RU2367829C1 - Test technique of bellows expansion joint - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to hydraulic or pneumatic tests of bellows expansion joint (BEJ) at action of static and periodic loads. Method consists in that two bellows expansion joints are installed co-axial one inside the other, both bellows expansion joints are by faceplates installed between mobile and immovable charging plates of test desk, it is provided rigid tight connection of faceplates of bellows expansion joints with charging plates, and it is created pressure of test medium in cavity between bellows expansion joints. Then to bellows expansion joints it is loaded periodic load by means of specified repeated movement of mobile charging plate.

EFFECT: product mix expansion of tested bellows expansion joints.

5 dwg

Description

The invention relates to hydraulic or pneumatic testing of bellows expansion joints (SC) under the influence of static and cyclic loads and can be used to test pipeline SC of large diameters and SC, designed to work with both internal and external pressure of the working medium.

Known methods for bench testing of SCs are that SCs are installed in a cylindrical chamber, sealed on end surfaces, create pneumatic pressure inside SCs, or outside SCs in the cavity between the chamber and outer SC walls, and then a cyclic load is applied by repeated movements along the SC axis of one of its ends. In this case, the value of the axial displacement is selected, the pressure is set, and the number of loading cycles is calculated by the revolution counter of the drive mechanism (see BN Burtsev, N. Metal bellows. M. - L., Mashgiz, 1963, p. 135, Fig. 112). This method is not suitable for hydraulic testing of SC with incompressible liquids.

There are also known methods of testing compensators (flexible metal hoses) for cyclic strength by repeatedly moving one of the ends of the compensator in its transverse plane. In this case, the compensator is installed between the load plates with the possibility of sealing along its end surfaces, creates excessive pressure inside it and then performs a cyclic load, moving the load plate free from fixation in the transverse plane of the compensator with the end face of the compensator fixed on it. This test method is used for shear compensators only with internal working pressure. A similar test method for cyclic strength is used for rotary compensators with internal working pressure by angular displacements of a movable loading plate in the longitudinal plane of the compensators (see Kryukov A.I., Glinkin I.M., Fionin V.I. Flexible metal hoses. M. , Engineering, 1977, p. 158-160, Fig. 6.5 (b), 6.4 (c)).

The methods for testing SC and flexible metal hoses described above are suitable for SC of small diameters with relatively low pressure of the working medium. When these methods are used to test SCs of large diameters or with a high pressure of the working medium, large spacer forces occur on the end load plates, which requires the creation of metal-consuming expensive bench equipment to ensure the sealing of the SC on its end surfaces.

There is a known method of testing SK with a cyclic load - to confirm the probability of failure-free operation, in which tests are carried out on stands that provide the necessary types and amplitudes of movements when exposed to internal or external hydraulic pressure (see GOST 28697-90. Program and test procedure for bellows expansion joints and seals, Section 3.6, Appendix 7, Figs. 8-16). In accordance with this method, SCs are installed with end surfaces between the fixed (lower) and movable (upper) loading plates of the stand, made in the form of plugs, fixed on them, and a hydraulic test pressure is created. Then, a cyclic load is applied to the SC by predetermined multiple movements of the movable plug relatively stationary until the specified number of SC loading cycles is reached or until its tightness is lost. This method of testing SK is taken as a prototype.

As practice shows, this method has been successfully used for cyclic testing of small diameter SCs with a small working pressure. However, for large diameter SCs (≥1400 mm) designed to operate under pressure, cyclic tests are carried out in the absence of working pressure, since the spacer forces acting along the SC axis exceed tens of tons and do not allow the use of existing bench equipment. The results of such tests are unreliable, since only approximately allow to evaluate the cyclic strength of the SC in terms of working pressure.

To compensate for large spacer efforts throughout the entire test period, expensive metal-intensive bench equipment is required.

The problem to which the invention is directed, is to create a universal method for testing bellows expansion joints of any type and diameter under the influence of internal or external working pressure of a gaseous or liquid working medium.

The solution to this problem is achieved as follows.

The method of testing bellows expansion joints is that the bellows expansion joint is installed by the end surfaces between the movable and fixed load plates of the bench, is fixed on them, a test medium is created by the test medium on the bellows expansion joint and then a cyclic load is applied to it by a predetermined multiple movement of the moving load plate.

According to the invention, a second bellows compensator is additionally installed coaxially with the bellows compensator, placing them one inside the other, provide a tight tight connection of the end surfaces of both bellows expansion joints with the load plates, and a test pressure is created in the cavity between the bellows expansion joints.

