Semi-Metallic and Metallic Type Gaskets
In recent years, the “semi-metallic” gasket has become extremely popular. Due in a large part to its unique capacity to meet the extreme effects of pressure and temperature fluctuations across flange faces; flange face imperfections; flange rotation stresses and bolt stress relaxation and creep
The combination of non-metallic filler for compressibility and metal for strength, resilience and chemical resistance and typically at higher temperatures and pressures than non-metallic types make this type of gasket applicable in a wide variety of situations.
The range of spiral-wound gaskets are widely used on high pressure joints throughout industry world-wide. These are generally used for higher temperatures and pressures. A variety of metals are available for the winding strip as well as for the support rings.
On raised face flanges, spiral wound gaskets have an outer support ring which locates inside the bolt circle, and they can also be supplied with an inner ring. These are usually for the higher pressure systems, or processes having high flow rates or abrasive media, as the inner ring reduces turbulence at the pipe bore.
Metal Jacketed Gaskets
Single and double-jacketed metal clad gaskets have been traditionally used as heat exchanger gaskets. Metals such as soft iron, carbon steel and stainless are used to encase a soft filler material, usually a non-asbestos composite. More typical today these are filled with graphite or, a mica-graphite filler. It should be noted that some heat exchanger flanges have stress raising ‘nubbins’ on one face, and the non-seamed side of a double jacketed gasket is intended to go against this face, so it is important that the joint is fitted the correct way around in the assembly.
This gasket type is generally a solid metal ring having a serrated tooth form profile on each side. A covering layer of graphite or PTFE is applied, which becomes compressed into the serrated surface when the gasket is loaded. These gaskets have a good level of sealing tightness and are frequently used to replace metal-jacketed joints on heat exchangers.
Metallic Gasket Types
Manufactured from one metal or a combination of metals in a variety of shapes and sizes for high temperature or pressure use. Due to the high pressures involved, the seating stresses are necessarily large to give sufficient gasket deformation to overcome any flange surface imperfections and to overcome the high system pressure forces.
Ring Joint -Oval & Octagonal Gaskets
These are commonly used on oilfield applications, and details of these joints are given in well recognized standards ASME B 16.20 and API 6A. The gaskets sit in a recess in the flange, which has a 23 degree angled wall.
There is much more that can be said about each type of semi-metal and metal gasket. To ensure you select the right type for your application contact Four States Gasket and Rubber, Inc.
In the Greater Denver Region –
Contact Steven Liparoto at 720-878-1053 or send to firstname.lastname@example.org
In the Four Corner area (New Mexico, Arizona, Utah, Southern Colorado)
Contact Bryan Crawford at 505-325-9806 or send an email
Or ask for Scott Blades at 505-325-9806