Trenchless renewal methods and innovations in construction continue to evolve. These methods are designed to provide a range of facilities, including replacement, rehabilitation, renovation, and upgradation, collectively known as the renewal method. This approach is used to give a new lease of life to an existing pipeline system. In contrast, when work is undertaken to increase the design life of a utility system, we refer to it as repair.
Trenchless renewal techniques are increasingly gaining popularity due to their efficiency and effectiveness. These methods involve the use of advanced technologies and materials that allow for the rehabilitation of existing pipeline systems without the need for excavation. By minimizing the need for digging, trenchless renewal methods significantly reduce the amount of disruption caused to the surrounding environment.
The renewal method also helps to reduce the costs associated with pipeline repairs and replacement. Trenchless renewal techniques can be used to repair pipelines of various sizes and materials, including PVC, ductile iron, and steel. Additionally, these methods can be used to repair pipelines that are located in challenging environments, such as under rivers and roads.
As trenchless renewal methods and innovations in construction continue to advance, they are expected to play an increasingly important role in the maintenance and renewal of pipeline systems. By minimizing the need for excavation and reducing costs, these methods are helping to provide a more sustainable and efficient approach to infrastructure maintenance.
Types of Trenchless Renewal Methods
The context mentions that there are several methods of renewal that can be classified according to a flow chart-1. However, no specific details are provided about what these methods are or how they are classified. Therefore, I cannot provide a detailed explanation of the methods of renewal without additional information.
Selection of Trenchless Renewal Methods
The renewal method selected for pipeline work is influenced by the current physical state of the pipeline system. Various factors come into play, such as the type, size, material, length, and number of manholes, service connections, and bends. Additionally, issues such as exfiltration or infiltration, misalignment, joint settlement, abrasion problems, or corrosion damage can affect the selection of a renewal method.
Furthermore, the applicability of methods, construction difficulties, cost considerations, and the durability of the pipe system are other relevant factors that should be taken into account. In some cases, the challenges presented by these conditions may make some renewal methods unsuitable or too costly for the project. Hence, it is essential to evaluate these factors and select the most appropriate renewal method for each specific case.
Process of Different Types of Trenchless Renewal Methods
A brief idea on each renewal method is explained in the following sections:
1. Cured-in-Place Pipe
The Cured In Place Pipe (CIPP) method is a technique used to renew existing pipelines. This method involves inserting a tube made of fabric into the existing pipeline, which can be done by using water, winching or air inversion. The fabric used in this method is unique as it is saturated with resin, which allows it to fill cracks and repair gaps by moving through pipe defects.
The CIPP method is a versatile technique that can be used for both structural and non-structural purposes. One of its main advantages is that it provides a higher strength than the original pipeline, which allows it to function as a system on its own.
The CIPP method uses impregnated polyester resin or ERC fibre glass, which provides high corrosion resistance. These materials ensure that the renewed pipeline is durable and long-lasting, and can withstand various types of environmental conditions.
Overall, the Cured In Place Pipe method is an effective and reliable technique for renewing pipelines. Its use of resin-saturated fabric and high-strength materials ensures that pipelines are repaired effectively and can withstand the demands of various applications.
2. Underground Coatings and Linings (UCL)
Trenchless renewal methods utilize mortar or resin to fill up the lining or serve as coatings by spraying in pipes where workers are not allowed. These linings and coatings provide better resistance against moisture and thus prevent corrosion. However, they do not play a role in increasing the structural integrity or fixing leaks or joints. The material used for this purpose includes polyester, polyurethane, vinyl ester, concrete sealers, and silicone. Remote-controlled sprayers that are portable and traveling types are used to apply these materials.
In the UCL method, workers can enter the pipe to carry out the lining process. The characteristics of underground linings and coatings are provided in table-1.
Fig.2: Underground Coatings and Linings Method of Lining
Table.1: Characteristics of Underground Linings and Coatings Method
3. Sliplining (SL) Method of Trenchless Renewal
Trenchless renewal methods are used to fill up linings and coatings in pipes without the need for workers to enter. These methods involve the use of mortar or resin, which can be sprayed onto the pipe surfaces. The purpose of these linings and coatings is to improve resistance against moisture, thereby preventing corrosion. However, they do not aid in increasing structural integrity or fixing leaks and joints. To accomplish this, materials such as polyester, polyurethane, vinyl ester, concrete sealers, and silicone are utilized.
Remote-controlled sprayers are employed in the application of these materials, which can be either portable or traveling types. They are responsible for spraying the materials onto the pipe surfaces, ensuring that the linings and coatings are applied evenly and uniformly. In contrast to other methods, such as the UCL method, trenchless renewal methods do not require workers to enter the pipe during the lining process.
Table-1 provides information on the characteristics of underground linings and coatings. This table serves as a reference point for identifying the different types of materials that can be used, their properties, and the benefits they offer. By utilizing this table, individuals involved in the selection and application of underground linings and coatings can make informed decisions based on their specific requirements.
Table-2: Characteristics of Sliplining
Fig.3: A real time Sliplining method
4. Modified Sliplining (MSL)
The MSL method involves the insertion of pipe sections that are nearly the same size as the existing pipeline system, with the annular space between them being filled with grouting material. There are three possible variations of the MSL method.