The use in the proposed test method of the second bellows compensator provides a significant reduction in spacer forces from the pressure of the test medium. Due to this, the proposed method is suitable for reliable cyclic testing of bellows expansion joints of any diameter under the influence of the working pressure of water or air. At the same time, two bellows-type compensators of the same type of movement can be tested, one of which is under external pressure and the other under internal working pressure. The same rigid fixation of both compensators between the load plates allows both compensators to inform both the static load and the same cyclic load in the direction of any kind for which they are intended, which also increases the versatility of the method.

To test the bellows compensator with an internal test pressure, a second SC is installed inside the test SC.

To test the bellows compensator with an external test pressure, the second SC is installed outside the test SC.

The proposed method for testing bellows expansion joints is illustrated by the drawings shown in figures 1-4.

Figure 1 shows the relative position of the bellows expansion joints in the proposed method for their testing.

Figure 2 is a schematic illustration of the application of shear load to bellows expansion joints.

Figure 3 is a schematic illustration of the load of the bellows expansion joints by bending moment.

Figure 4 is a variant of the location of the bellows expansion joints under axial cyclic loading.

Figure 5 is a fragment of a cross section of a bellows.

To test the bellows compensator (hereinafter - SK) 1 with internal working pressure, and SK 2 with external working pressure, SK 1 and SK 2 are installed between load plates made in the form of end rings 3 and 4 (Fig. 1). SK 1 and SK 2 are fixed between the end rings 3 and 4, for example by welding (not shown), and provide sealing of the cavity 5 formed between the inner side surface of SK 1 and the outer side surface of SK 2 with sealing joints (not shown). The end rings 3 and 4 are provided with channels 6 and 7 for supplying and discharging the test medium (for example, water or air) into the cavity 5 and to the pressure gauge 8. The pressure gauge 8 and the device for feeding the test medium (not shown) are connected to the channels 7 and 6, respectively through tubes with fittings 9.

When conducting static tests of SK 1 with internal pressure and SK 2 with external pressure for strength and tightness, the end rings 3 and 4 are fixed to exclude axial movement of the bellows, the cavity 5 is filled through the channels 6 in the end ring 3 with a test medium, a test pressure is created and it is kept under pressure during the time determined by the test program.

To conduct cyclic tests of SK 1 by internal pressure and SK 2 by external pressure, the end ring 3 is rigidly fastened in a snap with a bolted connection on a fixed base, made, for example, in the form of two channels 10 located parallel to each other (Figs. 2, 3, 4). Another end ring 4 is fixed on a movable base, which is made similar to a fixed base, in the form of two channels 11, kinematically connected to the channels 10 of the fixed base by means of rods 12, hinges 13 and connected to a hydraulic cylinder 14, the rod 15 of which can move in the direction of the arrow 16.

In particular, for cyclic tests of SK 1 and SK 2 with a shear load, the channels 10, 11 are interconnected by rods 12 and four hinges 13 with the formation of a four-link hinge mechanism that receives spacer forces (figure 2). The hydraulic cylinder 14 is connected by hinges 17 to the channels 11 of the moving base and the fixed support 18 and is located longitudinally to the channels 11, across the axis of the SK. The end ring 4 is set to cyclic displacements in the transverse plane of SK 1, 2 in the direction of the arrow 16 by actuating the hydraulic cylinder 14 after creating a working pressure in the cavity 5.

For cyclic tests of SK 1 and SK 2 by an angular load (by rotation), the channels of the movable base 11 are connected to the channels 10 of the fixed base by means of two coaxial swivel joints 13 that rotate the movable base in the longitudinal plane of the SK. The ends of the channels 11 are connected to the opposite ends of the channels 10 by the hydraulic cylinder 14 by means of hinges 17 (Fig. 3). After creating a working pressure in the cavity 5 of the movable end ring 4, a cyclic angular displacement in the longitudinal plane of SK 1, SK 2, relative to the initial neutral position, is set by a predetermined working angle determined by the displacement of the piston rod of the hydraulic cylinder 14.

It is advisable to carry out cyclic hydraulic tests with axial load simultaneously for two identical SK pairs: 1, 2 and 1 ', 2', - mounted in a snap coaxially, one above the other. While the channels 10, 11 of the fixed and movable bases are connected to the hydraulic cylinder 14 with the possibility of translational movement of the movable end ring 4 along the axis of SK 1, 2 (figure 4). On the other side of the movable end ring 4, SK 1 ', 2', similar in technical characteristics, are fixed, which are rigidly fixed on the stationary end ring 3 '. The ring 3 'is fixedly connected to the channel 10', rigidly connected to the channel 10 of the fixed base by means of rods 12 located at both ends of the channels 10, 10 '(Fig. 4). Through hole 4 is provided with through holes A communicating cavity 5 between SC 1, 2 and cavity 5 'between SC 1', 2 '. After filling the cavities 5 and 5 'and creating a working pressure in them, a hydraulic cylinder 14 is activated, which tells the movable ring 4 to move along the axes SK 1, 2 and 1', 2 '. When the end ring 4 moves towards the end ring 3, the pair CK 1, 2 is compressed, the pair CK 1 ', 2' is stretched, and the test medium partially flows from the cavity 5 into the cavity 5 'through the openings A in the end ring 4. When the end ring 4 is moved in the opposite direction to the end ring 3 ', the pair SK 1, 2 is stretched, the pair SK 1', 2 'is compressed, and the test medium partially flows from the cavity 5' back to the cavity 5.

