RU2723000C1 - Method and device for reducing head losses in relief pipeline - Google Patents

Abstract

FIELD: oil, gas and coke-chemical industries.

SUBSTANCE: invention relates to hydraulic engineering for transportation of liquids and gas-liquid mixtures via pipelines following the terrain. In liquid flow along raised pipeline after saddle point 2 it is possible to forecast formation of sedentary cavity in upper part of pipeline section. For this purpose, in the area of detected formation of a sedentary cavity the union for gas removal from the cavity is cut. Connecting pipe is located on the top generatrix of the pipe downstream of the expected boundary of the gas cavity, which should be specified at test connections of liquid pumping through the pipeline. Required condition for opening gas bleed pipe is considered to be exceeding preset maximum value of volume of sedentary gas cavity or exceeding, in excess of permissible, pressure drop at control section of pipeline between sensors shown in figures. Connecting pipe is closed as per reduction of pressure losses at the control section to an acceptable level, by reduction of the volume of the settled cavity to an acceptable value or by signal from the liquid sensor installed behind the outlet from the nozzle.

EFFECT: technical result is increase of pipeline efficiency.

7 cl, 6 dwg

Description

Technical field

The present invention relates to the field of hydraulic engineering for transporting liquids and gas-liquid mixtures through pipelines following the terrain; more narrowly - to the area of tasks of organizing and regulating their course on the descending sections of the route.

State of the art

Pipeline transportation of liquids and gas-liquid mixtures has been known since time immemorial. Moreover, it is known that practically any liquid stream contains free or dissolved gas in some amount, and liquid evaporation occurs at the liquid-gas interface, the intensity of which, like the rate of release of dissolved gas, depends on the temperature and pressure of the pumped media. The pressure of the medium in the relief pipeline ¹ ( ¹ ) Hereinafter, the pipeline following the terrain, in particular, deviating from it due to the characteristics of the route and in order to solve design problems.) Drops as it approaches the crossing point (due to energy consumption to overcome gravity).

It was established that gas inclusions in such flows tend to consolidate, with the formation of settled gas-filled cavities (or - bubbles) ² ( ² ) Settled cavities in the text of this Description); in particular, beyond the cross points of the tracks. It was also established that settled cavities, narrowing the flow section of the pipeline, create additional hydraulic losses in the pipeline, which can significantly reduce the throughput of the pipeline. Known today recommended ways to eliminate gas plugs in transport pipelines, such as:

- increasing the capacity of pumping pumping units, which is extremely energy-intensive, requires a design overstatement of the operating pressure in the pipeline (this directly leads to an increase in the metal consumption of all hydraulic equipment of the route) and, as a result, is ineffective, since the gas bubble is not completely eliminated, but only compressed inversely with the increase pressure in the pipeline;

- increasing the pressure of the medium in the pipeline by throttling it below the resulting plug (which inevitably reduces the pumping capacity);

- the launch of a scraper or ball piston (such as the provers used in calibration), which requires interruption of pumping and gives only a temporary effect.

This physical and technical problem has not yet attracted significant research interest and has not received wide coverage in the specialized literature, apparently, due to a lack of understanding of the physical nature of the phenomenon.

There are known theoretical and experimental studies and scientific and technical literature on free flows in gutters and pipelines. In particular, this topic is given attention in textbooks and teaching aids: Yu.A. Kraus "Design and operation of main pipelines", OmSTU, 2010, A.A. Gusev “Mechanics of liquid and gas”, Moscow, 2018, in a number of dissertations and scientific articles - M.V. Lurie, N.S. Arbuzov and others.

However, the free flow, in which the fluid flow in the pipeline does not experience significant impacts from the gas-filled part of the pipeline cross section (or can be neglected), is only partially an analogue of the flow around a settled gas bubble, which has a specific and significant effect on the fluid flow.

Accordingly, technical solutions aimed at overcoming the phenomenon under consideration are poorly presented in the patent information. The closest analogue, in terms of the physical nature of the solution, turned out to be the Russian patent for invention 2263178, “A method for protecting a dam of a hydraulic structure from destruction,” published on 10.27.2005 (priority dated 03.12.2003). The method proposed here involves pumping out an air plug blocking the main channel of the siphon using a vacuum unit using an ejector.

SUMMARY OF THE INVENTION

The technical task is to quickly remove or radically reduce the volume of a gas bubble (the same is a settled cavity) in the place of its stable and regular dislocation.

The technical result of the invention should be a radical increase in the productivity of the relief pipeline without significant additional energy costs.

