RU2457455C2 - Method of determining air-tightness of check valves of oil pipeline - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: pressure is generated on a bar graph inside a pipeline with closed check valves while ensuring pressure difference at points where the valves are installed. After generating pressure on a bar graph, the time and highest pressure in the section of the pipeline are determined. Due to overflow of the working medium through the closed check valve, pressure in the sections levels. The time for levelling the pressure and the pressure value are determined. The check valves between sections are then opened and working medium is pumped, while raising pressure to a predetermined highest pressure. Volume of the additional pumped medium is measured. Volume of leakage of the check valves per unit time is calculated from the measurement results and air-tightness of the check valves is determined.

EFFECT: easy determination of air-tightness of check valves while simultaneously increasing accuracy.

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Description

The present invention relates to pipeline transport, which allows to determine the tightness of the overlap of the cavity of the pipeline shutoff valves.

There is a method of determining the tightness of valves on a special stand (GOST 5762-2002. Industrial pipe fittings. Valves for nominal pressure not more than PN 250. General specifications. M: IPK publishing house of standards, 16 pp .; GOST 9544-2005. Pipe fittings Classes and norms of tightness of valves. M: Standartinform, 2008, 12 pp.), which can only be used for new or overhaul valves.

The closest technical solution to the claimed one is a method for determining the tightness of stop valves by calculating two constants characterizing the tightness of each valve (Azmetov Kh.A., Samoilov V.B. To check the health of linear fittings of oil trunk pipelines / Transactions of the All-Union Scientific Research Institute for Collection, preparation and transportation of oil and oil products. - Ufa: VNIISPTneft, 1972, p. 78-82).

The disadvantage is the difficulty of determining the tightness of valves and low accuracy.

The technical result of the invention is the simplification of determining the tightness of valves, while improving accuracy.

The technical result in the method for determining the tightness of the shutoff valves of an oil pipeline is achieved by the fact that in the formed step diagram of the pressure limited by the shutoff valves in the closed position, the boundary values and time of the pressure change from the upper to the lower boundary are measured and the volume of the working agent is measured when pumped into the pipeline and increased in it the pressure from the lower to the upper boundary in the open shutoff valves position, while the leakage volumes of shutoff valves are determined from the ratio

,

,

where V _Z - the volume of the pumped working agent;

L is the total length of the section of the pipeline, which determines the tightness of valves;

p _B , p _H - respectively, the upper and lower boundary values of the pressure of the working agent;

p _i - pressure of the working agent in the i-th section;

L _i - the length of the i-th section between the stop valves;

n is the number of simultaneously tested stop valves;

i - section and reinforcement numbers,

and the leakage volume of valves per unit time is determined by the ratio

where t ₁ , t ₂ - time changes in oil pressure from p _i to p _H.

The essence of the method is as follows. In the cavity of the pipeline with closed shutoff valves create pressure in a stepwise diagram, providing a pressure difference in the places of installation of valves (figure 1). It is believed that in the process of determining the tightness of valves, the working agent does not leak from the cavity of the pipeline into the environment and the mating sections of the pipeline. Due to the overflow of the working agent through the closed shut-off valves, pressure equalization in sections up to p _H will occur. By measuring the initial and final pressures and fixing the time of their achievement, it is possible to determine the leakage volumes of stop valves.

At a pressure p _H and open shutoff valves, a working agent is pumped into the cavity of a pipeline of length L until the oil pressure reaches p _B while measuring the injection volume. Thus, the proposed method eliminates the need for calculating constants characterizing the tightness of each valve, the deformation of the pipeline and the volume of the working agent under pressure.

The principle of the method is as follows. In the oil pipeline 1 (Fig. 1 and Fig. 2), in the left extreme section 2 with the position of the stop valves 3 open and closed, the stop valves installed on the border of the right end section 4, the control point 5 sends a command to the feeders 6 of the working agent, which is through a tap 7 with a check valve feeds the working agent. When in the i-th section of the pipeline 1 some pressure p _i measured by the sensor 8 is reached, the control unit gives a command to turn off the working agent supply device. Pressure measurement p _{i by} sensors is carried out in each section. Then the locking device is moved to the closed position. Thus, in the oil pipeline 1, pressure is generated in an increasing step diagram (Fig. 1), limited by shutoff valves.

After the creation of pressure in the step diagram and the closure of all fittings is completed, the time t ₁ and the highest pressure in the section p _{B of the} oil pipeline 1 are recorded. Due to the leakage of the shutoff valves, the pressure in the sections is equalized to p _H. The pressure equalization time t ₂ and pressure p _H are fixed. Then, with a supply device 5, with all open shutoff valves open, a working agent is fed into the oil pipeline 1 with a pressure increase from p _H to p _B and a measurement of the volume of injection of the working agent V _З.

