The 2015 International Mechanical Code (IMC), Chapter 3 – General Regulations lays out the baseline requirements for all piping systems, including hydronic, refrigerant, condensate, fuel oil. The Chapter, and more specifically Sections 301 and 305, covers how the pipe manufacturer must identify the pipe (e.g. this is the label we use in our QA efforts to ensure we are using the correct pipe), the materials that may be used to support pipe runs, the structural attachment(s) allowed, and more specifically it includes the maximum spans that piping can run without a proper support.
301.3 Identification. Each length of pipe and tubing and each pipe fitting utilized in a mechanical system shall bear the identification of the manufacturer.
The manufacturer is given the option of determining the type of marking for the material. If there is no applicable standard or the applicable standard does not require that a material be identified, identification of the manufacturer is still required by the code. Where the code indicates compliance with an approved standard, the manufacturer must comply with the requirements for marking in accordance with the applicable standard.
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305.1 General. Mechanical system piping shall be supported in accordance with this section.
Piping systems, including hydronic, refrigerant, condensate and fuel oil, must be supported as required by this section.
305.2 Materials. Pipe hangers and supports shall have sufficient strength to withstand all anticipated static and specified dynamic loading conditions associated with the intended use. Pipe hangers and supports that are in direct contact with piping shall be of approved materials that are compatible with the piping and that will not promote galvanic action.
As with all piping systems, the support of the system is as important as any other part of the overall design. Proper supports are necessary to maintain piping alignment and slope, to support the weight of the pipe and its contents, to control movement and to resist dynamic loads such as thrust. Inadequate support can cause piping to fail under its own weight, resulting in fire, explosion or property damage. Building design must take into consideration the structural loads created by the support of piping systems. Hangers or supports must not react with or be detrimental to the pipe they support. Hangers or supports for metallic pipe must be of a material that is compatible with the pipe to prevent any corrosive action. For example, copper, copper-clad or specially coated hangers are required if the piping system is constructed of copper tubing. Hangers and supports are typically constructed of noncombustible materials to prevent premature failure in a fire.
305.3 Structural attachment. Hangers and anchors shall be attached to the building construction in an approved manner.
A support or hanger can be no stronger than its attachment; therefore, the proper fasteners must be used and installed with the necessary workmanship. Supports for piping systems must also be attached to building construction so that they do not adversely affect the structural integrity of the building.
305.4 Interval of support. Piping shall be supported at distances not exceeding the spacing specified in Table 305.4, or in accordance with ANSI/MSS SP-58.
The Manufacturers Standardization Society of the Valve & Fittings Industry, Inc.’s (MSS) Pipe Hangers and Supports Standard SP-58 may be used to determine hanger spacing as an alternative to Table 305.4. The MSS standard recognizes the different support needs of piping relative to pipe diameter and specifies a greater interval between supports as the pipe increases in diameter. As the pipe diameter is increased, the material has a greater inherent (beam) strength (see Commentary Figure 305.4).
The support spacing listed in the table is intended to reduce sag and stress in the piping system. The maximum amount of sag occurs at a point halfway between supports and will increase over time if not properly supported. The mid-story guides required by Note c are necessary to prevent excess lateral motion in vertical installations of plastic pipe and tubing. Such lateral motion can result in damage to the pipe and joints.
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