Key Considerations for Secondary Support Design

II JAY SHRI KRISHNA II

Secondary Supports, often referred to as brackets, are crucial components in piping systems, providing essential structural support to piping lines. While their primary function is to ensure the structural integrity of the system, several critical design considerations must be taken into account to guarantee their long-term performance and safety.

Key Considerations for Secondary Support Design

One of the most important factors is the dynamic nature of piping loads. Unlike static loads, piping systems are subjected to various dynamic forces, including thermal expansion, vibration, and seismic loads. These forces can significantly impact the design and selection of secondary supports. Therefore, it's essential to conduct thorough stress analysis and vibration analysis to accurately assess the loads and select appropriate support types.

This article delves into key considerations for designing effective secondary supports.

Support Location and Configuration

Example of Secondary Support

When designing secondary support systems, careful consideration must be given to the location and configuration of supports to ensure optimal performance and cost-effectiveness.

Consolidated Support Design:

Rather than designing individual supports for each pipe line, it is often more efficient to consolidate multiple lines onto a single support structure. This approach offers several advantages:

Reduced Material Usage: By combining multiple lines onto a single support, the overall material usage can be significantly reduced, leading to cost savings.

Improved Structural Efficiency: Consolidated supports can be designed to optimize load distribution and minimize stress concentrations, resulting in a more robust and efficient structure.

Simplified Installation and Maintenance: A reduced number of supports simplifies installation and maintenance processes, saving time and labor costs.

L-Type Secondary Support: Considerations and Best Practices

L-type secondary supports, while commonly used, have certain limitations, especially when dealing with significant loads or long spans. To optimize their performance and minimize potential issues, consider the following:

Avoiding Unnecessary Projections:

Minimize L-Dimension: When the L-dimension becomes large, it can lead to increased stress concentrations and potential instability.

Connect the Loose End: If possible, connect the loose end "X" to a nearby structure to provide additional support and rigidity.

Increase Member Size and Connection Details: If connection to a nearby structure is not feasible, consider increasing the member size and reinforcing the connection at the insert plate.

Example of L-Type Support

Prioritizing Two-Ended Connections:

Whenever possible, opt for support details that connect both ends of the L-type support. Even for relatively short L-dimensions (around 350 mm), a two-ended connection can significantly enhance structural integrity.

By adhering to these principles, you can design L-type secondary supports that are both efficient and reliable.

T-Type Support Connection Details for Beams:

T-Type Supports: T-type supports offer better load distribution and stability, especially when supporting multiple lines.

Box-Type Supports: Box-type supports provide excellent rigidity and can accommodate heavy loads. They are particularly suitable for supporting multiple lines in a compact configuration.

When erecting T-type supports on beams, proper connection details are vital for ensuring structural integrity and safe operation. Here are some basic points & examples:

Importance of Connection Details:

Well-designed connections ensure the T-type support can effectively transfer piping loads to the beam without compromising either component.

Clear details also facilitate proper installation and maintenance.

Examples of Connection Details:

1. Welded Connection:

Suitable for high-load applications.

Requires qualified welders and proper inspection procedures.

2. Bolted Connection:

Offers good strength and can be disassembled for maintenance.

Requires sufficient bolt size and proper tightening procedures.

3. Clamped Connection:

A faster and simpler option for lower-load applications.

May not be suitable for high vibration or dynamic loads.

T-shaped support for two parallel pipe lines

Avoiding L-Type Supports:

While L-type supports are a common configuration, they can be less structurally efficient compared to other options, especially when dealing with significant loads or long spans.

Limited Load Capacity: L-type supports can be susceptible to bending moments, which can limit their load-carrying capacity.

Potential for Vibration: Long, slender L-type supports may be likely to vibration, particularly under dynamic loads.