The rationale for determining the amount of leakage through the valves of closed valves

1. Determination of the parameters of the deformation of the pipeline and the change in the volume of the working agent.

The volume of the working agent in the section between valves, reduced to normal conditions (Zhukovsky N.E. Complete Works, vol. VII. ONTI, 1937), will be

where D is the inner diameter of the pipeline;

L _i - the length of the i-th section between the stop valves;

δ is the wall thickness of the pipeline;

p ₁ - overpressure in the section;

β is the volumetric compression coefficient of oil;

E is the modulus of elasticity of steel.

When oil is pumped into the cavity of the pipeline and pressure p _{2 is} created in the pipeline, the volume of the working agent in the section will be

The difference between the volumes of V ₂ and V ₁ is equal to the volume of injection of the working agent into the cavity of the section of the pipeline to increase the pressure from p ₁ to p ₂ . From (1) and (2) we obtain

E=2100000 кг/см²; D=25÷100 см; δ=1,0÷2,0 см; p₁+p₂≤100 кг/см², составляющее уравнения (3)

составит не более 10^-8 и этим составляющим можно пренебречь. Тогда соотношение (3) имеет видGiven that for real conditions

E = 2,100,000 kg / cm ² ; D = 25 ÷ 100 cm; δ = 1.0 ÷ 2.0 cm; p ₁ + p ₂ ≤100 kg / cm ² constituting equation (3)

will be no more than 10 ^-8 and this component can be neglected. Then relation (3) has the form

With a known injection volume V _W and known p ₁ and p ₂ for determining the parameters of the deformation of the pipeline and changing the volume of the working agent, we have

, характеризующий деформацию нефтепровода и изменение объема рабочего агента под действием давления путем измерений объема закачки в полость участка нефтепровода с внутренним диаметром D и протяженностью L_i и двух значений p₁ и p₂ в нефтепроводе.The obtained dependence allows us to determine the complex parameter

characterizing the deformation of the pipeline and the change in the volume of the working agent under pressure by measuring the volume of injection into the cavity of the section of the pipeline with an inner diameter D and length L _i and two values of p ₁ and p ₂ in the pipeline.

2. Determination of leaks through valves of stop valves

Consider the circuit shown in figure 1, figure 2. More rational for determining leaks is loading the pipeline with pressure in a stepwise diagram. As shown in figure 1, the first section, located on the left, is loaded with the greatest pressure p _B , the second with pressure p ₂ , the third with p ₃ , etc. Moreover, p _B > p ₂ > p ₃ >...> p _n .

The feed agent of the working agent is connected to the first section, and pressure sensors are installed in each section. The creation of pressure in a step diagram is as follows. Closes the extreme right n-th stop valves (figure 1). The feed device in the section, limited to the right by closed valves, creates a pressure p _n . After creating p _{n, the} next (n-1) -th reinforcement closes. In this order, the shutoff valves are closed and pressures are created in the sections up to the first section, where pressure p _B. After the pressure p _B is created in the first section at the same moment, the working agent supply device is switched off, time t ₁ is fixed and pressure equalization begins due to the passage of liquid through the gate leaks. In the general case, all valves of shut-off valves, including new ones, to some extent, allow fluid to pass through, which is allowed by current standards (see GOST 5762-2002, GOST 9544-2005). At the time of the termination of the pressure change in all sections, the time t ₂ and the pressure p _H equal to the length L of the entire pipeline are fixed

Then all the shut-off devices are moved to the open position and the oil is supplied to the cavity of the oil pipeline by the feeding device, providing an increase in pressure in the oil pipeline from p _H to p _B and measuring the volume of liquid supply V ₃ .

Using equation (4), the leakage through the first stop valves from the first section to the second will be

The leakage from the second section to the third through the second stop valves will be

A leak through the third stop valve will

Leakage from the i-th section to the i + 1-th section through the i-th stop valve will be

Taking into account equations (5) and (6), we write relation (9) in the form

or

The leakage volume of the ith stop valve per unit time will be

The obtained relations (11) and (12) make it possible to determine the leakage volume through the valves of the nth number of shutoff valves by creating a pressure in a pipeline with several shutoff valves according to a step diagram limited by the tested shutoff valves, measuring the pressure equalization time in the pipeline, as well as the injection volume oil into the pipeline at a given pressure increase in it.

Claims (1)

A method for determining the tightness of shutoff valves of an oil pipeline, characterized in that in the formed step diagram of the pressure limited by the shutoff valves in the closed position, the boundary values and the time of the pressure change from the upper to the lower boundary are measured and the volume of the working agent is measured when pumped into the pipeline and increased in it pressure from the lower to the upper boundary in the open shutoff valves position, while the leakage volumes of shutoff valves are determined from the ratio

where V _Z - the volume of the pumped working agent;
L is the total length of the section of the pipeline, which determines the tightness of valves;
p _B , p _H - respectively, the upper and lower boundary values of the pressure of the working agent;
p _i - pressure of the working agent in the i-th section;
L _i - the length of the i-th section between the stop valves;
n is the number of simultaneously tested stop valves;
i - section and reinforcement numbers,
and the leakage volume of valves per unit time is determined by the ratio

where t ₁ , t ₂ - time changes in oil pressure from p _i to p _H.

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