In a world where the bones of our infrastructures are crisscrossed with pipes, one of the most overlooked, yet vital, components of these networks are pipe supports. These silent heroes bear the weight, literally, of our various systems, to help ensure smooth, unbroken service. This article will explore the diverse range of pipe support types, and their applications.
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A pipe support, sometimes referred to as a hanger, is a structural component designed to carry the weight of a pipe, its contents, insulation, and any other in-line equipment such as valves and fittings. They provide stability and manage the stresses incurred due to the movement or vibration of the pipes. Pipe supports are essential for maintaining the integrity and performance of the pipe systems.
There are various types of pipe supports designed to perform different functions. Some are designed to allow movement (such as expansion and contraction due to temperature changes), while others are meant to provide rigid, immovable support.
Choosing the right type of pipe support is critical as it directly influences the safety, functionality, and lifespan of the piping system.
Factors that influence this choice can include the material of the pipe, the substance being transported, the operating temperature, and environmental conditions.
Fixed point supports, also known as anchors, are a specific type of support used in a piping system that provides a rigid and immovable point of reference. They are designed to bear the weight of the pipe, along with its contents, and to absorb the various forces that the pipe system might experience, such as those due to thermal expansion, contraction, and other dynamic loads.
Guide supports allow axial movement of the pipe (along the length of the pipe), while preventing lateral (sideways) and angular (rotational) movements. In other words, they permit the pipe to expand or contract linearly while keeping it aligned along its originally designed path.
Guide supports are typically installed at regular intervals along straight pipe runs, particularly between changes in direction, and help maintain the alignment and positioning of the pipe.
Line stop supports or limit stop supports are used to prevent pipes from moving in either the axial or longitudinal direction. They keep the pipe in place and can be provided to facilitate favorable distribution or restriction of axial pipe movements.
Hanger rod supports, commonly known as hangers, are a type of pipe support used predominantly in the suspension of pipes from the ceiling or elevated structures. These types of supports are a common sight in industrial settings where large networks of pipes traverse across areas, often overhead.
Hanger rods are typically composed of a metal rod that is secured to a structural ceiling member at one end and a clamp or other attachment point that connects to the pipe at the other end. The length of the hanger rod can be adjusted to accommodate the distance between the pipe and the supporting structure in order to provide flexibility in pipe positioning.
Spring supports are used to reduce the impact of temperature changes and subsidence on pipes by absorbing their upward or downward movement. They can also be used with hanger rods to handle any horizontal movement.
U-bolts have two main purposes in a piping system: anchoring and guiding. Depending on the intended purpose, they provide support to pipes in different ways, but the ultimate goal is to enhance the support of the pipes.
Trunnions are essentially short sections of pipe welded to the elbow section or side of a pipe that allow it to rest on structural steel members. This design helps in distributing the load and pressure of the piping system to effectively reduce the amount of stress on the pipe. It also permits some rotational movement in the pipe system.
Trunnions are often used at changes of direction or bends in the pipe system, particularly where the piping system involves large horizontal runs. Trunnions effectively bear the weight of the pipe and the fluid it carries to minimize potential sagging or deformation due to gravity.
Saddle supports are a specific type of pipe support used primarily for large-diameter, horizontal pipes. Saddle supports are designed to distribute the weight of the pipe and its contents evenly across the structure to help reduce the stress on any one point.
The name “saddle” comes from their design, which looks like a saddle – it has a curved section that fits against the bottom of the pipe, and flat sections that rest on the supporting surface beneath. This design increases the contact area with the pipe, and distributes the weight more effectively to reduce the likelihood of local deformations due to concentrated loads.
In addition to their load-distributing role, saddle supports can also help to minimize movement or vibration in the pipe, to further enhance the stability of the piping system.
Pipelines need support from a foundation or structure. The loads of the pipes generally tend to fluctuate depending on the mass of the substance that flows inside them. Pipe supports are usually constructed on ground to enable them to exert an equal and opposite reaction. The fundamental functions of a pipe support are to anchor, guide, absorb shock and be able to manage varying loads. Moreover, some pipe supports may contain insulation materials if the pipes are used in high or low temperature applications.
