Tube Union Connector Manufacturer, Supplier & Exporter
A union connector (straight union) joins two tubes of the same outside diameter in a straight line, with a compression end on each side. Raaj Fittings manufactures and exports union connectors in double ferrule and single ferrule designs, in SS 316L, SS 304, duplex, super duplex and nickel alloys, for metric tubes from 3 mm to 25 mm OD and imperial tubes from 1/8" to 1" OD.
The union connector is the most commonly used tube fitting. It extends tubing runs, joins pre-bent sections, and allows a section of tubing to be removed for maintenance without disturbing the rest of the line — all without welding or threading the tube.
All union connectors are supplied with EN 10204 3.1 mill test certificates and full material traceability.
We export union connectors 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.
Union Connector Specifications
Metric 3–25 mm; imperial 1/8"–1" (same OD both ends)
Double ferrule and single ferrule compression; DIN 2353 bite type on request
Double ferrule up to 413 bar (6,000 psi); single ferrule up to 207 bar (3,000 psi), depending on tube OD, wall and material
Body with two compression ends, two nuts and ferrule sets
Double ferrule dimensionally compatible with Swagelok®; single ferrule with Parker® A-LOK®
Precision-machined from bar stock
EN 10204 3.1 mill test certificate; EN 10204 3.2 on request
Materials & Grades
We supply union connectors in the following materials and grades. All grades are supplied with EN 10204 3.1 / 3.2 Mill Test Certificates.
Stainless Steel Union Connectors
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 Union Connectors
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 Union Connectors
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 Union Connectors
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.
Using Union Connectors
Each end of the union connector takes a tube, a ferrule set and a nut. Tightening the nuts makes two independent compression joints, so either tube can later be released and remade. The body has a hex flat to hold it steady while the nuts are tightened.
- Extend tube runs — join standard tube lengths into longer runs.
- Join pre-bent sections — connect shop-bent tubing on site.
- Maintenance breaks — remove an instrument or section without cutting tube.
- Repairs — replace a damaged section with a short tube and two unions.
Related Configurations
To join two different tube sizes, use a reducing union. To change direction, use a union elbow, and to pass through a panel wall, a bulkhead union. To connect tubing to a threaded port, use a male connector or female connector.
Good Installation Practice
Cut the tube square and deburr it, insert it fully until it bottoms in the fitting, and tighten the nut by the number of turns specified for the fitting design. Use tubing of a suitable hardness and wall thickness for the pressure, and avoid mixing ferrules, nuts or bodies from different manufacturers within one joint.
Applications & Industries
- Instrument impulse lines in oil, gas and petrochemical plants
- Sample and analyser systems
- Chemical injection and hydraulic control tubing offshore
- Gas panels and calibration systems
- Pharmaceutical and food process instrumentation
Tube selection matters as much as the fitting. For stainless steel compression fittings, use fully annealed seamless or welded-and-drawn tubing of suitable hardness, with a wall thickness chosen for the working pressure. Tubing that is too hard, too thin or scratched on the outside can stop the ferrules from sealing. Union connectors are usually ordered in quantity alongside elbows, tees and connectors, and can be supplied cleaned and bagged for oxygen or high-purity service.
When ordering, give the tube OD, the fitting design (double or single ferrule) and the material grade. See all tube fittings we manufacture.
Testing, Inspection, Marking & Packing
Union connectors are produced under our quality assurance process:
- Bar stock verified by PMI testing, with full traceability
- Dimensional inspection of seats, bores, threads and hex sizes
- 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 Union Connectors?
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 — Union connectors 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.
Union Connectors — FAQs
It is a straight tube fitting with a compression end on each side, used to join two tubes of the same outside diameter.
A union joins two tubes of the same OD; a reducing union joins two tubes of different ODs.
Yes. Each compression joint can be disconnected and remade, which makes unions useful for maintenance breaks.
Double ferrule and single ferrule compression designs, and DIN 2353 bite type on request.
Metric tube ODs from 3 mm to 25 mm and imperial ODs from 1/8" to 1".
Follow the turns-from-finger-tight given for the fitting design and size, and use a gap inspection gauge where available. Over- or under-tightening can prevent the ferrules from sealing.
Yes. We supply union connectors 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.
