Exploring flange bolts: The unsung heroes of pipeline connections

In the intricate world of pipeline connections, the unsung heroes ensuring everything holds together are the bolts. These bolts, designed for connecting flanges, come in two primary types: single-end bolts and double-end bolts, all featuring the tried-and-true triangular metric coarse thread.

Single-End Bolts

Single-end bolts, also known as hex head bolts, are further divided into semi-finished and finished varieties. In low-to-medium-pressure industrial piping, semi-finished single-end bolts are the most commonly used.

These bolts are typically constructed from materials like Q235A, grade 35 steel, and 25Cr2MoVA. They find their prime utility in flange connections operating under a nominal pressure of 2.5MPa or less.

The applicable temperature range depends on the material; for instance, bolts made of grade 35 steel can withstand temperatures up to 350°C, while those crafted from 25Cr2MoVA steel can endure environments reaching up to 570°C.

Hot dip galvanized bolts

Double-End Bolts

When it comes to high-pressure and high-temperature flange connections, double-end bolts are the go-to choice in process piping. Most often, equal-length double-end finished bolts are the preferred selection.

These bolts can be constructed from a range of materials, including 35 steel, 30CrMoA, 35CrMoA, 25Cr2MoVA, 0Cr19Ni9, 0Cr15Ni25Ti2MoAlVB, and 37SiMn2MoVA. They operate effectively within a nominal pressure range of 1.6 to 32.0MPa and can withstand temperatures of up to 700°C.

Zinc plating of bolts and nuts

Nuts: The Perfect Partners

Nuts, commonly known as hex nuts, come in both semi-finished and finished varieties and are further categorized into A-type and B-type based on their structural design.

Semi-finished single-end bolts are often paired with A-type nuts, while finished double-end bolts commonly utilize B-type nuts. It’s essential to ensure that the hardness of the nut material does not exceed the hardness of the bolt material when selecting the appropriate pairing.

In the complex web of pipeline connections, flange bolts and nuts play a pivotal role. Whether in low-pressure or high-temperature applications, these unsung heroes ensure the integrity and stability of industrial piping systems.