In pipeline systems and pipeline fittings, gaskets of various designs are used. But the materials from which they are made differ by no less variety. These include paper, cardboard, cellulose, fiber, rubber, asbestos, graphite, metals (metal gaskets ─ made of steel, copper, aluminum, bronze, etc.), paronite, a wide range of polymer materials ─ polyethylene, fluoroplastic, polyvinyl chloride, other.
Requirements for cushioning materials
The conditions for ensuring tightness in gaskets, as in stuffing box seals, depending on the working medium’s properties ─ its pressure, temperature, aggressiveness. Decompression of gaskets in flange joints can be caused by absolute values of temperature and its fluctuations, which change the dimensions of the gasket and the mechanical properties of the material from which the gasket is made. The increase in temperature creates plastic deformation of the gasket caused by an increased tightening of the bolts or studs. On the other hand, as the temperature drops, the tightness decreases, and the gasket joint loses its tightness.
Following the tasks solved by gaskets, a whole set of requirements is imposed on gaskets, the most important of which are:
Cheapness and availability
These qualities are important as a factor in reducing the operating costs of pipeline valves due to the large volumes of use of gasket materials and the need for their frequent replacement;
Resilience is a quality necessary to ensure better tightness of gasket-sealed joints.
The gasket should not collapse under the influence of mechanical loads associated with its installation, i.e., when tightening bolts or studs; at the same time, the gasket material should not be so hard and strong as to deform the sealing surfaces, which can occur when using metals as gasket materials.
The gasket material should not lose its mechanical properties when exposed to high and low temperatures. Otherwise, it will melt and flow out at high temperatures or begin to crack and crumble at low temperatures;
Like mechanical stress and high temperatures, the working environment’s chemical action can cause destruction or loss of the gasket functionality.
Rubber – a product of rubber vulcanization ─ has a considerable number of advantages that make it advisable to use it as a material for gaskets’ manufacture. Chief among them are high elasticity and impermeability to liquids and gases. A good gasket manufacturing company that specializes in making custom gaskets will help you design and cut the gasket you need.
There are rubbers made based on natural rubber and its combination with other rubbers and rubbers based on synthetic rubbers. A distinctive feature of rubber is the ability to reversible elastic deformations in an extremely wide temperature range. This is facilitated by the presence in the composition of technical rubber of a considerable number (sometimes several tens) of components. The composition and manufacturing technologies have predetermined a wide variety of types of rubbers and their application areas, including sealing connections.
Gaskets from a rubber plate (heat-freeze-acid-alkali-resistant) are used in pipeline fittings that control media such as air, nitrogen, water (fresh, marine, technical), acids alkalis with a concentration of up to 20% at temperatures from -40 to +80 ° C.
Frost resistance of rubber means its ability to retain elasticity and other valuable properties at low temperatures. It is possible to achieve an increased frost resistance of rubber up to -55 ° C by controlling the crystallization of rubbers, selecting their appropriate mixtures, adding plasticizers and fillers.
In a somewhat narrower temperature range (from −30 to + 80 ° C), gaskets from a rubber (oil and petrol resistant) plate work. Following the name of rubber, gaskets made from it are used in fittings that move oils, gasoline, and other petroleum-based fuels and air, nitrogen, and other gases.
The working range of heat-resistant rubber is shifted towards higher temperatures. The gaskets can be used at temperatures from -30 to + 90 ° C and for steam at temperatures up to 140 ° C. The temperature determines the heat resistance of rubber after reaching a decrease in tensile strength and relative elongation.
Another type of rubber from which gaskets are made is “food” rubber, which is safe in contact with food. The gaskets can be used when moving media such as milk, vegetable oil, fruit juices, beer, etc.…