Panel Lining (PL)
The modified Sliplining technique is typically utilized for pipelines with a diameter that exceeds 48 inches. It is considered a renewal method as it provides a completely new design life for the pipeline system. One of the benefits of this method is its ability to take on various shapes, including non-circular cross sections.
The use of fiber glass material is common in this method of pipe lining. This material is typically utilized to reinforce and strengthen the pipeline. As a result, the pipeline becomes more resistant to corrosion and other types of damage, which can extend its lifespan significantly.
Overall, the modified Sliplining technique is a highly effective method for rehabilitating large pipelines. It offers many advantages over traditional pipeline repair methods and has become increasingly popular in recent years. With the use of fiber glass material and other innovative technologies, this method can significantly improve the longevity and durability of pipeline systems.
Spiral Wound
The spiral wound method is a technique used to renew existing pipes. This method involves the use of grout and layered composite PVC. The ribbed texture of the PVC, when combined with the grout and existing pipe, creates a strong integrated structure. The technique involves layering the composite PVC and grout in a spiral pattern around the existing pipe, resulting in a renewed and strengthened pipeline. The ribbed texture of the PVC adds to the overall strength of the structure, ensuring that the pipeline is durable and long-lasting. Overall, the spiral wound method is an effective way to renew aging pipes and improve their structural integrity.
Formed in Place pipe
The MSL method is commonly used for renewing diameters ranging from 8 to 12 inches in various utilities such as wastewater, storm water, and culverts. This method is particularly useful in the rehabilitation of these types of infrastructures.
Table 3 presents the main characteristics of the MSL method, which is a cost-effective and efficient way to repair and renew pipelines. By utilizing this method, it is possible to extend the lifespan of existing infrastructure while reducing the need for costly replacements.
Overall, the MSL method is a reliable solution for pipeline renewal and maintenance, especially for diameters within the 8 to 12-inch range. It is a popular choice in the industry due to its practicality and effectiveness in improving the functionality of pipelines.
Table-3: Characteristics of Modified Sliplining Method
5. In line Replacement (ILR)
In the context of pipeline systems, the issue of limited capacity can be addressed through the use of in line replacement methods. This approach involves three stages of in line replacement, which aim to improve the overall capacity of the system. The first stage involves rewriting the existing context in paragraphs, in order to better understand the current capacity limitations and identify areas for improvement. This step is crucial for ensuring that the subsequent stages are effective in addressing the capacity issue.
a. Pipe Bursting
Pipe bursting is a process that involves breaking an old pipe while simultaneously pulling and replacing it with a new one. There are different methods used in pipe bursting, and these include pneumatic pipe bursting, static pipe bursting, and hydraulic pipe bursting.
Pneumatic pipe bursting uses a pneumatic hammer to break the old pipe. This method is suitable when there is a need for brute force to break the pipe. However, it creates noise during the process. Static pipe bursting, on the other hand, uses a pulling machine to remove the old pipe. This method is ideal when the old pipe is highly ductile and does not require much force to break. Unlike pneumatic pipe bursting, this method is noise-free.
Finally, hydraulic pipe bursting involves using a bursting head that articulates to create a burst in the old pipe. This method is also noise-free and is suitable for breaking pipes where moderate force is required. Each of these methods has its advantages and is used based on the specific requirements of the pipe bursting project at hand.
b. Pipe Insertion
The method known as pipe insertion or pipe expansion involves the insertion of a new pipe into an existing pipe. Typically, this method utilizes clay or ductile iron pipes.
c. Pipe removal
The method referred to as “pipe eating” is an approach used for replacing old pipes that involves the complete destruction of the existing pipe. The old pipe is removed by breaking it down into a slurry, which can be accomplished using either a Horizontal Directional Drilling (HDD) rig or an MT Machine. The key characteristics of the pipe bursting method are outlined in Table 5.
Table.5: Characteristics of Pipe Bursting Method
6. Close Fit Pipe (CFP)
A method has been developed for renewing pipelines, which involves temporarily reducing the diameter of the pipe and inserting it into the existing pipeline. This allows for a close fit with the old pipeline system. The method can be used for both structural and non-structural purposes. The pipe used for lining is deformed to a reduced diameter using either heat or pressure. There are two versions of the close fit pipe, one for structural purposes and one for non-structural purposes. The characteristics of the close fit pipe are shown in Table-6.
For non-structural purposes, the close fit renewal method is illustrated in the figure below. This involves inserting the reduced diameter pipe into the existing pipeline and then expanding it back to its original diameter. This results in a close fit between the old and new pipelines. The method has proven to be effective and efficient for renewing pipelines.
Fig.5: A close fit pipe going through diameter reduction
Table-6: Characteristics of The Close Fit Pipe
The three different types of close fitting pipes that are available are:
There are three different methods used for close fit lining systems in pipes. The first method involves using a deformed pipe, which is inserted into the host pipe by folding it. This technique allows for large diameter reductions of up to 50%, and can be done either at the factory or on-site.
