Foreword: ASME B31.1 support spacing table 121.5, tells us that the distance between pipe supports is roughly pipe diameter + 10. In other words, the distance between supports on a 1 inch pipeline would be 1 inch + 10 (3350mm), while on a 6 inch pipeline, for example, the distance would be 6 inches + 10 (4500mm).
There are of course exceptions, for example, pipe supports should be placed as close as possible to concentrated weights such as valves, flanges, vertical risers, etc. From a stress perspective, the best possible location for support is directly on the equipment.
Maximum span between Pipe Supports
The locations of piping supports are dependent upon four factors.. pipe size, piping configuration, locations of valves and fittings, and the structure available for support. Individual piping materials have independent considerations for span and placement of supports.
Pipe size relates to the maximum allowable span between pipe supports. Span is a function of the weight that the supports must carry. As pipe size increases, the weight of the pipe also increases. The amount of fluid which the pipe can carry increases as well, thereby increasing the weight per unit length of pipe.
| NPS | Water Service |
Steam, Gas, Air Service |
| 1 | 2.1 M | 2.7 M |
| 2 | 3.0 M | 4.0 M |
| 3 | 3.7 M | 4.6 M |
| 4 | 4.3 M | 5.2 M |
| 6 | 5.2 M | 6.4 M |
| 8 | 5.8 M | 7.3 M |
| 12 | 7.0 M | 9.1 M |
| 16 | 8.2 M | 10.7 M |
| 20 | 9.1 M | 11.9 M |
| 24 | 9.8 M | 12.8 M |
Suggested maximum spacing between pipe supports for horizontal straight runs of standard and heavier pipe at maximum operating temperature of 750°F (400°C)
The spacing is based on a fixed beam support with a bending stress not exceeding 2,300 psi (15.86 MPa) and insulated pipe filled with water or the equivalent weight of steel pipe for steam, gas, or air service, and the pitch of the line is such that a sag of 0.1 in. (2.5 mm) between supports is permissible.
Does not apply where span calculations are made or where there are concentrated loads between supports, such as flanges, Valves, specialties, etc.
The configuration of the piping system affects the location of pipe supports. Where practical, a support should be located adjacent to directional changes of piping. Otherwise, common practice is to design the length of piping between supports equal to, or less than, 75% of the maximum span length where changes in direction occur between supports. Refer to the appropriate piping material chapters for maximum span lengths.
Valves require independent support, as well as meters and other miscellaneous fittings. These items contribute concentrated loads to the piping system. Independent supports are provided at each side of the concentrated load.
Location, as well as selection, of pipe supports is dependent upon the available structure to which the support may be attached. The mounting point shall be able to accommodate the load from the support. Supports are not located where they will interfere with other design considerations. Some piping materials require that they are not supported in areas that will expose the piping material to excessive ambient temperatures. Also, piping is not rigidly anchored to surfaces that transmit vibrations. In this case, pipe supports isolate the piping system from vibration that could compromise the structural integrity of the system.
Spacing is a function of the size of the pipe, the fluid conveyed by piping system, the temperature of the fluid and the ambient temperature of the surrounding area. Determination of maximum allowable spacing, or span between supports, is based on the maximum amount that the pipeline may deflect due to load. Typically, a deflection of 2.5 mm is allowed, provided that the maximum pipe stress is limited to 1,500 psi or allowable design stress divided by a safety factor of 415, whichever is less. Some piping system manufacturers and support system manufacturers have information for their products that present recommended spans in tables or charts. These data are typically empirical and are based upon field experience.
Remark(s) of the Author...
Pipe Span Charts
Pipe Span Charts are very nice, but not more than a guide. I've seen several tables and charts, all with different values. You should consider the material used, wall thickness, density of the medium, isolation, etc. For really good assessment of working stresses and deflections, pipe stress calculations are needed. Also, the engineer must be determine what kind of support he wants to use. Should there be limits to the movements, or even a fixed point etc. Supporting is a profession.
The .pdf articles below tells you why supporting is a profession.
