different nominal sizes, working pressures or connection families to operate within the same assembly.

Both mating sides must use compatible dimensions, bolting arrangements, RTJ grooves, gasket types and bore profiles. Two components with the same nominal bore will not necessarily connect correctly.

For replacement and retrofit projects, the original drawing, flange marking, RTJ ring number and verified measurements provide a more reliable basis than nominal size alone.

Main API 6A Flange Types

Flange Type	Main Function	Typical Application	Key Selection Data
Double Studded Adapter Flange	Connects two dissimilar flange interfaces	Wellhead-to-tree, wellhead-to-BOP and frac tree transitions	Both-side size, pressure, flange family, RTJ groove, bore and thickness
API 6A Blind Flange	Closes an unused pressure-containing outlet	Wellhead side outlets, Christmas tree outlets and manifold isolation	Size, pressure, RTJ groove, ports and material
API 6A Test Flange	Provides a controlled pressure-test connection	Wellhead, tree, seal, valve and manifold testing	Working pressure, test pressure, port type and orientation
API 6A Crossover Flange	Changes size, pressure or connection family	Casing spool, tubing head, flowhead and BOP transitions	Both mating interfaces, bore alignment and stack height
Flanged Weld Neck Adapter	Connects an API flange to pipe or flowline	Production, well testing, flowback and injection lines	Pipe OD, wall thickness, bore, material and weld preparation
Threaded Flange Adapter	Connects a flange to a threaded outlet	Gauges, test pumps, injection and annulus monitoring	Thread form, pressure, engagement length and orientation
Drawing-Based Special Flange	Provides a project-specific connection	Monitoring, testing, replacement and retrofit work	Approved drawing, bore, bolt pattern, ports and operating function

Manufacturing and Supply Scope

SGPE supports standard flange orders, engineered adapters and replacement wellhead projects. We handle requirements ranging from one urgent replacement component to complete production batches for wellheads, Christmas trees and pressure-control packages.

For older or unsupported equipment, customers can provide original drawings, equipment nameplates, RTJ ring numbers, inspection reports, verified dimensions or qualified samples. These references help our engineering team confirm the correct connection and reduce the risk of dimensional errors.

SGPE manufactures forged pressure-containing bodies with controlled heat treatment, precision CNC machining, RTJ groove inspection, applicable nondestructive examination and complete project documentation.

For corrosive service, we offer stainless steel, duplex stainless steel, 316L weld overlay, Alloy 625 weld overlay and other project-approved CRA solutions.

A complete connection package may include the flange body, studs, nuts, RTJ gasket, sealing-surface covers and installation drawings.

Supply Capability	Project Support
Standard flange matching	Review of size, pressure, API 6B/API 6BX family and RTJ interface
Custom DSA manufacturing	Matching of both flange sides, ring grooves and through bore
Replacement flange supply	Review of drawings, nameplates, measurements and qualified samples
Forged flange bodies	Project-approved low-alloy steel and corrosion-resistant options
Precision machining	Bore, RTJ groove, bolt circle, tapped holes and auxiliary ports
Sour-service review	Material and hardness review based on actual operating conditions
Complete flange packages	Flange, studs, nuts, RTJ gasket and protective covers
Quality documentation	MTR, dimensional reports, NDE records and COC
Third-party inspection	Purchaser-approved independent inspection
Export preservation	Sealing-surface protection and export packing

API 6A Working-Pressure Classes

The following pressure classes commonly apply to wellhead flange and adapter projects. Metric values are rounded engineering conversions.

Rated Working Pressure	Approximate Metric Pressure	Typical Application	Main Review Focus
2,000 psi	13.8 MPa	Lower-pressure wellhead and production connections	Flange type, size and applicable dimensions
3,000 psi	20.7 MPa	Drilling wellheads and selected production equipment	RTJ groove, bolt pattern and mating interface
5,000 psi	34.5 MPa	Wellheads, Christmas trees and workover equipment	Bore, material, flange family and bolting
10,000 psi	69.0 MPa	High-pressure trees, gas wells and test equipment	API 6BX options, full bore and bolting
15,000 psi	103.4 MPa	Frac trees, high-pressure gas wells and intervention equipment	Material, erosion, bore and inspection
20,000 psi	137.9 MPa	Selected ultra-high-pressure applications	Size limits and engineered connection design

The overall manufacturing range does not mean that every nominal size is available at every pressure rating.

Final availability depends on the exact flange family, RTJ groove, bore, body geometry, material and mating equipment.

API 6A Double Studded Adapter Flange

A Double Studded Adapter Flange connects two components with different flange interfaces. It is also known as a DSA flange, DSAF, studded adapter flange, wellhead adapter flange or pressure crossover flange.

The body has a through bore and one studded interface on each side. Drilled and tapped holes allow the adapter to remain shorter than many conventional adapter spools, helping reduce the overall height of the wellhead or pressure-control stack.

