U-Bolt Basics

U-bolts are bolts bent in the shape of the letter U, with both ends threaded to attach pipe and other cylindrical shapes to a structure using nuts and washers. U-bolts come in either standard length, or long tangent configurations. Standard length u-bolts use 1 nut on each leg, while a long tangent u-bolt is typically accompanied by 2 nuts for each leg. Long tangent refers to the length of the straight leg portion of the u-bolt which is longer than that of a standard u-bolt, resulting in longer legs and more thread. The longer legs work perfectly for mounting pipe to structural materials or thick flanges and the longer thread length allow u-bolts to be installed with a nut locked on either side of the mount to allow for a stand-off, rather than cinching the u-bolt down onto the pipe. Since u-bolts have primarily been used to support pipes through which fluids and gases pass, u-bolts are called out by the size of pipe. In addition to supporting pipe, u-bolts have a wide range of uses such as securing tubing, roundbar, wood or steel posts, and can be embedded into concrete as anchor bolts. U-bolts are designed to be inserted into pre-drilled or punched holes.

U-Bolt Materials

Carbon Steel U-Bolts

Carbon steel is a common material for fasteners due to its cost-effectiveness, good tensile strength and ability to bear loads. It responds well to heat-treatments with minimal work hardening and brittleness. It is easy to machine and can meet the tight tolerances required for threading and fastener configurations.

304 Stainless Steel U-Bolts

Manufactured from austenitic 304 stainless steel. They have a chromium content of 17-19% and nickel content of 8-10%, yielding the common term 18-8 stainless steel. 304 stainless steel U-Bolts are known for their corrosion and heat resistance. Austenitic grade steels are high in chromium, with varying amounts of nickel, manganese, nitrogen and some carbon. The 10.5% minimum chromium content makes the metal approximately 200 times more resistant to corrosion than metals without chromium. 304 stainless u-bolts are commonly used in applications that require general atmospheric corrosion resistance, such as chemical and food processing equipment, as well as marine and coastal facilities and other corrosive environments.

316 Stainless Steel U-Bolts

Manufactured from 316 stainless steel, an austenitic alloy which differs from 304 stainless steel by its molybdenum content (2-3%) and a higher nickel content (10-14%) allowing for higher corrosion resistance. 316 stainless steel u-bolts are known for their corrosion and heat resistance. Austenitic grade steels are high in chromium, with varying amounts of nickel, manganese, nitrogen and some carbon. The 10.5% minimum chromium content makes the metal approximately 200 times more resistant to corrosion than metals without chromium. 316 stainless steel u-bolts are commonly used in applications that require general atmospheric corrosion resistance, such as chemical and food processing equipment, as well as marine and coastal facilities and other corrosive environments.

Common Finishes of U-Bolts

U-Bolts are available in a variety of finishes and coatings, which play a role in the suitability of the fasteners in different applications, such as enhancing resistance to corrosion from environmental elements or chemicals. Coatings on u-bolts can also effect consistency of torque values for installations and ease removal at the end of service.

Galvanized U-Bolts

Galvanized U-Bolts are coated with a sacrificial zinc coating that acts as an anode to prevent the fastener underneath from corroding.

• Hot Dipped Galvanized: Fasteners are dipped in a bath of molten zinc.

Plated U-Bolts

U-Bolts are coated with a thin layer of zinc, typically via electroplating.

• Plated U-Bolts will not corrode as quickly when covered with this protective coating, even when a scratch or cut exposes the steel to air or moisture. Zinc or cadmium plating acts as a sacrificial anode and will always tarnish and corrode first thereby protecting the steel underneath.

Neoprene Coated Galvanized U-Bolts

U-Bolts are coated with a sacrificial zinc coating that acts as an anode to prevent the fastener underneath from corroding, then coated with a rubberized coating. The rubber coated U-Bolt allows for movement without damage to the pipe coating.

• Hot Dipped Galvanized: Fasteners are dipped in a bath of molten zinc.