RU2487331C2 - Method to detect location of leak in closed hydraulic manifold equipped with flow booster and hydraulic-pneumatic compensator of temperature change of working fluid volume - Google Patents

Abstract

FIELD: test equipment.

SUBSTANCE: when realising the method to detect location of a leaking point in a closed hydraulic manifold equipped with a flow booster and a hydraulic-pneumatic compensator of temperature change of working fluid volume, medium pressure is reduced in the gas cavity of the hydraulic-pneumatic compensator to the level of this pressure stabilisation within the limits of measurement error. After confirmation of leak availability previously medium pressure is established in the gas cavity of the hydraulic-pneumatic compensator, and this pressure is equal to measured pressure of atmosphere in a room tightly isolated from the environment P_a, and reduction of this pressure to the specified level of stabilisation is carried out with the connected working fluid flow booster, at the same time actual head $$P_h^a$$

is measured, being developed by the specified flow booster. Stabilisation pressure P_s is fixed and recorded, losses of measured head are determined per unit of length of the hydraulic manifold q_l, as well as head losses at the inlet to the flow booster ΔP_in. Afterwards location of the leaking point of the hydraulic manifold is determined on the basis of the ratio given in the invention claims.

EFFECT: development of a simple and efficient method, safe for operators working in residential premises tightly isolated from external media, to determine location of a leaking point in a hydraulic manifold of a system of facility thermal control after confirmation of leak availability.

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Description

The invention relates to mechanical engineering, specifically to methods for determining the location of an unpressurized area in a closed hydraulic line of a temperature control system that is hermetically isolated from the external environment of a living room, equipped with a flow inducer and a hydropneumatic compensator for temperature changes in the volume of the working fluid.

The invention can be applied in the operation of closed hydraulic systems of great length, the lines of which are located in hard-to-reach places in hermetically isolated from the external environments inhabited premises.

As is known (patent RU No. 2242102, 02/10/2005, IPC: G01M 3/00 (2006.01), B64G 1/50 (2006.01), V.N.Serebryakov “Fundamentals of the design of life support systems for spacecraft,” Moscow, “ Mechanical Engineering ”, 1983, pp. 73-74), the basis of hydraulic thermal control systems for manned spacecraft or similar inhabited objects is closed hydraulic circuits filled with liquid working bodies (coolants). Each such circuit is a closed hydraulic line, combining heat exchangers for various purposes, a motive agent for the working fluid (hydraulic pump), valves, means for controlling the flow of the working fluid, sensor equipment, etc. To compensate for temperature changes in the volume of the working fluid, a hydropneumatic compensator is included in the hydraulic line.

The compensator is a spherical or cylindrical container, hermetically divided into two cavities - liquid and gas - by moving separation of the media. As such separators, elastic rubber or plastic membranes (diaphragms), as well as volumetric metal bellows, are usually used. The liquid cavity of the compensator is filled with a working fluid and connected to the hydraulic line, usually at the inlet to the hydraulic pump, and the gas cavity is filled with nitrogen or air with a certain pressure. Compensation of the temperature change in the volume of the working fluid in the hydraulic line is ensured by moving the media separator and the corresponding compression (expansion) of gas in the gas cavity of the compensator, which is accompanied by a corresponding change in pressure in the hydraulic line.

For such hydraulic systems for thermal control of space objects or similar systems, hermetically isolated from the external environment of the premises, the main structural parameter that determines their reliability and durability is the tightness of the hydraulic lines filled with the working fluid.

This is due to the fact that the pressure of the working fluid in the hydraulic lines of the thermal control systems of such objects can be several times higher than the atmospheric pressure of their inhabited compartments or rooms due to the significant length of the hydraulic lines due to their design features and the high consumption of the working fluid in these lines. In addition, tightness directly determines the performance of such highways.

