NOTE Hangers and supports support the deadweight, thermal, and seismic loads of piping and equipment and transfer those loads into the building structure through a verified load path. (1.2)

NOTE A support that is correctly load-rated but attached to an unverified structural element has not solved the problem — it has only moved the unknown one connection up. The governing question for every assembly is not "will the hanger hold the pipe?" but "will the complete chain from pipe to building steel hold the rated load under deadweight, thermal travel, and the design seismic event?" This Standard therefore treats the pipe attachment, the rod or member, and the structural attachment as one engineered assembly that must be designed and verified together. (1.3)

NOTE The hanger is the most-installed and least-inspected component in a mechanical system. A 250-foot chilled-water main may carry several hundred individual supports; a single under-rated beam clamp or a rigid hanger on a thermally active line is invisible until the pipe sags, the fitting cracks, or the AHJ red-tags the seismic bracing. Getting the spacing table, the rod size, the spring selection, and the seismic exemption check right at specification time is far cheaper than chasing field failures. (1.4)

NOTE Vibration isolation and seismic resilience mounts for rotating or reciprocating equipment — spring isolators, neoprene pads, inertia bases, and seismic snubbers — are specified in Vibration Isolation And Seismic Restraint, not here. (1.5.1)

NOTE Fire sprinkler piping hangers and seismic sway bracing are governed exclusively by NFPA 13 and belong to the fire protection discipline. (1.5.2)

NOTE Where a single trapeze, strut, or structural attachment supports both mechanical piping and fire sprinkler piping, that shared member is a coordinated assembly: see the Seismic Restraint section for the governing rule. (1.5.4)

NOTE HVAC ductwork supports are specified in Hvac Ductwork; pipe insulation and the thermal design of insulation protection saddles are specified in Mechanical Insulation (this Standard specifies only the support-side shield and saddle hardware at hanger points). (1.5.5)

NOTE MSS SP-58 is the primary governing document; the 2025 edition is current and supersedes the 2018 edition. (2.3)

NOTE The 2025 edition matters for high-temperature work specifically: it revised the allowable stresses for metal framing channel and updated the temperature limits for hot-dip galvanized components. Specifications written against the 2018 edition for steam or high-temperature condensate service may carry obsolete galvanizing temperature assumptions; verify against SP-58-2025. (2.4)

NOTE MSS SP-69 was partially absorbed into SP-58 beginning with the 2009 edition but remains an active document and is still cited for hanger-type selection by service condition. MSS SP-127 is the companion specifically for seismic, wind, and dynamic bracing design. (2.5)

NOTE Nonstructural seismic design follows ASCE 7-22 Chapter 13, which IBC 2024 adopts by reference. ASCE 7-22 introduced a revised component force (Fp) formula replacing the ASCE 7-16 equation; any seismic parameter cited in project documents shall reference ASCE 7-22, not the superseded ASCE 7-16. (2.6)

NOTE Hanger and support components shall be the product of a manufacturer regularly engaged in their production and shall be marked or otherwise identifiable to their MSS SP-58 type and load rating. (4.1)

NOTE A note on delegated design (4.2)

NOTE Seismic bracing and complex spring-support layouts are commonly delegated to the Contractor's engineer; delegation transfers the calculation, not the responsibility for a coordinated result. (4.2.1)

NOTE The Engineer of Record retains responsibility for defining the design basis — Seismic Design Category, component importance factor, and the systems requiring bracing — while the delegated engineer is responsible for the means that satisfy that basis. Specifying "support as indicated" without a design basis or a required submittal is the most common way uncontrolled, uncalculated supports reach the field. (4.2.2)

NOTE Material and finish selection shall account for the installed environment, because corrosion of a structural attachment is a load-path failure, not a cosmetic defect. (5.1)

NOTE Galvanized components carry a temperature ceiling that plain steel does not. Hot-dip galvanizing can delaminate or embrittle under sustained elevated temperature; the controlling limit is defined in MSS SP-58-2025. Standard carbon-steel hangers are rated to 750 °F per MSS SP-58. (5.2)

NOTE Hanger type shall be selected from MSS SP-58/SP-69 by pipe material, service temperature, pipe size, and the movement the support must accommodate. The type number is not a style preference; it encodes the load mechanism, the temperature suitability, and whether the support permits or restrains pipe movement. (6.1)

NOTE A clevis hanger that swings freely accommodates the small axial drift of a nominally stationary line but does nothing for a pipe that grows half an inch when it heats; that pipe needs a guide, a spring, or both. Matching the type to the movement is the difference between a support and a future failure. (6.2)

NOTE Omitting protection shields on insulated lines is one of the most common and most damaging specification errors. Without a shield, the hanger crushes the insulation at every support, creating a thermal bridge and a cold spot where moisture condenses; on chilled-water and refrigerant lines this drips, corrodes, and eventually rots the insulation along the entire run. The shield is not optional hardware — it is part of the support. (6.4)

