RU2467299C1 - Method of hydraulic impact test and rehabilitation of pipeline, which is implemented during its increased pressure loading in field conditions - Google Patents

Abstract

FIELD: test equipment.

SUBSTANCE: invention refers to test equipment, and namely to the pipeline test procedure, and is intended to improve the efficiency of construction and/or overhaul of the pipeline owing to optimising the use of available pipes. Essence of the invention: section of pipeline is chosen using non-destructive examination. Mechanical properties of pipes are calculated considering stress and strain state of the pipeline section. Increased pressure loading parameters of the above section are determined, and the section is isolated from the pipeline by means of chambers or plugs. First, air is removed from the pipeline section when the water is being filled. The section is loaded with impact pressure involving stepped pressure rise, which is performed at the specified speed and intervals of pressure to the specified pressure value, and further pressure release at the speed exceeding pressure rise speed. When the pressure is being released, compression stresses preventing further crack propagation are created in defective pipe metal zones, and when the specified value of residual deformation of pipe metal is reached, hydraulic impact tests of the pipeline section and its rehabilitation is completed.

EFFECT: higher efficiency of construction and/or overhaul of pipelines owing to using available pipes.

3 cl, 5 dwg

Description

The invention relates to the field of testing equipment, in particular to the technology of testing pipelines, and is aimed at improving the efficiency of construction and / or overhaul of the pipeline by optimizing the use of existing pipes. According to the invention, the method includes loading a section of a pipeline consisting of both new pipes and pipes with minor crack-like defects, impact pressure in the elastoplastic deformation zone by the stress test method, subsequent pressure relief at a speed exceeding the pressure rise rate. When the pressure is released in the defective zones of the pipe metal, compression stresses are created that prevent further crack growth. Criteria and conditions for the selection of pipes for their rehabilitation and the parameters of the hydraulic shock test of a section of the pipeline are determined by calculation.

The invention relates to the transport of gas, oil, oil products through gas pipelines, oil pipelines and oil pipelines, can be used in hydraulic tests with increased pressure of pipelines, including both linear sections of main pipelines, and piping systems of compressor or pumping stations of main pipelines.

When testing new pipelines, factory defects and installation defects are detected, and during operation, the properties of the metal of the pipes and the development of microdefects can occur up to the formation of cracks of critical dimensions, which increases the likelihood of emergency situations on the pipelines.

To prevent accidental destruction of pipelines during operation, they are examined, a comprehensive assessment of the technical condition of the pipes, repair and rehabilitation of the pipelines is carried out.

A known method of hydraulic testing of a pipeline, based on the injection of water by a pumping unit from a source into a test pipeline with a pressure equal to the pressure in the source, followed by a rise in pressure to a predetermined value and recording flow, temperature and water pressure [Instruction VD TÜV 1051 “Hydraulic testing of underground pipelines method of measuring pressure ”, p. 2-8, Ed. “German Technical Supervision Union”, 10.3834b, 4300, Essen 1, 1980]. The specified method provides loading with increased pressure of the pipeline from a pressure equal to the pressure in the source to a pressure corresponding to a tensile stress equal to 95% of the guaranteed minimum yield strength in the direction around the circumference of the pipe. The disadvantage of this method is that this method does not determine the mechanical properties of the pipe metal and does not take into account the stress-strain state of the pipeline when it is loaded with pressure in the elastoplastic zone of pipe deformation to a pressure that causes the onset of plastic deformation of each pipe of the tested pipeline. For these reasons, this method does not take into account the dynamics of pressure and water flow during the passage of the shock wave along the pipeline, which does not allow to determine the parameters for its rehabilitation.

Also known is a method of hydraulic testing and rehabilitation of a pipeline in the field, including pumping water from a source into a pipeline with a pressure equal to the pressure in the source, followed by a rise in pressure to a predetermined value, recording flow, temperature and pressure [RU patent No. 2296310].

The disadvantage of this method is that the method does not provide for loading the pipes with shock pressure depending on the flow rate during the passage of the shock wave along the pipeline, which excludes the possibility of assessing the carrying capacity of the pipeline and determining test parameters for rehabilitation of the pipeline.