The most dangerous emergency situation that can occur in such systems during long-term operation is loss of tightness by pipelines and other elements of the hydraulic line due to various technological and operational reasons (corrosion of piping material, manifestation of latent factory technological defects, accelerated aging of rubber joint seals, incorrect operation, etc.). As a result of depressurization of the hydraulic line, the working fluid of the system with varying degrees of intensity can enter the atmosphere of inhabited compartments or rooms and spread through a closed volume by means of ventilation, causing certain negative consequences for both operators and automation devices and other equipment. To counter such a situation, it is necessary to quickly determine the location of the leak, to repair or replace the damaged area, or to exclude it from the hydraulic line by shunting.

Because of its simplicity, the hydrostatic method for determining the leaky section of the hydraulic lines of aircraft systems is known and widely used in industry (V. M. Sapozhnikov “Installation and testing of hydraulic and pneumatic systems on aircraft”, Moscow, “Mechanical Engineering”, 1977, pg. 196-197).

The method involves filling the hydraulic line with a working fluid and loading it with rated working pressure, and the place of leakage is determined visually by the appearance of droplets of the working fluid on the pipelines of the hydraulic line (the so-called “fogging” of the system) or by wiping the pipelines and structural elements of the test section with filter paper, followed by control the spot size of the traces of the working fluid.

With regard to the possibility of using this method in a hermetically isolated from the external environment inhabited premises, it has the following disadvantages:

- the search for leaks in the section of the hydraulic line of the system takes a considerable time at the nominal operating pressure in the system, therefore, during the search for such a section, the working fluid will enter the inhabited room, which, for example, is completely unacceptable for completely sealed rooms;

- the method does not allow to locate unsealed sections and elements of systems coated with thermal insulation or located in hard-to-reach places of the room or compartment where it is easy not to notice and not to collect any drops of the working fluid on filter paper. The method is also not suitable if the leaky area is located outside the facility or premises.

Known and also widely used in industry is the pneumatic method for checking the tightness of the pneumatic and hydraulic systems of aircraft, which allows you to determine the location of an unsealed section of the hydraulic line (V. M. Sapozhnikov "Installation and testing of hydraulic and pneumatic systems on aircraft", Moscow, "Engineering", 1977, pp. 200-203).

The method involves filling the hydraulic lines of the systems with air or nitrogen with a pressure equal to the nominal operating pressure in the system, and applying foam emulsion to the inspected areas and places with subsequent visual observation of its condition. The tightness of the tested section of the hydraulic line is determined by the number of gas bubbles fixed in the emulsion for a certain time. If the number of bubbles in the emulsion exceeds the standard value stipulated by the documentation, the inspected area is considered leaky and rejected. The method is used to control the tightness of hydraulic systems before refueling with working fluid; after refueling, such systems cannot be used.

There are also known methods of searching for leaking sections of systems using a control helium gas or a mixture of helium with air (V. M. Sapozhnikov “Installation and testing of hydraulic and pneumatic systems in aircraft”, Moscow, “Mechanical Engineering”, 1977, p.203- 212), using mass spectrometers or halide leak detectors. These methods are designed to determine the leakage of "dry" hydraulic systems in the process of their manufacture; these methods cannot be used to search for damaged areas of refueling systems.

A well-known luminescent method for determining the location of an unsealed portion of a charged hydraulic system, which allows to determine the location of leaks and damaged sections of the hydraulic line (V. M. Sapozhnikov "Installation and testing of hydraulic and pneumatic systems on aircraft", Moscow, "Engineering", 1977, pp. .197-198).

The method involves pre-filling the hydraulic system with a mixture of a working fluid (~ 98%) and a luminescent composition of ~ 2%, loading the system with nominal working pressure and irradiating the test areas with an ultraviolet lamp with registration of the glow of the control fluid under the influence of ultraviolet rays. At the same time, the hydraulic system is considered leakproof if luminous spots and stripes are not found in the areas being tested.

The luminescent search method for an unsealed section of a hydraulic highway has the following disadvantages:

- although the working fluids of modern hydraulic thermal control systems located in sealed inhabited compartments or rooms contain phosphors, the method is ineffective in searching for leaking sections of the hydraulic system located in hard-to-see and inaccessible places or places covered by thermal insulation;

- the method requires significant search time and does not ensure the safety of operators, because it is based on determining the luminosity of the working fluid with a luminescent composition already displaced from the hydraulic line into the atmosphere of the inhabited pressurized compartment or premises by the working pressure in the system;

- the method is practically unsuitable for determining leaking sections of hydraulic lines located outside hermetically isolated from the external environment inhabited premises.

