Stainless Steel U Bolt

Choosing the Right U-Bolt

What is a U-bolt & when to use it?

A U-bolt is a U-shaped rod with threads on both legs, used mainly to clamp or support round and flat members.

Use a U-bolt when you need to:

Support or clamp pipes/tubes to structures (pipe supports, racks, cable trays)

Fix round sections (pipes, poles, rods) to steel, concrete or timber

Hold down equipment, channels, or small beams using the U shape and a saddle/plate

Typical applications:

Pipe support systems – horizontal/vertical pipelines

Exhaust and duct supports

Mounting poles, masts, cable trays, and small structural members

Hold-downs on skids, frames, trailers, machinery

Environment & corrosion – material selection (A2 vs A4)

For stainless U-bolts:

A2 (304) stainless U-bolt

Use in indoor and general outdoor environments

Standard plant piping, structural supports, light process work

A4 (316) stainless U-bolt

Use in marine, coastal, chemical, or chloride-rich environments

Offshore, seafront, poolside, water treatment, chemical plants, food & pharma wash-down

Match the system:

A2 U-bolt with A2 nuts, washers, and saddles/clamps

A4 U-bolt with A4 nuts, washers, and saddles/clamps

Pipe / member size vs U-bolt size

The first selection step is usually the pipe / member size you want to clamp:

Nominal pipe size

U-bolts for pipe are usually designated by pipe OD (or DN with matching OD).

Ensure the inside radius and inside width of the U-bolt fit comfortably around the pipe with the saddle/clamp.

Rod/section size

For solid rods or small sections, choose a U-bolt whose inside width and radius suit the outside size of the member.

Then choose the rod diameter of the U-bolt based on load:

Smaller pipes / lighter loads → smaller rod diameter (e.g., M6, M8)

Larger pipes / higher loads → larger rod diameter (e.g., M10, M12, M16 …)

Capacity depends on both rod diameter & grade and how the U-bolt is used (simple guide, clamp, support, or hold-down).

Support type – guide, hold-down, or restraint

How the U-bolt is used in the pipe/structural system matters:

Guide / alignment support

Allows pipe to slide axially while holding it laterally.

U-bolt is not highly tensioned – mainly for location & light restraint.

Clamp / fixed point / hold-down

U-bolt is tightened to clamp pipe firmly to a saddle, plate, or steel.

Higher tension in the legs → more important to check bolt strength and pipe shell crushing.

Restraint / anchor

Used to resist thermal expansion, wind, or seismic loads.

Requires proper engineering design (pipe stress, structural calcs).

Simple rule:

Light guide / support → focus on fit around pipe and corrosion resistance.

Heavy clamp / restraint → also consider rod diameter, grade, and saddle/pipe contact pressure.

Mechanical Properties (Guide) – Stainless Steel U-Bolts

U-bolts behave mechanically like two threaded rods bent into a U-shape.
Their tensile strength is defined by the material and property class, but actual usage is often governed by bending, clamping load, and pipe/structure capacity.

A2-70 Stainless U-Bolts

Material: A2 (304) stainless steel

Property class: 70

Minimum tensile strength ≈ 700 MPa

Typical proof strength ≈ 450 MPa

Use with: A2-70 nuts and appropriate washers/saddles.

Typical applications:

General indoor/outdoor pipe supports

Clamping tubes, cable trays, small beams, poles in non-marine environments

A4-70 Stainless U-Bolts

Material: A4 (316) stainless steel

Property class: 70

Similar mechanical strength to A2-70, with better corrosion resistance

Use with: A4-70 nuts and matching saddles/washers.

Typical applications:

Marine & coastal pipe supports

Chemical plants, water treatment, food & pharma areas with aggressive cleaning

Outdoor structures exposed to salt, chlorides, and harsh atmospheres

Key mechanical points

For any given size (e.g., M10 A4-70 U-bolt):

The tensile capacity in each leg is comparable to an M10 A4-70 threaded rod.

Overall performance depends on:

Rod diameter & grade

Bend radius and how tightly it clamps the pipe

Number of U-bolts used in the support

Pipe wall / structural member strength and the saddle/contact area

In many pipe support applications, the limiting factor is:

Pipe shell crushing,

Support steel strength, or

Anchor design,
rather than pure tensile failure of the U-bolt itself.