The upper and lower connections may differ in nominal size, pressure rating, API 6B or API 6BX family, RTJ ring number, bolt-circle diameter and stud arrangement.

A typical enquiry may state:

4-1/16-inch 10,000 psi API 6BX × 3-1/8-inch 5,000 psi API 6B

This identifies the main transition but does not fully define the finished adapter. The RTJ groove on each side, minimum through bore, overall thickness, PSL, material class, temperature class, thread engagement and service environment must also be confirmed.

Typical DSA Technical Definition

DSA Design Item	Side A	Side B	Project Requirement
Nominal size	Project-specific	Project-specific	Must match each mating component
Working pressure	Project-specific	Project-specific	Lowest-rated interface normally limits the assembly
Flange family	API 6B or API 6BX	API 6B or API 6BX	Mixed connections require dimensional review
RTJ groove	R, RX or BX as applicable	R, RX or BX as applicable	Exact ring numbers must match
Bolt pattern	According to mating flange	According to mating flange	Bolt-circle interference affects practical thickness
Through bore	Common or transitioned bore	Common or transitioned bore	Must meet flow or tool-passage requirements
Stud arrangement	Tapped holes with studs	Tapped holes with studs	Engagement and projection require checking
Body thickness	One approved thickness	One approved thickness	Depends on groove separation and bolt geometry

DSA flanges commonly connect wellheads to Christmas trees, casing spools to tubing heads, wellheads to BOP equipment and frac trees to flowheads.

They also support surface well-testing stacks, workover systems, coiled tubing equipment and wireline pressure-control packages.

Replacement DSA flanges can be manufactured from approved drawings, verified dimensional records or qualified sample information.

DSA Flange vs. Adapter Spool

A Double Studded Adapter Flange and an adapter spool can both connect dissimilar interfaces, but their structures and preferred applications differ.

Comparison Item	Double Studded Adapter Flange	Adapter Spool
Construction	Compact body with tapped holes on both sides	Longer body with separated flange ends
Main advantage	Reduces connection length and stack height	Provides more space for bore transitions and ports
Bore transition	Short and compact	Can provide a longer, smoother transition
Side outlets	Normally limited	Can include side outlets
Bolt-circle interference	May limit practical thickness	Longer body separates overlapping bolt circles
Stud access	May become restricted	Usually provides better installation access
Typical use	Simple size or pressure transition	Complex transition or side-port requirement
Selection basis	Mating interfaces and practical thickness	Stack drawing, bore, ports and equipment loads

A compact DSA works well when both bolt circles fit within the available body thickness and sufficient thread engagement can be maintained.

An adapter spool is more practical when the bolt circles overlap, the bore changes significantly, side outlets are required or additional stack height is needed.

API 6A Blind Flange

An API 6A Blind Flange closes an unused pressure-containing outlet on a casing head, casing spool, tubing head, Christmas tree, valve, cross, tee or production manifold.

The flange may remain solid or include auxiliary connections for pressure monitoring, testing, controlled bleeding, chemical injection or fluid sampling.

A gauge port can support wellhead monitoring, while a bleed port allows controlled depressurization. Other configurations can include high-pressure test connections, transmitter ports, chemical-injection fittings and annulus-monitoring outlets.

API 6A Blind Flange Port Options

Port Item	Typical Option	Selection Basis
Port quantity	No port, one port or multiple ports	Required operating function
Port type	Threaded or small flanged connection	Pressure class and project specification
Thread option	NPT, API line pipe thread or specified oilfield thread	Connected gauge, valve or fitting
Port orientation	Axial, radial or drawing-defined	Equipment access and installation layout
Port service	Gauge, bleed, test, injection, sampling or transmitter	Operating procedure
Wetted material	Base material or CRA-protected area	Fluid composition and corrosion requirement

An API 6A blind flange with a test port can support wellhead pressure testing, annulus monitoring or controlled bleeding without adding a separate adapter.

API 6A Test Flange

An API 6A Test Flange provides a controlled connection for pressure testing wellheads, Christmas trees, valves, seals and manifolds.

It can include threaded or flanged ports for a high-pressure test pump, calibrated gauge, pressure recorder, bleed valve, pressure transmitter or hydraulic test manifold.

During a casing head, tubing head or Christmas tree test, one port may introduce the test medium while another supports pressure recording or controlled bleeding.

In a workshop, the flange can connect a high-pressure test unit and digital data-acquisition instruments.

API 6A Test Flange Information

Test Item	Information Required	Why It Matters
Rated working pressure	Equipment pressure class	Defines the primary flange connection
Required test pressure	Approved test procedure	May differ from working pressure
Test medium	Water or approved test fluid	Affects testing and preservation
Port quantity	One or more ports	Supports pressurizing, recording and bleeding
Port connection	Threaded or flanged	Must match hoses, valves and instruments
Port orientation	Drawing-defined	Prevents interference with test equipment
Recording method	Gauge, chart or digital recorder	Defines instrument connections
Witness requirement	Manufacturer, purchaser or third party	Affects inspection documentation

The final body, port arrangement, bolting and sealing configuration depend on both the rated working pressure and the approved test procedure.