Basically, there are two types of pipe support structures, primary and secondary supports. Primary supports are directly attached to the pipeline, whereas secondary pipe supports are attached directly to the foundation or structure supporting the pipe.
Pipe supports are broadly classified on the aspects of their construction and function (purpose).
Based on construction details, pipe supports are broadly classified in three types as:
Rigid Supports:
As the name suggests, rigid pipe supports are designed to allow no movement in at least one direction. This support system is used the maximum in piping. It directly rests on the foundation or structure that is supporting the pipe and cannot be adjusted to the erection tolerances.
The most common types of rigid supports are shoe type (with clamp), shoe type (welded), valve holder, and support brackets (Secondary Support).
Adjustable Supports:
Adjustable pipe supports are rigid type in construction, but they can be manually adjusted as there nuts and bolts arrangements for adjusting the supports. These nuts and bolts are used in order to adjust the support with respect to the actual erected condition of the pipe. Basically, for the erection tolerances in the piping, the support can be adjusted. Most essentially, almost all types of rigid supports can be modified to adjustable supports by using a certain type of bolts and nuts arrangements.
Elastic Supports:
Such pipe supports are commonly used in supporting hot piping. Elastic pipe supports are able to support pipes even when they are constantly moving up or down due to the pressure and flow of substances inside the pipe. Variable type spring supports and constant type spring supports are most common types of elastic supports used for piping.
As we mentioned earlier, there are pipe supports that are classified on the basis of their functions or purposes. The different supports classified as per their functions are - loose support, longitudinal support, transverse support, fixed (non-welded type) or anchor (welded type) support, limit support and special supports. We are the leading producers of structural steel products across North America. Get in touch with us to know more about our projects and steel fabrication processes.
Pipe support, often overlooked, proves to be an indispensable element in industrial infrastructure. Whether in power plants or manufacturing, having the right piping support ensures safety, prevents misalignment, and makes operations more efficient. Read on to learn more about piping supports.
Piping support is a designed element that transfers the load from a pipe to the supporting structures, referring to mechanisms or structures crafted to hold and stabilize pipes in a specific position within an industrial facility.
Piping supports play a crucial role in maintaining the integrity of the piping system by preventing sagging, vibration, or excessive movement. Properly designed and installed piping supports ensure the safe and efficient operation of the entire piping network, contributing to the longevity and reliability of industrial structures.
A pipe support serves four primary functions: anchoring, guiding, absorbing shock, and supporting a designated load. These supports may include insulation materials in applications with high or low temperatures. The design of a pipe support assembly depends on the specific loading and operating conditions.
There are several piping supports that are known in the industry.
These pipe supports are usually primary, directly connecting to the pipe to bear the load of the piping system. The installation specifics depend on the chosen support’s size and design. Typically, these supports are either bolt-fastened or welded.
Pipe Support Design
Function
Advantage
Pipe Shoes Provide axial support and prevent movement Distribute the load evenly, reducing stress on the pipe Pipe Saddles Offer lateral support and restrain movement Efficient for maintaining pipe alignment and minimizing vibration Pipe Trunnions Allow rotational movement of the pipe Ideal for supporting pipes with thermal expansion and contraction Wear Pads Reduce friction and protect against wear Extend the life of the pipe by minimizing abrasion and friction
To ensure similar behavior when welded and comparable performance under piping process elements or environmental factors, it’s essential for support materials and fasteners to resemble those of the supported pipes.
Dynamically loaded pipe supports serve as either primary or secondary supports, offering variable resistance to movement influenced by factors like compression. These supports play a crucial role in minimizing the impact of abnormal dynamic conditions, such as seismic activity, pump trips, safety/relief valve discharge, or rapid valve closure.
Due to their varying resistance, they enable standard movements during normal operation while maintaining precise movement tolerances during abnormal conditions. This ensures the stability and integrity of the piping system under changing circumstances, contributing to safe and efficient operation.
