Packing of stuffing boxes: composition, types, application.

Packing gland is a widespread sealant, which is used for sealing in different devices. The principle of operation of the gasket is simple: with the help of it, tightness is achieved at the joints of the parts. Omentums are used not only in the mobile units of mechanisms, but also function remarkably in the sealing of static adhesions (for example, in pipelines).

What it consists of

The stuffing box stuffing is made from threads in the form of a cord of rectangular or square cross-section. Depending on the application conditions (pressure, dynamic loads, temperature conditions), the gasket is made of graphite threads of TRG, improved by reinforcing substrates from all sorts of materials or from ropes of polytetrafluoroethylene (PTFE).

Where to use

Packing for glands is used, as already mentioned above, for sealing:

• Fixed and movable clutches of pipelines;
• Autoclaves;
• Pumps;
• Compressors;
• Fittings;
• Mixers and other aggregates.

Also in the fields of industry:

• Gas production;
• Oil producing;
• Processing;
• Food;
• Atomic.

Working environments:

• oil;
• Superheated steam;
• water;
• Gases (including liquefied gases);
• Aggressive chemicals;
• Oil products.

Features

The stuffing box has the following essential qualities:

• Chemical stability (inertness) to different aggressive conditions;
• A small indicator of friction (a noticeable decrease in the depreciation of mobile components of plants);
• Radiation resistance;
• Strength;
• Tightness;
• Heat resistance;
• Ecological safety;
• Inconvenience to aging (does not dry up when keeping and operating);
• Elasticity (extension of the use of equipment).

What properties should stuffing stuffing boxes have?

The established rules impose special requirements on the bundles. Here are the most important.

1. The gasket must be chemically inactive. At the very least, raw materials should not react when they come into contact with the medium to be separated or change their basic qualities. For example, if the stuffing box is used to seal the installation (column, scrubber) in which corrosive gases or alkalis and acids act, then the gland base must be acid- and alkali-resistant. The same applies to hydrocarbons (gasoline, oils, fats). Dissolving the stuffing box, of course, can lead to depressurization, accident, loss of reagents and so on.
2. The gland packing must withstand high temperatures and high pressures. In particular, in distillation columns, distillation of oil is carried out at high temperature. Depressurization can lead to a deterioration in the composition of the products of distillation, ignition, release of vapors to the outside and even explosion.
3. If the seals are used in the guide mixes, they must be resistant to volatile loads. For example, to seal moving parts of 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, fluoroplastic.

Do not neglect the rules

Each specific production has its own norms, how best to use and install the stuffing box packing. All items of requirements include such an important factor as security. Failure to comply with the installation conditions (condition, tightness of connections, number of rings of the gasket) and operation may result in the worst consequences. And therefore all the points should be considered:

• Rules of application;
• Choice of material;
• Schedule for changing gland seals;
• Installation of sealed communications and apparatus.

Types of stuffing boxes

Since the gasket, in fact, is a cord made of different materials, its differences will consist only in the cross-section, composition and structure of the weaving. The most well-known are:

• Graphite;
• Asbestos;
• Fluoroplastic;
• A lining made of synthetic fibers;
• Asbestos free.

Graphite packing

Made from reinforced foil. The advantages of these gaskets are that they are characterized by low thermal conductivity and a coefficient of friction. Disadvantages - they are not allowed to use in environments with a high concentration of nitrogen, chloride and chromium-containing compounds.

Asbestos variety

This packing gland is used in aggressive environments, as it copes well with increased temperature and pressure. Its markings: AC, AP, AIR, AGP. These gaskets are used in the oil, metallurgical and gas industries, as well as in the automotive industry.

Fluoroplastic

Elastic and resistant to aggressive conditions. Specificity of such packings is that they are forbidden to use in environments where there is chlorine. They are used in the pharmaceutical, oil and chemical industries.

Synthetic filament packings

Such gaskets are resistant to abrasives. They are exploited in the pulp and paper, chemical and petroleum industries.

Asbestos-free

There may be different types: some of them are reinforced with brass wire, and some are impregnated with fatty additives. Depending on the scope of use, a certain type is selected.

According to the structure of the core, the gaskets differ through, single-layered and multilayered weaving. The stuffing box packing can be from 3 to 50 mm, depending on its purpose.