In the design of pressure vessels, one of the critical components is the saddle support. The saddle support is the component responsible for carrying the weight of the vessel and the internal contents, while also allowing for movement due to thermal expansion and contraction. Proper design of the saddle support is essential to ensure that the pressure vessel can operate safely and efficiently.
1. Overview of Saddle Supports
Saddle supports are typically used for horizontal pressure vessels, but can also be used for vertical vessels when there is a need to raise the center of gravity. The saddle support consists of two half-round supports that extend along the length of the pressure vessel. The supports are welded or bolted to the bottom of the vessel and rest on a pedestal or a structural member.
One of the critical aspects of the saddle support design is understanding the loads and stresses placed on the support. The primary loads on the saddle support include the weight of the vessel and its contents, as well as any external forces such as wind or seismic activity. Additionally, the saddle support must account for thermal expansion and contraction, which can cause significant movements in the vessel.
2. Design Considerations for Saddle Supports
When designing a saddle support, several factors must be considered to ensure that the support can withstand the loads and stresses placed upon it. These factors include materials selection, welding procedures, and the use of support pads.
2.1. Materials Selection
The material selection for the saddle support must be appropriate for the maximum operating conditions of the pressure vessel. Typically, carbon steel or stainless steel is used for the support material. However, for high-temperature applications, the use of alloy steels may be necessary.
Additionally, the material selection must consider the corrosive properties of the vessel contents. If corrosion is a concern, the use of coatings or lining materials may be necessary to protect the saddle support from corrosion.
2.2. Welding Procedures
The saddle support is typically welded to the bottom of the pressure vessel. The welding procedures used must meet the requirements of the design code and ensure that the welds are of sufficient quality to withstand the loads and stresses placed upon them.
One critical aspect of the welding procedure is ensuring proper penetration of the weld. Insufficient weld penetration can lead to stress concentration, which can result in premature failure of the support.
2.3. Support Pads
To reduce the stresses on the saddle support, the use of support pads may be necessary. Support pads are typically made of a material that can accommodate thermal expansion and movement between the vessel and the support.
When using support pads, it is important to ensure that the pads are correctly sized and positioned to distribute the load evenly across the support surface.
3. Design Codes for Saddle Supports
The design of saddle supports is typically governed by industry standards or regulations. In the United States, the ASME Boiler and Pressure Vessel Code provides guidelines for the design, fabrication, and inspection of pressure vessels.
Section VIII of the ASME Code provides specific requirements for the design of saddle supports. These requirements include minimum thicknesses for the saddle support, maximum allowable stresses, and criteria for determining the strength of the welds used to attach the support to the vessel.
4. Conclusion
The saddle support is a critical component in the design of pressure vessels. It is responsible for supporting the weight of the vessel and its contents while allowing for movement due to thermal expansion and contraction.
Proper design of the saddle support must consider the materials selection, welding procedures, and the use of support pads to ensure that the support can withstand the loads and stresses placed upon it.
Design codes such as the ASME Boiler and Pressure Vessel Code provide guidelines for the design of saddle supports, ensuring that they are designed to meet industry standards for safety and reliability.