NOTE Hanger rod is sized to the rated load with a generous safety factor; the default rod diameters below follow MSS SP-58 Table 1 and ASME B31.9 and represent the 80% case for single-rod hangers on water-filled metallic pipe. (7.1)

NOTE Support spacing depends on pipe material, diameter, and the weight of the fluid, and each material/fluid combination has its own span table. Applying a steel-pipe span to plastic pipe, or a gas-filled span to a water-filled line, is a direct route to sag, pooling, and overstressed fittings. (8.1)

NOTE The most common spacing error is borrowing a single table. Steel pipe carrying water spans far more than the same steel pipe carrying steam-weight gas would suggest is conservative, while CPVC spans a fraction of steel and loses span as it warms. Select the span from the table that matches both the material and the contents. (8.2)

NOTE The structural attachment is where the load enters the building, and it is the connection most often left to field judgment. Every attachment method has a correct application and a way to be wrong: a beam clamp on a flange too thick to grip, a wedge anchor in a seismic zone that the AHJ will reject, a powder-actuated pin into the bottom of a hollow deck flute. The attachment shall be selected for the actual structural element and the actual load, not for installer convenience. (9.1)

NOTE On seismic ductility (9.2)

NOTE In Seismic Design Category C and above, authorities having jurisdiction routinely reject standard expansion (wedge) anchors used for piping and equipment restraint unless the anchor is qualified for cracked-concrete seismic service and designed per ACI 318-19 Chapter 17. Specifying "expansion anchor" without that qualification invites a field rejection and rework. (9.2.1)

NOTE A pipe that changes temperature changes length, and that movement has to go somewhere. Left uncontrolled, thermal growth concentrates at the weakest fitting and eventually fails it. Anchors and guides control where the movement goes: an anchor fixes a point so the pipe grows away from it in a known direction, and a guide lets the pipe slide axially through it while restraining it laterally so it does not buckle or whip. Together they convert uncontrolled growth into a designed expansion pattern. (10.1)

NOTE Anchor and guide layout is engineering, not field discretion. The locations follow from a thermal expansion analysis of the run — the operating temperature range, the coefficient of expansion, the anchor-to-anchor lengths, and the expansion device or loop that absorbs the growth. Delegating the layout to the installer without that analysis produces pipe that moves in unintended directions and fittings that crack. (10.2)

NOTE When a pipe moves vertically as it heats, a rigid hanger cannot follow it. At the cold position the rigid hanger may be overloaded; at the hot position the pipe lifts off it and sags between supports, throwing its weight onto adjacent hangers and fittings. A spring support follows the vertical travel while continuing to carry the load, which is why thermally active piping needs springs, not rods. (11.1)

NOTE There are two kinds of spring support, and the difference is the load they deliver through the travel. A variable-spring hanger uses a coil spring, so the supporting force changes as the spring compresses and extends — acceptable when the load change across the travel is small. A constant-effort support uses a linkage that delivers a nearly constant force over its entire travel — required where the displacement is large or where even a modest load change would overstress the pipe, as on high-temperature mains and at connections to sensitive equipment. (11.2)

NOTE Spring supports left with their travel stops in place are a classic commissioning failure: the stop turns a spring into a rigid hanger, defeating the entire reason it was specified. Stop removal is a verifiable closeout item, which is why this Standard requires it to be recorded per support. See Commissioning for system turnover verification. (11.3)

NOTE In moderate and high seismic regions, piping and equipment must be braced so they do not swing, fall, or tear loose during an earthquake and become a hazard or a continuity-of-operation failure. The governing requirements are in ASCE 7-22 Chapter 13, adopted by IBC 2024; Section 13.6 addresses mechanical and electrical components specifically. The bracing system that resists this lateral load is engineered and is distinct from the deadweight hangers above. (12.1)

NOTE ASCE 7-22 provides a meaningful exemption, and applying it correctly avoids bracing piping that does not need it. Under Section 13.1.4, a component is exempt from seismic design where it weighs no more than 400 lb and its center of mass is no more than 4 ft above the floor (with the further trade-size and distribution-system allowances in that section). The exemption is checked against the as-built condition, not assumed. (12.2)

NOTE The shared-member rule (12.3)

NOTE NFPA 13 fire sprinkler hangers and sway braces are governed solely by NFPA 13; nothing in this Standard modifies those requirements except to require coordination on shared structures. (12.3.3)

NOTE Floor- and structure-mounted mechanical equipment is supported and anchored to carry its operating weight and to resist the seismic forces that would otherwise slide or overturn it. The anchorage is engineered to a bolt pattern and an anchor design, not chosen by available holes in a housing. Where the equipment is vibration-isolated, the anchorage works through or around the isolation system, which is specified in Vibration Isolation And Seismic Restraint. (13.1)

NOTE Hangers and supports shall be installed so the completed system hangs level, drains as designed, and presents a verified load path at every support. The execution rules below close the gap between a correct schedule and a correct field result. (14.1)

NOTE Installed supports shall be verified before the system is concealed or placed in service, because a missed under-rated attachment is far cheaper to find on a walkdown than after a failure. (15.1)