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Swing Bolt Design

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Swing bolts are commonly used in industrial applications where frequent access to equipment or machinery is required. They provide a secure and reliable method of holding together two components or pieces of machinery while allowing for easy removal and replacement.

Simply put, a swing bolt gets its name from the fact that the bolt can swing around a plane while being fixed or restricted in the other two. Fig. 0.1 show a typical swing bolt assembly, with bolt, washer, pin and lugs.

Fig. 0.1 - Typical Swing Bolt Assembly

This is just one configuration for the swing bolt but there are many others. With the information in this article you can create six configurations using two types of bolts & pin and 3 types of lugs.

1. Bolt & Pin Types

There are two types of bolts and pins that can be used in a swing bolt assembly (see Fig. 1.1):

Type (a): eye bolt (DIN 444 or other related code), machined pin, washer and nut
Type (b): hex bolt (DIN 933 or other related code), machined pin with through-all threaded hole and washer

Fig. 1.1 - Bolt and Pin types

Note (1):

Some people call the eye bolt as swing bolt but here we call swing bolt the group composed by the lug, bolt, nut (in some cases) and washer.

2. Lug Types

There are three types of lugs:

Type (a): folded lug with the folded side welded to the vessel wall
Type (b): straight separated lug with the smaller part welded to the vessel wall
Type (c): folded lug with the folded side facing downward

Fig. 2.1. - Lug Types

3. Analytical Analysis

4. Finite Element Analysis

4.1. Model Simplification

Fig. d - Typical Swing Bolt Assembly

4.2. Mesh

Fig. g - Typical Swing Bolt Assembly

Swing bolts are often used in applications where regular maintenance and updates to machinery are necessary. The primary purpose of a swing bolt is to hold two objects securely together while being easily removable when needed.

These bolts are commonly used in applications such as valve assemblies, filter housings, and other types of machinery that require frequent disassembly and reassembly.

2. Components of Swing Bolts

A standard swing bolt typically consists of three distinct components: a threaded rod, a head and a retaining ring. The threaded rod is often cylindrical in shape and features threads on both ends to allow for easy installation and removal. The head is usually machined within a socket or position hole, and is designed to fit snugly around the retaining ring when the bolt is tightened.

The retaining ring is a critical component of the swing bolt and is often made of high-strength steel or other robust materials. It holds the swing bolt securely in place and prevents the bolt from loosening and falling out over time.

3. Design Considerations for Swing Bolts

When designing swing bolts, several factors must be considered to ensure they can handle the loads and stresses placed upon them. These factors include material selection, geometric design, and proper installation procedures.

3.1. Material Selection

Material selection is a crucial part of swing bolt design. The choice of materials should be based on factors like the maximum operating conditions under which the bolt will be used, environmental factors, and any chemical agents that may be present.

Swing bolts should typically be made of high-strength materials that can resist wear and tear over time. Commonly used materials include stainless steel, brass, and carbon steel. Specialty alloys such as Monel or Inconel may also be used in applications where strength and corrosion resistance are crucial.

3.2. Geometric Design

Geometric design is another essential consideration when designing swing bolts. The shape and size of the bolt must factor in the stressors that will be placed upon it during use. This includes considerations like the load-bearing capacity of the bolt and the torque required to tighten and loosen it.

The geometric design of a swing bolt also determines its compatibility with other components and parts. Thus, proper alignment between parts and components is necessary to ensure excellent functioning between the bolt and any other related assemblies.

3.3. Proper Installation Procedures

Proper installation procedures must be followed to ensure that swing bolts function correctly and safely. The installation process involves inserting the threaded rod through the hole, then tightening the retaining ring to secure the bolt in place.

It's worth noting that improper installation may result in loose swing bolts, causing mishaps or accidents. Inappropriate usage includes overtightening or undertightening, incorrect bolt placement, or inadequate weight distribution.

4. Conclusion

Swing bolts provide an efficient and reliable method of holding together two components or pieces of machinery while allowing for easy removal and replacement. Proper consideration should be taken in material selection, geometric design, and installation procedures to ensure they can handle the loads and stresses placed upon them.

Swing bolts find their primary application in industries, including marine, oil and gas, chemical, and others. They are highly popular hinge-type fasteners due to their versatility and robustness.