In the process of all types of tests (static and cyclic), the working pressure is recorded by a manometer 8 and is constant while maintaining the integrity of all SC and the absence of leakage of the test medium in the supply valve. Cyclical tests are carried out until loss of tightness, or until loss of stability of one of the SC, or until a specified number of load cycles are achieved.

Similarly, tests of SC are carried out by external pressure, for which the tested SC is installed in the position of SC 2, and the second auxiliary SC in the position of SC 1 (Figs. 1-4), i.e. the test SC is set inside the auxiliary. Then, the similar actions described above are performed to fill the test medium with a cavity 5 between SC 1, 2 (Figs. 1-4) and a cavity 5 'between SC 1', 2 '(Fig. 4), create working pressure in them (Fig. 1 -4) and applying cyclic load during cyclic testing (Fig.2-4).

In addition, it is obvious that the proposed test method for SC can be used to simultaneously test two different SC with similar technical characteristics (shear, rotary, axial), one of which operates under internal working pressure, and the other under external working pressure.

When testing one SC internal pressure in the usual way described in the prototype, spacer forces Q _p act on the load plates, determined by the formula:

,

,

where p _isp - test pressure,

F _eff - the effective cross-sectional area of the bellows, equal to the area of the circle bounded by the effective diameter D _eff (Fig.1, 5):

,

,

where D _in - the inner diameter of the bellows, N - the height of the corrugations of the bellows

When testing SK 1 using the second - auxiliary SK 2 (Figs. 1-4), smaller spacer forces Q _p act on the end rings 3, 4, 3 ', which are limited by the cross-sectional area of the cavity 5 (5') and are determined by the formula:

,

,

where F _eff1 and F _eff2 are the effective cross-sectional areas of the bellows, respectively SK 1 and SK 2, determined by the effective diameters of the bellows:

, для СК2:

,for SK1:

, for SK2:

,

where D _B1 is the inner diameter of the bellows SK1, H ₁ is the height of the corrugations of the bellows SK1;

D _H2 - the outer diameter of the bellows SK2, H ₂ - the height of the corrugations of the bellows SK2.

Given the expressions (5), (6), (2), the formula for determining the spacer forces (4) can be represented as:

.

.

Comparison of the spacer forces by formulas (1) and (4) after appropriate substitutions of the values of F _eff1 and F _eff2 in them shows that when testing SK with a diameter of ≥1500 mm by the proposed method, the expansion forces Q _p acting on the load plates (end rings 3, 4 , 3 ') can be reduced by more than 6 times. This makes it possible, in contrast to the known methods for testing SK:

- conduct reliable cyclic tests of large diameter SCs (over 1400 mm) under the necessary conditions of exposure to test pressure;

- abandon the metal-consuming and expensive stationary bench equipment necessary to compensate for the large spacing efforts, and use simple cheap equipment for testing, which, due to simple installation and dismantling, also allows you to quickly free up production space if necessary.

Thus, the proposed method for testing bellows expansion joints, in contrast to the prototype, is universal:

- due to the possibility of use for virtually any type of static and cyclic tests;

- due to the suitability for testing SCs of both small and large diameters under real working loads;

- due to the possibility of testing with both internal and external test pressure;

- due to the possibility of using both liquid and gaseous test media;

- due to the suitability for simultaneous testing of two different SC with similar technical characteristics (shear, rotary, axial), one of which operates under internal working pressure, and the other under external working pressure;

- through the use of simple universal equipment.

In addition, the proposed test method for SCs is reliable for SCs of large diameters and economical due to low spacer forces acting on load plates (end rings), which allows for cyclic tests under operating pressure and the use of inexpensive simple collapsible equipment.

Claims (1)

The method of testing bellows expansion joints, which consists in the fact that the bellows expansion joint is installed with end surfaces between the movable and fixed load plates of the bench, is fixed on them, test medium is applied to the bellows expansion joint by the test medium, and then a cyclic load is applied to it by a predetermined multiple movement of the moving load plate, characterized in that, coaxially with the bellows compensator, an additional second bellows compensator is additionally installed, disposing and one inside the other, provide a tight rigid connection of both end surfaces of bellows-loaded plates, and the test pressure creates a cavity between the bellows.

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