Gasket

One of the more desirable properties of an effective gasket in industrial applications for compressed fiber gasket material is the ability to withstand high compressive loads. Most industrial gasket applications involve bolts exerting compression well into the 14 MPa (2000 psi) range or higher. Generally speaking, there are severaltruisms that allow for best gasket performance. One of the moretried and tested is: "The more compressive load exerted on the gasket, the longer it will last".
There are several ways to measure a gasket material's ability to withstand compressive loading. The "hot compression test" is probably the most accepted of these tests. Most manufacturers of gasket materials will provide or publish the results of these tests. lens gaskets for high pressure
[edit]Gasketdesign
Gaskets come in many different designs based on industrial usage, budget, chemical contact and physical parameters:
[edit]Sheet gaskets
The premise is simple in that a sheet of material has the gasket shape "punched out" of it. This leads to a very crude, fast and cheap gasket. In older situations the material was compressed asbestos, but now generally a fibrous material such asgraphite is used. These gaskets can fill many chemical requirements based on theinertness of the material used and fit many budgetary restraints. Common practice prevents these gaskets from being used in many industrial processes based on temperature and pressure concerns.
[edit]Solid material gaskets
The idea behind solid material is to use metals which cannot be punched out of sheets but are stillcheap to produce. These gaskets generally have a much higher level of quality control than sheet gaskets and generally can withstand much higher temperatures and pressures. The key downside is that a solid metal must be greatly compressed in order to become flush with the flange head and prevent leakage. The material choice is more difficult; because metals are primarily used, process contaminationand oxidation are risks. An additional downside is that the metal used must be softer than the flange — in order to ensure that the flange does not warp and thereby prevent sealing with future gaskets. Even so, these gaskets have found a niche in industry.
[edit]Spiral-wound gaskets
Spiral-wound gaskets comprise a mix of metallic and filler material. Generally, the gasket has a metal (normallycarbon rich or stainless steel) wound outwards in a circular spiral (other shapes are possible) with the filler material (generally a flexible graphite) wound in the same manner but starting from the opposing side. This results in alternating layers of filler and metal. The filler material in these gaskets acts as the sealing element, with the metal providing structural support.
These gaskets haveproven to be reliable in most applications, and allow lower clamping forces than solid gaskets, albeit with a higher cost.
[edit]Constant seating stress gaskets
The constant seating stress gasket consists of two components; a solid carrier ring of a suitable material, such as stainless steel, and two sealing elements of some compressible material installed within two opposing channels, onechannel on either side of the carrier ring. The sealing elements are typically made from a material (expanded graphite, expanded polytetraflouroethylene (PTFE), vermiculite, etc.) suitable to the process fluid and application. Constant seating stress gaskets derive their name from the fact that the carrier ring profile takes flange rotation (deflection under bolt preload) into consideration. With allother conventional gaskets, as the flange fasteners are tightened, the flange deflects radially under load, resulting in the greatest gasket compression, and highest gasket stress, at the outer gasket edge.
Since the carrier ring used in constant seating stress gaskets take this deflection into account when creating the carrier ring for a given flange size, pressure class, and material, the...