Heat exchangers are critical to the operation of power generation facilities, and leakage is the enemy of any heat exchanger. Breakdowns, often the result of thermal expansion, can be extremely costly and also have the potential to create safety hazards. Gasket failure usually gets the blame when leaks occur—but what if a change in bolting could help prevent leaks?
The fact is, nearly 95% of fastener failures are the consequence of poor fastener selection or improper installation. Not only are the resulting failures expensive, but they can even have catastrophic consequences. Choosing the right bolt for the application becomes of paramount importance.
Progressive plants with innovation-minded maintenance supervisors, engineers, and reliability teams who work together for long-term plant performance improvements are turning to bolts that accurately indicate their own load and easily display the information.
Valley Forge & Bolt manufactures a variety of sophisticated load indicating fasteners, which use proprietary technology to indicate actual bolt load from within the joint, displayed in real time. Engineers and maintenance personnel can conveniently verify critical joint load at any time, reading tension as a percentage of load from an analog gauge at one end of the bolt, a digital display from a hand-held meter, or a remote transmission from a wireless unit.
As a result, it becomes more apparent when bolts are beginning to lose tension and when joint failure might be imminent. Perhaps even more important, load indicating fasteners assist with applying the correct tension at the installation of the bolts. Proper initial preload can help prevent bolts from loosening while in service, improving equipment reliability and extending time between preventive maintenance cycles.
There are a number of assemblies found in most power generation facilities—fossil, thermal, hydro, and nuclear—where load indicating fasteners add integrity to the bolted joints. Here are three applications where the benefits are most obvious for maximizing plant safety and efficiency. In each of these applications, alerting maintenance staff to even the smallest loss of tension in real time allows them to immediately investigate, diagnose, and prevent equipment failure. Load indicating fasteners can prevent an issue before it occurs rather than perpetuate the cycle of fail, fix, repeat.
- Valve Flanges
Flanged assemblies provide the greatest bolting challenge in most power generation facilities. While many of these gasketed applications pose no issues, there are always a few critical pathways that have joints that leak on startup, have a steam ring around them, or experience chronic gasket seating problems. Using a load indicating fastener in these instances produces a well-sealed flange, free from leakage. When an assembly is able to be inspected at regular intervals, bolt load can be assured and trouble-free operation of the mechanical joint can be achieved from shutdown to turnaround.More accurate tensioning at installation will mean reduced severity of tension loss later on. Plus, the ability for maintenance staff to easily read critical joint load makes prevention much easier—and much more likely. Also consider that, for large valves, it can be difficult to achieve correct load for bolts over 1 inch by using torque tightening methods. Valley Forge manufactures its own bolts and is able to include its Load Indicating Technology in even the largest of them.
- Leak-Free Startups
All tightening tools have some level of inherent inaccuracy because a large percentage of the applied load is lost due to friction; however, standard torque and tensioning tools are no match for a load indicating fastener. Load indicating fasteners display bolt load, in real time, on the actual assembly. There’s no guesswork, since the operator can see the percentage of proof load applied. The measurements of load indicating fasteners are accurate to within +/-5% of load, whereas torque is notoriously unreliable and can only achieve approximately +/-20% accuracy. Being able to apply repeatable bolt load is a key to helping ensure an efficient and trouble-free assembly.
These pressurized access points can be found throughout the plant on critical equipment, and most have a common need for gasketed sealing. The strength of the seal is only as good as the tension provided by the bolts at installation. With pressure topping 2000 psi in some applications, accurate tension is necessary not only to help ensure smooth operations, but also to protect worker safety. The ability to accurately read bolt tension, as afforded by load indicating fasteners, represents a giant leap forward in providing a higher degree of confidence that bolts are tensioned correctly.
Using technology to improve the operational efficiency of power plants is not a new idea, but it has gained a foothold throughout the industry. As a part of this movement, proactive engineers and maintenance supervisors should also consider the data gained through the use of load indicating fasteners.
Valley Forge offers meters from which the gathered information can be uploaded to digital monitoring systems. Plant maintenance teams can use this data to form a larger picture of both the individual components and overall plant health, and then to formulate maintenance plans, troubleshoot hotspots before downtime occurs, and maximize uptime without compromising safety.
Load indicating fasteners are a relatively inexpensive way to use technology to improve the functioning of a plant. We’re at a watershed moment where the excuses of the past, often related to cost, are no longer valid. Who will be the ones to step up and embrace the ability to prevent maintenance issues instead of merely dealing with them? Time will tell.
About Valley Forge & Bolt
Valley Forge & Bolt Mfg. Co. is a domestic manufacturer of patented bolting products for critical applications. These bolts and studs are widely trusted for their unrivaled quality, extraordinary performance, and enduring reliability. Email: POWER@vfbolts.com. Call: 1 (602) 269-5748. On the web: https://www.vfbolts.com/.