What Is a Pipe Clamp? Attachment Types

Pipe clamps secure pipes to structural supports, walls, or equipment without welding directly to the pipe. They wrap around the pipe outer diameter (or insulation) and transfer the pipe weight and lateral loads to the supporting structure through bolted connections. Clamps are standard components on pipe racks, vertical risers, and equipment connections.

Pipe Clamp Types

Clamp Type	Description	Pipe Size Range	Typical Use
U-bolt	U-shaped threaded rod clamped over the pipe onto a channel or beam	NPS 1/2 to NPS 24	Light to medium loads, horizontal pipes on beams
Two-bolt pipe clamp	Split-ring clamp with two bolts, lined or unlined	NPS 1/2 to NPS 36	General-purpose horizontal pipe support
Three-bolt pipe clamp	Heavy split clamp with three bolts for higher loads	NPS 4 to NPS 48	Heavy pipes, high vibration, or dynamic loads
Riser clamp	Ring clamp with a bearing lip to support vertical pipe weight	NPS 1 to NPS 24	Vertical pipe runs through floors or on structures
Hold-down clamp	Clamp bolted to a pipe shoe or beam to prevent pipe lift-off	NPS 2 to NPS 48	Wind uplift, two-phase flow, vacuum lines
Cushion clamp	Rubber-lined clamp to isolate vibration and prevent metal contact	NPS 1/2 to NPS 12	Instrument tubing, compression fittings lines, vibrating equipment
Beam clamp	Clamp that grips the flange of a support beam (no drilling required)	N/A (beam-side)	Temporary supports, fast installation

Load Ratings

Pipe clamp load ratings depend on size, material, and the number of bolts. The following values are representative for carbon steel clamps per MSS SP-58:

Nominal Pipe Size	U-Bolt (Max Load)	Two-Bolt Clamp (Max Load)	Three-Bolt Clamp (Max Load)
NPS 2	5 kN (1,125 lbf)	8 kN (1,800 lbf)	N/A
NPS 4	8 kN (1,800 lbf)	14 kN (3,150 lbf)	22 kN (4,950 lbf)
NPS 8	12 kN (2,700 lbf)	22 kN (4,950 lbf)	36 kN (8,100 lbf)
NPS 12	16 kN (3,600 lbf)	30 kN (6,750 lbf)	50 kN (11,250 lbf)
NPS 24	22 kN (4,950 lbf)	45 kN (10,125 lbf)	75 kN (16,875 lbf)

Common Mistake

U-bolts should not be used as axial restraints or pipe anchors. They resist vertical gravity loads and minor lateral forces but are not designed to carry significant axial thrust from thermal expansion.

Material Selection

Pipe Material	Clamp Material	Liner Required?
Carbon steel	Carbon steel (A36 / EN 10025 S235)	No (optional felt or rubber liner)
Stainless steel 304/316	Stainless steel 304/316 or carbon steel with isolation liner	Yes (PTFE, rubber, or composite)
Copper / nickel alloy	Carbon steel with isolation liner	Yes (prevents galvanic corrosion)
Insulated pipe (any)	Carbon steel (oversized to clear insulation)	Insulation protection shield required

For stainless and duplex pipes, carbon steel clamps with composite isolation liners are a cost-effective alternative to full stainless clamps, provided the liner prevents direct metal contact.

Selection Criteria

Choosing the right clamp requires matching the support function to the pipe condition:

• Gravity support only: U-bolt or two-bolt clamp
• Lateral restraint (guide): Two-bolt or three-bolt clamp with guide lugs
• Vertical load bearing (risers): Riser clamp with load-bearing lip
• Vibration isolation: Cushion clamp or spring-mounted clamp, often near rotating equipment
• Uplift prevention: Hold-down clamp bolted to pipe shoe or beam

Applicable standards include MSS SP-58 (materials, design, and manufacture), MSS SP-69 (selection and application), and MSS SP-89 (fabrication and installation). Clamp spacing follows the same pipe span rules used for pipe sleepers and rack supports, governed by pipe size, schedule, and content weight.

Read the full guide to steel plates