Reducing Union & Adapter Manufacturer, Supplier & Exporter
A reducing union joins two tubes of different outside diameters, with a compression end sized for each tube. Adapters join a tube or thread of one size or standard to another — for example NPT to BSP, male to female, or metric tube to imperial tube. Raaj Fittings manufactures and exports reducing unions and adapters in double ferrule and single ferrule designs, in SS 316L, SS 304, duplex, super duplex and nickel alloys.
These fittings solve the size and standard mismatches that occur in every real instrument system — where a 1/2" impulse line meets a 1/4" transmitter connection, where metric and imperial tubing meet on an international project, or where NPT equipment must connect to BSP ports.
All reducing unions and adapters are supplied with EN 10204 3.1 mill test certificates and full material traceability.
We export reducing unions & adapters to instrumentation contractors, OEMs and distributors across the Middle East and GCC, Europe and the Americas, in metric and imperial tube sizes with NPT or BSP ends to suit each market.
Reducing Union & Adapters Specifications
Metric 3–25 mm; imperial 1/8"–1", in any reducing combination
Reducing unions, port connectors, male and female thread adapters, metric-to-imperial adapters
NPT (ASME B1.20.1), BSPT and BSPP (BS 21 / ISO 7-1), in male and female combinations
Double ferrule and single ferrule compression
Double ferrule up to 413 bar (6,000 psi); single ferrule up to 207 bar (3,000 psi), depending on size and material
Precision-machined from bar stock
EN 10204 3.1 mill test certificate; EN 10204 3.2 on request
Materials & Grades
We supply reducing unions & adapters in the following materials and grades. All grades are supplied with EN 10204 3.1 / 3.2 Mill Test Certificates.
Stainless Steel Reducing Unions & Adapters
Stainless steel is the standard material for instrumentation tube fittings across oil and gas, petrochemical, pharmaceutical, and offshore applications. SS 316L is the most widely specified grade.
The industry default for instrumentation tube fittings — low carbon content prevents sensitisation; molybdenum addition provides superior chloride and acid resistance versus 304 grades.
Superior chloride and acid resistance — used where chloride exposure, marine atmosphere, or mild chemical service requires better corrosion resistance than 304.
General corrosion resistance at lower cost than 316L — suitable for water, steam, mild chemical, and food-grade applications where chloride exposure is limited.
Duplex & Super Duplex Stainless Steel Reducing Unions & Adapters
Duplex and super duplex grades provide approximately twice the yield strength of 316L with excellent resistance to chloride stress corrosion cracking — the preferred choice for offshore and subsea instrumentation where standard 316L may be susceptible to SCC.
(UNS S31803 / S32205) Offshore topsides instrumentation, seawater injection, and chemical injection systems
(UNS S32750) Subsea instrumentation, high-chloride offshore service, and FPSOs — PREN ≥ 42
Nickel Alloy Reducing Unions & Adapters
For aggressive chemical, sour gas, and high-temperature service where duplex stainless steel is insufficient — specified in chemical injection, downhole instrumentation, and severe process environments.
(UNS N06625) Outstanding corrosion resistance in offshore, subsea, and chemical service; widely specified for downhole instrumentation and subsea chemical injection tubing
(UNS N10276) Broad-spectrum resistance to aggressive acids, chlorides, and oxidising media; chemical and FGD process sample systems
(UNS N04400) Hydrofluoric acid service, seawater, and marine instrumentation systems
(UNS N08020) Sulfuric acid and aggressive chemical process sample and instrumentation systems
Special Grades & High-Purity Reducing Unions & Adapters
For semiconductor, pharmaceutical, and high-purity gas applications requiring electropolished internal surfaces and ultra-low extractable contamination.
Pharmaceutical and biotech grade — electropolished internal surface for sterile process piping, pure steam, WFI, and clean compressed air systems in GMP-compliant facilities.
Semiconductor grade — ultra-high-purity electropolished finish for process gas delivery, specialty gas distribution, and wet chemistry in semiconductor fabs.
Exceptional corrosion resistance in seawater and oxidising media at low density — used in desalination and marine instrumentation where weight is a factor.
Types of Reducing Fitting and Adapter
- Reducing union — compression ends for two different tube ODs, e.g. 1/2" × 1/4".
