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Nominal Size: DN6-DN200
Design Standard: ASME B16.3
Material: ASTM A197/A197M (Malleable Cast Iron)
Size Range: 1/8" (DN6) - 8" (DN200)
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Product description
Malleable iron pipe fittings are suitable for pipeline connection pieces used in the transportation of media with a nominal size ranging from DN6 to DN200, a service temperature of -29°C to 175°C, and a maximum working pressure of 2.1 MPA. They are an important part of the pipeline systems in the fields of gas, fire protection, water affairs, and heating, ventilation and air conditioning, and can meet the connection requirements of various pipeline systems. Whether it is a straight pipeline or a curved pipeline, or whether it is a pipeline with the same diameter or different diameters, malleable iron pipe fittings can provide a firm and reliable American standard threaded connection, which is convenient for on-site construction.
Product function
Value advantage
Premium Material
Superior Corrosion Resistance
Precision Threads
Comprehensive Product Range
Fast Service
High Cost Performance
Our Malleable Iron Flat Seat Union provides a secure threaded connection that can be disconnected for pipeline maintenance without rotating or cutting the connected pipes.
Manufactured from ASTM A197/A197M malleable iron to ASME B16.3, the range covers 1/8" to 8" (DN6–DN200). Black and galvanized finishes and different thread requirements can be supplied according to the target market and piping specification.
Compared with a permanent straight connection, the detachable union structure is particularly useful around valves, meters, pumps, equipment connections and pipeline sections requiring periodic inspection or replacement.
For wholesalers, distributors, contractors and OEM customers, flat seat unions can be consolidated with our complete range of Malleable Iron Pipe Fittings for bulk purchasing.
• Size Range: 1/8"–8" / DN6–DN200
• Material: ASTM A197/A197M Malleable Iron
• Design Standard: ASME B16.3
• Type: Flat Seat Threaded Union
• Connection Options: Female/Female or Male/Female according to product specification
• Thread Options: NPT / BSP according to order requirements
• Finish Options: Black / Galvanized
• Service Temperature: -29°C to 175°C
• Maximum Working Pressure: Up to 2.1 MPa
• Order Type: Wholesale, Distributor, Project and OEM Orders
| Parameter | Specification |
|---|---|
| Product | Malleable Iron Flat Seat Union |
| Material | ASTM A197/A197M Malleable Iron |
| Design Standard | ASME B16.3 |
| Size Range | 1/8"–8" / DN6–DN200 |
| Connection | Threaded Union |
| Connection Options | F/F or M/F according to specification |
| Thread Options | NPT / BSP |
| Seat Type | Flat Seat |
| Surface Finish | Black / Galvanized |
| Service Temperature | -29°C to 175°C |
| Maximum Working Pressure | Up to 2.1 MPa |
| Typical Media | Water, Gas, Air, Oil and Steam |
| Applications | Plumbing, HVAC, Gas, Fire Protection and Industrial Piping |
| Supply Type | Bulk / Wholesale / OEM / Project |
| Customization | Marking, Labeling and Packaging |
For accurate quotation, please provide the union size, connection type, required thread, surface finish and quantity for each SKU.
A threaded coupling creates a simple straight connection between two pipes. However, disconnecting that joint may require one of the pipes to be rotated.
A Malleable Iron Flat Seat Union solves this problem with a detachable multi-part structure.
By loosening the union nut, two connected pipeline sections can be separated without rotating the complete pipe run.
This makes flat seat unions especially useful near:
• Valves
• Water meters
• Pumps
• Filters
• Regulators
• Heating equipment
• Mechanical equipment
• Pipeline inspection sections
For installations expected to require future servicing, this detachable design can significantly simplify maintenance.
Both products provide straight threaded connections, but they serve different installation requirements.
| Feature | Flat Seat Union | Threaded Coupling |
|---|---|---|
| Primary Function | Connect and allow disconnection | Permanent straight connection |
| Pipeline Disassembly | Easy | More difficult |
| Pipe Rotation Required for Removal | Normally no | Often required |
| Structure | Multi-piece union | One-piece fitting |
| Typical Location | Equipment and maintenance points | General straight pipe runs |
| Relative Cost | Higher | Lower |
For simple permanent straight connections, a Malleable Iron Threaded Coupling is generally sufficient.
Where regular removal or maintenance is expected, a threaded union provides greater installation flexibility.
The required connection configuration should be clearly stated in the purchase specification.
A Female Threaded Union has internal threaded connections on both sides and connects two compatible male-threaded pipes or fittings.
It is commonly used for detachable straight-line connections in plumbing, mechanical and industrial piping systems.
A Male Female Threaded Union combines one male threaded connection with one female threaded connection.
This configuration can simplify certain piping layouts by allowing direct connection to a female fitting, valve or component without adding another nipple.
For bulk orders, clearly state F/F or M/F for each SKU to avoid connection-type errors.
International malleable iron fitting catalogs commonly distinguish between flat seat and taper/conical seat unions.
A flat seat union uses a flat mating interface, while a taper seat union uses a tapered metal seating geometry.
The correct design should be selected according to the required standard, sealing arrangement, operating medium and project specification.