Closest to the proposed method of hydraulic testing and rehabilitation of the pipeline, carried out when it is loaded with high pressure in the field, the technical essence and the achieved result is a method of hydraulic testing for shock and rehabilitation of the pipeline, carried out when it is loaded with high pressure in the field, based on injection water pumping installation from the source to the pipeline with a pressure equal to the pressure in the source, followed by a rise in pressure to a predetermined value and recording the flow rate, temperature, water pressure, which consists in the fact that the pipeline section is selected by non-destructive testing methods, the mechanical properties of the pipes are calculated taking into account the stress-strain state of the pipeline section, the parameters of its loading with increased pressure are determined and separated by chambers or plugs from the pipeline , water is pumped into the cavity of the pipeline section and tested with high pressure and rehabilitation of pipes with crack-like defects [pat EN RU No. 2324160].

The disadvantage of this method is that the method does not provide for a stepwise pressure increase followed by a pressure release carried out at a given speed to create a compression stress that prevents further growth of cracks in the defective zones of the pipe metal, and also does not take into account the pressure change during the propagation of a shock wave along the pipeline section . The basis of the invention is the task of increasing the efficiency of construction and / or capital repairs of pipelines due to:

- rehabilitation and optimal use of existing pipes with minor crack-like defects by loading them with water shock pressure in the elastoplastic deformation zone, followed by pressure release at a speed exceeding the pressure rise rate, which allows compressive stresses to be created in the defective zones of the pipe metal to prevent further crack growth;

- determination of the size of defects and, taking into account, the assessment of conditions for the rehabilitation of pipes;

- taking into account the values of flow jumps and pressure surges during the passage of the shock wave along the pipeline section when determining the effective stresses and strains in the pipes.

The objectives are achieved in that in the method of hydraulic impact testing and rehabilitation of the pipeline, carried out when it is loaded with high pressure in the field, based on the injection of water by the pumping unit from the source to the pipeline section with a pressure equal to the pressure in the source, followed by a rise in pressure to a predetermined values and registration of flow, temperature, water pressure, which consists in the fact that the pipeline section is selected by non-destructive testing methods, the indicator is calculated whether the mechanical properties of the pipes, taking into account the stress-strain state of the pipeline section, determine the parameters of its loading with increased pressure and are separated by chambers or plugs from the pipeline, water is pumped into the cavity of the pipeline section and tested by increased pressure and rehabilitation of pipes with crack-like defects, according to the invention, initially when filled with water, the air is removed from the pipeline section and the pipeline section is loaded with shock pressure in the elastoplastic deformation zone pipes by the stress test method, which includes a stepwise pressure increase carried out at a given speed and at predetermined pressure intervals to the pressure value causing tensile stress in the pipe metal in the circumferential direction up to 110% of the standard yield strength, and subsequent pressure release at a speed exceeding the rate of pressure rise, and when the pressure is released in the defective zones of the pipe metal, they create compression stresses that prevent further crack growth, and after reaching the specified value of the residual pipe metal formations hydraulic tests of the pipeline section for impact and its rehabilitation are completed.

After selecting a test section of the pipeline by non-destructive testing methods for each pipe with crack-like defects, the size of the defects is determined by the given algorithm and, taking into account each pipe in the pipeline section, the actual destructive loads and the corresponding minimum test pressure and maximum test pressure, which create the walls of the pipes tensile stress in the circumferential direction from 85% to 110% of the yield strength of the metal pipes, and in the process of hydraulic tests when filled with water at the site of pipeline pressure is raised to a value equal to the minimum test pressure, followed by addition of water to the extent necessary for an elastoplastic deformation tubes while maintaining a predetermined guaranteed reserve plasticity, wherein the selection condition for pipe rehabilitation determined by the formula

where σ _T is the standard yield strength of the pipe metal, MPa;

- относительное давление в трубе с номером i (i=1,2,3,…n);

- relative pressure in the pipe with number i (i = 1,2,3, ... n);

P _i - absolute pressure in the pipe, MPa;

P _in - pressure at the inlet to the pipeline section, MPa;

P _{100% σ} is the pressure corresponding to the standard yield strength of the pipe metal, MPa;

- относительное расстояние до трубы;

- relative distance to the pipe;

x _i is the longitudinal coordinate of the pipeline section, m;

L is the total length of the pipeline section, m;

- относительное время испытаний;

- relative test time;

ω is the water velocity in the discharge pipe, m / s;

τ is the test time, s;

S is the wall thickness of the pipe, mm;

K _f - coefficient of attenuation of the pipe;

D _i - the outer diameter of the pipe, mm;

i - serial number of the pipe.

