The types of detachable fixed joints with elastic and plastic sealing are considered, their disadvantages are indicated. A new design of the sealing unit for fixed and movable joints is presented, eliminating these disadvantages. The tightness of the structure is ensured by increasing the hydraulic resistance of the leakage channel of the sealed medium, which has a cross-section in the form of an equilateral triangle. The channel is spirally placed in the contact zone of the sealing surfaces, the inlet and outlet of which are located along the inner and outer diameters of the mating surfaces, respectively. Expressions for calculation of the proposed type of joints for real conditions of its use are presented.

In the petrochemical, nuclear and gas industries, high technological parameters are used, and first of all, they include temperature and pressure. Technological processes, as a rule, are carried out in capacitive equipment, the reliability of which is determined by the tightness of its detachable joints. In the period of integration of the development, manufacture and use of equipment for chemical, petrochemical and other industries, there is a need for common regulatory documents for their calculations and manufacture. In different areas, there are already many common European standards applied in individual countries. Recently, the issue of creating uniform standards in the field of tightness of detachable joints has arisen. The analysis of literary sources and, first of all, the existing standards of leading industrial countries for the calculation of detachable joints for strength and tightness is given.

The airtightness of a detachable joint depends on the load on its sealing surfaces and is determined by the magnitude of the leakage of the sealing medium or its viscosity, where the value of the latter depends on temperature. When a gas is heated, leakage decreases, while when a liquid is heated, leakage increases. An analysis of the influence of temperature on the airtightness of detachable joints is presented and recommendations are given for reducing this effect.

Московский политехнический университет», г.Москва, Россия;

The calculating relationships required for determining the desired (optimal) gasket width, on which the leak-tightness of the joint, materials consumption, and cost of the joint depend, are presented. An example of calculation of the width of a fluoroplastic-4 (Teflon) gasket is given.

Formulas for determining the required tightening force of the threaded elements of joints that experience particular changes in the course of use, such as variable loads, variations in the temperature of the working medium, and relaxation of the stresses in individual elements of the joint, are presented. An estimation of the length of the safe operation period of the joint until its next inspection is presented.

The paper analyzes the nature of deformation of a sealing element when subjected to a specific load from tightening of joint fasteners.The formula for determining the design pressure causing destruction in the sealing element was obtained.The experiments to verify the validity of analytically obtained formulas were conducted.To assess the possibility of destruction of the sealing element we propose to use a dimensionless factor relating the geometrical parameters of a sealing element and conditions for its operation.

A face gland seal in which the packing is not divided into individual chambers is presented. The packing is pressed by the end face of an axially moveable ring caused by a force created by the pressure of the compacted medium. This force produces a minimal unit axial load that is uniformly distributed along the length of the packing and is specified by the air-tightness condition. The tightening force of the threading elements and losses of power caused by friction of the packing are reduced. Required computational expressions are presented.

УТОЧНЕНИЕ КОЭФФИЦИЕНТА ОСЕВОЙ ПОДАТЛИВОСТИРЕЗЬБОВОГО ЭЛЕМЕНТА РАЗЪЕМНОГО СОЕДИНЕНИЯ В

Equations for use in determining the basic parameters of a multichamber face gland seal, such as the number of chambers and the forces of pre-loaded fastening elements, are presented. A uniform distribution of the load on the packing along the length of the seal in the case of a minimal load (based on the airtightness of the connection) is thereby achieved, thus assuring a decrease in the losses in power caused by friction in the seal.

Results of an analysis of three types of gland seals with soft packing and inside seating of the pressure flange are presented. The packing had a cylindrical or trapezoidal cross section with standard or tapered o-ring gaskets. It was shown that gland seals with packing o-ring gaskets that were pressed beforehand in special matrices or directly in the gland body were most effective.

Breakdown of air tightness due to a variation in load is possible in detachable airtight joints as the temperature of their constituent elements varies. Methods of assuring the constancy of the load independently of any variation in temperature for the flange connection and a stuffing box seal with soft stuffing and calculations of the parameters necessary to achieve this objective are presented.

A comparative analysis of gland seals with inside and with outside seating of the pressure flange that demonstrates the advantages of inside seating is presented. In this case there arises self-sealing and the load on the packing decreases and is distributed more efficiently. These factors together reduce the materials consumption of the elements of the joint while maintaining its air tightness.