API 6A Crossover Flange

An API 6A Crossover Flange changes the nominal size, pressure class, flange family or RTJ interface between two pieces of wellhead or pressure-control equipment.

Also known as a wellhead crossover flange, pressure crossover flange, API flange reducer or high-pressure flange adapter, it provides a controlled transition between dissimilar connections.

A compact crossover may use a DSA-style body. An adapter spool is normally more suitable when the design requires greater bolt-circle separation, additional thread engagement, side outlets or a gradual bore transition.

Crossover flanges can connect casing spools to tubing heads, tubing heads to tree adapters and wellheads to BOP stacks. Other arrangements connect Christmas trees to flowheads, wellheads to frac trees, frac trees to frac heads and production manifolds to flowlines.

A custom API 6A crossover flange for a BOP stack must be reviewed against both the wellhead connection and the pressure-control equipment interface.

API 6A Flanged Weld Neck Adapter

An API 6A flanged weld neck adapter connects a wellhead flange interface to an oilfield pipe, production flowline or fabricated pressure-containing assembly.

It may also be described as a wellhead weld neck adapter, API 6A weld neck flange adapter, flanged weld adapter or high-pressure flowline flange.

Typical applications include Christmas tree outlets, production lines, surface well-testing lines, frac flowback systems, gas-gathering lines and injection flowlines.

Because the weld end must match the connected pipe, the pipe OD, wall thickness, internal bore, material and weld preparation need to be confirmed before manufacturing.

Weld-End Information Required

Weld-End Item	Typical Data	Engineering Purpose
Pipe outside diameter	Actual pipe OD	Defines the external weld-end profile
Wall thickness or schedule	Project pipe wall	Defines weld-end thickness
Internal bore	Full or transitioned bore	Controls alignment and flow restriction
Pipe material	Carbon, low-alloy, stainless or CRA	Supports welding material selection
Welding bevel	Approved drawing or WPS	Controls workshop or field welding
Corrosion allowance	When specified	Supports the required service life
Internal overlay	316L, Alloy 625 or approved CRA	Protects wetted surfaces
PWHT requirement	Project-dependent	Must match the material and welding procedure

API 6A Threaded Flange Adapter

An API 6A Threaded Flange Adapter combines a flanged wellhead interface with a threaded oilfield connection.

Common applications include pressure-gauge connections, annulus-monitoring lines, chemical-injection points, high-pressure test-pump connections, bleed lines and transmitter ports.

Threads may include API line pipe threads, NPT, API tubing connections or project-specific oilfield threads.

The thread type, nominal size, pressure rating, material, engagement length and orientation must match the connected valve, fitting or instrument.

Special and Drawing-Based Wellhead Flanges

Terms such as target flange, companion flange, instrument flange and monitoring flange may describe specialized project components. They do not always represent one universal API configuration.

These flanges should therefore be manufactured according to an approved drawing and clearly defined operating function.

A custom design may include gauge ports, transmitter connections, annulus outlets, chemical-injection passages, bleed ports or sampling points. Other projects may require a special bore profile, nonstandard body thickness or customer-defined bolt arrangement.

Typical API 6A Wellhead Flange Specifications

Technical Item	Typical Available Range or Option
Applicable standard	API Spec 6A and ISO 10423
Main types	DSA, DSAF, blind, test, crossover, threaded and flanged weld neck adapters
Nominal size	1-13/16 inches to 21-1/4 inches in selected configurations
Working pressure	2,000, 3,000, 5,000, 10,000, 15,000 and selected 20,000 psi
Flange family	API 6B or API 6BX
Sealing system	Ring Type Joint
Ring-gasket type	R, RX or BX, as applicable
Product Specification Level	PSL 1, PSL 2, PSL 3, PSL 3G or PSL 4, subject to product scope
Performance requirement	As applicable to the selected product
Material class	Selected according to fluid and service conditions
Temperature class	Selected according to design temperature
Body construction	Forged or engineered pressure-containing body
Typical body materials	AISI 4130, AISI 4140 or approved low-alloy steel
Corrosion-resistant options	Stainless steel, duplex, nickel alloy, cladding or weld overlay
Sour service	Available for approved H₂S-containing environments
Manufacturing	Forging, heat treatment, machining and inspection
Pressure testing	Provided when required by product scope or purchase order
Bolting	Studs and nuts available
Surface protection	Phosphate, paint, offshore coating or specified finish
Documentation	MTR, dimensional report, NDE records, applicable test report and COC
Customization	Bore, thickness, ports, materials, overlay and connection combination

The table describes SGPE’s general manufacturing and supply range. It does not mean that every size, pressure class and material can be combined without engineering review.

API 6B vs. API 6BX Flange

API 6B and API 6BX are different standardized wellhead flange families. Their dimensions, bolting arrangements, ring grooves and gaskets are not the same.

