U-bolts

01

Size the U-bolt to what it clamps

Haiyan Bolt, a fastener maker, describes a U-bolt as a curved section forming the U shape with two straight threaded ends; the curve fits around an object, such as a pipe, rod or other cylinder, and nuts on the threaded legs tighten it. It cites uses securing pipes to supports to prevent movement and vibration, attaching exhaust, suspension and drive-shaft parts on vehicles, fastening structural members, and installing electrical conduit and cable trays. It lists U-bolts from 3/8-16 to 1-8 inch diameter and lengths up to 40 inches, specialising in custom U-bolts and other bent bolts made to drawing, and supplies them assembled with hex nuts and a fender washer plate. [1]

Editorial note: send a drawing, or the clamped object's actual outside size and the thickness of the support, plate and washers, so the supplier can set the inside width, crown shape and leg and thread lengths.

Give the supplier the clamped object and its outside size, crown shape (round or square), inside width and leg length, thread size and pitch, thread length, material and grade, finish (plain, zinc, hot-dip galvanized, coated, stainless), nuts, washers and plates, applicable standard, certificates, packaging, and quantity.

02

Choose material, grade and finish

Haiyan says U-bolts are made from carbon steel for strength and durability, stainless steel where corrosion resistance matters outdoors or in wet places, and alloy steel for high-strength needs, and offers plain, zinc, hot-dip galvanized and Xylan finishes and 303 or 316 stainless steel. [1] ASTM A307 covers carbon-steel bolts and studs from 1/4 to 4 inches: Grade A bolts, studs and threaded rod with 60 ksi minimum tensile strength for general applications, and Grade B with 60–100 ksi tensile strength for flanged joints in piping systems with cast-iron flanges; suitable nuts are in ASTM A563. [2] ASTM F2329 covers hot-dip zinc coating of carbon and alloy steel bolts, screws, washers, nuts and special threaded fasteners, centrifuged to remove excess zinc. [3]

Editorial note: A307 does not name U-bolts specifically; if you call it up for a carbon-steel U-bolt, state the grade and how the supplier will test bent parts, and name the coating specification separately.

03

Check the allowable normal and side load for pipe U-bolts

Deepwater Corrosion Services publishes a load table for its NU-BOLT carbon steel pipe U-bolts, supplied with four finished hex nuts in black or galvanized finish for 1/2 in to 36 in pipe, and states compliance with Federal Specification A-A1192A (Type 24), WW-H-171-E (Type 24), ANSI/MSS SP-69 and MSS SP-58 (Type 24). Each pipe size has a rod size and maximum normal load at 650 °F and 750 °F plus a maximum side load at 650 °F: for example 1/4 in rod on 1/2 in pipe, 580 lb / 454 lb normal and 145 lb side; 1/2 in rod on 2 1/2 in pipe, 2,700 / 2,114 lb and 675 lb side; 5/8 in rod on 6 in pipe, 4,320 / 3,382 lb and 1,080 lb side; 7/8 in rod on 12 in pipe, 8,960 / 7,016 lb and 2,490 lb side. Where normal and side loads act together it gives the check Pn/Pna + Ps/Psa ≤ 1, and states that nuts must be snug tight to achieve the listed side loads. [4]

The material and coating standards above set the bolt and zinc properties; this table adds the load the bent bolt may carry on a given pipe. [2] [3] [1]

Editorial calculation: on a 4 in pipe, a 1,000 lb pipe load with a 300 lb side load gives 1,000/2,700 + 300/675 = 0.37 + 0.44 = 0.81, within the ≤ 1 check; the side-load rating is 25–28% of the 650 °F normal load in the listed sizes.

For pipe supports, give the supplier the pipe size, design temperature, normal and side loads and finish, and ask for the load table of the exact U-bolt figure rather than a generic rating.

04

Compare what suppliers offer

Suppliers linked to this page list U-bolts; each card links to the page reviewed.

Listings include standard and custom U-bolts and bent bolts in carbon, alloy and stainless steels in plain, zinc, hot-dip galvanized and Xylan finishes, supplied with nuts and plates; ask each for dimensional drawings, material certificates and coating thickness.

05

Trace what the order must fix

This is a reference built from the sources cited; it is not one maker's drawing.

06

Fill the specification fields with values for your project

A U-bolt quotation needs values for your project. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the clamped size, thread and finish together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Clamps: [pipe/rod/beam; outside size]
Shape: [round; square; inside width]
Thread: [size; pitch; thread length]
Legs: [length]
Material: [carbon; alloy; stainless; grade]
Finish: [zinc; HDG; Xylan]
Hardware: [nuts; plates]
Quantity: [pcs]

See manufacturer records Send an enquiry through CNFX