Example:

Instead of designing separate supports for two parallel pipe lines, a single T-shaped support can be used to accommodate both lines. This consolidated support can be anchored to a structural beam or column, providing a strong and efficient solution.
Example of T-Type Support
Alternative Configurations:

Example:

Instead of using an L-type support to support a pipe line, a T-type support can be used to provide additional stability and load-carrying capacity. The T-type support can be connected to a structural beam or column to ensure a secure and reliable installation.

T-type support replacing an L-type support

Optimizing Support Spacing:

Proper support spacing is crucial to accommodate thermal expansion and contraction of pipes. Insufficient spacing can lead to excessive stress and potential failures, while excessive spacing can result in excessive deflection and vibration.

Thermal Expansion: Consider the expected thermal expansion of the pipe and ensure that the support spacing allows for free movement without inducing stress.

Vibration: Adequate support spacing helps to minimize vibration and resonance, particularly for long spans and flexible piping systems.

Example: Supporting Hot Pipes and Addressing Horizontal Loads

Accommodating Thermal Expansion:

When designing secondary support structures for hot pipes, it's crucial to account for thermal expansion. This involves providing sufficient clearance between the pipe and the support to allow for movement without inducing stress.

Minimum Clearance: A minimum clearance of 200 mm is generally recommended.

Additional Considerations: Factors such as wind load, seismic loads, and other dynamic forces can further influence the required clearance.

Connecting Small T-Post Structures:

For smaller T-post structures, it's advisable to connect them to nearby structures whenever possible. This connection, while often minimal in cost, significantly enhances the overall structural integrity and stability of the support system.

Addressing Horizontal Loads Due to Friction:

It's important to recognize that horizontal loads, often overlooked, can be substantial. These forces, arising from friction between the pipe and the support, can be up to 25-35% of the vertical load.

To mitigate the impact of these horizontal forces, consider the following strategies:

Roller or Ball Bearing Supports: Implementing roller or ball bearing supports can significantly reduce friction and allow for smoother pipe movement.

Low-Friction Materials: Using materials like Grafoil or Teflon sheets between the pipe shoe and the support structure can minimize friction and facilitate easier pipe movement.

By addressing these critical factors, engineers can design secondary support systems that are not only structurally sound but also capable of accommodating the dynamic loads and thermal expansion associated with hot piping systems.

Dynamic Load Considerations:

Vibration Analysis: Conduct vibration analysis to identify potential resonance frequencies and take necessary measures to mitigate vibration-induced stresses.

Seismic Design: Design supports to withstand seismic loads, considering local seismic codes and standards.

Thermal Expansion: Account for thermal expansion and contraction of pipes by providing adequate clearances and flexible connections.

Structural Integrity:

Material Selection: Choose materials that are suitable for the operating conditions, including temperature, pressure, and corrosive environments.

Stress Analysis: Perform rigorous stress analysis to ensure that the support structure can withstand the combined loads, including static, dynamic, and seismic loads.

Fatigue Life Assessment: Evaluate the fatigue life of the support structure, especially in areas prone to cyclic loading. Consider the impact of potential vibration and thermal cycling.

Construction and Maintenance:

Accessibility: Design supports with easy access for inspection, maintenance, and repair. Avoid obstructed areas or tight spaces that hinder maintenance activities.

Modular Design: Consider modular support designs that can be easily assembled and disassembled, reducing installation time and costs.

Corrosion Protection: Implement appropriate corrosion protection measures, such as coatings or galvanization, to extend the service life of the support structure.

By adhering to these design considerations, engineers can ensure the long-term reliability and safety of piping systems.

Conclusion:

The design and implementation of secondary supports are critical factors in ensuring the long-term performance and safety of piping systems. By carefully considering factors such as support location, configuration, dynamic loads, structural integrity, and maintenance accessibility, engineers can design effective and reliable secondary support systems.

Adhering to industry standards and best practices, as well as conducting thorough analysis and design calculations, is essential to minimize the risk of failures and optimize system performance. By prioritizing proper secondary support design, engineers can contribute to the overall safety, efficiency, and longevity of piping systems.

By carefully considering these factors, engineers can design secondary support systems that are both structurally sound and cost-effective.

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