An analysis of the failure conditions of gaskets made of thermal-expansion graphite and polytetrafluoroethylene (PTFE) is presented, computational expressions for determining the parameters that lead to failure of gaskets are obtained, and recommendations are given for eliminating potential failure of gaskets. The technique presented here may also be used for gaskets produced from other materials besides those discussed in the article.

Deformation of stuffing, which indicated that the load on its internal perimeter exceeds that on its external perimeter, is analyzed. Expressions are presented for recalculation of the coefficient of lateral pressure when its value obtained for one section of the stuffing is related to the value required by the other section. Application of this computational procedure will permit a reduction in wear of the stuffing and loss of thicknes due to friction of the part being sealed against the stuffing with retention of a given degree of airtightness of the sealed coupling.

Results are presented for studies conducted on the airtightness of a frontal stuffing-box seal with four sealing elements. Losses of the frictional capacity of the stuffing-box packing are determined. Feasibility of effective use of frontal stuffing-box seals for rotating shafts is indicated. Recommendations are given for selection of the packing material, proceeding from values of the coefficient of friction and penetrability factor.

An analysis of the influence of gasket material, gasket size, and pressure of the working medium on the selection of the initial width of the gasket is presented for the first time. Based on this analysis, a previously derived equation was used to determine the width of a compressed gasket placed between flanges in the working state. To perform the analysis, we used the investigation results that showed that an annular gasket expands only along its outer boundary when pressed axially and there are no limitations to its radial deformation. The materials for these gaskets are rubber, fluoroplastic-4 (polytetrafluoroethylene, tradename Teflon), and AD-grade aluminum; the diameters of the sealed holes are 100, 200, and 300 mm, and the pressure of the medium being sealed is 5–10 MPa. These data helped assess the influence of the mechanical properties of the gasket material, the gasket size, and the operation conditions (pressure of the medium being sealed) on the selection of the appropriate gasket width. Two versions of gasket positioning between the flanges are examined: in one the sealing flange surfaces are smooth, in the other the joints are of the projection–depression type. The investigations demonstrated that in the test case the method of positioning of the gasket between flanges does not materially influence the selection of the required gasket width. While taking the properties of the gasket material (rubber and Teflon) into account, we assumed that the material is incompressible (Poison’s ratio close to 0.5). In the case of aluminum, we took the influence of compressibility of the material into consideration. The obtained analysis results are somewhat approximate because the force of friction between the surfaces of the flanges and the gasket that is deformed radially was not taken into account, and the force of preliminary compression of the gasket was taken as the average value between the yield limit of the gasket material and the limit load on the gasket, at which the elasticity of the gasket material is retained under the operating conditions. The data presented on the selection of the initial appropriate gasket width will doubtlessly become the essential material for designing flange joints.

A method is examined for the synthesis of methanol in a three-phase system: a copper-zinc catalyst, a gaseous mixture of hydrogen and carbon oxides, and an inert hydrocarbon liquid. In the system, the liquid phase ensures isothermic synthesis, while a moving catalyst bed creates more complete contact between it and the gaseous mixture. Instead of the existing 4–4.5%, the output of methanol with one-time contact between the gaseous mixture and catalyst is increased to 15–20%. This allows for a reduction in power consumption, and simplification of the process required for the production of methanol, as well development of a small-scale portable plant.

Correctly selected gasket width for forced-type detachable sealed joint is one of the conditions of leak-tightness of the joint under the operating conditions at minimal material content of the joint itself. In this article, the calculation of the initial gasket width has been made more precise taking account of the real nature of radial deformation of the gasket upon axial loading. The calculating expression obtained has been used to determine the initial appropriate width of the gasket. Experiments have been carried out to study the conditions of radial deformation of the gasket. The experimental and calculated results are virtually congruent. The data reported in this article help disclose the real nature of gasket deformation in flanged joint, which allows one to remove errors from the calculating expressions used, determine the allowance for reducing the material content without impairing the leak-tightness of the flanged joint and the strength of its constituent elements, and select a more optimal flanged joint design.

The pattern of the radial deformation of an annular component (gasket) is examined during its axial loading. It is demonstrated that as the gasket deforms axially, its outside radius increases, and its inside radius remains essentially constant. Working expressions are derived for determination of the neutral radius, the increase in the outside radius, and the change in the inside radius during axial deformation of the gasket. A device was built to verify the working relationships obtained, and experiments substantiating their practical applicability were conducted. It is recommended that information on tolerances for the diametrical dimensions of the gaskets and annular groves for their seating be incorporated in regulatory materials.