Pipe Union

Manufactured to ASME B16.11 (Forged Fittings, Socket-Welding and Threaded). Full material traceability, EN 10204 3.1 certificates, and third-party inspection available.

Design Standard	ASME B16.11
Size Range	NPS 1/8″ – 4″
End Connection	Threaded (NPT/BSPT) / Socket Weld
Materials	ASTM A105, A182 F304/F316, A350 LF2
Pressure Class	Class 2000 / 3000 / 6000
Seat Type	Flat / Metal-to-Metal, optional soft seat
Temp Range	A105: -29°C to 425°C / F304-F316: up to 600°C (A350 LF2: -46°C)
MOQ	1 Piece
Lead Time	7 – 15 Days (Stock) / 15 – 30 Days (Custom)

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Product Description

Provides a quick-connect, easily disassembled joint for pipe systems. Ideal for maintenance access where the line must be opened frequently.

Available in standard sizes with custom options per drawing. Each item is 100% inspected and supplied with material certificates.

Applications

Pipe unions create a demountable threaded or socket-welded joint that can be assembled and disassembled repeatedly without disturbing adjacent piping. They are essential on instrument manifolds, filter housings, pump seal oil lines, equipment skids, and any small-bore system requiring routine maintenance access. Forged to ASME B16.11, they are rated Class 2000, 3000, and 6000 for high-pressure service.

Typical applications include pressure gauge connections, strainer and filter changes on cooling water lines, sample cooler isolation, boiler blowdown valve connections, and hydraulic control manifolds. In chemical plants, unions allow removal of control valves and transmitters without cutting pipe. Carbon steel A105 handles -29°C to 425°C; A350 LF2 extends to -46°C for cryogenic service.

Stainless F304/F316 unions serve corrosive chemical injection lines, food and beverage product transfer, and pharmaceutical CIP systems. Available in threaded NPT/BSPT or socket weld end configurations, with flat or metal-to-metal seats and optional soft seats for enhanced sealing.

Quality Assurance & Certification

Each union is forged from certified bar stock and machined to ASME B16.11 dimensional tolerances, with threads gauged per ASME B1.20.1. The seating surfaces are precision-machined for leak-tight assembly. We supply EN 10204 3.1 material certificates with heat chemistry and mechanical property data. Hardness reports confirm suitability for sour service where required.

NDT options include magnetic particle inspection on carbon steel body components and liquid penetrant testing on stainless parts. Pressure shell integrity is verified by hydrostatic testing on sample lots per ASME B16.11 requirements. Third-party inspection by SGS, BV, or TUV is available for export orders.

Unions are disassembled for packing and coated with rust inhibitor on carbon steel units. Threads are protected with plastic caps. They are packed in cartons or wooden cases for export, with each union labeled by size, class, end type, material grade, and heat number. Replacement seats and gaskets can be supplied separately.

ASME Standard Data

ASME B16.11 covers factory-made wrought threaded and socket-welding forged fittings. The table below lists fitting types, class designations and NPS size ranges transcribed from ASME B16.11 Table 7.

1. Fitting Types, Class Designations and NPS Size Ranges (ASME B16.11, Table 7)

Description	SW Class 3000	SW Class 6000	SW Class 9000	Threaded Class 2000	Threaded Class 3000	Threaded Class 6000
45-deg / 90-deg elbows, tees, crosses, couplings, half-couplings, caps, bosses, couplets	1/8–4	1/8–2	1/2–2	1/8–4	1/8–4	1/8–4
Street elbows	…	…	…	…	1/8–2	1/8–2
Square, hex, round plug; hex and flush bushing	…	…	…	1/8–4 ⁽¹⁾	1/8–4 ⁽¹⁾	1/8–4 ⁽¹⁾

Source: ASME B16.11-2016, Table 7 (Types of Fittings by Class Designation and NPS Size Range). "…" denotes not applicable in the standard. NOTE (1): Plugs and bushings are not identified by class designation; they may be used for ratings up to Class 6000.

2. Standard coverage note — Union

ASME B16.11 does not cover union fittings; union dimensions reference MSS SP-83.

Source: ASME B16.11 coverage review — no "union" entry exists anywhere in B16.11 (scope para. 1.1 and Table 7 list only elbows / tees / crosses / couplings / half-couplings / caps / bosses / couplets / street elbows / plugs / bushings). Union (由壬 / 活接头) dimensional and rating data are governed by MSS SP-83, not transcribed in this corpus pending verification.

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