As already mentioned, settled cavities, narrowing the flow section of the pipeline, reduce the throughput of the pipeline.

The proposed method of reducing pressure losses due to the formation of settled cavities in the relief pipeline is characterized in that the gas is removed from the settled cavity so that the residual filling does not create significant resistance to fluid flow in the pipeline.

The set of theoretical and empirical data currently being formed allows one to determine with a high degree of certainty the probable zones of formation of such cavities both during the design of the pipeline and during its trial operation.

The technical solutions of the present invention are based on the forced removal of gas from the formed settled cavity. At the same time, the practical clarification of the dislocation of a settled gas-filled cavity is made when testing the constructed pipeline system - for example, with modern introscopy tools. Dependent Items 2-5 protect some features and implementation options of the proposed method.

Required for the implementation of the aforementioned method, devices of pipeline systems and equipment are protected in paragraphs. 6 and 7 of the claims. Moreover, p. 7 of the formula protects one of the most economical options for the implementation of a gas removal device using its own energy capabilities of a liquid stream.

Brief Description of the Drawings

In FIG. 1 is a schematic diagram illustrating a method for removing gas from a settled gas-filled cavity in the most general case.

Here:

1 - relief liquid (or gas-liquid) pipeline,

2 - crossing point,

3 - settled (gas-filled) cavity,

4, 5 - pressure sensors of the pumped medium in the pipeline,

6 - distributed introscopic control system of a settled cavity,

7 - gas outlet with controlled shut-off valve,

8 - gas pumping pump,

9 - sensor for the appearance of liquid.

In FIG. 2 - a variant of the method according to claim 3 of the formula (discharge into the atmosphere of gas that does not have commercial value and does not harm the environment).

Here:

1 - relief liquid (or gas-liquid) pipeline,

2 - crossing point,

3 - settled (gas-filled) cavity,

4, 5 - pressure sensors of the pumped medium in the pipeline,

6 - distributed introscopic control system of a settled cavity,

7 - gas outlet with controlled shut-off valve,

8 - gas pumping pump,

9 - sensor for the appearance of liquid,

10 - diffuser with a filter.

In FIG. 3 - a variant of the method according to claim 4 of the formula (discharge into a storage tank of gas of commercial value and capable of harming the environment).

Here:

1 - relief liquid (or gas-liquid) pipeline,

2 - crossing point,

3 - settled (gas-filled) cavity,

4, 5 - pressure sensors of the pumped medium in the pipeline,

6 - distributed introscopic control system of a settled cavity,

7 - gas outlet with controlled shut-off valve,

8 - gas pumping pump,

9 - sensor for the appearance of liquid,

11 - cumulative capacity.

In FIG. 4 - a variant of the method according to claim 5 of the formula (gas extraction from a settled gas cavity with return to the pipeline downstream).

Here:

1 - relief liquid (or gas-liquid) pipeline,

2 - crossing point,

3 - settled (gas-filled) cavity,

4, 5 - pressure sensors of the pumped medium in the pipeline,

6 - distributed introscopic control system of a settled cavity,

7 - gas outlet with controlled shut-off valve,

8 - gas pumping pump,

9 - sensor for the appearance of liquid,

12 - gas bypass line,

13 - return fitting with check valve.

In FIG. 5 is a diagram of a device (pipeline system) according to claim 6 of the formula — for gas extraction from a settled cavity with return to the pipeline, with an autonomous process monitoring and control system.

Here:

1 - relief liquid (or gas-liquid) pipeline,

2 - crossing point,

3 - settled (gas-filled) cavity,

4, 5 - pressure sensors of the pumped medium in the pipeline,

6 - distributed introscopic control system of a settled cavity,

7 - gas outlet with controlled shut-off valve,

8 - gas pumping pump,

9 - sensor for the appearance of liquid,

12 - gas bypass line,

13 - return fitting with check valve

14 - autonomous system unit for process control and management.

In FIG. 6 is a diagram of a device (piping system) according to claim 7 of the formula containing a liquid intake line at a high pressure section and an ejector pump.

Here:

1 - relief liquid (or gas-liquid) pipeline,

2 - crossing point,

3 - settled (gas-filled) cavity,

4, 5 - pressure sensors of the pumped medium in the pipeline,

6 - distributed introscopic control system of a settled cavity,

7 - gas outlet with controlled shut-off valve,

9 - sensor for the appearance of liquid,

11 - fitting return gas-liquid mixture with a check valve,

14 - autonomous system unit for process control and management,

15 - bypass line of the gas-liquid mixture,

16 - nozzle for fluid sampling in the area of high pressure with a shut-off valve,

17 - ejector pump for pumping gas.