Comparison Item	API 6B Flange	API 6BX Flange
Typical gasket	Type R or RX, as specified	Type BX
Typical equipment	Casing heads, casing spools, tubing heads and tree adapters	High-pressure wellheads, frac trees and flowheads
Pressure context	Standard and selected high-pressure service	Selected higher-pressure or larger-bore service
Make-up	According to the applicable connection	Controlled make-up with the matching BX ring
Selection data	Size, pressure, groove, bolt circle and bore	Size, pressure, BX ring, bolt pattern and bore
Interchangeability	Not directly interchangeable with API 6BX	Not directly interchangeable with API 6B

The connection family, RTJ groove, bolt arrangement and mating dimensions must be verified before an API 6B or API 6BX flange quotation is confirmed.

API 6A RTJ Flanges and Ring Gaskets

API 6A wellhead connections use metal Ring Type Joint sealing systems. These connections may also be described as high-pressure RTJ flanges, ring-joint wellhead flanges or oilfield RTJ flanges.

RTJ Gasket Type	Profile and Use	Typical Connection	Selection Note
Type R Oval	Traditional oval metal ring	Selected API 6B grooves	Must match the specified R number
Type R Octagonal	Octagonal metal ring	Selected API 6B grooves	Must match the applicable R groove
Type RX	Pressure-energized ring	Applicable API 6B/RX connections	Must match the designated RX groove
Type BX	High-pressure metal ring	API 6BX connections	Requires the exact BX groove

R, RX and BX gaskets are not interchangeable. The gasket type and ring number must match the actual groove.

For replacement equipment, the drawing, existing ring number, flange marking or verified groove measurements provide the most reliable identification.

How to Select an API 6A Wellhead Flange

Confirm the Required Function

Begin by identifying whether the project requires a DSA, blind flange, test flange, crossover flange, threaded adapter, weld neck adapter or special monitoring connection.

The function determines the bore, body thickness, auxiliary ports and inspection scope.

Confirm Both Mating Connections

A standard flange normally requires the nominal size, working pressure, connection family and RTJ ring number.

A DSA or crossover flange requires information for both sides.

Required DSA Data	Side A	Side B
Nominal size	Required	Required
Working pressure	Required	Required
API 6B or API 6BX	Required when known	Required when known
RTJ ring number	Required when known	Required when known
Mating equipment	Wellhead, tree, BOP, spool or other	Wellhead, tree, BOP, spool or other
Drawing or dimensions	Recommended	Recommended
Required through bore	Project bore	Project bore
Studs and nuts	Required or excluded	Required or excluded

Check the Through Bore

The bore should follow the approved flow path without creating an unnecessary restriction.

This is particularly important for frac trees, high-pressure flowheads, surface well-testing systems and high-rate gas production. Coiled tubing and wireline equipment must also provide enough clearance for tools, plugs and intervention components.

Review Body Thickness and Stack Height

Body thickness affects thread engagement, ring-groove spacing, installation access and total equipment height.

When bolt circles overlap or a compact body cannot provide sufficient engagement, an adapter spool may be more suitable than a DSA.

Verify the RTJ Groove

The gasket must match the exact connection family and RTJ groove number.

Useful references include wellhead drawings, Christmas tree drawings, BOP stack drawings, existing ring numbers, flange markings, original equipment records and dimensional inspection reports.

Photographs may support preliminary identification but normally cannot confirm critical groove dimensions.

Check the Lowest-Rated Interface

A higher-rated flange side does not increase the rating of the lower-rated equipment.

The lowest-rated component or connection normally limits the allowable working pressure of the complete assembly.

API 6A Wellhead Flange Materials

Material or Protection Option	Typical Use	Main Selection Factors
AISI 4130 forged low-alloy steel	Wellhead, tree and adapter bodies	Strength, hardness, impact properties and heat treatment
AISI 4140 forged low-alloy steel	Selected high-strength applications	Mechanical properties and project specification
Stainless steel	Selected corrosive service and instrument connections	Fluid compatibility and operating temperature
Duplex stainless steel	High-chloride and offshore service	Chloride resistance and stress-corrosion risk
316L weld overlay	Internal corrosion protection	Wetted area and finished thickness
Alloy 625 weld overlay	Sour, CO₂-rich or high-chloride service	H₂S, CO₂, chloride level and CRA specification
Other nickel alloy or CRA	Severe project-specific service	Operator specification and corrosion study

Forged AISI 4130 and AISI 4140 commonly serve as body materials for API 6A wellhead flanges and adapters.

Pressure rating alone does not determine the correct material. Operating temperature, well-fluid composition, material class, hardness limits and corrosion conditions must also be considered.

High-chloride injection service or offshore production may require stainless steel, duplex material or internal CRA overlay. Sour gas and CO₂-rich production may require Alloy 625 or another approved corrosion-resistant alloy.

H₂S Sour-Service API 6A Flanges

API 6A Wellhead Flanges can be supplied for approved sour-service projects.

