UNION

Overview of Pipe Union

A Pipe Union​ is a precision-engineered piping component designed to create a detachable connection​ between two pipe sections, enabling easy maintenance, inspection, and system modifications without cutting or permanent alterations . Unlike welded or threaded joints, unions feature a three-part design (nut, female end, and male end) that allows for quick assembly and disassembly while maintaining a leak-proof seal under pressure . Manufactured from materials such as stainless steel, brass, carbon steel, and PVC, unions withstand temperatures from -20°C to 150°C and pressure ratings up to 3000 PSI, depending on the material and design standards (e.g., ASME B16.39) . Their versatility makes them critical in industrial plumbing, chemical processing, oil and gas pipelines, and water supply systems where frequent disassembly is required .

With a service life exceeding decades under proper conditions, unions provide a reliable alternative to permanent fittings by combining robust sealing with operational flexibility . Their standardized dimensions (e.g., NPT, BSPP threads) ensure compatibility with global piping systems, while designs like ground joint, flange, and hydraulic unions cater to specific pressure and media requirements .

Key Features of Pipe Union​

1. Detachable Design for Maintenance Efficiency​
   Unions feature a nut-based locking mechanism​ that allows repeated assembly and disassembly without damaging pipes or seals . This eliminates the need for welding or threading during repairs, reducing downtime in industrial systems .
   Example: A loose nut can be tightened or loosened with standard tools, enabling swift component replacement .
2. Leak-Proof Sealing Under Pressure​
   Precision-machined seating surfaces (e.g., conical, flat-faced) with gaskets or metal-to-metal contact ensure bubble-tight seals​ up to 3000 PSI . Materials like EPDM or PTFE gaskets add chemical resistance for aggressive media .
   Application: Hydraulic systems use unions with O-rings to prevent fluid leakage under dynamic pressure .
3. Material Versatility for Diverse Environments​
   Available in stainless steel (304/316)​ for corrosion resistance, brass​ for water applications, and PVC​ for chemical compatibility, unions adapt to various media including steam, oils, and acids . Special coatings (e.g., zinc plating) enhance durability in outdoor or marine settings .
4. Pressure and Temperature Resilience​
   Unions maintain integrity across extreme conditions:
   • Temperature Range: -20°C to 150°C (standard); up to 300°C for high-temperature alloys .
   • Pressure Ratings: 150 PSI to 3000 PSI, depending on size and material .
     Standard Compliance: ASME B16.39, ISO 4144, and DIN standards ensure safety .
5. Easy Installation with Standard Tools​
   Lightweight and compact, unions require only wrenches for assembly, avoiding specialized equipment . Their uniform thread patterns (NPT, BSP) prevent cross-threading errors .
   Benefit: Reduces installation time by up to 50% compared to welded joints .
6. Alignment Tolerance for Misalignment Compensation​
   Flexible designs (e.g., swing unions) accommodate angular deviation or vibration, preventing stress accumulation in pipelines . Ideal for pumps, compressors, and rotating equipment .

Typical Applications of Pipe Union​

• Industrial Maintenance: Enable quick disassembly for pump, valve, or instrument servicing in chemical plants .
• Hydraulic Systems: Provide leak-free connections in high-pressure fluid power applications .
• Water Treatment: Facilitate filter or pump replacement in municipal water plants with brass or stainless unions .
• HVAC and Refrigeration: Copper unions allow easy compressor or coil maintenance without brazing .
• Oil and Gas Pipelines: Flanged unions withstand high pressure in upstream and midstream operations .

Technical Specifications​

Table: Standard Pipe Union Specifications

SIZE	Number	D1	D2	D3	L1	L2
DN15	YL15	20.3	26.3	54	47	16.5
DN20	YL20	25.3	31.9	63	59	19
DN25	YL25	32.35	39.95	73.5	67	22.5
DN32	YL32	40.4	49.8	84.5	76	26.5
DN40	YL40	50.45	60.25	98	80	31.5
DN50	YL50	63.5	75.9	119	94	38
DN65	YL65	75.5	88.91	150	120	44
DN80	YL80	90.55	105.15	169	152	51.5
DN100	YL100	110.6	127.39	190	175	61.5

Frequently Asked Questions (FAQs)​

Q1: How does a union differ from a coupling?​

Unions are detachable​ via a nut mechanism, while couplings are permanent (threaded/welded). Unions suit frequent maintenance, couplings for fixed connections .

Q2: Can unions handle abrasive or corrosive fluids?​

Yes, materials like 316 stainless steel or PTFE-lined unions resist corrosion/abrasion. Specify gasket compatibility (e.g., Viton for chemicals) .

Q3: What is the lead time for custom unions?​

Samples: 1–2 weeks; bulk orders: 3–4 weeks. Customization includes size, material, and pressure ratings .

Q4: How to ensure a leak-proof union connection?​

Use thread sealant (e.g., Teflon tape) on threads, tighten the nut evenly, and avoid over-torquing to prevent gasket damage .

Q5: Are unions reusable?​

Yes, if undamaged. Inspect threads and sealing surfaces before reuse; replace worn gaskets/O-rings .