What Is a U-Bolt?
A U-bolt is a bolt used to secure a pipe to a trestle, bracket, or stay during a piping installation. The bolt is U-shaped and threaded at both ends, making it possible to easily and securely fasten a pipe with a single U-bolt.
JIS F3022, U-bolts for mounting steel pipes for ships, were previously used as the standard of U-bolts but were discontinued on August 10, 2006, due to its low frequency of use and limited track record. However, some products are still manufactured according to the old standard. Currently, specifications and dimensions are stipulated by each manufacturer.
Uses of U-Bolts
U-bolts are mainly used for fixing pipes. U-bolts are sized according to a pipe’s outside diameter, and the bolts are rounded and bent to follow accordingly, making them easy to fit on curved surfaces and provide good compatibility.
In addition to piping, U-bolts are also used for fastening leaf springs and axles in the rear suspension of heavy vehicles such as trucks and buses.
When the object to be fastened is rectangular, such as a square pipe or channeling, a square-shaped U-bolt is used instead of a rounded U-bolt.
Principle of U-Bolts
U-bolts, like normal bolts, use nuts to secure the object, but since the U-shaped bolt clamps the object, it is important to correctly measure the diameter of the object and select a bolt that is compatible with it.
When fixing a pipe in a piping application, the “nominal size” of the U-bolt is indicated by the pipe’s outer diameter (nominal or outer diameter), so a U-bolt with the same “nominal size” as the pipe outer diameter should be selected.
When using U-bolts for square pipes, select the “nominal size” of the U-bolt that indicates the required square pipe size.
If the member to which the pipe is to be fastened is thick, a foot-long U-bolt with a longer overall length should be used.
Since the JIS standard for U-bolts has been abolished, it is necessary to note that there may be variations with varying detailed dimensions among manufacturers.
Common materials for U-bolts include mild steel, austenitic stainless steel (SU304, SUS316, SUS316L), etc. Mild steel is available with surface treatment such as unichrome plating or hot dip zinc plating as a corrosion prevention measure. Select a material suitable for the application and operating environment.