Final material selection requires information about H₂S concentration or partial pressure, CO₂ concentration, chloride content, water cut, working pressure, operating temperature, well-fluid composition and required material class.

These conditions determine the base material, heat treatment, hardness limits and need for CRA protection.

The phrase “sour service” alone is not sufficient for final material confirmation.

Studs, Nuts and RTJ Gaskets

The flange can be supplied individually or as a complete connection package.

Component	Supply Option	Technical Confirmation
Studs	Complete set or excluded	Grade, diameter, length, coating and engagement
Nuts	Complete set or excluded	Grade, coating and dimensional compatibility
R gasket	When applicable	Exact ring number and material
RX gasket	When applicable	Exact ring number and material
BX gasket	When applicable	Exact ring number and material
Protective covers	Available	Flange-face and RTJ groove protection
Installation documents	Available when specified	Drawings and supplied-component list

Stud projection deserves particular attention on compact DSA flanges. Excessive projection can interfere with valves, actuators, BOP bodies, choke and kill lines or control tubing, while insufficient engagement can invalidate the approved design.

Manufacturing, Inspection and Traceability

Production begins with an approved forging or another project-approved material form. Before machining, the heat number, chemical composition, mechanical properties, heat-treatment condition and material certificate are reviewed. Traceability remains linked to the finished flange throughout production.

The body receives the heat-treatment cycle required for the selected material and mechanical properties. Depending on the grade and purchase specification, this may include normalizing, quenching, tempering or stress relieving.

Precision machining covers the through bore, flange faces, RTJ grooves, bolt circles, tapped stud holes, threaded ports and external profiles. For a Double Studded Adapter Flange, both sides must maintain the required alignment and concentricity.

Because the RTJ groove forms the metal-to-metal sealing interface, its dimensions and surface condition require careful control. Inspection can cover the groove number, pitch diameter, width, depth, included angle, surface finish and concentricity.

Depending on the selected PSL and purchase specification, the inspection plan may include ultrasonic testing, magnetic-particle inspection, liquid-penetrant inspection, hardness testing and weld-overlay examination.

Hydrostatic or leakage testing can be provided when required by the approved product scope, design or purchase order. Some loose flange components do not require individual hydrostatic testing; in those cases, material control, dimensional inspection and applicable NDE support final acceptance.

Inspection and Documentation

Inspection or Document	Typical Scope	Availability
Material Test Report	Heat number, chemistry and mechanical properties	Available
EN 10204 3.1 certificate	Material inspection certificate	Available when specified
Heat-treatment record	Furnace cycle and material batch	Available when required
Hardness report	Body, bolting or overlay hardness	Available
Impact-test report	Low-temperature toughness	Available when applicable
Dimensional report	Bore, bolt pattern, thickness and overall dimensions	Available
RTJ groove report	Groove number and critical measurements	Available
UT, MPI or LPI report	Applicable nondestructive examination	Available when specified
Pressure-test report	Pressure, holding time, medium and result	Available when applicable
Weld-overlay report	Chemistry, thickness, surface and NDE	Available when applicable
Coating report	Surface preparation and coating result	Available when specified
Certificate of Conformity	Compliance with approved order requirements	Available
Manufacturing Data Record	Consolidated project quality file	Available for approved projects
Third-party report	Independent inspection record	Available when arranged

Inspection by SGS, BV, DNV, ABS, TÜV or another purchaser-approved agency can be arranged when required.

Witness points, hold points and final documentation requirements should be agreed before order placement.

Oilfield Applications

Application	Typical Flange Products	Main Engineering Focus
Drilling wellheads	DSA, crossover and adapter flanges	Wellhead-to-BOP compatibility and stack height
Well completion	Tubing-head adapters and test flanges	Tree matching, seal testing and bore access
Christmas trees	API 6B/6BX flanges and adapters	RTJ groove, pressure rating and alignment
Hydraulic fracturing	High-pressure 6BX, DSA and crossover flanges	Pumping pressure, erosion and full bore
Surface well testing	Test, blind and crossover flanges	Test pressure and instrument connections
Workover and well killing	DSA and pressure-control adapters	Tool access and BOP connection
Coiled tubing and wireline	Crossover and threaded adapters	Tool passage and stack matching
Production and injection	Weld neck and manifold adapters	Pressure, temperature and corrosion
Offshore wellheads	CRA-protected and coated flanges	Corrosion, impact testing and documentation
Replacement projects	Custom DSA and drawing-based flanges	Dimensional verification and compatibility

During drilling and completion, API 6A flanges connect casing heads, casing spools, tubing heads and tree adapters. Interface checks may also cover transitions to BOPs, drilling spools, completion trees, wireline equipment and coiled tubing stacks.

High-pressure API 6BX, DSA and crossover flanges support frac trees and high-rate stimulation systems. Selection should consider maximum pumping pressure, minimum bore, flow rate, proppant conditions and expected erosion.

Blind, test and crossover flanges connect flowheads, test trees, choke manifolds, production test manifolds and pressure-recording equipment during surface well testing.