Disclosure of invention

As indicated, gas inclusions in the fluid flow flowing through the relief pipeline tend to consolidate, with the formation of settled gas-filled cavities (or - bubbles) - beyond the crossing points of the routes.

A fundamentally necessary chain of elements necessary for the removal of gas from the cavity of the present invention is shown in FIG. 1. In the fluid flow through the relief pipeline 1 after the crossing point 2 marked in the figure, it is possible to predict the formation of a settled gas-filled cavity 3 in the upper part of the pipeline section.

Therefore, already at the design stage, it is possible to provide here for the installation of pressure sensors 4 and 5, and if this is necessary, the placement of a distributed introscopic control system for the settled cavity 6, as well as the insert of the nozzle 7 for gas removal from the cavity. The fitting is located on the upper generatrix of the pipe downstream of the expected boundary of the gas cavity, which should be clarified by introscopy methods (for example, ultrasonic) with test connections for pumping fluid through the pipeline.

Pressure sensors in the pipeline 4 and 5 are installed before and after (respectively) the proposed zone of the settled cavity. By the magnitude of the pressure drop in the pipeline between the inset points of these sensors, one can assume the formation of a settled cavity here, and, having verified its formation and clarified its boundaries, use this data to make a decision to give a command to open the nozzle 7.

Distributed introscopic system 6 allows you to reliably record the fact of the formation of a gas cavity during the pumping process, to determine (or clarify) its configuration and to further monitor its volume.

Distributed introscopic control system of the settled cavity 6 can be completely autonomous, its creation does not require large expenditures, and therefore it is one of the most important elements that determine the effectiveness of measures. In this case, it is extremely important to ensure reliable prediction of the location of the cavity during the preliminary examination and to position the scanning zone of the system 6 so that it covers the entire probable zone of the gas-filled cavity 3. The scanning zone of the introscopic system 6 should cover the predicted zone of the gas-filled cavity 3 with a margin defined based on the estimate of the probability of unaccounted deviations.

Upon the fact of the formation of a settled cavity and / or its development to the shape and size at which it can impede the operation of the pipeline with a given capacity, open the valve mounted on the fitting 7 for gas extraction from the settled cavity 3.

It is proposed to consider a prerequisite for opening the gas sampling nozzle 7 to be an excess of a predetermined maximum volume of a settled gas cavity, or an excess (above the permissible) differential pressure in the control section of the pipeline (between sensors 4 and 5 shown in the figures). Although there are other possible logic of the decision to open fitting 7; for example, by the critical value of reducing the fluid flow in the pipeline with the pumping system pumping power unchanged, either by the critical change in energy consumption parameters reflecting the load of the pumping unit, or by a combination of the above and other criteria.

The fitting 7 is closed to reduce the pressure loss in the control area to an acceptable level, to reduce the volume of the settled cavity 3 to an acceptable value, or by a signal from the liquid emergence sensor 9 installed outside the outlet of the fitting 7.

Pump 8 is not a fundamentally necessary element if the pressure in this section of the pipeline is high enough to squeeze the gas out of the cavity, given the overcoming of the resistance that it encounters along the removal path.

Non-commercial and environmentally friendly gas taken from a settled gas cavity is discharged into the atmosphere through a diffuser with a filter 8, as shown in FIG. 2.

Gas of commercial value or harmful to the environment, taken from a settled gas cavity, is sent for disposal through storage tank 7, according to FIG. 3.

The gas taken from the settled gas cavity can also be returned to the pipeline downstream to the area where the formation of a settled gas cavity is physically impossible, and the pressure in the transport pipeline is obviously lower than at the gas extraction point, according to FIG. 4. The need for the presence of pump 8 in this scheme or the possibility of its absence is determined by calculation, based on the ratio of the pressures in the pipeline at the gas extraction point and at the return point, taking into account pressure losses in the gas bypass line.

In FIG. 5 shows a diagram of a device (system) for removing gas from a settled cavity according to independent claim 6 of the claims intended for implementing the method according to claims. 1 and 5, - in the most complete composition of the elements.

In FIG. 6 shows a diagram of a fully autonomous system for removing gas from a settled cavity containing a gas transfer pump 6 (uniquely, an ejector in this case), driven by a stream of liquid taken from the pipeline at a high pressure section, preceding the rise to the said transit point, delivering a gas-liquid mixture into the pipeline below the place of formation of the settled gas-filled cavity, to the reduced pressure section.

