High chemical and thermal resistance are the most important properties of FA flat gaskets. These properties are obtained by using a nonwoven supporting material of extremely resistant fibres that is impregnated with NBR. This creates a sealing material that remains strong regardless of the direction of pull, making it ideally suited to sealing flanges on pipes, units and fittings.
A nonwoven fabric is the base material used in Merkel FA flat gaskets.
In a special procedure, carefully proportioned aramid and glass fibres are processed to form a nonwoven fabric with a clearly defined structure.
Unlike fibre-reinforced flat gaskets, which are manufactured using the calendar process, a carefully determined fibre layer assumes the supporting function here.
In this way, an optimised structure is created for the application in the very first stage of production.
The nonwoven fabric is then impregnated with a special blend of dispersed fillers and NBR latex.
The advantage of this patented impregnation process is the water solubility of latex.
This means that solvents are not required for the production of fibrous flat gaskets, thereby reducing the environmental pollution caused by the production process, simplifying the necessary plant structure and rendering superfluous the need for explosion prevention measures.
After this, the flat gasket material is thermally solidified between rotating heated cylinders.
Depending on requirements, up to ten layers of the flat gasket material can be laminated onto one another in a different part of the process.
The amount of layers depends on the required thickness of the seal.
Heat and pressure are used in a calendar to create a gastight bond out of the individual layers.
This continual process allows for standard flat gasket material thickness of between 0.3 and 2mm.
Special thicknesses are also possible.
The continual production process means that the flat gasket material can be made available as an exact cut-to-size piece or, more economically, as an uncut continual roll.
In its uncut state, shapes can quickly and easily be stamped or cut out using water jet or laser cutting, thereby guaranteeing customers the exact shape and size they need.
Small, detailed contours or boreholes can be cut easily and safely from this flat gasket material.
In short, the seal can be constructed exactly in line with the customer's demands.
The sealing material can be used at temperatures of between -100 and +260C.
For nonpolar media such as heat transfer oils, the flat gasket can even be used at temperatures of up to 300C.
It is resistant to many substances including solvents, watery solutions, alcohols and glycols.
Concentrated acids and alkali solutions can be sealed to moderate temperatures.
Diluted acids and alkali solutions at high temperatures do not pose a problem either.
FA flat gaskets can generally be used at pressures of up to 100bar.
Characteristic parameters show that the combination of the special fibres in the non woven fabric and the special NBR impregnation gives FA flat gaskets the following advantages: excellent adaptation for installation; low warm-setting behaviour; good sealing properties and high flexibility as well as excellent cyclic load resistance in long-term tests.
Proof of the broad range of applications for this sealing material is provided by the list of releases and authorisations which have been applied for and its proven technical safety level according to various tests.
The DVGV (German Gas and Water Association), for example, investigated the material's gasproof properties and its behaviour under high temperatures for the high-temperature resistance (HtB) release while the BAM (Federal Institute for Material Research and Testing) investigated the flat gasket's suitability for use with oxygen.
FA flat gaskets are ideally suited for flanges, pipe joints, manholes, boilers and columns.
Thanks to their low setting values, the seals do not generally have to be tightened, a fact that simplifies maintenance enormously.
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