Flange and flued bellows can be the right answer to piping, ducting and vessel thermal growth problems over that of conventional thin walled metal bellows.
The advantages of a heavy convolution (with thicknesses up to 1/2") is its ability to hold up to mechanical damage. Dents and gouges create stress risers in thin bellows which results in fatigue cracks over time. Cracking of any type is very difficult to weld repair on thin bellows (typically .06" wall or thinner) but can be performed with plant maintenance staff on heavy walled bellows.
The thicker wall also hold up better to corrosion attacks - an added benefit is the common use of carbon steel material which is almost never used on thinner bellows in lieu of stainless steel or nickle alloys. drain couplings can also be added to the bottom of the flanged and flued convolution to prevent a build up of condensate.
The most common application for flanged and flued expansion joint is ASME code heat exchangers, and is the preferred bellows of choice as the movement is exclusively axial. The heavy walled, deep convolution is durable, and should last the life of the exchanger. The down side to the heavy wall design is the increase in stiffness which can over-stress the heat exchanger tube sheet.
Many engineering firms have banned the use of thin walled bellows expansion joints in process piping due to fear of field misapplications that may result in a failure. With a flanged and flued bellows those fears are unfounded as the heavy wall is about as fool proof an expansion joint as can be expected.
There are many different flange standards to be found worldwide. To allow easy functionality and inter-changeability, these are designed to have standardised dimensions. Common world standards include ASA/ANSI (USA), PN/DIN (European),[
ANSI designations such as ANSI 150, ANSI 300 and so on are often followed by a # (hash symbol). The ANSI number does not directly relate to a pressure rating, but to a class of flange. For example, the hash (#) or 'pound' reference; e.g. 300 pound, can be misleading in that an ANSI 300 flange is actually rated for a test pressure of 740 psi (~5100 kPa), and only within a certain working temperature range (-20 to 100 deg F.)
In most cases these are not interchangeable (e.g. an ANSI flange will not mate against a JIS flange). Further many of the flanges in each standard are divided into "pressure classes", allowing flanges to be capable of taking different pressure ratings. Again these are not generally interchangeable (e.g. an ANSI 150 will not mate with an ANSI 300). These "pressure classes" also have differing pressure and temperature ratings for different materials. "Pressure Classes" of piping are usually developed for a process plant or power generating station; these "pressure classes" may be unique to the specific corporation, Engineering Procurement and Construction (EPC) contractor, or the process plant owner.
The flange faces are made to standardized dimensions and are typically "flat face", "raised face", "tongue and groove", or "ring joint" styles, although other obscure styles are possible.