For production, injection and offshore service, the review may also cover H₂S, CO₂, chloride level, operating temperature, CRA overlay, low-temperature impact testing, coating and corrosion-resistant bolting.

Replacement projects should use original drawings, nameplates, RTJ ring numbers and verified dimensional reports wherever possible. A worn sample should not be used as the only engineering reference because corrosion, erosion and deformation may alter critical dimensions.

API 6A and API 16A Application Boundary

API 6A primarily applies to wellhead and Christmas tree equipment, including casing heads, casing spools, tubing heads, tree adapters, valves, chokes, crosses, tees, adapter spools and related flange connections.

API 16A primarily applies to drill-through and well-control equipment such as annular BOPs, ram BOPs, drilling spools, BOP adapters and hydraulic connectors.

A component installed inside a BOP stack should not automatically be described as an API 6A Wellhead Flange.

Where an adapter connects API 6A wellhead equipment to API 16A pressure-control equipment, its function, installation position, dimensions, testing and certification scope should be reviewed before the final product description is confirmed.

API 6A Flange Price and Quotation Factors

The price of an API 6A flange depends on the complete connection, body material, pressure class, inspection scope and supply package.

Price Factor	Effect on Quotation
Size and pressure rating	Larger and higher-pressure bodies require more material and machining
API 6B or API 6BX connection	Changes body dimensions, RTJ groove and bolting
DSA interface combination	Two different sides require additional engineering review
Body material	Forging grade and heat treatment affect cost
PSL and inspection scope	Additional NDE, testing and documents increase scope
Sour-service requirement	Material control and hardness limits affect production
CRA overlay	Overlay alloy, area, thickness and inspection affect cost
Auxiliary ports	Extra machining and pressure connections add work
Studs, nuts and RTJ gasket	Complete packages include additional components
Third-party inspection	Adds agency and coordination costs
Quantity	Batch production can reduce setup cost per unit
Delivery schedule	Urgent delivery can affect production planning

A reliable API 6A flange price cannot be calculated from nominal size alone. Connection details, quantity, material, inspection scope and available drawings are required for an accurate quotation.

Why Choose SGPE as Your API 6A Flange Supplier?

An API 6A Wellhead Flange affects pressure containment, RTJ sealing, bore alignment, stud access, stack height and compatibility with nearby equipment. It should not be treated as a generic machined steel component.

SGPE supports standard flange matching, custom DSA design, API 6B-to-6BX transitions, crossover review, replacement flange manufacturing, forged body production, controlled heat treatment, CNC machining and RTJ groove inspection.

For corrosive or sour environments, the technical review can include material selection, hardness limits, CRA overlay and additional inspection.

A complete supply package can include studs, nuts, RTJ gaskets, protective covers, drawings and project quality documents.

Whether the requirement involves one replacement DSA flange or a production batch for a complete wellhead package, the actual connection is reviewed before supply is finalized.

Information Required for an API 6A Flange Quotation

You do not need every technical detail before contacting SGPE.

For a preliminary enquiry, provide the flange type or intended function, nominal size, pressure rating and quantity. A drawing, nameplate, RTJ ring number or equipment photograph can also help.

For a DSA or crossover flange, provide the known data for both sides. The available information can be reviewed first, followed by a request for any critical dimensions still needed.

Technical Category	Information Required
Connection	API 6B or API 6BX, size, pressure and RTJ groove
DSA configuration	Full connection information for Side A and Side B
Bore	Minimum through bore or transition requirement
Dimensions	Body thickness, stack height and mating-equipment drawing
Materials	Body grade, material class and temperature class
Specification level	PSL and performance requirement where applicable
Service environment	H₂S, CO₂, chlorides, water cut and fluid composition
Bolting	Stud and nut grade, coating, length and supply scope
Ports	Size, thread, quantity, orientation and function
Corrosion protection	CRA overlay, coating or alloy requirement
Inspection	NDE, pressure testing and witness requirements
Documentation	MTR, dimensional report, COC and MDR requirements

Frequently Asked Questions About API 6A Wellhead Flanges

1. What Is an API 6A Wellhead Flange?

An API 6A Wellhead Flange creates a pressure-containing connection between surface wellhead, Christmas tree and flow-control components. Operators use these flanges to connect casing heads, casing spools, tubing heads, tree adapters, master valves, tree crosses, flowheads, frac trees and production manifolds.

Some flanges connect equipment with identical interfaces. Others change the nominal size, pressure rating or flange family between two components. Therefore, engineers cannot select a flange from the nominal bore alone. They must also check the rated working pressure, API 6B or API 6BX connection, RTJ groove, through bore, bolt pattern, material class, temperature class, PSL and mating-equipment dimensions.

API 6A Wellhead Flanges support drilling, well completion, production, hydraulic fracturing, surface well testing, workover and well-intervention operations. Correct interface matching helps prevent sealing, bolting and installation problems during field assembly.

