Duplex Steel Instrumentation Fittings

Duplex Tube Fittings are high-performance piping components manufactured from duplex stainless steel, a two-phase alloy having approximately equal proportions of austenitic and ferritic microstructures. These fittings consist of approximately 22–25% chromium, 4–6% nickel, and 2–3% molybdenum, along with trace amounts of nitrogen elements. The dual-phase structure offers a minimum yield strength of 450 MPa, about double that of standard austenitic stainless steel grades. The Duplex Tube Fittings offer excellent resistance to stress corrosion cracking, pitting, and crevice corrosion in industries like oil and gas, chemical processing, marine, and water treatment, where reliable performance under high pressure and corrosive environments is crucial.

Duplex Steel Tube Fitting Prices

The price of Duplex Tube Fittings often depends on grade, size, wall thickness, and order quantity. The following are the key pricing elements to consider before placing an order.

Approximate Price Range

The Duplex tube fittings often range between Rs 250 and Rs 1,875 per piece, depending on the fitting type and dimensions. Compression fittings are on the lower end; forged and butt-weld fittings command higher pricing.

Factors Affecting Price

There are several factors that affect the cost of UNS S32205 and S31803 pipes. As these are higher alloy grades, they are more expensive than standard stainless steel. Tube pricing depends on size, wall thickness, diameters and schedules like Sch 80S, Sch 160, and XXS require more raw material, which increases the cost. Ordering in bulk can reduce the cost per piece. Additional requirements, such as EN 10204 3.2 certification or third-party inspection, increase the final price. The price changes of chromium, nickel and molybdenum can influence the total cost of a tube.

Duplex Tube Fittings Grades

The Duplex tube fittings are offered in three primary grades; each grade is selected based on its operating conditions, corrosion resistance, and mechanical qualities.

Duplex Steel UNS S32205 Tube Fittings
Duplex Steel UNS S31803 Tube Fittings
Duplex Steel 2205 Tube Fittings

Types of Duplex Tube Fittings

The Duplex tube fittings are manufactured in 3 primary types, each conforming to specific ASTM standards. The selection depends on the connection method, pressure class, and installation requirement.

Buttweld Pipe Fittings (ASTM A815)
Forged Fittings (ASTM A182)
Compression / Tube Fittings

Duplex Tube Fittings Specifications

The table below covers the complete technical specifications for duplex tube fittings across all standard grades and connection types.

Parameter	Specification
Material Grades	Duplex 2205, UNS S31803, UNS S32205
Product Type	Duplex tube fittings for instrumentation and process tubing
Size Basis	Tube OD-based sizing, not pipe schedule-based
Common Size Range	1/8" to 2" and metric 3 mm to 50 mm
Connection Types	Compression, ferrule, tube-to-male, threaded, socket weld, butt weld
Pressure Rating	Up to 3,000 psi, 6,000 psi, 10,000 psi; some fittings up to 11,000 psi
Standards Mentioned	ASTM A182, ASTM A276, ASTM A479
Manufacturing	Forged, cold drawn, CNC precision machined
Marking / Certification	MTC, EN 10204 3.1 / 3.2, traceability is commonly supplied
Temperature Capability	Up to 600°F / 315°C in many service listings
Mechanical Strength	Yield strength around 450 MPa minimum
Corrosion Resistance	Strong resistance to stress corrosion cracking, pitting, and uniform corrosion
Typical Applications	Oil and gas, chemical processing, marine, hydraulics, pneumatic and instrumentation lines

Duplex Tube Fittings Size Chart

The size chart below lists wall thickness values in millimetres across standard schedule ratings for each tube OD. Use this to confirm compatibility with your system pressure class before ordering.