Previously, before the start of hydraulic tests, the pumping unit and the pipeline section work characteristics are calculated when the shock wave propagates in the pipes along the pipeline section, the ratio between the pressure rise rate proportional to the tensile speed of the pipe metal and the pressure relief proportional to the compression rate is set for each pipe metal pipes, and the magnitude of the shock pressure and flow rate jumps in the pipes behind the front of the shock wave is determined of formula

- относительное давление в трубе с номером i (i=1,2,3,…n);Where

- relative pressure in the pipe with number i (i = 1,2,3, ... n);

ρ is the density of water, kg / m ³ ;

ω is the water velocity in the discharge pipe, m / s;

C is the shock wave propagation velocity, m / s;

g is the acceleration of gravity, m / s ² ;

P _I - pressure at the inlet to the pipeline section, MPa;

α, β - approximating coefficients:

λ is the coefficient of hydraulic resistance of the pipeline section;

D _VN - inner diameter of the pipe, mm;

x _i is the longitudinal coordinate of the pipeline section, m;

L is the total length of the pipeline section, m;

Δh is the difference in elevations in the pipeline section, m

The operating conditions of pipelines with long operating hours and crack-like defects associated with corrosion, thinning of the pipe wall, stress-strain state, change in the mechanical properties of the metal of the pipes under the influence of operational loads do not allow controlling the change in the mechanical properties over time with the specified frequency and in the required volumes metal pipes, their geometry, therefore, the physical model of loading the pipeline adopted in the invention during its hydraulic impact test ana on the fact that by changing the volume of water injected into the conduit proportional to the increment of the pressure in the pipe walls, the passage of the shock wave along the pipeline, creates deformation proportional voltages. And since the method of hydraulic tests during the rehabilitation of the pipeline is connected with the pressure medium, and the stress test is carried out in the elastoplastic zone of pipe deformation, it is the patterns of pressure parameters that determine the level and distribution of stresses in the pipes.

Therefore, when distributing pipes and connecting parts of pipelines having crack-like defects according to the categories of repairs, according to the invention, pipes having defects are selected for rehabilitation, the further development of which can be stopped by stress test tests of pipes under the influence of shock pressures, creating ring rings in the defective zones of the metal of the pipes stresses from 85% of the yield strength of the metal at the lower point of the pipeline to 110% of the yield strength of the metal of the pipes at the upper point of the pipeline.

The figure 1 presents a diagram of a biaxial stress-strain state of a pipeline with a diameter of D _i with a wall thickness S under the influence of internal pressure R. The following conventions are used in figure 1: σ _к - ring stresses; σ _a - longitudinal stresses; ξ _to - relative deformation in the circumferential direction; ξ _p - relative deformation in the axial direction; a is the length of the crack; in - the depth of the crack; D _i is the outer diameter of the pipe; S is the wall thickness of the pipe.

For an underground pipeline (ξ _n = 0, σ _p = µσ _t ), the relationship between deformation and stress was presented as

where µ is the Poisson's ratio;

E - modulus of elasticity of steel, MPa;

ξ _к - relative deformation in the circumferential direction,%;

σ _to - ring stress, MPa.

To determine the annular stresses σ _k arising in the wall of a pipe having defects in the form of a crack with a length of a (mm) and a depth of (mm) under the influence of internal pressure P, the well-known boiler formula was used in the form

where σ _to - ring stress, MPa;

P _{100% σ} is the pressure corresponding to the standard yield strength of the pipe metal, MPa;

S is the wall thickness of the pipe, mm;

K _f - coefficient of attenuation of the pipe;

a is the length of the crack, mm;

in - the depth of the crack, mm;

D _i - the outer diameter of the pipe, mm;

i is the pipe number.

