RU2811635C1 - Method for testing products operating under excessive pressure - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: invention relates in particular to pneumatic methods for testing the strength of products operating under internal excess pressure from 0.001 to 100 MPa, the operating mode of which implies the possibility of an instantaneous (up to 5 seconds) drop in pressure of the internal environment from working to vacuum, for example, bellows expansion joints. The declared technical result is achieved by implementing a method for testing products operating under excess internal pressure, which consists in installing end caps on the test product, placing the product in a chamber, heating the internal cavity of the product to a temperature of 210±20°C and at the same time creating a pressure difference between the internal cavity of the test product and the chamber cavity of up to 0.5 MPa by creating an excess pressure inside the test product of up to 0.6 MPa, and in the chamber cavity of up to 0.1 MPa, maintaining a pressure drop for up to for at least two minutes. The valve opens and within 5 seconds, no more, the pressure is released from the internal cavity of the test product to an excess pressure value of 0 MPa, while maintaining the pressure in the chamber cavity equal to 0.1 MPa. The test product is held for 2-10 minutes, while ensuring a pressure difference between the internal cavity of the test product and the cavity of the chamber corresponding to a vacuum of -0.1 MPa.

EFFECT: expanding the arsenal of technical means for testing, reducing the labour costs by simplifying the test method, reducing the material consumption of the stand, providing the simulation of real operating conditions and universality of testing for all types of products operating under excess internal pressure, including any diameters.

2 cl, 1 dwg

Description

The invention relates to the field of testing equipment, in particular to pneumatic methods for testing the strength of products operating under internal excess pressure from 0.001 to 100 MPa, the operating mode of which implies the possibility of an instantaneous (up to 5 seconds) drop in the pressure of the internal environment from working to vacuum, for example bellows compensators (SC).

Modern bellows expansion joints are designed to provide flexible, hermetic connection of oil pipelines, gas pipelines, pipelines and units of hydraulic, gas, air, fuel and oil systems of ground-based equipment. SCs are manufactured with nominal diameters from 15 to 5000 mm, operate at ambient temperatures from minus 250 to plus 550°C and higher when using non-standard materials and structures, and at ambient pressures from 0.001 to 10 MPa, as well as in vacuum.

There is a test program and methodology SK GOST 28697-90 that describes strength tests. However, the test method for an instantaneous change in pressure from excess to vacuum pressure has not yet been used.

Currently, various testing methods are known, in particular, for bellows expansion joints.

Thus, from the description of the RF patent No. 2156392 (published on September 20, 2000), a method for testing bellows compensators is known, in which a device is used that contains a bellows, movable and stationary flange supports, rigidly connected to a force loader-hydraulic drive, consisting of a hydraulic cylinder, a piston, stock The channels supply and drain working fluid into the upper and lower cavities of the hydraulic cylinder. The stroke is adjusted for tension and compression. The tightness of the bellows is checked by supplying air through a channel in the movable flange support inside the bellows.

The closest analogue to the patented invention is a method for testing bellows expansion joints, which consists in the fact that two bellows expansion joints are installed coaxially one inside the other, both bellows expansion joints with their end surfaces are installed between the movable and stationary load plates of the test stand, providing a rigid, hermetic connection of the end surfaces of the bellows expansion joints with load plates and create pressure of the test medium in the cavity between the bellows compensators. Then a cyclic load is applied to the bellows expansion joints by a specified multiple movement of the movable load plate (RF patent No. 2367829, published on September 20, 2009).

The main disadvantage of the known solutions is the inability to test for a sharp drop in pressure from working pressure to vacuum. Also, difficulties in implementing the required tests are the complexity of testing, the inexpediency, from an economic point of view, of creating real operating conditions on a stand on a scale of 1 to 1 to confirm the performance of the product with an instantaneous drop in pressure from working to vacuum (working units/devices/installations and piping pipelines).

The objective of the patented solution is to eliminate these shortcomings, as well as to confirm the performance of the product when the medium pressure instantly changes from excess to vacuum pressure.

The technical result of the invention is to expand the arsenal of technical means for testing, reduce labor costs by simplifying the test method, reduce the material consumption of the stand, provide simulation of real operating conditions and universality of testing for all types of products operating under excess internal pressure, including any diameters

The claimed technical result is achieved by implementing a method for testing products operating under excess internal pressure, which consists in installing end caps on the test product, placing the product in a chamber, heating the internal cavity of the product to a temperature from 20 to 550°C and at the same time creating pressure difference between the internal cavity of the test product and the cavity of the chamber is 0.1 MPa due to the creation of excess pressure in the internal cavity of the product and in the chamber and maintain the pressure drop for 2-10 minutes, then release the pressure from the internal within 3-5 seconds product cavity to an overpressure value of 0 MPa, while maintaining the pressure in the chamber cavity equal to 0.1 MPa, hold the test product for 2-10 minutes, while ensuring a pressure difference between the internal cavity of the product and the chamber cavity corresponding to vacuum -0.1 MPa.

In this case, the temperature value of the internal cavity of the test product is selected according to the operating conditions of the product, depending on the technology for transporting the medium - oil products, gas, acids, etc.

After which the test product is removed from the chamber, visual measurement control and leak testing are carried out in any known way, which depends on the product and is installed by the manufacturer. For example, for bellows expansion joints, a leak test is carried out using the bubble method, the test medium being air.

The test is considered successfully passed if the test sample is sealed and no mechanical damage, signs of rupture in the metal and welded joints, or loss of axial stability of the product (if applicable for a specific type of product) were observed with an instantaneous change in pressure.

A bellows compensator can be taken as a test product.