Tube OD / NPS	Sch 5S	Sch 10S	Sch 40S / STD	Sch 80S / XS	Sch 160	XXS
1/8"	0.886 mm	1.24 mm	—	—	—	—
1/4"	1.24 mm	1.65 mm	2.24 mm	—	—	—
3/8"	1.24 mm	1.65 mm	2.31 mm	—	—	—
1/2"	1.65 mm	2.11 mm	2.77 mm	3.73 mm	4.78 mm	4.77 mm
3/4"	1.65 mm	2.11 mm	2.87 mm	3.91 mm	5.56 mm	5.57 mm
1"	1.65 mm	2.24 mm	3.38 mm	4.55 mm	6.35 mm	6.35 mm
1 1/4"	1.65 mm	2.24 mm	3.56 mm	5.08 mm	6.35 mm	6.35 mm
1 1/2"	1.65 mm	2.24 mm	3.56 mm	5.16 mm	7.11 mm	7.11 mm
2"	1.65 mm	2.77 mm	3.91 mm	6.35 mm	8.18 mm	8.18 mm

Schedule Chart of Duplex Tube Fittings

The schedule chart below reflects wall thickness values in mm across six schedule ratings from Sch 5S to XXS. Cross-reference tube OD with your required pressure class to identify the correct schedule.

Tube OD / NPS	Sch 5S	Sch 10S	Sch 40S / STD	Sch 80S / XS	Sch 160	XXS
1/8"	0.886 mm	1.24 mm	—	—	—	—
1/4"	1.24 mm	1.65 mm	2.24 mm	—	—	—
3/8"	1.24 mm	1.65 mm	2.31 mm	—	—	—
1/2"	1.65 mm	2.11 mm	2.77 mm	3.73 mm	4.78 mm	4.77 mm
3/4"	1.65 mm	2.11 mm	2.87 mm	3.91 mm	5.56 mm	5.57 mm
1"	1.65 mm	2.24 mm	3.38 mm	4.55 mm	6.35 mm	6.35 mm
1 1/4"	1.65 mm	2.24 mm	3.56 mm	5.08 mm	6.35 mm	6.35 mm
1 1/2"	1.65 mm	2.24 mm	3.56 mm	5.16 mm	7.11 mm	7.11 mm
2"	1.65 mm	2.77 mm	3.91 mm	6.35 mm	8.18 mm	8.18 mm

Key Features of Duplex Tube Fittings

Duplex tube fittings combine 8 structural and chemical advantages that make them the preferred choice for demanding industrial service conditions.

High Corrosion Resistance
Superior Strength
Good Weldability
Excellent Fatigue Strength
Good Thermal Conductivity
Low Thermal Expansion
Resistance to Erosion and Abrasion
Resistance to Pitting and Crevice Corrosion

Applications of Duplex Tube Fittings

Duplex tube fittings serve across 10 high-demand industries where corrosion control, pressure integrity, and long service life are critical requirements.

Oil and Gas Industry
Chemical Processing Plants
Marine Applications
Power Generation Plants
Water Treatment Plants
Pharmaceutical Industry
Pulp and Paper Industry
Food and Beverage Industry
Mining and Mineral Processing
Pollution Control Equipment

How to Choose the Right Duplex Tube Fittings Supplier and Manufacturer?

Choosing the right duplex tube fittings supplier can directly affect system safety, compliance, and overall cost. Consider the following four criteria before finalising a supplier.

Selecting the Right Supplier and Manufacturer

Select a reliable supplier which usually offers proper stock availability and full material traceability. It is also important to check if they can provide mill test certificates and EN 10204 3.1 or 3.2 certification when needed for the project.

Technical Considerations

Ensure that the supplier maintains an inventory of the required size range, from 1/8" to 2", in the designated grades, such as UNS S31803, UNS S32205, or Duplex 2205. It is essential to check that the fittings adhere to the required pressure rating according to the designated pressure class, such as 3,000 psi, 6,000 psi, or 10,000 psi. Request dimensional inspection reports and hardness test data from the supplier.

Evaluating Supplier Credibility

Choose a supplier with proven quality certificates like IBR, PED, or NACE that match your project requirements. A good duplex tube fittings supplier should also conduct in-house testing on their products, such as PMI (Positive Material Identification), hydro testing and dimensional inspection, rather than relying solely on third-party testing facilities. It's also essential that the delivery performance be a key factor, as a request for written confirmation of stock and average lead times helps to prevent any delays which may impact the entire piping installation.

Procurement Strategy

When working with large projects, it's beneficial to purchase everything from one supplier so that you can keep all the fittings the same grade and make it easy to document the traceability. When ordering smaller or urgent quantities, check with the supplier to ensure that they are carrying duplex grades, as they may not always be available. To minimise the chance of material substitution, it is also important to have a material test report and ensure that the heat numbers match the fittings' markings when they are delivered.