Taking into account formulas 1, 4, as well as the distribution of pressures along the length of the pipeline section and the time of shock wave propagation during hydraulic testing of the pipeline section, on both sides limited by plugs or chambers, the conditions for the selection of pipes with crack-like defects for rehabilitation in the invention were presented in the form the ratio

where σ _T is the standard yield strength of metal pipes, MPa;

- относительное давление в трубе с номером i;

- relative pressure in the pipe with number i;

- относительное расстояние до трубы (отношение расстояния от начала участка до трубы с номером i трубопровода к общей протяженности участка трубопровода);

- the relative distance to the pipe (the ratio of the distance from the beginning of the section to the pipe with number i of the pipeline to the total length of the pipeline section);

x _i is the longitudinal coordinate of the pipeline section, m;

- относительное время испытаний (отношение произведения скорости воды в нагнетательном трубопроводе на время к общей протяженности участка трубопровода);

- relative test time (the ratio of the product of the water velocity in the injection pipeline by the time to the total length of the pipeline section);

S is the wall thickness of the pipe, mm;

K _f - coefficient of attenuation of the pipe;

D _i - the outer diameter of the pipe, mm;

i - serial number of the pipe.

в момент времени прохождения ударной волны вдоль участка трубопровода, ограниченного заглушками или камерами, зависит от изменения расхода воды на «левой» и «правой» границах участка трубопровода в начале процесса заполнения его водой, то есть в момент гидравлического удара с максимальной величиной ударного давления. Скачок расхода на «правой» границе участка трубопровода длиной L при распространении возмущений в воде со скоростью С приведет к изменению расхода на «левой» границе q(0, t) в момент времени

=1, где

.Pipe relative pressure

at the time of passage of the shock wave along the pipeline section, limited by plugs or chambers, depends on the change in water flow at the “left” and “right” boundaries of the pipeline section at the beginning of the process of filling it with water, that is, at the time of the hydraulic shock with the maximum value of the shock pressure. A jump in the flow rate at the “right” boundary of a pipeline section of length L during the propagation of disturbances in water at a speed C will lead to a change in flow rate at the “left” border q (0, t) at a time

= 1, where

.

Moreover, in accordance with the formula of N.E. Zhukovsky, the pressure jump | P | and flow rate jump | q | are related by

where P _i is the pressure jump in the pipe with the number i, MPa;

q _i is the flow rate jump in the pipe with number i, m ³ / s;

C is the speed of propagation of shock wave in water in a pipeline section, equal to the speed of sound, m / s.

Signs (+) or (-) are selected in accordance with the direction of wave movement. The magnitude of the jump in flow rate | q | for a wave propagating “to the left”, it satisfies the relation

where Ф is a coefficient reflecting the influence of friction forces.

Before the wave front P _- = P ₀ ; q _- = 0; | P | = P ₊ -P ₀ ; | q | = q ₊ -q _- = q ₊

where λ is the coefficient of hydraulic resistance of pipes;

c is the shock wave propagation velocity in the pipeline section, m / s;

D _VN - inner diameter of the pipe, mm;

q ₊ is the water flow rate behind the wave front, m ² / s;

P ₊ is the water pressure behind the wave front, MPa;

q _- - water flow before the wave front, m ² / s;

P _- - water pressure in front of the wave front, MPa.

Equation 7 with regard to 6 and 8 was presented in the form

In the general case, after linearizing equation 9 in the form Φ = -αq-βP, we obtained the equation

The solution of equation 10 was presented as

where q is the flow rate of water, m ³ / s;

q ₀ - productivity of the pumping unit, m ³ / s;

α, β - approximating coefficients:

λ is the coefficient of hydraulic resistance of the pipeline;

ω is the water velocity in the discharge pipe, m / s;

D _VN - inner diameter of the pipe, mm;

c is the shock wave propagation velocity in the pipeline section, m / s;

x _i is the longitudinal coordinate along the length of the pipeline section, m;

L is the total length of the pipeline section, m

The left and right sides of equation 6 were divided into P _in and, after solving equations 11 and 6 together, the formula for calculating the change in shock pressure along the pipeline section depending on the change in water flow rate was presented as

- относительное давление в трубе с номером i (i=1, 2, 3,…n);Where

- relative pressure in the pipe with number i (i = 1, 2, 3, ... n);

