In some applications, equipment or machinery may be too large to use a single-piece gasket. In these situations, a segmented gasket which is fabricated from multiple sections of material joined together, must be used. Applications where segmented gaskets are often used include those in the power generation, marine, oil and gas, pulp and paper, waste treatment, and other industries.
Segmented gaskets are fabricated by joining together multiple sections of material. Joining techniques employed include butt-joining, dovetailing (also known as “puzzle-locking”) and beveling using the technique of skiving.
When joining together the sections of a segmented gasket, it is critical to ensure that the thickness of the gasket remains uniform throughout its entire circumference. Should there be any variations in thickness within a segmented gasket, sealing quality and performance could be adversely affected. The pros and cons of the various joining methods employed to produce segmented gaskets are discussed below.
Butt-joining involves the joining together of two flat edges. In butt-joining, two flat edges of the same thickness are brought together and bonded with the use of a suitable adhesive. The adhesive used will determine the strength of the butt-joint – the adhesive must be compatible with the materials being joined and must be capable of supporting the application media, service temperatures and pressures, and mechanical loads.
Dovetailing creates an interlocking pattern, similar to that on jigsaw puzzle pieces, along the section edges to be joined. These patterns fit together when the sections are brought together and mated. Dovetailing creates a joint that is stable and which “tightens up” when a mechanical load is applied to the gasket. Dovetailed joints are typically long-lasting and produce a dependable seal.
Skiving is an advanced fabrication technique where the gasket material is beveled along the section edges that are to be joined. When two well-skived edges are mated and bonded together, the result is an even and smooth join where the overlapping bevels are uniform in thickness. At CRG, we often fabricate segmented gaskets using single- and double-skived joints that are made by hand or through the use of highly-specialized skiving machinery.
When joining skived edges, it is important to carefully select the adhesive that will be used. Not only must the adhesive create a failure-free bond, it must be capable of resisting mechanical loading forces, service temperatures and pressures, and any chemical attack from the application media.
It is generally agreed that dovetailing produces the strongest and most durable joints when fabricating segmented gaskets. As described above, dovetailed joints are stable and actually strengthen when a mechanical load is applied. In contrast, butt-joining tends to be the weakest joining method – of all the joining methods presented above, butt-joints typically have the smallest surface area where the joining surfaces meet, resulting in weaker bonds.
As a joining technique, skiving lies in between butt-joining and dovetailing in terms of strength and durability. With skiving, it is also difficult to obtain smooth, even joints without steps or transverse grooves. The presence of these can produce variations in joint thickness as well reduce the available surface area to be bonded.
As noted above, with all three joining methods, a gasket fabricator must take care to ensure that there is no variation in thickness across any of the joined surfaces in the gasket.
Segmented gaskets can be produced from a variety of rubber compounds. At CRG, we fabricate segmented gaskets from compounds including EPDM, SBR, Silicone, Nitrile, Butyl, Neoprene, Viton, Pure Gum, and others. The material chosen to fabricate segmented gaskets should always be based upon the application being serviced. This will require considering the media which must be supported, the service temperature and pressures, and the mechanical loading forces involved in the application.
CRG has produced segmented gaskets that have exceeded 20 feet in diameter; the image used in this blog shows a segmented gasket 12 feet in diameter that we recently produced. If you have an application that requires segmented gaskets, CRG can review your needs, provide guidance on material selection, and produce the finished gasket. To find out more about how CRG can solve your segmented gasket challenges, please contact our sales team directly at email@example.com.
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