Buyers should therefore confirm:
• Seat type
• Connection configuration
• Thread standard
• Nominal size
• Operating pressure
• Operating temperature
• Sealing requirements
Do not substitute one union design for another solely because the nominal pipe size is the same.
Thread standard is an important part of international union procurement.
NPT threaded fittings are widely used in North America, while BSP/BSPT connections are common across Europe, Asia, the Middle East, Africa and many other markets.
Because NPT and BSP use different thread geometries, they should not be treated as interchangeable.
For distributors serving several markets, different thread types can be managed through separate:
• SKUs
• Product markings
• Carton labels
• Barcodes
• Packaging configurations
Black unions are commonly specified for compatible gas, compressed-air, steam and general industrial piping systems where a galvanized coating is not required.
Galvanized unions use a zinc-based protective surface to improve resistance to corrosion in suitable water, outdoor, humid and building-service environments.
For bulk galvanized orders, thread condition is inspected together with surface quality because excessive coating around threaded areas can affect assembly.
Our Malleable Iron Flat Seat Unions are supplied for wholesalers, project companies and commercial purchasing programs rather than small retail orders.
Typical customers include:
• Pipe fitting wholesalers
• Plumbing distributors
• Building material importers
• Fire protection suppliers
• Gas equipment distributors
• HVAC wholesalers
• Industrial supply companies
• EPC and MEP contractors
• OEM and private-label brands
A typical distributor order may include multiple union sizes together with Malleable Iron Threaded Tees, elbows, couplings and nipples.
Consolidated purchasing helps simplify supplier management, inspection, packaging and international shipping.
A union contains several mating components, so dimensional consistency is especially important.
Our quality control focuses on the areas that affect assembly and sealing performance.
Material and casting conditions are controlled to reduce cracking, porosity and other defects that could affect mechanical strength or pressure integrity.
Thread dimensions and alignment are inspected to reduce cross-threading, difficult installation, insufficient engagement and pipe misalignment.
The union components must fit together consistently.
Critical dimensions and mating surfaces are therefore controlled to support correct assembly across production batches.
Finished pipe fittings undergo pressure-related inspection to identify leakage and through-wall defects before shipment.
Black and galvanized surfaces are checked before packing to maintain consistent appearance and corrosion protection.
For established distributors and fitting brands, we support commercial customization requirements such as:
• Product marking
• Customer branding
• Carton design
• Barcode and SKU labels
• Size-specific packaging
• NPT/BSP differentiation
• Black or galvanized finish
• Mixed-size orders
• Combined fitting shipments
If your product range also requires detachable directional connections, our Malleable Iron Flat Seat Union Elbow can be included in the same purchasing program.
Malleable Iron Flat Seat Unions are commonly installed where a threaded pipeline may need to be disconnected for maintenance.
Water Systems
Used around valves, meters and equipment where future servicing may require pipeline disassembly.
Gas Piping
Suitable for compatible threaded gas systems according to project and local code requirements.
HVAC Systems
Used around heating and mechanical equipment that may require replacement or maintenance.
Fire Protection
Threaded unions can be incorporated into compatible fire protection piping according to the approved system design.
Compressed Air
Used around filters, regulators and equipment connections in workshop and industrial compressed-air systems.
Industrial Piping
Suitable for detachable connections in compatible utility piping carrying air, oil, water, steam or other approved media.
HULU has worked in the foundry industry since 1995 and supplies a broad range of pipe fittings, valves and pipeline products.
For bulk purchasers, our supply system focuses on:
• Broad fitting size coverage
• Controlled malleable iron casting quality
• Precision threaded connections
• Black and galvanized options
• Multiple fitting types from one source
• OEM marking and packaging
• Factory quality inspection
• Repeat distributor and project supply
Customers can also combine unions with Malleable Iron Threaded Nipples and other fittings to build a complete commercial product range.
It is a detachable threaded pipe fitting used to connect two pipeline sections. The union nut allows the connection to be separated without rotating the complete pipe run.
A coupling is mainly intended to create a straight connection. A union is designed to allow easier future disassembly, making it more suitable near valves, meters, pumps and equipment requiring maintenance.
The current product range covers approximately 1/8" to 8", corresponding to DN6–DN200. Specific configuration availability should be confirmed with the required size list.
Different threaded configurations can be supplied according to product and purchasing requirements. Specify F/F or M/F for every required SKU when requesting a quotation.
Yes. NPT and BSP thread requirements can be coordinated according to target market and project specification.
Yes. Black and galvanized malleable iron fitting options are available for different piping environments.
Yes. Bulk orders can contain multiple union sizes and can be consolidated with elbows, tees, couplings and other malleable iron fittings.
Yes. Product marking, labels, customer SKUs, cartons and other private-label packaging requirements can be discussed for commercial orders.
Looking for Malleable Iron Flat Seat Unions for wholesale distribution, OEM branding or project procurement?
Send us your required sizes, F/F or M/F configuration, NPT/BSP requirement, black or galvanized finish and quantity for each SKU.
HULU can supply flat seat unions individually or consolidate them with elbows, tees, couplings, nipples and other malleable iron fittings for bulk and recurring purchasing programs.
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