The declared technical result is achieved by the fact that the prototype (bellows compensator) is exposed to an equivalent load on the test bench, which is in accordance with real operating conditions, which is created by a rapid change in pressure, which corresponds to the load at an instantaneous (up to 5 seconds) changing pressure from the maximum calculated to vacuum due to a similar pressure drop.

The test setup is quite simple, mobile, testing does not take much time and does not require special training.

This invention makes it possible to test compensators of different overall dimensions by creating a chamber larger in size than the dimensions of the products.

The solution is further illustrated in Figure 1, which shows a diagram of the test bench.

The stand consists of chamber 1, manifold 2 and compressor 3 to create excess pressure. The camera body is made of low-alloy steel, cylindrical in shape and of the required thickness to ensure structural strength under pressure. A bellows compensator 4 is installed inside the chamber, hermetically sealed at the end sides with plugs (carbon steel plates) with fittings (not shown). The bellows compensator 4 is surrounded by an electric heater 5 of the tape type. The internal cavity of chamber 1 is connected to compressor 3 through manifold 2, while a shut-off valve V1 is installed on the air supply pipeline to the chamber. Also, compressor 3 is connected through manifold 2 and pipeline 6 to the internal cavity of the test product (bellows compensator 4); shut-off valve V2 is installed on pipeline 6. Also, the internal cavities of the chamber 1 and the bellows compensator 4 are connected to pressure relief pipelines 7, equipped with shut-off valves V3 and V4. On the air injection line, pressure release from the internal cavity of the bellows compensator 4 and on chamber 1, pressure gauges P1, P2 and P3 are installed, respectively. In addition, the chamber is equipped with a safety valve VS1.

The method is carried out as follows.

Test conditions: product - shear bellows compensator LRR 06.0500.040.3 (455194); method - pneumatic, test medium - air; design data: temperature of the test medium (inside the product), according to operating parameters during operation - 210±20°C, medium pressure, according to operating parameters during operation - 0.5 MPa. The operating mode during vacuuming is the internal pressure drop from 0.5 MPa to vacuum in 5 seconds.

Chamber 1 includes special end caps to seal the product with the necessary fittings for connection to the air injection line and the pressure relief line. A bellows compensator 4 is welded to the end plugs through stiffening elements (nozzles, corners, frame elements) so that the compensator 4 is in the middle of the chamber and the volume of the secondary circuit is the same on all sides. All necessary connections for supplying pressure are connected and the internal cavity of chamber 1 is sealed. After closing the chamber cavity, compressor 3 is started and compressed air is supplied to the external (chamber) and internal (test product, bellows compensator) circuits, while simultaneously heating the internal cavity of the product with using a belt electric heater 5 to a temperature of 210±20°C. When the pressure reaches 0.6 MPa, the supply of compressed air is stopped, valves V1, V2 are closed, and the compressor is turned off. When the required temperature is reached, pressure is released from the internal cavity of the product 4 using valve V4. Thus, when releasing pressure, real operating conditions are simulated - a pressure difference between the external and internal circuits is achieved with loads equivalent to real conditions under vacuum. Maintain for 2-10 minutes to assess the performance of the product. Pressure is then released from external circuit 1 using valve V3. After releasing the pressure, chamber 1 is opened to disconnect the auxiliary pipes and remove the product. After which product 4 is inspected and tested for leaks.

Thus, the full-scale test method can be divided into the following phases in the internal and external circuits:

1st phase: pressurize P g. up to 0.6 MPa in the internal circuit, P g. up to 0.1 MPa in the external circuit, held for at least 2 minutes. This ensures a pressure/load difference between the internal and external circuits: 0.6-0.1=0.5 MPa.

Phase 2: within 5 seconds, no more, release pressure from the internal circuit to Pg = 0 MPa. The external circuit pressure Pg = 0.1 MPa remains unchanged. An equivalent load arises due to the pressure difference when the pressure is suddenly released to vacuum in a short time.

Phase 3: pressure is maintained in the internal circuit to 0 MPa, pressure is maintained in the external circuit to 0.1 MPa, held for at least two minutes.

Thus, a pressure/load difference is provided between the internal and external circuits corresponding to the vacuum state: 0-0.1=-0.1 MPa.

The result is a load equivalent to the load that occurs when the pressure drops from the maximum design pressure of 0.5 MPa (design pressure according to the working documentation) to vacuum (relatively taken as P excess equal to 0 MPa).

Next, visual measurement control and testing of the compensator for leaks is carried out (the test method is established by the design documentation for the product, usually bubble, test medium - air).

The use of the proposed method makes it possible to conduct this type of test with any products, the operation of which implies the possibility of an instantaneous drop in the pressure of the internal environment from working to vacuum, on a bench without recreating real operating conditions on a scale of 1 to 1.

Claims (2)

1. A method for testing products operating under excess internal pressure, characterized by the fact that end caps are installed on the test product, the product is placed in a chamber, the internal cavity of the product is heated to 20÷550°C and at the same time a pressure difference is created between the internal cavity of the test product and chamber cavity of 0.1 MPa, due to the creation of excess pressure in the internal cavity of the product and in the chamber, and maintain a pressure drop for 2-10 minutes, then within 3-5 seconds the pressure is released from the internal cavity of the product to the excess pressure value equal to 0 MPa, while maintaining the pressure in the chamber cavity equal to 0.1 MPa, hold the test product for 2-10 minutes, while ensuring a pressure difference between the internal cavity of the product and the chamber cavity corresponding to a vacuum of -0.1 MPa . 2. The method of testing products operating under excessive internal pressure, according to claim 1, characterized by the fact that the test product is a bellows compensator.