Jacketed Corrugated Double Jacketed
This was the standard refinery gasket
Still common for large diameters and applications with more than
circumferential sealing surfaces
Soft compressible filler material is contained within a thin “wrapper”
Corrugations provide the seal, and a labyrinth leak path
PPF-R00-21
Types of Gaskets
Jacketed and Filled
The outer “wrapper” on a jacketed gasket makes the gasket more rugged by protecting the soft inner material from damage. It also provides some resistance to blow out.
Corrugated jackets are more rugged than flat jackets because the deformations add strength to the system. They also can provide a better seal because the sealing force is concentrated at the peaks of the corrugations; it is not spread over the gross surface of the gasket. The “labyrinth” path referred to means that it is a complex path with a lot of twists and turns, difficult to pass through. If the fluid finds its way past one corrugation, there is another waiting.
Jacketed gaskets, especially the corrugated style, require less seating force than spiral wound gaskets.
This type of gasket is sometimes used in large diameter, often low pressure applications, where a spiral wound gasket may tend to unravel or “spring” apart during handling. The problem is particularly acute for vertical sealing surfaces. When the spiral wound gasket is removed from its backing cardboard, it’s quite unstable. For a horizontal sealing surface, the gasket can lie atop one of the flanges. Regeneration Tower body flanges and large diameter access openings on FCC Reactor and Regenerators are examples of where they are used. Jacketed gaskets are also used for specialty exchanger gaskets, such as channel gaskets that also seal at the baffle between passes. It would be difficult, if not impossible, to wind a spiral wound gasket to include the diametrical piece.
EDS-2004/FL-64
A serrated metallic filler sandwiched between two layers of
sealing material
Upon bolt-up the sealing material deforms into and is held
by the serrations
Seal stress is concentrated at the peaks of the serrations,
while the valleys prevent the sealing material from flowing
Metallic filler can be reused
Becoming more popular, especially in Europe PPF-R00-22
Types of Gaskets
Kammprofile
The serrated filler is fabricated of solid metal and has concentric grooves machined into the faces. This greatly reduces the gasket contact area on initial tightening, thereby reducing the total required bolt load.
The gasket material flows into the serrations of the metallic filler which holds the gasket in place. Blow-out of this style gasket is nearly impossible, and no special flanges (e.g., with grooves) are necessary. The assembly is mostly metal, hence it is rugged and requires less careful handling than other gaskets. No grooves or projections on the flange are necessary. The soft gasket material must be changed each time the flange is opened.
EDS-2004/FL-65
Gaskets for which an increase in the pressure to be
contained increases the sealing pressure.
Examples are O-rings, K-rings, and to a lesser degree,
gaskets for ring joint flanges.
Gasket material must be soft and deformable.
Acceptable materials have low limiting temperatures (200-400°F). O-Ring Pressure Seal Seal Pressure Seal Seal PPF-R00-23 K-Ring
Types of Gaskets
Self Actuated
This the type of gasket used in the Dur-O-Lok coupling.
The seal with this style of gasket is based on the internal pressure. Internal pressure deforms the gasket and seals it against the outside of the groove. The greater the pressure, the greater the provided seal.
Self actuated gaskets must be changed every time the flange is opened because they are soft and depend upon the ability to plastically deform. After use, they cannot be reliably removed and then re-deformed into another, slightly different, configuration to seal the flange again.
EDS-2004/FL-66
Ring joint gaskets are either oval or octagonal (oval is preferred because it works in the current and old groove shapes)
Made of a variety of hard metallic materials to avoid distortion Must be compatible with the
internal atmosphere and softer than the flange material
Must be no rougher than 63 microinch Ra
Hard to handle
PPF-R00-24
Types of Gaskets
Ring Joint
The rings are fabricated of solid metal, usually soft iron, soft steel, Monel, 4-6 percent chromium, or stainless steels. Oval rings will work in the current octagonal grooves and the older oval grooves. Octagonal gaskets only work in octagonal grooves.
The alloy steel rings must be heat treated to soften them. The gasket must be softer than the flange material to insure that it is the gasket that flows and fills imperfections, i.e., the gasket distorts upon use. The gasket can be replaced, although they are frequently reused. One reason for reuse is that if the flange or groove distorts during operation, the existing gasket (which also distorted) will continue to provide a seal. A new gasket may not function as well because it may not fit well into the distorted grooves. The second reason is that the gasket is made of soft metal that is not crushed or strained well beyond its yield point as other gasket materials and styles are. The gasket can, therefore, function as well on reuse as the initial use.
The gaskets are wedged into the grooves in the flanges. They fit against the sides of the groove and do not touch the bottom.
An internal ceramic rope is frequently provided to shield the gasket from the worst of the internal atmosphere.
EDS-2004/FL-67
Composed of alternating layers of compressible filler
material and metal rings wound in a spiral, forming a labyrinth leak path sealed at the peaks
Most common type of gasket in refinery service
PPF-R00-25