2. What Types of API 6A Wellhead Flanges Does SGPE Supply?

SGPE supplies API 6B flanges, API 6BX flanges, Double Studded Adapter Flanges, DSAF flanges, blind flanges, test flanges, crossover flanges, threaded flange adapters, flanged weld neck adapters and drawing-based special flanges.

Each design serves a specific purpose. For example, a blind flange closes an unused wellhead, Christmas tree or manifold outlet. A test flange adds ports for a high-pressure test pump, pressure gauge, recorder or bleed valve. Meanwhile, a Double Studded Adapter Flange or crossover flange connects equipment with different sizes, pressure ratings or RTJ interfaces.

A flanged weld neck adapter connects an API wellhead interface to a production, flowback, surface well-testing or injection line. In addition, SGPE can manufacture custom flanges with gauge ports, annulus-monitoring outlets, chemical-injection connections, transmitter ports, special bore profiles or corrosion-resistant weld overlay when the approved project specification requires them.

3. What Is an API 6A Double Studded Adapter Flange?

An API 6A Double Studded Adapter Flange uses one studded flange interface on each side of a compact pressure-containing body. The industry also refers to this component as a DSA flange, DSAF, studded adapter flange, wellhead adapter flange or pressure crossover flange.

The two sides may differ in nominal size, working pressure, API 6B or API 6BX family, RTJ ring number and bolt pattern. As a result, a DSA can connect a casing spool to a tubing head, a wellhead to a Christmas tree, a wellhead to BOP equipment or a frac tree to a flowhead.

Because the DSA combines both interfaces in one short body, it often reduces the total stack height. However, the design still needs enough body thickness, thread engagement, stud clearance and through-bore capacity. Engineers must review these details against the actual wellhead, Christmas tree or pressure-control stack before production.

4. Can a DSA Flange Connect Different Sizes and Pressure Ratings?

Yes. Engineers often use a custom DSA flange to connect equipment with different nominal sizes, pressure classes or flange families. For example, one side may use a 4-1/16-inch 10,000 psi API 6BX connection, while the other side uses a 3-1/8-inch 5,000 psi API 6B connection.

However, the two connection descriptions do not fully define the finished adapter. SGPE also checks the RTJ groove number, bolt-circle geometry, minimum through bore, body thickness, material class, temperature class, PSL, stud engagement and service environment.

The higher-rated side does not raise the pressure rating of the lower-rated equipment. Instead, the lowest-rated component or connection normally limits the allowable working pressure of the complete assembly. This principle matters when selecting a wellhead-to-BOP adapter, frac tree crossover flange or replacement DSA for an existing pressure-control stack.

5. What Is the Difference Between a DSA Flange and an Adapter Spool?

A Double Studded Adapter Flange uses a compact body with drilled and tapped stud holes on both sides. By contrast, an adapter spool uses a longer central body with two separated flange ends.

A DSA works well when the project needs a short connection and the two bolt patterns fit within a practical body thickness. Therefore, operators often select it for straightforward size, pressure or API 6B-to-API 6BX transitions where stack height matters.

An adapter spool provides more room for a gradual bore transition, additional stud clearance, side outlets, gauge ports or monitoring connections. It usually offers a better solution when bolt circles overlap, the bore changes significantly or the equipment arrangement needs more installation height.

The final choice should follow the complete wellhead, Christmas tree or BOP stack drawing. Connection names alone cannot show whether the design provides enough thread engagement, access and structural space.

6. What Is the Difference Between an API 6B Flange and an API 6BX Flange?

API 6B and API 6BX follow different standardized connection geometries. They use different flange dimensions, bolt arrangements, RTJ grooves and metal ring gaskets. Therefore, operators cannot directly interchange them.

An API 6B flange may use a Type R or Type RX gasket when the applicable connection specifies it. An API 6BX flange uses the corresponding Type BX ring and commonly appears on selected high-pressure or larger-bore wellhead, frac tree and flowhead equipment.

Before SGPE prepares a quotation, the engineering team checks the nominal size, rated working pressure, flange family, RTJ ring number, bolt pattern and through bore. When a project needs to connect API 6B equipment to API 6BX equipment, SGPE may recommend a custom DSA flange, crossover flange or adapter spool, depending on the available stack height and bore requirements.

7. How Do I Identify the Correct RTJ Ring Gasket for an API 6A Flange?

Start with the approved equipment drawing, RTJ ring number, flange marking or original equipment record. These references usually provide the most reliable basis for identifying the correct gasket.

Type R, RX and BX gaskets use different profiles, so they do not work as interchangeable sealing rings. The selected gasket must match the exact flange family, groove profile and ring number. A clear photograph may help identify the general connection style, but it normally cannot confirm the critical groove dimensions.

For replacement wellhead flanges or obsolete Christmas tree equipment, SGPE can also review verified groove measurements and dimensional inspection reports. This step becomes especially important for custom API 6B-to-API 6BX adapters. An incorrect RTJ ring may prevent proper make-up, damage the sealing surfaces or compromise the pressure-containing connection.