The second method, called die drawing, was the first close fit lining system developed in the 1980s. This method requires the lining to undergo a reduction in diameter through heating at a temperature of around 100 degrees Celsius. The liner is then inserted into the pipe using a winch, and once it is in place, the winch force is released so that the liner can revert to its original shape. This process must be completed continuously, as any issues with maintaining the winch force can cause the liner to revert to the wrong location.
Finally, the roll down method involves permanently reducing the diameter of the liner before inserting it into the host pipe. This is done using a set of hemispherical rollers, resulting in a 10% reduction in diameter and an increase in wall thickness. The liner is then reverted to its original dimension by applying pressurized cold water. This method is less suitable for liners with thinner walls, but requires less winch load compared to other methods.
7. Point Source Repair (PSR) Method
In pipelines that are structurally active, there is a higher likelihood of finding local defects. In such situations, point source or localized repairs are often suitable. These repairs typically involve sealing defects with diameters ranging from 4 to 24 inches using resin, which is sprayed onto the damaged area using specialized machines that are widely available.
However, this method encounters four main challenges:
- Maintaining the loose structural part of the masonry: When repairing the pipeline, it is important to ensure that any loose structural parts of the masonry are properly maintained to prevent further damage or weakening of the pipeline structure.
- Providing local structural capacity: The repair must also provide sufficient structural capacity locally to assist the damaged pipes and enable them to sustain the loads they are designed to carry. This is crucial to ensure the long-term durability and integrity of the pipeline.
- Sealing to avoid infiltration and exfiltration: The repaired area must be effectively sealed to prevent infiltration of external materials, such as water or other contaminants, into the pipeline, as well as exfiltration of pipeline contents into the surrounding environment.
- Replacement of missing pipe sections: In some cases, pipe sections may be missing or severely damaged, requiring replacement. This adds another layer of complexity to the repair process, as the replacement of these sections must be carefully coordinated and integrated into the overall repair strategy.
Overall, addressing these challenges is essential to ensure the successful repair and restoration of structurally active pipelines with localized defects, and to maintain the integrity and functionality of the pipeline system.
Fig.6: Localized source repair- sealing
Injecting or forcing grout into defective joints under high pressure is a more effective method to reduce leakage compared to lining alone. This approach, known as chemical grouting, involves applying the grout from the surface, which efficiently seals leaks and stabilizes the soil surrounding the pipe. Chemical grouting is particularly effective when the soil around the pipe contains voids or stability issues. Another method of grouting is fill and seal, where the sealing process starts from one end of the pipe and continues to the other end, with fillings done in between in a continuous operation.
8. Thermoformed Pipe (ThP)
A commonly used technology in North America is the insertion of folded PVC or PE pipes into areas with very small cross sections of pipelines. This method involves inserting the folded pipe into an existing pipe and allowing it to thermoform to the required dimensions of the host pipe. Although the inserted pipes have a lower performance and structural capacity, they exhibit great chemical and abrasion resistance. These characteristics are displayed in Table-7 and make PVC and PE pipes ideal for this method.
Table-7: Characteristics of Thermoformed Pipe
Thermoformed pipe liners can be categorized into two main classes: deformed and reformed pipelines, or fold and form pipe liners. Regardless of their class, these liners temporarily alter the cross-section of the pipes they are inserted into, which can take the form of U, C, or H shapes. To insert these liners into the host pipe, a winch cable is used, and access must be provided on both ends of the pipe due to the pulling process involved.
After insertion, steam is utilized to heat the pipe liners. This causes them to expand with pressurized steam and heat until they take on the shape of the host pipe. To ensure proper fit and stability, the liners are cooled. This method is both cost-effective and promises a higher quality outcome.
9. Lateral Trenchless Renewal Methods
The paragraph states that various methods can be employed to address the issues that arise in lateral service systems. These methods include close fit pipe, pipe bursting, spray-on lining, and chemical grouting techniques. To provide a better understanding of lateral renewal, Table 8 presents the key characteristics of this process.
Table.8: Characteristics of Lateral Renewal
10. Sewer Manhole Renewal (SMR)
Proper maintenance of manholes is crucial to prevent surface water inflow and ground water infiltration. This can be achieved through manhole renewal, which can help avoid structural damage and corrosion of materials. However, there may be instances where manhole renewal is not a cost-effective option and manhole replacement may be a better alternative.
Before deciding on the appropriate method, it is important to analyze the physical characteristics of the structure, including its age, type, and condition. By doing so, one can make an informed decision and choose the most suitable method for sewer manhole renewal. Table-9 provides the main characteristics of sewer manhole renewal, which can be helpful in making this decision.
Table.9: Characteristics of Sewer Manhole Renewal
Chemical grouting has played a crucial role in renewing manholes, as seen through historical evidence. Recently, new chemical compositions have been introduced which not only provide water tightness but also enhance the structural durability of sewer manholes. This method not only delivers exceptional performance but is also economically advantageous. Engineers are using chemical grouts as an additional measure in areas where liners are being installed to ensure proper internal treatment. It is an effective way to solidify the area around the manhole, thus improving the overall quality of the treatment.