Pros & Cons of Using a Weld Neck Flange

            There are over a dozen different types of flanges commonly used in industrial piping systems, the most common flange being used today is known as a weld neck flange. A weld neck flange is a type of flange which “features a long tapered hub that can be welded with a pipe.”¹ This is done to ensure that none of the product flow is lost or restricted. Among the many versatile uses for a welding flange, its most common application is in piping systems which have great fluctuations in temperature and/or pressure, as well as in piping systems which transport hazardous fluids. In short, a weld neck flange is ideal for extreme conditions in piping systems. However, there are some major drawbacks to the weld neck flange, namely the price tag on a weld neck flange compared to the potential use of another flange, such as a slip-on flange. Let’s dive right in and explore the advantages of using weld neck flanges.

            Weld neck flanges are able to withstand great extremes in pH, temperature and pressure fluctuations. “The resilience of this type of flange is achieved by sharing the environmental stress with the pipe with which it is welded.”² Some weld neck flanges have “been used successfully at pressures up to 5,000 psi.”³ And while weld neck flanges can be used exclusively in such piping systems, it is advised to consult an engineer regarding where weld neck flanges should be applied.

            Another major advantage to weld neck flanges is their ease of installation. Though a skilled welder is required for the installation of a weld neck flange, there are not many variables required to take into consideration. “When using the butt flanges it is easier to determine pipe length applications because the calculations do not have to account for the space taken up by threads on bolt-on applications. Slip-on flanges also require calculation using the insertion amount.”⁴ Because of this welded connection, the weld neck flange is quite durable– though there are disadvantages, mainly in regard to the price of a weld neck flange.

            Weld neck flanges can run up a check! Yes, despite their size and simple construction, weld neck flanges can be more expensive than an alternative, similar type of flange. The increased cost is mostly due to the additional material in the construction of the flange: “The production of these flanges is more expensive because of the long necks that are present.”⁵ Besides the (typically) more favorable price for similar, cheaper flanges such as slip-on flanges, the weld neck flange, the next most common disadvantage for weld neck flanges is their potential to leak: “each connection has to pass a radiography test. When the tests are complete and the weld is sufficient there could still be air bubbles in the weld that the test did not detect. Over time these bubbles will develop leaks. Regardless of the welder’s skill set these bubbles occur and leaks will develop over time. These leaks can be repaired without replacing the entire flange.”⁶ It should be noted that pipe flange radiography is a relatively easy process.

            All in all, there aren’t many disadvantages to using a weld neck flange: They’re easy to install, remarkably resilient and definitely durable. Still, the main disadvantages for these weld neck flanges, though sometimes negligible, are the cost for weld neck flanges, and the fact that a weld neck flange can sometimes leak if not radiographed properly, which can practically negate the entire purpose of a flange if the leaking is excessive and (though rare) unable to be mitigated and requiring replacement. Again, EMC is not making a definitive recommendation to any of its customers to always use a weld neck flange whenever applicable based on the information in this article alone: for a recommendation into which flange to go with for your own unique application, please contact EMC today! We recommend emailing us at jpwoods@equipmac.com and our team of industry experts with over 45 years of experience will get back to you as soon as possible with a recommendation.

1          https://blog.projectmaterials.com/flanges/flange-types-piping/ 

2          https://www.weldflange.com/application-and-advantage-of-weld-neck-flange.html

3          Same as ²

4          http://weldneckflange.weebly.com/benefits-of-using-weld-neck-flanges.html

5          Same as ⁴

6          Same as ⁴