- Port connector — joins a tube to a fitting port directly, allowing a reduction without an extra nut and ferrule.
- Thread adapter — male × female or male × male, converting NPT to BSP or changing thread size.
- Metric-to-imperial adapter — joins metric tubing to imperial tubing on mixed-standard projects.
Why Adapters Matter
International projects often combine equipment from the Americas, Europe and Asia, each with its own thread and tube standards. NPT and BSP threads look similar but do not seal against each other, and metric and imperial tubes of similar size are not interchangeable. A purpose-made adapter is the safe way to bridge them, rather than forcing a mismatched joint.
Related Fittings
For same-size tube joints, use a union connector. To connect tube to a threaded port, use a male connector or female connector, which can themselves combine a small tube with a larger thread. Keep to one fitting design throughout so that all ferrules and nuts are matched.
Applications & Industries
- Instrument hook-ups where impulse line and instrument sizes differ
- Mixed metric and imperial tubing systems on international projects
- Connections between NPT and BSP equipment
- Manifolds and analyser systems
- Offshore and petrochemical instrumentation
Adapters are especially useful during plant modifications and equipment replacement, when a new instrument or valve arrives with a different thread or tube size from the one it replaces. Keeping a small stock of common adapters — NPT × BSPP, metric × imperial and standard reducing unions — saves time during shutdowns. We can supply adapter kits in SS 316L to suit your site standards, together with matching unions, connectors and tubing.
When ordering, give the size and type of each end, the fitting design and the material grade — for example 1/2" OD × 1/4" OD reducing union, double ferrule, SS 316L. See all tube fittings.
Testing, Inspection, Marking & Packing
Reducing unions and adapters are produced under our quality assurance process:
- Bar stock verified by PMI testing, with full traceability
- Dimensional inspection of seats, bores and hex sizes
- Thread gauging of every threaded end
- Pressure testing on request
- Marking with material grade and heat code
Supplied with EN 10204 3.1 mill test certificates; EN 10204 3.2 certificates and third-party inspection on request.
Fittings are capped and bagged to keep ports clean, then boxed and packed in seaworthy wooden cases for export; marking, tagging and packing to your specification are available on request.
Why Choose Raaj Fittings for Reducing Unions & Adapters?
Raaj Sagar Steels has supplied piping components since 2003 and today manufactures tube fittings at two plants in India for buyers in the Middle East, Europe and the Americas.
- Manufactured in-house — Reducing unions & adapters are made in our own plants, so material, dimensions and delivery stay under our control.
- Ready stock, short lead times — common sizes and grades are held in stock for prompt dispatch; other sizes, grades and specials are manufactured to order.
- Certified quality — ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certified; PED 2014/68/EU supply available, and NACE MR0175 / ISO 15156 material on request.
- 100% material verification — PMI testing on incoming material and EN 10204 3.1 mill test certificates with every order; 3.2 certificates on request.
- Third-party inspection ready — we regularly work with SGS, Bureau Veritas, TÜV and DNV.
- Export documentation — MTCs, certificates of origin, packing lists and inspection reports to suit projects in the GCC, Europe and the Americas.
- Export packing — seaworthy packing with end and face protection, and packing to your specification on request.
- Fast response — our team replies to enquiries within one business day.
Reducing Unions & Adapters — FAQs
A reducing union is a straight tube fitting with compression ends for two different tube outside diameters.
An adapter connects one size or standard to another — for example NPT to BSP threads, male to female, or metric tube to imperial tube.
Yes, with a metric-to-imperial adapter. Metric and imperial tubes of similar size should never be forced into the wrong fitting.
Not directly, as they have different thread angles and pitches. Use an NPT × BSP adapter.
SS 316L, SS 316, SS 304 / 304L, duplex 2205, super duplex 2507, nickel alloys and electropolished 316L.
Yes. Non-standard adapters, such as unusual thread combinations or special lengths, can be machined to your drawing in the same materials as our standard fittings.
Yes. We supply reducing unions & adapters for projects under the European Pressure Equipment Directive (PED 2014/68/EU), with EN 10204 3.1 certificates as standard and 3.2 on request. NACE MR0175 / ISO 15156 compliant material is available for sour service in the Middle East and the Americas.