ρ is the density of water, kg / m ³ ;

ω is the water velocity in the discharge pipe, m / s;

c is the shock wave propagation velocity in the pipeline section, m / s;

g is the acceleration of gravity, m / s ² ;

R _I - pressure at the inlet to the pipeline section, MPa;

α, β - approximating coefficients

λ is the coefficient of hydraulic resistance of the pipeline section;

D _VN - inner diameter of the pipe, mm;

x _i - the longitudinal coordinate of the pipeline section, m;

L is the total length of the pipeline section, m;

Δh is the difference in elevations in the pipeline section, m

In the proposed method, a hydraulic shock test and rehabilitation of the pipeline:

- loading of the pipeline section by shock pressure in the elastoplastic zone of pipe deformation by stepwise pressure increase at a given speed and subsequent pressure release at a speed exceeding the pressure rise rate, it is possible to create compression stresses in the metal of pipes having crack-like defects, which helps to create conditions to prevent further crack development;

- calculation according to a given algorithm of the sizes of defects, breaking loads for each pipe with crack-like defects, in contrast to the prototype, allows you to determine the compliance of each pipe with the conditions for testing, as well as reject pipes for repair or replacement with new ones;

- preliminary calculations of the characteristics of the pumping unit and the pipeline section during the propagation of a shock wave in the pipes along the pipeline section allow you to set the values of the regulation parameters of the pumping unit and the optimal stress test parameters of the pipes in the elastoplastic deformation zone, which, in turn, unlike the prototype allows impact the pipes with shock loads representing controlled hydraulic shocks, while maintaining a guaranteed plasticity margin t rub.

The present invention is illustrated by the following detailed description of the method of hydraulic impact testing and rehabilitation of the pipeline with reference to the illustrations in figures 2 ÷ 5.

The figure 2 presents a diagram of the proposed method of hydraulic shock testing and rehabilitation of the pipeline, carried out when it is loaded with high pressure in the field, where: 1 - section of the pipeline; 2 - test chamber; 3 - a stub; 4 - source of water; 5 - filling pump; 6 - suction pipe; 7 - flow meter; 8 - pumping unit; 9 - discharge pipeline; 10 - purge pipe; 11 - pressure and temperature transducer; 12 - measuring laboratory; 13 - drain pipe; 14 - water sump; 15 - cable line; 16 - impulse line; 17 - control cable of the pumping unit; 18 - strain gauges; 19 - cable line.

In figures 3 and 4, as an example of the implementation of the claimed technical solutions, graphs are presented that characterize the dynamics of change of the shock pressure calculated by formula 2 in pipe No. 3149 (figure 3) and pipe No. 2750 (figure 4) during the passage of the shock wave during the loading of the pipeline section by pressure water: on the ordinate axis, the ratio of the shock pressure to the pressure at the inlet to the pipeline section, on the abscissa axis, the time. The graphs show the maximum and minimum absolute pressures in the pipes, as well as the initial (minimum test) absolute pressure at the inlet to the pipeline section, equal to 9.0 MPa, corresponding to a voltage of 85% of the yield strength of the pipe metal.

The figure 5 shows graphs of the parameters measured on the pipe No. 3149 during the passage of the shock wave, namely: pressure jump, pressure pulsation and deformation in the circumferential direction.

The proposed method of hydraulic impact testing and rehabilitation of the pipeline was carried out by sequentially performing the following operations (see figure 2).

At the compressor station, which includes five parallel-connected gas pumping units (GPU), a section of the pipeline at the outlet of the GPA with a length of 110 meters and an outer diameter of 1420 mm was allocated for overhaul. Working pressure was 7.35 MPa.

The pipeline is mounted from nine 10G2FB (K60) steel pipes with a wall thickness of 16 mm. The difference in elevations was 1 meter.

The parameters of the Gaussian statistical distribution of mechanical properties (in accordance with the manufacturer's certificates) for steels in the pipes of the pipeline section are given in table 1.

