The pressure ratings of China black pipe union fittings can vary depending on factors such as the material, design, size, and intended application of the fitting. However, typical pressure ratings for China black pipe union fittings are often standardized to meet industry standards and specifications.

Here are some general guidelines:

1. Material: China black pipe union fittings are typically made from malleable iron, which is known for its strength and durability. Malleable iron fittings are commonly used in plumbing, HVAC, and industrial applications due to their resistance to corrosion and high pressure.

2. Design: China black pipe union fittings are designed to provide a leak-proof and detachable connection between two pipes or fittings. They consist of three main components: a male end, a female end, china black pipe union fitting   and a central nut or ring that allows for easy assembly and disassembly without the need for tools.

3. Size: China black pipe union fittings are available in various sizes to accommodate different pipe diameters and applications. Common sizes range from 1/4 inch to 4 inches, with larger sizes available for specialized applications.

4. Pressure Ratings: The pressure ratings of China black pipe union fittings are typically expressed in pounds per square inch (psi) or bars and indicate the maximum allowable pressure at which the fitting can safely operate. Pressure ratings may vary depending on factors such as temperature, pipe material, and application.

   • For standard-duty applications, China black pipe union fittings may have pressure ratings ranging from 150 psi to 300 psi, depending on the size and design of the fitting.

   • For heavy-duty or high-pressure applications, China black pipe union fittings may have higher pressure ratings, ranging from 300 psi to 2,000 psi or more, depending on the size and design of the fitting.

It's important to consult the manufacturer's specifications and product documentation for precise information on the pressure ratings of specific China black pipe union fittings. Additionally, consider factors such as temperature, fluid compatibility, and system design requirements when selecting fittings to ensure they meet the performance and safety requirements of your application.