As a filtration component supplier, our view on industrial piping systems tends to be unique. We see individual piping circuits as being small pieces of a larger overall puzzle, altogether serving an aggregate operational objective. Sometimes that objective is manufacturing a series of products, other times the goal is generating a utility service to power a facility, and so forth. In all cases, each smaller step within the process needs to support being isolated, serviced, managed, and validated independently of the rest of the system, as each step's health influences the next. We often find ourselves inserting filtration solutions within one step so as to improve the next step in line, a concept that not only works for process performance but for physical installation and maintenance as well. This analogy for breaking apart processes into smaller pieces translates quite well over to the piping materials and fittings that they’re built out of, which brings us to the topic of piping flanges - a key piping component that allows systems to be physically broken down into discrete segments for a wide range of benefits during installation and far beyond. By definition, flanges are piping fittings installed on separate piping segments that can be disconnected and reconnected using threaded fasteners. Flanges are resilient fittings able to withstand significant hydraulic forces and are sealed against leaks using gaskets placed between flanges. Here's a visual:
Why do we use flanges in industrial process piping? Multiple reasons, including:
- Installation Ease - in many applications, bolting together piping segments with flanges makes installation much easier than in-place welding, threading, or fusing. Especially with large, long, heavy piping runs, flanges break circuits down into smaller chunks that can be more easily handled.
- Component Connection - piping circuits almost always connect to many separate components such as valves, instruments, filters, strainers, pumps, vessels, and more. Flanges facilitate making such connections in the field by simply bolting up piping spools to each component.
- Serviceability - after piping segments are installed and placed into use, maintenance will surely be necessary at some point during the circuit's life. To make this maintenance easier, piping flanges are strategically located along piping runs so that they can be disconnected and reconnected for service at any time.
- Future Upgrades - as processes evolve, piping circuits often require rerouting, old components swapped out for new ones, or entire new circuits added in. Piping flanges make such changes much easier than cutting and welding, most notably saving time and potential issues introduced by intrusive tool processes.
- Technical Design Elements - piping flanges offer solutions to technical challenges encountered in circuit design, such as joining dissimilar materials, facilitating rapid change-over, isolating electrical and thermal energy continuity, and providing structural reinforcement at key stress locations.
Pipe Flange Styles - An Overview
Below we'll cruise through the most common pipe flange styles available for metallic and thermoplastic piping systems. As with most engineered products, there are certainly more selections available for special, industry-specific, and/or custom applications, which we'll touch on in the last section of this article.
Application Considerations for Flanged Pipe Connections
Continuing with the design concept of breaking industrial process systems down into smaller segments that can be more easily managed, we urge readers to break down their technical requirements into smaller factors that will ultimately influence which flange style they select for their systems. As general information, the below factors are the most common application considerations we review in our filtration and piping projects:
- Applicable Standards - most applications fall under a governing technical standard, such as ASME, AWWA, ANSI, or API, which will dictate what styles and specifications will be required. When in doubt, assume that ANSI B16.5 (up to D24") or ANSI B16.47 (D26" and over) is in play by default, and check with a qualified engineer for more insight.
- Pressure Ratings - flanges are classified by their pressure ratings, using figures such as "150#" to "2500#" to denote their nominal safe pressure capacity. Flange ratings must be considered not just for normal operating pressures, but also for catastrophic failure pressures.
- Faces - piping flanges have different face designs available that serve different pressure, force, gasket, and stress variables. Examples include Flat Face, Raised Face, Tongue, and Groove Face, and more.
- Materials - flange materials should be selected for compatibility with the piping material in use, the media flowing through the piping circuit, and the external environment. Carbon steel, stainless steel, ductile iron, PVC, and CPVC are the most common industrial choices.
- Other Technical Requirements - too often, non-standard critical technical requirements are overlooked when selecting piping components and must be considered. Examples include catastrophic failure pressures and temperatures, inclement weather impacts, environmental corrosion (such as with seawater exposure), contamination and sourcing traceability, and quality control documentation.
- Gaskets and Bolting - a flanged piping connection is only as good as the gasket and bolting components used along with it. Gasket material, style, thickness, and service life must be considered, along with bolt material, diameter, and holding force.
- Installation Details - flanges make field installation easier and faster than other means, but this does not infer that they are more forgiving in installation accuracy and integrity. Flange alignment, spacing/gapping, bolting torque, and re-torquing after thermal cycling are very important details.
- Standardization - all industrial process systems should be as standardized in component specifications as possible. In other words, piping components including flanges should be of the same style, design, and installation requirements as much as possible, so as to limit the chance of errors and incompatible flanges being mated together.
Recap
For most applications, a professional engineer and/or piping designer should be consulted to make sure flange selections (and all other technical details) are made with safety and reliability in mind.
When chosen correctly, piping flanges offer huge benefits for industrial process piping systems, not just by making piping segments easier to install and service, but by offering built-in opportunities for expansion and modification over time. Just as we often find when adding filtration equipment into existing piping circuits, having strategically positioned flanges can make all the difference between an afternoon cut-over and a much longer complete re-fit and re-weld installation.