Where can I find the span requirements for steel pipes lined with plastic?

Use the span applicable to ordinary steel pipes; lining with plastic has no impact on the span.

The span requirements for steel pipes lined with plastic are generally not specified with clear standards in general water supply and drainage design manuals or piping engineering manuals. Since lined pipes are considered composite pipes, the common practices currently in use are as follows: 1. Consult the manufacturer’s product catalogs and technical manuals: Reputable manufacturers generally provide installation instructions for their products, which specify the required spacing between supports. 2. Relevant industry or local standards and specifications: Some regions or industries have specific technical regulations for lined pipes (such as in the chemical and electronics industries), which include the maximum allowable span for installation supports. 3. Make appropriate reductions by referring to standards for similar metal pipes: Due to the relatively low strength of the plastic lining layer and the resulting slightly lower overall rigidity, it is generally recommended to reduce the span by approximately 10%–20% based on the standards for ordinary metal pipes, in order to enhance safety. In summary, the most direct and reliable method is to consult the technical documentation provided by the supplier or manufacturer. If such documentation is not available, a conservative approach can be adopted by applying a slight reduction based on metal pipe standards, or by referring to the corresponding requirements in local industry standards. .