Table 1 The parameters of the statistical distribution of Gaussian pipe steels by mechanical properties (grade 10G2FB (K60), pipe of the Khartsiz pipe-rolling plant with a diameter of 1420 * 16 mm). Mean value (expectation) Relative extension, % Distribution parameters The standard deviation of the yield strength / tensile strength (Kσ _T / Kσ _BP ), MPa The displacement distribution center (entropy *) H (Kσ _T) / H (Kσ _Bp) MPa Yield strength σ _t , MPa Temporary resistance σ _bp , MPa 460.85 617.4 twenty 19.85 / 29.4 6.38 / 6.95

* - entropy of the Gaussian distribution

According to the results of flaw detection performed by non-destructive testing methods, defects were detected, the sizes of pipe defects were determined, and the attenuation coefficients K _{f of} each pipe were calculated.

The results of the calculation of pipe attenuation coefficients are shown in table 2.

table 2 Pipe attenuation factors K _f Defect Parameters Pipe serial number 4263 3149 2845 2781 2750 3700 3788 1184 4246 Depth mm 4.9 3,1 6.9 1,2 1,5 1.8 2.7 4.4 5.2 Length mm 82 64 150 fifteen 41 21 52 106 85 K _f 0.31 0.19 0.43 0.08 0.09 0.11 0.17 0.27 0.33 1-K _f 0.69 0.81 0.57 0.92 0.91 0.89 0.83 0.73 0.67

To assess the compliance of the pipes with the conditions for their rehabilitation, the following parameters were determined that are included in formulas 1 and 2:

- The minimum test pressure for defect-free pipes, causing ring stresses equal to 85% of the yield strength of metal pipes:

- The maximum test pressure for defect-free pipes, causing ring stresses equal to 110% of the yield strength of metal pipes:

- The rate of pressure rise was taken based on the fact that the step of loading the pipeline with pressure is limited by the class of pressure transducers used. For example, with a deadweight tester gauge class of 0.1% and a loading step of 0.01 MPa pressure, the minimum time for recording pressure between two adjacent measurements on a pressure gauge of this class is 2 seconds.

и времени

, соответствует

.The rate of pressure rise, providing smooth loading of pipes in the permissible zone of elastoplastic deformation, from the condition of its correspondence to the load per 1% deformation, i.e.

and time

corresponds

.

Moreover, the corresponding value of the strain rate during tensile metal in the circumferential direction was calculated by the formula

- скорость деформации металла;Where

- metal deformation rate;

µ is the Poisson's ratio;

S is the wall thickness of the pipe, mm;

D _VN - inner diameter of the pipe, mm;

E is the modulus of elasticity of the pipe metal, MPa;

- скорость подъема давления (0,3 МПа/мин).

- pressure rise rate (0.3 MPa / min).

The strain rate for defect-free pipes (K _f = 0) was

- The productivity of the pumping unit for raising the pressure by 2.7 MPa from the minimum pressure of 9.0 MPa to the maximum pressure of 11.7 MPa in the pipeline section with a volume of 176.6 m ³ will be

where V is the geometric volume of the pipeline section, m ³ ;

- скорость подъема давления, МПа/мин;

- pressure rise rate, MPa / min;

ΔР is the difference between the maximum and minimum test pressures, MPa.

The time for raising the test pressure from minimum to maximum in the elastoplastic zone of pipe deformation was determined:

where V is the geometric volume of the pipeline section, m ³ ;

q is the productivity of the pumping unit, m ³ / min.

The water speed in the discharge pipe with a diameter of 250 mm will be

where ω is the water velocity in the discharge pipe, m / s;

q is the productivity of the pumping unit, m ³ / min;

F is the cross-sectional area of the discharge pipe, m ² .

.Deformation of defect-free pipes in the circumferential direction during the time of pressure rise from minimum to maximum will be 9 × 0.245 = 2.19 mm, which will be in relation to the diameter of the pipeline

.

- Taking into account the size of the defects, we calculated the stress values for each pipe in the pipeline section using formula 4, the strain rates using formula 13, and the shock pressures behind the wave front using formula 2.

The results of the calculation of deformations and stresses in the pipes of the pipeline section under test pressure are shown in table 3.