Dynamically Loaded Support
Function
Advantage
Energy Absorbers Absorb and dissipate energy from sudden movements Mitigate the impact of abrupt changes, reducing stress on the piping system Hanger Supports Provide vertical support and dampen vertical movement Efficiently suspend and stabilize pipes, minimizing vibration and ensuring proper alignment Pipe Whips or Hold Down Restraints Restrict horizontal movement during dynamic events Prevent excessive lateral movement, enhancing the overall stability of the piping system Snubbers Control and limit the movement of pipes Ensure controlled and gradual movement, preventing abrupt shifts and reducing stress on the piping components Struts Offer support and limit movement in a specific direction Provide directional stability, preventing unwanted movement and maintaining proper alignment Sway Braces Control lateral movement and sway in piping systems Minimize lateral displacement, enhancing the system’s ability to withstand dynamic forces and maintaining alignment
Constantly loaded supports in pipe systems maintain a steady load, offering consistent resistance against gravitational forces or fixed loads. Unlike dynamically loaded supports, which adjust resistance based on various factors, constantly loaded supports, also known as constants, sustain a static resistance level. This design makes them well-suited for applications with extremely high loads or systems where movements and loading conditions create significant variability.
Constantly Loaded Support
Function
Advantage
Horizontal Provides steady lateral support and resistance Ideal for countering side-to-side movements and maintaining stability Vertical Offers consistent vertical support and resistance Efficient for sustaining upward or downward loads and ensuring stability
Variable spring supports in piping systems are essential devices for supporting pipes, especially when dealing with changing loads. These supports play a crucial role in balancing the concentrated gravitational load of pipe sections while accommodating thermal movement.
In piping design, controlling the direction and amount of movement in different pipe sections is a significant function. Variable supports use coiled springs to bear a load and allow movement. The resistance of the coil to a load change during compression, similar to dynamic supports, earning them the name “variables.”
Unlike other designs, variable springs typically collaborate with slide plates made from stainless steel, PTFE, or graphite in a secondary support manner, rather than attaching directly to the pipes as primary support. This approach ensures flexibility and stability in accommodating varying loads, contributing to the safe and efficient operation of the entire piping network.
Threaded members are like bars or rods with screw-like ends. They are used to connect different parts of pipe support systems. The threaded ends make it easy to adjust and fit them to different pipes. By connecting with other support parts through threading, these members help keep the piping system stable.
Pipe hangers are tools that hold pipes up from structural elements, preventing them from sagging or moving too much. There are different types of hangers, such as clevis hangers and loop hangers, chosen based on factors like the size and weight of the pipes. Pipe hangers play a key role in keeping pipes aligned correctly, reducing vibrations, and ensuring the entire piping system stays strong and reliable.
Threaded Members and Pipe Hangers
Design Function
Advantage
Stainless Steel U-Bolts U-shaped bolts with threads Securely fasten pipes to structural elements Resistant to corrosion, providing durability and strength Clevis Hangers U-shaped hangers with a pin Suspend pipes, allowing vertical movement Facilitate easy adjustments and are suitable for various pipe sizes 2-Bolt Pipe Clamps Clamps with two bolts Hold pipes in place and prevent lateral movement Quick and simple installation, providing effective lateral support Riser Clamps Clamps for vertical pipes Support vertical pipes, accommodating thermal expansion Enable vertical movement while providing stability, reducing stress on pipes 3-Bolt Pipe Clamps Clamps with three bolts Offer additional stability for holding pipes in position Distribute load evenly, reducing stress on pipes and enhancing overall stability Heavy-Duty Beam Attachments Attachments for support beams Connect pipes to support beams in heavy-duty applications Provide robust support in demanding conditions, ensuring long-term reliability
When used with the proper fasteners, these supports offer strong, long-lasting, and reliable support for pipes of almost any size.
Pipe supports play a crucial role in carrying and spreading the weight or pressures within a piping system. They are particularly vital for managing unusual situations like sudden increases in load, rapid temperature fluctuations, and changes in the structure’s position or settling.
Piping supports ensure that pipes remain stable and properly aligned within an industrial structure. By preventing sagging or excessive movement, these supports maintain the intended position of pipes, contributing to the overall stability of the piping system.
The primary function of piping supports is to distribute the weight and forces acting on pipes evenly. By doing so, they prevent concentrated stress points, reducing the risk of damage or deformation. Proper load distribution is critical for the longevity and structural integrity of the entire piping network.
