Gland packing is a widely used seal used for sealing in various applications. The principle of operation of the gasket is simple: with the help of it, tightness is achieved at the joints of the parts. Oil seals are used not only in mobile units of mechanisms, but also function remarkably when sealing static adhesions (for example, in pipelines).
What it consists of
Gland packing is woven from threads in the form of a cord of rectangular or square section. Depending on the conditions of use (pressure, dynamic loads, temperature conditions), the gasket is made of TRG graphite threads, improved with reinforcing bases from various materials or from polytetrafluoroethylene (PTFE) ropes.
Where used
Gland packing is used, as mentioned above, for sealing:
- fixed and movable pipeline couplings;
- autoclaves;
- pumps;
- compressors;
- rebar;
- mixers and other units.
Also in industries:
- gas production;
- oil producing;
- processing;
- food;
- atomic.
Working environments:
- oil;
- superheated steam;
- water;
- gases (including liquefied gases);
- harsh chemicals;
- petroleum products.
Features
Gland gasket has the following required qualities:
- chemical resistance (inertness) to various aggressive conditions;
- a small indicator of friction (a noticeable decrease in the depreciation of moving components of installations);
- radiation resistance;
- strength;
- sealed;
- heat resistant;
- environmental safety;
- non-aging (does not dry out during maintenance and operation);
- elasticity (prolonging the life of equipment).
What properties should stuffing boxes have
Established rules impose special requirements on harnesses. The most important ones are listed here.
- The gasket must be chemically inactive. At the very least, the raw material should not react upon contact with the separated medium or change its basic qualities. For example, if stuffing box packing is used to seal an installation (column, scrubber) in which aggressive gases or alkalis and acids act, then the stuffing box base must be acid and alkali resistant. The same applies to hydrocarbons (gasoline, oils, fats). Dissolutionoil seal can certainly lead to depressurization, accident, loss of reagents and so on.
- Gland valve packing must withstand high temperatures and high pressures. In particular, distillation of oil in distillation columns is carried out at high temperature. Depressurization can lead to deterioration of the composition of the distillation products, ignition, release of vapors to the outside, and even an explosion.
- If oil seals are used in guide mixes, they must be resistant to variable loads. For example, to seal the moving parts of pumps, stuffing box packing 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.
Don't break the rules
Each specific production has its own standards for how best to use and install stuffing boxes. All points of requirements include such an important factor as safety. Failure to comply with the conditions of installation (condition, degree of tightening of connections, number of gasket rings) and operation can result in the most serious consequences. And so all points must be considered:
- rules of application;
- material selection;
- Gland packing change schedule;
- installation of sealed communications and devices.
Types of gland packings
Since the gasket is, in fact, a cord made of different materials, thenits differences will consist only in the cross section, composition and structure of weaving. The most famous packing compositions are:
- graphite;
- asbestos;
- PTFE;
- synthetic fiber pad;
- asbestos-free.
Graphite packings
Made from 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 gland packing is used in aggressive environments, as it copes well with elevated temperatures and pressures. Its markings: AS, AP, AIR, AGP. These gaskets are used in the oil, metallurgical and gas industries, as well as in the automotive industry.
PTFE
Elastic and resistant to aggressive conditions. The specificity of such packings is that they are forbidden to be used in environments where there is chlorine. They are used in the pharmaceutical, oil and chemical industries.
Packings made of synthetic threads
These gaskets are resistant to abrasives. They are used in the pulp and paper, chemical and oil industries.
Asbestos-free
There can be different types: some of them are reinforced with brass wire, and some are impregnated with fat additives. Depending on the scope of use, a specific type is selected.
By structurethe core of the gasket is distinguished by through, single-layer and multi-layer weaving. Pump stuffing box packing can be from 3 to 50 mm, depending on its purpose.
