1. Scope of the Standard
This regulatory document establishes a complex set of technical requirements for forged unions intended for installation in piping systems. The specification covers products made of carbon, alloy, high-alloy (stainless) steels, and precision nickel alloys. Products supplied by EV Group China meet strict quality standards and are intended for integration into systems via socket welding or threaded connections.
2. Classification by Nominal Pressure
To ensure reliable operation of systems under high pressure, classes 3000 and 6000 are provided. The nominal performance characteristics of the unions must strictly comply with the parameters regulated in the corresponding standardization tables. Pressure class designations directly correlate with pipe schedules according to ASME B36.10.
Table 1. Union Class Correspondence to Pipe Wall Thickness
| Union Class Designation | Pipe Wall Thickness Standard (Schedule) |
| 3000 | Schedule 80 |
| 6000 | Schedule 160 |
Note: The table above is for reference purposes and does not limit engineering decisions regarding the use of pipes with other wall parameters depending on project design loads.
In cases where the ASME B36.10 standard does not specify Schedule 160 parameters for small diameters (NPS 1/8, 1/4, and 3/8), it is necessary to follow the values presented in the following table:
Table 2. Nominal Pipe Wall Thickness (Schedule 160)
| Nominal Pipe Size (NPS) | Nominal Wall (Schedule 160), inches |
| 1/8 | 0.124 |
| 1/4 | 0.145 |
| 3/8 | 0.158 |
3. Dimensional Characteristics
The geometric parameters of the unions are determined by the nominal pipe size (NPS), which ensures installation versatility and component compatibility within the piping system.
4. Technical Design Description
The assembled union consists of three key elements: the male end, the female end (socket), and the union nut. Table 3 lists industry terminology for these components.
Table 3. Industry Terminology
| Primary Term | Synonyms |
| Male End | External thread, nipple, ball end |
| Female End | Internal thread, body, conical seat |
| Nut | Union nut, coupling ring |
The sealing assembly is designed based on a metal-to-metal (spherical-conical) hermetic mating principle. Threaded parts are manufactured in accordance with ASME B1.20.1 requirements. The external profile of the body parts can be round or hexagonal, ensuring convenient wrench grip during installation in confined spaces.