Piping supports play a crucial role in minimizing vibrations and controlling movement caused by various factors, such as fluid flow or thermal expansion. This control not only enhances the safety of the piping system but also ensures smooth operation without undue stress on the pipes.
In response to temperature changes, pipes may expand or contract. Piping supports are designed to accommodate this thermal movement, preventing issues like buckling or distortion. By allowing controlled expansion and contraction, these supports contribute to the durability of the piping system.
Piping supports serve as a protective measure against potential structural damage. By providing reliable support, they reduce the risk of pipes shifting or exerting excessive force on surrounding structures. This prevention of structural damage ensures the overall safety and reliability of the industrial facility.
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ASME B31.3, in Chapter II and Section 321, outlines the rules for supports and devices restraining pipes. It lays down overall requirements for these supports and describes the conditions they should be designed for. While elements like springs and hanger rods fall under ASME B31.3, the structures these supports connect to are not covered. The goal is for support to meet the design objectives, handling both ongoing and occasional loads, along with thermal displacement, ensuring the stability of the piping system.
In conclusion, having a good grasp of piping supports is crucial for you as a piping engineers. It ensures the reliability and safety of industrial piping systems by understanding how to design proper supports, distribute loads effectively, and control alignment. This knowledge is critical in preventing structural problems, maintaining stability, and avoiding potential dangers. Piping engineers with this expertise play a vital role in creating a secure and efficient industrial environment.
If you are looking for the opportunity to enhance your skills in piping design, inspection, and maintenance following industry standards, Petrosync provides a comprehensive ASME B31.3 training program. This training focuses on the details of piping systems, covering design requirements, inspection procedures, and maintenance practices in line with ASME B31.3 standards.
You will gain valuable insights into the critical aspects of piping engineering, ensuring you are well-prepared to meet industry demands and uphold the highest standards of safety and compliance.
by James N. Britton ()
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Corrosion at pipe supports is one of the leading causes of topside process piping failure. This paper will discuss the various corrosion mechanisms that occur at pipe supports if they are not adequately protected. I-Rod, a proven method of prevention with a long record of successful application will be presented. This paper also discusses inspection strategies for pipe supports and provides a simplified visual screening method that has proved useful in mechanical integrity programs.
The writer's company is engaged in the inspection of offshore oil and gas facilities in the Gulf of Mexico as well as other international production areas. A major part of those inspections is the integrity of topside process systems, piping, and associated vessels and tanks. There is no doubt that statistically, corrosion at pipe supports is the most common cause of external piping corrosion failure. It is for this reason that the writer's company developed the solution most widely employed in the Gulf of Mexico to eliminate this problem (I-Rod® brand pipe supports).
1. Standard beam support:
The pipe is rested on, or secured to, a support member usually of a standard structural shape (I-beam, wide flange beam, angle, channel, etc.). The pipe may be secured to this member with a stabilizing U-bolt (Figures 1 and 2 below).
Figure 1 - Typical I-beam pipe support (note that the pipe is in full contact with the I-beam)
Figure 2 - U-Bolt stabilized beam supports
2. Saddle clamp:
Pipe is clamped between two rolled plates. One of these plates has a structural element welded to it which attaches the pipe to the support structure (Figures 3 & 4 below).
Figure 3 - Typical half-saddle clamp
Figure 4 - Full-saddle clamp
3. Welded support
This type of support involves welding a part to the pipe which is usually free to move at the interface to the support. There are a number of variations on this theme, and is a common approach for insulated piping systems. (Figure 5 below).
Figure 5 - Typical welded pipe support. Allows for movement at support interface, but allows corrosion as well.
4. Others
There are a number of other methods used, such as flange bolt supports, various type of pipe hangers and other specialty-type supports. However, the first two categories account statistically for better than 95% of support points on a typical offshore structure.
