Stuffing box packing is a widespread sealant used for sealing in various devices. The principle of operation of the gasket is simple: with it, tightness is achieved at the joints of the parts. Oil seals are used not only in mobile nodes of mechanisms, but also work wonderfully when sealing static adhesions (for example, in pipelines).
What does it consist of
The stuffing box is woven from threads in the form of a cord of rectangular or square cross section. Depending on the conditions of use (pressure, dynamic loads, temperature conditions), the gasket is made of graphite threads , improved with reinforcing substrates from all kinds of materials or from polytetrafluoroethylene (PTFE) ropes.
Where is used
Packing for oil seals is used, as mentioned above, for sealing:
- fixed and movable pipe couplings;
- autoclaves;
- pumps;
- compressors;
- fittings;
- mixers and other units.
Also in the areas of industry:
- gas producing;
- oil producing;
- processing;
- food;
- atomic.
Working environments:
- oil;
- superheated steam;
- water;
- gases (including liquefied);
- aggressive chemicals;
- petroleum products.
Features
Gland packing has the following necessary qualities:
- chemical resistance (inertness) to various aggressive conditions;
- a low friction index (a noticeable decrease in the depreciation of the moving components of the plants);
- radiation resistance;
- strength;
- tightness;
- heat resistance;
- environmental safety;
- a tendency to aging (does not dry out during maintenance and operation);
- elasticity (extension of the use of equipment).
What properties should the stuffing box packing have?
The established rules impose special requirements on the harnesses. The most important are listed here.
- The gasket must be chemically inactive. At least, the raw materials should not react when in contact with the separated medium or change their basic qualities. For example, if the stuffing box packing is used to seal the installation (columns, scrubber), in which aggressive gases or alkalis and acids act, then the base of the stuffing box should be acid- and alkali-resistant. The same applies to hydrocarbons (gasoline, oils, fats). The dissolution of the gland, of course, can lead to depressurization, accident, loss of reagents and so on.
- The valve packing must be able to withstand high temperatures and high pressures. In particular, in distillation columns, the distillation of oil is carried out at high temperature. Depressurization can lead to a deterioration in the composition of the products of distillation, ignition, vapor release to the outside, and even an explosion.
- If gasket gaskets are used in guide mixtures, they must be resistant to variable loads. For example, to seal the moving parts of the pumps, the stuffing box must be resistant to friction. In addition, the gaskets must be resistant to abrasion. To do this, they are supplemented with various substances, for example, fluoroplast.
Do not neglect the rules.
Each specific production has its own standards, how the packing of the glands should be used and installed better. All points of the requirements include such an important factor as security. Failure to comply with the installation conditions (condition, tightness of the joints, number of gasket rings) and operation can result in the most serious consequences. And therefore, all points should be considered:
- application rules;
- material selection;
- packing change schedule;
- installation of pressurized communications and devices.
Types of stuffing box packing
Since the gasket, in fact, is a cord made of different materials, its differences will consist only in the section, composition and structure of weaving. The most known such compositions of the gaskets:
- graphite;
- asbestine;
- fluoroplastic;
- synthetic fiber gasket;
- asbestos-free.
Graphite packing
Made of reinforced foil. The advantages of these gaskets are that they are characterized by low thermal conductivity and coefficient of friction. Disadvantages - they are not allowed to be used in environments with a high concentration of nitrogen, chloride and chromium compounds.
Asbestos variety
This stuffing box is used in aggressive environments, as it copes with high temperature and pressure. Its markings: AS, AP, AIR, AGP. These gaskets are used in the oil, metallurgy and gas industries, as well as in the automotive industry.
PTFE
Flexible and resistant to aggressive conditions. The specificity of such gaskets is that they must not be used in environments where there is chlorine. They are used in the pharmaceutical, oil and chemical industries.
Synthetic yarn packs
These pads are abrasive resistant. They are exploited in the pulp and paper, chemical and petroleum industries.
Asbestos-free
They can be of various types: some of them are reinforced with brass wire, and some are impregnated with fatty additives. Depending on the scope of use, a specific type is selected.
According to the structure of the core, the gaskets differ in through, single-layer and multi-layer weaving. The stuffing box packing can be from 3 to 50 mm in section, depending on its purpose.