8. Are 20,000 psi API 6A Wellhead Flanges Available in Every Size?

No. Manufacturers only produce selected 20,000 psi API 6A flange configurations for specific nominal sizes, flange families, materials and engineered connection designs.

The practical range depends on the API 6BX or other approved interface, RTJ groove, bolt geometry, minimum through bore, body thickness, mechanical properties and mating equipment. Therefore, a product range that includes 20,000 psi does not mean that every flange type or nominal size can carry that rating.

For ultra-high-pressure wellhead, frac tree or test applications, SGPE reviews the complete interface and service conditions before confirming availability. The review may include the maximum working pressure, test pressure, temperature range, fluid composition, material class, PSL, erosion conditions, inspection scope and required documentation.

9. What Materials Does SGPE Use for API 6A Wellhead Flanges?

SGPE commonly uses forged AISI 4130 and AISI 4140 low-alloy steel for API 6A wellhead flange and adapter bodies. The project requirements determine the final material, heat treatment and mechanical properties.

Pressure rating alone does not define the correct material. Engineers also review the operating temperature, API material class, well-fluid composition, hardness limits, impact requirements and corrosion conditions.

For corrosive production, injection or offshore service, SGPE may use stainless steel, duplex stainless steel, nickel alloy or corrosion-resistant protection on the wetted surfaces. Depending on the service conditions, available options may include 316L weld overlay, Alloy 625 overlay or another project-approved CRA system.

H₂S, CO₂, chloride content, water cut and operating temperature can all influence the final material selection. For this reason, SGPE confirms the complete service environment before selecting the base material and internal corrosion protection.

10. Can SGPE Supply API 6A Flanges for H₂S Sour Service?

Yes. SGPE supplies API 6A Wellhead Flanges for approved H₂S-containing service when the customer provides the actual operating conditions and project requirements.

The technical review should include the H₂S concentration or partial pressure, CO₂ level, chloride content, water cut, working pressure, minimum and maximum temperatures, well-fluid composition and required material class. These values help SGPE determine the appropriate base material, heat treatment, hardness limits, nondestructive examination and CRA protection.

The phrase “sour service” does not provide enough information for final material selection. For example, a sour-gas wellhead flange, offshore production flange and injection-well adapter may face very different corrosion risks.

Therefore, SGPE reviews each sour-service requirement against the complete operating environment and approved project specification before confirming the material and inspection scope.

11. What Inspection and Documentation Can SGPE Provide?

SGPE can provide a Material Test Report, EN 10204 3.1 certificate, heat-treatment record, hardness report, dimensional inspection report, RTJ groove report, applicable pressure-test report and Certificate of Conformity.

The selected PSL and purchase specification determine the final inspection scope. Depending on the project, SGPE may also perform ultrasonic testing, magnetic-particle inspection, liquid-penetrant inspection, impact testing, weld-overlay examination and coating inspection.

For projects that require a consolidated quality file, SGPE can prepare a Manufacturing Data Record that combines the approved material, manufacturing, inspection and test documents.

SGS, BV, DNV, ABS, TÜV or another purchaser-approved agency can perform third-party inspection when the order requires it. To avoid delays, the purchaser should define witness points, hold points, report formats and final documentation requirements before production begins.

12. What Information Does SGPE Need for an API 6A Wellhead Flange Quotation?

For a preliminary quotation, provide the flange type, nominal size, rated working pressure, quantity and intended application. A wellhead drawing, Christmas tree drawing, BOP stack drawing, equipment nameplate, flange marking, RTJ ring number or clear photograph can also support the initial review.

For a Double Studded Adapter Flange or crossover flange, provide the available connection details for both sides. These details should include the size, pressure rating, API 6B or API 6BX family and RTJ ring number when known.

The required through bore, body thickness, available stack height, material class, temperature class, PSL, bolting, auxiliary ports and inspection scope will help SGPE prepare a more accurate proposal.

Complete dimensional information is not necessary for the first enquiry. Customers can send the available documents first, and SGPE will identify any missing measurements or service details before preparing the final technical and commercial quotation.

Request an API 6A Wellhead Flange Quotation

SGPE supplies standard, custom and replacement API 6A Wellhead Flanges for drilling, completion, production, hydraulic fracturing, surface well testing, workover and well-intervention projects.

For a preliminary quotation, provide the flange type, nominal size, rated working pressure and quantity. For Double Studded Adapter Flanges, crossover flanges or other transition connections, include the known details for both mating sides.

You may also send a wellhead, Christmas tree or BOP stack drawing, equipment nameplate, flange marking, RTJ ring number or clear photograph. When available, include the required bore, body thickness, stack-height limit, material, PSL, bolting, auxiliary ports, sour-service conditions and inspection requirements.

Complete technical information is not required for the first enquiry. SGPE will review the available data, identify any missing dimensions or service details, and prepare the corresponding technical and commercial quotation.

E-Mail:
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