Table 3 Deformations and stresses in the pipes of the pipeline section under test pressure Parameter Pipe serial number 4263 3149 2845 2781 2750 3700 3788 1184 4246 Strain rate at 0.355 0.302 0.43 0.266 0.265 0.275 0.295 0.336 0.366 tensile mm / min Compression strain rate, mm / min 0.426 0.363 0.516 0.319 0.318 0.33 0.354 0.4 0.439 Ring stress, MPa 567.9 483.5 687.2 425.8 426.4 440.1 471.9 536.5 584.5 Attitude roundabout stress to limit 1.23 1.05 1.49 0.92 0.93 0.95 1,02 1.16 1.27 fluidity Elongation,% 0.246 0.21 0.298 0.184 0.185 0.19 0.2 0.232 0.253

Taking into account the data given in table 3 and graphs (figures 3 and 4), the changes in shock pressure in pipes No. 3149, 2750 calculated according to formula 2, pipes No. 3149, 2781, 2750, 3700 and 3788 were selected for rehabilitation, since these pipes met the conditions corresponding to formula 1, that is, the magnitude of the ring stresses acting in the pipe walls when they are loaded by shock pressure with deformation in the elastoplastic zone does not exceed 110% of the standard yield strength of the pipe metal. After replacing the rejected pipes that do not meet the rehabilitation conditions, the pipeline section 1 for hydraulic tests was limited to test chamber 2 and a plug 3 was installed on the opposite side from test chamber 2.

The cavity of the pipeline section 1, the discharge pipe 9 and the suction pipe 6 of the pumping unit 8 through the filling pump 5 are connected to a water source 4.

To purge the air from the cavity of the pipeline section 1, a purge pipe 10 was mounted when filling it with water, and a drain pipe 13 was mounted to drain the water into the settling tank 14. Temperature and pressure transducers 11 were installed on test chamber 2, and a flow meter was mounted on the suction pipe 6 of the pumping unit 8 7. Strain gauges 18 were mounted on the pipeline section 1. Temperature and pressure transducers 11 by impulse line 16, flow meter 7 by cable 15, and strain gauges 18 by cable 19 were connected to the measuring lab oratorio 12. The control of the pumping unit 8 was carried out via cable 17 from the measuring laboratory 12. At the first stage, the section of pipeline 1 was filled with water from source 4 and air was removed through the purge pipeline 10. Air removal was completed after the water outlet by closing the valve on the purge pipe 10 and water was pumped into the pipe section 1 by the pumping unit 8 from the source 4 to a pressure at the inlet to the pipe section equal to 9.0 MPa, which characterizes the initial stage of pipe deformation in the elastoplastic region, wherein the pressure rise was carried out at a speed of 0.3 MPa / min and during the pressure rise, temperature, pressure, water flow rate, and deformation were continuously measured and controlled. The stress test of the pipes of the pipeline section 1 was carried out by sequentially performing the following procedures:

- By depressurizing at a speed of 0.36 MPa / min from a pressure of 9.0 MPa to a working design pressure of 7.65 MPa for a time equal to 3.35 min, compression stresses were created with pipe deformation;

- By raising the pressure from the working design 7.65 MPa to a maximum test pressure of 11.7 MPa, tensile stress was created in the pipe walls with pipe deformation in the elastoplastic zone. Moreover, in order to maintain a guaranteed margin of ductility of pipes, the pressure rise rate was set to 0.42 MPa / min, proportional to the allowable rate of deformation of pipes 0.245 mm / min with a corresponding relative deformation of 0.154%.

- The alternation of the compression-tension cycles by depressurizing to a value of 2.0 MPa, followed by a rise in pressure to a maximum test pressure of 11.7 MPa, and holding for a time until the pressure and temperature of the water in the pipeline section 1 equalize.

Hydraulic shock tests and rehabilitation of the pipeline section were completed when the acceptable relative deformation of 0.225% was reached, after which the pressure was relieved to 8.92 MPa, and the value of the residual relative deformation was 0.09%.

To compare the measured parameters and the parameters calculated by the formula 2, figure 5 shows graphs of changes in pressure jump, pressure pulsation and pipe deformation in the circumferential direction in pipe No. 3149. A flow jump during loading of pipe No. 3149 led to a shock jump in pressure from 8.92 MPa to a pressure of 9.68 MPa, while the strain in the circumferential direction was 0.225%. The measured parameters of pressure shock and deformation are consistent with the corresponding parameters calculated by formula 2 and are given in table 3. Thus, the method of hydraulic impact testing and rehabilitation of the pipeline, carried out when it is loaded with high pressure, allows to achieve the stated goal: it increases the efficiency of construction and / or overhaul of pipelines through the use of existing pipes.