Not surprisingly, it is the beam supports and the saddle clamps that have historically caused the majority of the problems. They have the following undesirable features in common:
1. Crevice forming - This is the root of the problem: the formation of a crevice at the pipe surface.
2. Water trapping - These support types all allow water to be trapped and held in contact with the pipe surface.
3. Poor inspectability and maintainability - These support types make it virtually impossible to paint or otherwise maintain some areas of the pipe at the support. Visual inspection is often difficult, and until fairly recently, it was also very difficult to inspect these areas with NDT methods.
4. Galvanic couple forming - Some of these support types may develop bi-metallic contact. Even though both the pipe and support are steel, the metallurgical differences can still provide a small potential difference to create a corrosion cell.
It is a common misconception that metal-to-metal contact coupled with water entrapment is the major cause of corrosion at these points. This is not the case; the sequence of events is as follows:
1. Water is trapped - The very nature of the supports allows water to be held in contact with the painted pipe surface as well as the paint on the support element.
2. The paint system fails - Even if the paint on the pipe and support beam are perfect, the paint system is designed for atmospheric exposure and not immersion service. The longer the paint surface is continuously exposed to water, the more it softens. As the pipe softens, it is inevitable that the steel substrate will be directly exposed to the water.
3. Corrosion is initiated - The small area of steel now exposed to oxygenated water (often with high chlorides) starts to corrode.
4. Corrosion undercuts paint film - The initial corrosion soon undercuts and spreads (Fig. 6 below). Soon the whole support area is bare steel.
5. Crevice corrosion starts - From this point on, the crevice corrosion driven by differential aeration takes over from the general corrosion mechanism that initiated the corrosion. As corrosion products build, they further restrict oxygen diffusion and the oxygen concentration gradient gets steeper. Pitting now becomes the main problem with corrosion rates accelerating by an order of magnitude. (Fig. 7 below)
6. Pipe fails - If the inspection program is not set up to detect this mostly concealed wall loss, the pipe will fail.
Figure 6 - Paint is progressively undercut away from initiation site
Figure 7 - Advanced crevice corrosion
The industry has long been aware of the problem but has failed to appreciate the true causes; this is evidenced by some of the following solutions that have been implemented to stop the problem which have actually accelerated the problem.
As previously stated, it was thought that the metal-to-metal contact was the main problem causing pipe support corrosion. As a result, initial designs incorrectly targeted this aspect of the supports. Some operators still use rubber pads of varying types in an attempt to solve this problem, despite industry knowledge that they are counter-productive. (Fig. 8 below) In fact, rubber pads under pipes do a wonderful job of reducing the life of the pipe. The crevice that was formed without the rubber pad is mild in comparison to the new crevice, which now has the ability to suck water in (by capillary action). Not only does the pad invite water in, it is better at holding it trapped against the pipe surface since air circulation and natural evaporation is eliminated. The situation is further worsened by the length of the crevice which allows an oxygen concentration gradient to go from full natural concentration to anaerobic in a few centimeters.
Figure 8 - Rubber pads accelerate crevice corrosion
Contoured pads attached to the pipe at support points (Fig. 9 below). Obviously, another attempt to eliminate metal-to-metal contact. This is better than the rubber pads, but still allows a crevice to be formed at the pipe's surface.
Figure 9 - Fiberglass contoured pads still risk crevice corrosion failure
The welded support is a viable solution. However, it adds significant cost to a typical project both in terms of construction and inspection. In some situations, it would be undesirable to make so many external longitudinal welds to a pressured piping system. There have been some other solutions adopted, none of which really addresses the major cause of the problem: Water entrapment.
Clearly, the solution must address the root causes of the problem and should have certain features that make application practical. The important features of one successful solution that is in widespread use throughout the offshore community are as follows:
1. The crevices at the pipe surface and the ability to trap and hold water in contact with the pipe surface must be eliminated.
