How Are External Nozzle Loads Incorporated Into Pressure Vessel Design?

External Nozzle Loads Pressure Vessel

Pressure vessels are essential components of many industrial processes because they are used to store and transport gases and liquids under high pressure. The design of these vessels is crucial to ensuring their safe and dependable operation, and one crucial component of that design is the incorporation of external nozzle loads. External nozzle loads are the forces and moments that piping, equipment, and other externally attached parts exert on the pressure vessel. If these loads are not properly taken into account during the pressure vessel design, they can result in significant stress and deformation, which could lead to failure and pose safety risks.

We will discuss the various loads that can be applied to pressure vessels, the methods used to analyze and calculate these loads, and the design considerations that must be taken in order to guarantee their safe and dependable operation in various industrial applications. Whether you are a mechanical engineer, a plant operator, or simply interested in how industrial processes work, this blog will provide insightful information about the critical role that external nozzle loads play in pressure vessel design.

Types Of External Nozzle Loads

It is crucial to take into account the external nozzle loads that the pressure vessel will experience while in use when designing the pressure vessel. There are various types of these external loads, including:

  1. Thermal loads: These are brought on by the piping that is connected to the nozzle’s thermal expansion or contraction. The piping expands or contracts as the temperature of the fluid inside the vessel changes, which can exert strong forces on the nozzle.
  2. Weight loads: These are brought on by the weight of any attached machinery and the piping that is connected to the nozzle. The nozzle may bend or deform as a result of the equipment’s heavyweight.
  3. Wind loads: These are brought on by the wind’s force on the nozzle-connected piping and machinery. Particularly if the vessel is situated in an area with high wind speeds, wind loads can be very high.
  4. Seismic loads: These are brought on by the ground shifting during an earthquake. The nozzle may experience significant forces from seismic loads, particularly if the vessel is situated in an earthquake-prone area.
  5. Pressure loads: These are brought on by the fluid pressure inside the vessel. The nozzle needs to be built to withstand the loads because the pressure can exert sizable forces on it.

Methods For Calculating External Nozzle Loads

Calculating external nozzle loads is a critical step in pressure vessel design, as failure to properly account for these loads can result in catastrophic failure. There are several methods for calculating external nozzle loads, each with its own advantages and limitations. Here are a few commonly used methods:

1). WRC 107 and WRC 297 Methods

These methods were developed by the Welding Research Council (WRC) and are widely used in pressure vessel design. WRC 107 is applicable for external loads that are applied perpendicular to the nozzle axis, while WRC 297 is applicable for loads that are applied at an angle. These methods are based on experimental data and provide conservative estimates of the maximum allowable loads.

2). Finite Element Analysis (FEA)

FEA is a numerical method used to analyse the behaviour of structures under loading conditions. It is a powerful tool for calculating external nozzle loads, as it allows for the modelling of complex geometries and loading conditions. FEA requires a detailed understanding of the structure being analysed and is best used by experienced engineers.

3). API 650 and API 653 Methods

Tanks with external nozzles are frequently designed using these techniques. While API 653 is used for tank repairs and modifications, API 650 is used for new tank construction. Based on the geometry, material characteristics, and operating circumstances of the tank, these methods offer guidelines for the maximum allowable loads.

4). ASME Section VIII, Division 2

The design of pressure vessels with external nozzles is governed by this code. It has provisions for calculating nozzle loads according to the geometry, orientation, and loading circumstances of the nozzle.

It’s crucial to remember that these approaches are not mutually exclusive, and engineers may combine approaches to get the most precise results. Additionally, some techniques might be better suited for a specific class of pressure vessel or set of loading circumstances than others. A qualified engineer should assess each situation separately and choose the best strategy for the circumstances.

Design Considerations For Incorporating External Nozzle Loads

A number of factors need to be carefully taken into account when designing a pressure vessel that can withstand external nozzle loads. Following are some design factors for including external nozzle loads:

1). Allowable Stresses

The designer must make sure that the stresses brought on by the external nozzle loads are within the tolerances for the pressure vessel’s material. The designer should determine the stresses and make sure they are within acceptable limits using suitable stress analysis methods, including finite element analysis (FEA).

2). Nozzle Stiffness

On the stresses brought on by external loads, the stiffness of the nozzle can have a significant effect. For the nozzle to have enough stiffness to handle the loads, the designer should take the nozzle’s geometry and thickness into account.

3). Nozzle Orientation

The stresses induced in the vessel may also depend on how the nozzle is positioned in relation to the applied loads. The orientation of the nozzle and its interaction with the external loads should be taken into account by the designer.

4). Support Conditions

The support conditions of the pressure vessel and the nozzle can also have an impact on the induced stresses. The designer should consider the support conditions and ensure they are appropriate for the loads and geometry of the nozzle.

5). Fatigue Life

The designer should also consider the fatigue life of the pressure vessel, taking into account the cyclic loading induced by external nozzle loads. Fatigue life analysis should be performed to ensure the vessel will have an acceptable service life.

Final Thoughts

To ensure the safety and integrity of the vessel, it is essential to incorporate external nozzle loads into pressure vessel design. Different kinds of external nozzle loads, such as pressure thrust, moments, and forces, must be taken into account. The vessel’s ability to withstand these loads can be increased through the use of suitable calculation techniques and design considerations, such as the choice of suitable materials and supports. 

Ultimately, the key to ensuring a secure and effective design is to collaborate with experienced engineers who are familiar with the pertinent codes and standards. Pressure vessels can be designed and built to meet the specific needs of your company while ensuring safety and regulatory compliance with careful planning and attention to detail.

Contact Sherwood Design & Engineering Today

If you are in need of pressure vessel design and engineering services, including the incorporation of external nozzle loads, Sherwood Design & Engineering can provide expert assistance. With over 40 years of experience in the industry, our qualified engineers can design pressure vessels to Australian Standards and provide detailed calculations and drawings. Contact us today to discuss your project needs and how we can help.

Give us a call at (02) 9437 3566 or leave an enquiry if you would like to learn more about our pressure vessel engineering design and support services.