News and technology in the global energy industry
National Defense Daily subscribers and registered users, please log in here to access the content.
We receive the most important news in the industry the first time in your inbox-to make you smarter and one step ahead in this rapidly changing and competitive market.
© 2021 Access Intelligence, LLC-All rights reserved
We receive the most important news in the industry the first time in your inbox-to make you smarter and one step ahead in this rapidly changing and competitive market.
The two most important elements in any construction or upgrade project are safety and speed of completion. Although one way to improve safety is to eliminate hot work as much as possible, the reality is that many tasks around power plants require welding. However, one area that may not always require welding is the installation or expansion of piping systems.
Although the piping connection method is essential for high-pressure, high-temperature process piping systems, it is not the case for plant balancing piping systems. Services such as cooling water, reverse osmosis, fire protection, chemical treatment, lubricating oil, and compressed air can use alternative flameless connection methods-some of which can provide installation speeds up to 10 times faster than welding. Grooved mechanical piping is one option.
Slotted mechanical pipe joints consist of four components: slotted end pipe, gasket, coupling housing and fasteners. The pipe groove is formed by cold forming or machining at the pipe end. The gasket enclosed in the coupling housing is placed around the two butt-connected grooved pipe ends, and the key part of the housing is engaged with the groove. The bolts and nuts are tightened with a socket wrench or impact wrench to fix the shell parts together.
In the installed state, the coupling housing wraps the gasket and engages with the groove on the pipe circumference to form a leak-proof seal in the self-constraining pipe joint. In addition to pipe-to-pipe joints (Figure 4), grooved joints can also be used to connect pipes to grooved end valves, fittings and accessories to create a complete piping system.
Roll grooving is the most common method of pipe end preparation. The rolling grooving process displaces a small part of the tube wall radially, forming a groove around the circumference of the tube, which is recessed on the outside and recessed on the inside. This method can be used for size 5 to size 80, carbon steel, stainless steel, copper, and aluminum pipes with diameters ranging from 0.75 inches to 72 inches.
There are two types of grooved couplings: rigid and flexible. Rigid couplings are not allowed to move, and can be used wherever pipe joint rigidity is required, similar to welding or flange joints. The flexible coupling allows a limited amount of linear and angular motion to accommodate thermal and seismic motion as well as vibration and misalignment. Most grooved couplings used in power plants are rigid, and flexible couplings are only used around rotating equipment to isolate noise or vibration. This allows the system to be supported and guided in accordance with the American Society of Mechanical Engineers (ASME) B31.1 power piping standard.
A key advantage of grooved pipe is its flameless installation. The assembly of grooved pipe joints does not require welding, flame or heating, and does not generate smoke. In terms of preparation, there is no need to remove or clean the surrounding combustibles, and there is no need to increase ventilation or fire prevention. During the assembly process, cutting torches and storage tanks are not required, and the pipe installer will not be exposed to flames, sparks, slag or smoke. No fire duty is required. Therefore, the groove system reduces the risk of personnel and property.
Minimizing welding allows certified welders to focus on critical process systems, while pipe fitters are responsible for handling the factory balance system, which helps to complete the project on time. Slotted pipes and assembled joints do not require special certification or training; these procedures are easy to teach and transfer.
These advantages were used in the construction of the South Hedland Power Station in the Pilbara region of Western Australia (Figure 5). With rapid growth requiring substantial investment in power projects, the facilities owned by Horizon Power chose trench products due to tight timeliness and remote locations. Selected for diesel fuel, raw water/fire fighting water, softened water, drinking water and instrument air systems, grooved pipes can be installed quickly and safely without high temperature work and simplify on-site pipe end manufacturing.
The safety advantages of grooved pipes complement the speed and ease of system installation. The installation speed of standard grooved joints is five times faster than that of welded joints and three times faster than flanged joints. Out-of-the-box couplings can double the time savings. No special tools are required to assemble grooved couplings, and most couplings have no torque requirements. In addition, the groove system provides visual confirmation of correct assembly.
Speed and ease of installation played an important role in the construction of the Alstom gas test facility in Birr, Switzerland (Figure 6). By using grooved joints, valves and fittings to connect cooling and firefighting water piping systems, Alstom was able to reduce installation time by 50% compared to traditional connection methods, resulting in significant cost savings and faster project completion. The grooved parts can also be easily maintained and repaired.
Slotted couplings reduce maintenance downtime, and there is a union at each joint to simplify system access when needed. The coupling is easy to disassemble and remove from the joint. After the work is completed, the coupling can be reassembled as quickly as the initial installation. This feature simplifies maintenance, repair, and future expansion or modification. When properly installed and operated within the design specifications, the grooved mechanical coupling is designed to extend the life of the system without leakage or failure.
The groove system brings many advantages to construction and upgrade projects, from fast, flameless installation to simplified maintenance. Most importantly, grooved mechanical piping provides factory owners with a way to speed up project completion while maintaining a safe environment. ■
—Mitch Lee is a Victaulic power market business development expert, and Victaulic is a manufacturer of mechanical pipe connections and fire protection systems. He is also a member of the Construction Industry Institute.
More operation and maintenance news
On-demand until October 28, 2022
Available on demand until October 13, 2022
© 2021 Access Intelligence, LLC-All rights reserved