2. As a secondary concern, metal-to-metal contact should be eliminated if possible.
3. The solution should allow easy maintenance and inspection of the pipe at the support point.
4. The system must provide complete support to the piping system.
5. The system will ideally be non-size-specific.
6. It must be applicable to new construction and retrofits, and should require no hot work to install.
7. It must be cost-effective.
The half round, high-strength thermoplastic I-Rod® (Fig. 10 below), meets all of the above requirements. The half-round configuration minimizes the crevice at the pipe and allows no water accumulation. The standoff provided allows easy inspection and maintenance at the support. The metal-to-metal contact is eliminated, and if used with an insulated bolt (Fig. 11 below), the pipe can be totally isolated from the support structure. The low-cost material has been selected and configured to optimize compressive strength while exhibiting very low creep. The material can be deployed as a continuous dressing to the top of a pipe-support beam (Fig. 12 below), or can be integrated with a stabilizing U-bolt (Fig. 13 below). Either way allows cold work installation for new construction or retrofit applications.
When using U-bolts, it is important to apply a polyolefin sleeve over the shank of the bolt. This reduces the risk of cracking the paint film around the pipe as the bolt is torqued down.This material provides the right combination of hardness and durability to protect the pipe paint but avoids setting up a capillary crevice around the circumference of the pipe.
Figure 10: The half-round pipe-support interface (trademarked as I-Rod®)
Figure 11 - Rod installed with polyolefin-sheathed U-bolt
Figure 12 - Rod installed as beam dressing
Figure 13 - Typical rod and U-bolt stand-alone support
The I-Rod® system described above was first introduced in the mid s; now there are thousands of offshore structures worldwide using this system. The first platform to be completely fitted with the material was installed in the Gulf of Mexico in . A more recent re-inspection in revealed no corrosion at any pipe-support points, and no degradation of the material. These pictures show the pipe support condition after 13 years offshore (Fig. 14 - 16 below).
Figure 14 - Beam dressing supports after 13 years offshore
Figure 15 - Rod in place under pig-launch barrel after 13 years
Figure 16 - More rod and bolt combinations after 13 years offshore
A side benefit to the application of this system was discovered by a major Gulf Coast fabricator. When using the material, which was attached to the upper surface of pipe racks with a special double-sided adhesive tape, it was discovered that the pipe fitting and installation was accomplished with virtually no installation damage to the paint system on the piping. This was particularly valuable in reducing the number of spot repairs that had to be made before delivery of the deck structures.
As one would expect with such an apparently simple solution, there have been many attempts to copy it. This usually results in an unsatisfactory result, as most of these materials do not possess the required properties. The materials will usually crush under the load (Fig. 17 below) or will creep with time causing the support to loosen (Fig. 18 below). In either case, the crevice control and desirable properties are lost.
Figure 17 - Imitations made of low-grade material are crushed under load
Figure 18 - Some "look-alike" materials creep with time
While cataloging the extent and severity of the problem, it was necessary to develop inspection strategies that would allow high-risk items to be addressed before failure. In recent years, improvements in guided-wave ultrasonic inspection have allowed a more quantitative approach to this type of inspection, but this is a costly and relatively time-consuming process. It was necessary to have a visual guideline that would help to screen the supports that required further inspection. While deceptively simple, the system has worked very well, and – when combined with other risk-based drivers that affect likelihood and consequence of failure – should allow rapid screening of large numbers of support points:
The corrosion that we are looking for is crevice corrosion, as opposed to general corrosion. This corrosion is then graded in three levels: light moderate and heavy. Definitions used to define these are as follows:
CC-L (Light Crevice Corrosion) - Corrosion products visible but no evidence of layered scaling.
CC-M (Moderate Crevice Corrosion) - A single layer of corrosion scale is visible at the edge of the crevice.
CC-H (Heavy Crevice Corrosion) - Copious corrosion product leaching and visible multi-layer corrosion scale is visible.
When investigated more closely, the CC-H situations normally show a wall loss at the deepest pit of >40%. A visual guide is provided for inspectors to assist in making the correct call (Fig. 19 below).
Figure 19 - Comparison of crevice corrosion severity at pipe supports
When designing pipe supports, avoid the use of saddle clamps wherever possible. Never use a rubber pad between a pipe and a pipe support if the area is exposed to a corrosive environment. When using U-bolts to stabilize piping, always use polyolefin-sheathed bolts. The half-round rod solution has proven to be very effective in controlling pipe-support corrosion over the last 15 years on thousands of offshore structures.
No reports of pipe support failures or even repairs have been received from structures fitted with the I-Rod® system.
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