The implementation of the invention

The present invention can be applied both to the design of newly created and reconstructed objects, and during operation.

In the process of design development of relief pipeline routes for transporting liquids (and, especially, gas-liquid mixtures), it is advisable to conduct their virtual analysis to identify potential places of formation of settled gas cavities in pipelines. It is obvious that the scientific and technical data already available today are enough to provide the designer with a simple testing program for the designed tracks. Upon detection of potentially dangerous places, you should either modify the profile of the route, or, if the first is not possible, put one of the technical solutions of the present invention into the project.

Identification of places of regular formation of settled gas bubbles during operation is also not too difficult, with a certain skill. The main symptom suggesting such a probability is a decrease in the throughput of the pipeline system after some time of pumping liquid through it, which cannot be eliminated even with a permissible increase in the capacity of the pumping pump system.

The most effective method for identifying settled cavities and clarifying their location and configuration is introscopy, for example, ultrasound examination of potentially places of the pipeline through which the stream flows. At the stage of preliminary examination, it can be performed by mobile means of introscopy.

The section of the pipeline in which the settled cavity was formed can also be determined by the pressure drop of the pumped medium over its length, significantly exceeding the value determined by the calculation - taking into account the known features of the shape of the pipeline in this section and the presence of structural elements in it that increase the flow resistance.

Special experimental work and experience in the operation of relief pipelines using the technical solutions proposed here will allow us to develop and improve methods and tools for the effective determination of the places of formation of settled cavities in liquid pipelines and their configuration, as well as the actual dynamics of these processes.

After determining (clarifying) the zone of formation of a settled cavity, in size and configuration that significantly affects the throughput of the pipeline, it is necessary:

• insert into the pipe wall 1 gas outlet 9;

• install the necessary outlet pipes, shut-off valves and sensors necessary for this case;

• install a system for monitoring and controlling a settled cavity (system unit 14 and other elements).

The most important component of the development of the proposed innovations is the construction of a reliable and cost-effective system of diagnostics and control of the processes of formation and elimination of settled cavities in the fluid flow transported through a relief pipeline.

A combined option is also possible: the use of introscopy (for example, ultrasound examination by mobile means) at the stage of diagnosing the formation of settled cavities and during control checks, in combination with the establishment of constant monitoring of hydraulic pressure losses in the identified area of their formation - as a component of an autonomous system for monitoring the flow condition .

Claims (7)

1. A method of reducing pressure losses caused by the formation of settled gas-filled cavities in a liquid or gas-liquid flow in the descending sections of the profile of the profile of a relief transport pipeline, characterized in that the gas is forcibly removed from the settled cavity in the pipeline completely or so that its residual volume does not create a significant hydraulic resistance to flow in the pipeline. 2. The method according to p. 1, in which the place of formation of a settled gas-filled cavity is pre-determined by calculation or experiment, or detected by introscopic observation. 3. The method according to p. 1, in which the gas is removed from the settled cavity when the pressure drop of the liquid in the control section of the transport pipeline has become greater than the allowable value, or when its volume, measured introscopically, has exceeded the specified limit value, and is completed when the pressure drop in the flow at the control section of the pipeline will decrease to an acceptable value, either when the volume of the settled cavity decreases to an acceptable value, or by a signal from a liquid appearance sensor installed on the gas outlet fitting from the settled cavity. 4. The method according to p. 1, in which the gas, not having commercial value and not harmful to the environment, taken from a settled cavity is discharged into the atmosphere. 5. The method according to p. 1, in which a gas of commercial value or harmful to the environment, taken from a sedentary cavity, is sent for disposal. 6. The method according to p. 1, in which the gas taken from the settled cavity is returned to the transport pipeline below the formation of the settled cavity in the area where the formation of a settled gas cavity is physically impossible, in particular, due to the high flow rate, and the pressure is obviously lower than at the gas sampling point. 7. A device that implements the methods of PP. 1-5, containing a small cross-section pipeline, if necessary equipped with a gas transfer pump, connected at one end to a gas outlet fitting from a settled cavity through a controllable valve, and at the other end to a gas return point to a transport pipeline, through a non-return valve, or to a device discharging gas into the atmosphere, characterized in that for the removal of gas from the settled gas cavity, an energy-independent system is used with an ejector gas evacuation pump driven by a stream of liquid taken from the transport pipeline at the high pressure section and discharging the gas-liquid mixture into the transport pipeline at the section low pressure, behind the place of formation of a settled gas cavity.

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