Claims (3)

1. The method of hydraulic shock testing and rehabilitation of the pipeline, carried out when it is loaded with high pressure in the field, based on the injection of water by a pumping unit from a source into a section of the pipeline with a pressure equal to the pressure in the source, followed by a rise in pressure to a predetermined value and recording the flow rate, temperature, water pressure, which consists in the fact that the pipeline section is selected by non-destructive testing methods, indicators of the mechanical properties of the pipes are calculated taking into account the stress-strain state of the pipeline section, the parameters of its loading with high pressure are determined and separated by chambers or plugs from the pipeline, water is pumped into the cavity of the pipeline section and tested with increased pressure and rehabilitation of pipes with crack-like defects, characterized in that it is initially filled with water from the section the air is removed from the pipeline and the pipeline section is loaded with shock pressure in the elastoplastic zone of pipe deformation by the stress test method, including m step-by-step pressure rise carried out at a given speed and at predetermined pressure intervals to a pressure value that causes tensile stresses in the metal of the pipes in the circumferential direction up to 110% of the standard yield strength, and the subsequent pressure release at a speed exceeding the pressure rise rate, and when dumping the pressure in the defective zones of the pipe metal creates compression stresses that prevent further crack growth, and after reaching the specified value of the residual deformation of the pipe metal, hydraulic tests The thaw of the pipeline section for impact and its rehabilitation is completed. 2. The method according to claim 1, characterized in that after the selection of the test section of the pipeline by non-destructive testing methods for each pipe having crack-like defects, the size of the defects is determined according to a given algorithm and, taking into account each pipe in the pipeline section, the actual breaking loads and corresponding these loads, the minimum test pressure and maximum test pressure, creating tensile stresses in the pipe walls in the circumferential direction from 85% to 110% of the yield strength of metal pipes, and, during the hydraulic test when filling with water, the pressure in the pipeline section is raised to a value equal to the minimum test pressure, followed by the addition of water in the volume necessary for elastoplastic deformation of the pipes while maintaining the specified guaranteed plasticity margin, and the condition for selecting pipes for rehabilitation is determined by the formula:

where σ _T is the standard yield strength of the pipe metal, MPa;

- relative pressure in the pipe with number i (i = 1, 2, 3, ... n);
P _i - absolute pressure in the pipe, MPa;
P _in - pressure at the inlet to the pipeline section, MPa;
P100% σ is the pressure corresponding to the standard yield strength of the pipe metal, MPa;

- relative distance to the pipe;
x _i - the longitudinal coordinate of the pipeline section, m;
L is the total length of the pipeline section, m;

- relative test time;
ω is the water velocity in the discharge pipe, m / s;
τ is the test time, s;
S is the wall thickness of the pipe, mm;
K _f - coefficient of attenuation of the pipe;
D _i - the outer diameter of the pipe, mm;
i - serial number of the pipe. 3. The method according to claim 1, characterized in that before the start of the hydraulic tests, the characteristics of the pumping unit and the pipeline section are calculated when the shock wave propagates in the pipes along the pipeline section, for each pipe, the ratio between the pressure rise rate proportional to the speed is set tensile metal pipes, and the rate of pressure relief, proportional to the compression rate of the metal pipes, and the magnitude of shock pressures and flow surges in the pipes a shock wave is determined by the formula:

Where

- relative pressure in the pipe with number i (i = 1, 2, 3, ... n);
ρ is the density of water, kg / m ³ ;
ω is the water velocity in the discharge pipe, m / s;
C is the shock wave propagation velocity, m / s;
g is the acceleration of gravity, m / s ² ;
P _in - pressure at the inlet to the pipeline section, MPa;
α, β - approximating coefficients:

,

λ is the coefficient of hydraulic resistance of the pipeline section;
D _VN - inner diameter of the pipe, mm;
x _i - the longitudinal coordinate of the pipeline section, m;
L is the total length of the pipeline section, m;
Δh is the difference in elevations in the pipeline section, m

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