Manufacturer, Supplier & Exporter of UNS S31803 Spool

UNS S31803 Spool refers to prefabricated piping spool assemblies made from Duplex Stainless Steel Grade S31803, a highly versatile duplex alloy known for its excellent balance of strength and corrosion resistance. A spool is typically a combination of pipes, elbows, tees, reducers, flanges, and other fittings welded together according to engineering drawings for easy installation at project sites. Duplex UNS S31803 contains a mixed microstructure of austenite and ferrite, giving it exceptional mechanical strength and making it suitable for demanding applications involving high pressure and aggressive environments. These spools are widely used across the oil & gas, petrochemical, power generation, desalination, and marine industries where long-term reliability and corrosion resistance are crucial...

UNS S31803 is known for its high chromium (~22%), molybdenum (~3%), and nitrogen-enriched composition, providing excellent resistance to pitting, crevice corrosion, and chloride-induced stress corrosion cracking. Compared to standard stainless steels like 304 and 316, S31803 offers almost double the yield strength, allowing thinner pipe walls without compromising structural integrity. This makes S31803 spools lighter, stronger, and more cost-effective for severe service applications. The material also demonstrates good fatigue resistance, high toughness, and excellent performance in seawater-based or chemical-rich environments, making it ideal for offshore platforms, desalination units, and chemical processing plants.

UNS S31803 spools are fabricated using precision welding techniques such as GTAW/TIG, SMAW, and orbital welding to ensure the duplex phase balance is maintained throughout the welding process. Riddhi Siddhi Impex works with advanced fabrication facilities capable of producing fully customized spools according to project drawings, P&ID diagrams, and isometric plans. These spools can include flanges, bends, reducers, tees, branch outlets, and special fittings based on client specifications. Each spool undergoes dimensional inspection, hydrotesting, and NDT testing to ensure image-perfect assembly and leak-free performance once installed on site..

Riddhi Siddhi Impex is one of India’s prominent suppliers, exporters, and stockists of Duplex Stainless Steel UNS S31803 Spool assemblies. With years of experience in supplying duplex and super duplex materials, the company has established itself as a reliable partner for EPC contractors, process industries, offshore developers, and pipeline installation firms. Riddhi Siddhi Impex ensures that each UNS S31803 spool complies with international standards such as ASME, ASTM, EN, and API. Their product range includes pipe spools, fabricated spools, welded assemblies, duplex fittings, and custom pipeline modules designed specifically for industrial applications...

To guarantee long-term reliability, UNS S31803 spools from Riddhi Siddhi Impex undergo multiple quality checks including radiography testing (RT), ultrasonic testing (UT), dye penetrant testing (DPT), magnetic particle testing (MPI), and hydrostatic pressure testing. Material Test Certificates (MTC) as per EN 10204 3.1 or 3.2 are provided along with complete documentation covering raw material traceability, weld maps, and project-specific inspection reports. This rigorous quality protocol ensures that each spool meets mechanical, chemical, and corrosion-resistance requirements before being dispatched to clients..

UNS S31803 Spool – Specification, Composition, Properties & Grades

Specification

Product Name	UNS S31803 Spool
Manufacturer & Supplier	Riddhi Siddhi Impex
Material Grade	Duplex Stainless Steel UNS S31803 / ASTM A182 F51
Forms	Pipe Spool, Fabricated Spool, Welded Spool, Custom Spools
Size Range	1/2” NB to 24” NB (Custom on request)
Type	Seamless, Welded, Fabricated
End Connections	Flanged, Beveled End, Plain End, Threaded
Standards	ASTM, ASME, EN, DIN, ISO
Applications	Oil & Gas, Petrochemical, Marine, Desalination, Chemical Plants

Chemical Composition (UNS S31803)

Element	Content (%)
Chromium (Cr)	21.0 – 23.0
Nickel (Ni)	4.5 – 6.5
Molybdenum (Mo)	2.5 – 3.5
Carbon (C)	0.03 Max
Manganese (Mn)	2.0 Max
Silicon (Si)	1.0 Max
Nitrogen (N)	0.14 – 0.20
Phosphorus (P)	0.03 Max
Sulfur (S)	0.02 Max

Mechanical Properties

Property	Value
Tensile Strength	≥ 620 MPa
Yield Strength	≥ 450 MPa
Elongation	≥ 25%
Hardness	≤ 290 HB
Impact Toughness	High, even at low temperatures

Dimension Chart (Nominal)

Nominal Pipe Size (NB)	Outside Diameter (mm)	Wall Thickness (mm)	Spool Length
1/2"	21.3	2.77	Custom
1"	33.4	3.38	Custom
2"	60.3	3.91	Custom
4"	114.3	6.02	Custom
6"	168.3	7.11	Custom
10"	273.1	9.27	Custom
16"	406.4	12.70	Custom

Equivalent Grades

Standard	Grade
UNS	S31803
ASTM	A182 F51
EN	1.4462
DIN	X2CrNiMoN22-5-3
Other	Duplex 2205

Equivalent Standards

Standard	Description
ASTM A182	Forged or Rolled Alloy Steel Pipe Flanges & Parts
ASTM A790	Seamless & Welded Duplex Stainless Steel Pipes
ASME SA-182	Flanges and Forged Fittings
EN 10272	Stainless Steel Bars for Pressure Purposes

Other Types of Spools

Type	Description
Super Duplex Spool	For extreme corrosion & high-pressure systems
Stainless Steel 316L Spool	For general industrial applications
Carbon Steel Spool	For low-pressure or structural piping
Nickel Alloy Spool	For highly corrosive chemical environments

As one of the well-recognized UNS S31803 Spool Domestic Suppliers, Riddhi Siddhi Impex supplies duplex spools across major Indian industrial hubs such as Mumbai, Delhi, Bengaluru, Hyderabad, Chennai, Kolkata, Pune, Ahmedabad, Surat, Vadodara, Rajkot, Nagpur, Indore, Bhopal, Jaipur, Kanpur, Lucknow, Agra, Varanasi, Amritsar, Chandigarh, Mysuru, Udaipur, Jodhpur, Visakhapatnam, Coimbatore, Madurai, Kochi, Thiruvananthapuram, Mangalore, Nashik, Kolhapur, Chandrapur, Akola, and many others. Their strong domestic logistics network ensures timely delivery to industrial zones like Dahej, Ankleshwar, Narmada, Navsari, Valsad, Somnath, Vilayat, and Rajpipla, making them preferred partners for refinery turnaround projects, pipeline expansions, and new plant installations..

Frequently Asked Questions (FAQs)

Q1: What are the applications of UNS S31803 Spool?

A1: It is widely used in oil & gas pipelines, desalination plants, chemical processing, offshore platforms, and high-pressure systems.

Q2: Do you offer customized spools?

A2: Yes, we manufacture fully customized UNS S31803 spools according to drawings, isometrics, and project specifications.

Q3: Is UNS S31803 suitable for seawater environments?

A3: Yes, UNS S31803 offers excellent resistance to seawater corrosion, pitting, and stress-corrosion cracking.

Q4: Do you supply spools across India?

A4: Yes, Riddhi Siddhi Impex supplies UNS S31803 Spools in Mumbai, Delhi, Bengaluru, Hyderabad, Chennai, Pune, Ahmedabad, Surat, Vadodara, and all major industrial cities.