A known method for determining an unpressurized portion of the hydraulic line of the thermal control system of a space object in flight (patent RU No. 2322377, 04/20/2008., IPC: B64G 1/50, 1/46, 1/12 (2006.01)).

The method involves breaking the hydraulic line into separate hydraulically unrelated sections and checking for leaks using the proposed device for the stability of the control pressure in each section.

The disadvantages of the method include:

- the considerable complexity of the method, due to the large amount of work on the preparation of work areas where the breakdown of the hydraulic line is carried out (dismantling of equipment and devices, cable trunks that impede access to collapsible joints of the hydraulic line, etc.);

- relatively large expenditures of working time for exposure under control pressure of each section of the hydraulic line.

A known method of regulating the pressure in a hydraulic thermal control system with a gas-liquid compensator for a spacecraft is protected by patent RU No. 2160217, 12/10/2006, IPC: B64G 1/50 (2006.01), F16L 35/10 (2006.01), adopted by the author as a prototype.

The method, after establishing the fact of depressurization, determines the speed and direction of the pressure change in the gas cavity of the compensator. With an increase in pressure, the gas of the compensator cavity is pressurized; with a drop in pressure, gas is released from the gas cavity of the compensator. These operations are carried out until the pressure in the gas cavity of the compensator is stabilized within the error of pressure measurement, while the temperature of the coolant in the thermal control system and the pressure of the atmosphere in the pressurized compartment are kept constant.

The disadvantage of this method is that it does not allow to determine the linear coordinate (distance) of the leak in the hydraulic line from any characteristic point in the same hydraulic line.

The objective of this technical solution is to create a simple and safe for operators working in hermetically sealed habitable rooms from the external environment, an operational way to determine the location of an unsealed section of the hydraulic line of the thermal control system of an object after the fact of leakage has been established.

The technical result of the proposed technical solution is that in comparison with the currently known technical solutions, it allows you to:

- to ensure the prompt determination of the linear coordinate of the leak point with respect to the control point in the hydraulic line;

- automate the search for leaks using the computer system (VC) facility.

In addition, for its implementation, the method does not require special equipment and is based on those tools that already exist in a typical hydraulic thermal control system.

, создаваемый побудителем расхода, фиксируют и регистрируют давление стабилизации P_с, определяют потери измеренного напора на единицу длины гидравлической магистрали q_л и потери напора на входе в побудитель расхода ΔP_вх, после чего определяют местоположение негерметичного участка гидравлической магистрали из соотношенияThe technical result is achieved by the fact that in the method of regulating the pressure in the hydraulic thermal control system with a gas-liquid compensator of the spacecraft, including the operation of reducing the pressure of the medium in the gas cavity of the hydropneumatic compensator to the level of stabilization of this pressure within the measurement error, after establishing the fact of depressurization, the systems are pre-installed in the gas cavity hydro-pneumatic compensator medium pressure equal to the measured pressure of the surrounding osfery sealingly insulated from the outside environment space P _a, and the decrease of pressure to said level stabilizing produce driving force when the working fluid flow, the actual measured pressure $$P_n^f$$

Generated driving force flow, fixed and recorded stabilization _pressure P, the measured pressure loss is determined on a unit length of the hydraulic line _L and q head loss at the inlet of the flow stimulus ΔP _Rin, after which the location unpressurized hydraulic line portion ratio of

$$\ell =\frac{\left(P_n^f-\Delta P_{\mathrm{at}x}\right)-\left(P_a-P_c\right)}{q_l}-{\ell }_{\mathrm{at}x},gde\left(\mathrm{one}\right)$$

ℓ - the distance to the location of the leaky section of the hydraulic line along the movement of the working fluid from the point of connection of the hydropneumatic compensator to the hydraulic line;

- фактический напор, создаваемый побудителем расхода рабочего тела; $$P_n^f$$

- the actual pressure created by the stimulator of the flow of the working fluid;

ℓ _in - the length of the section of the entrance to the hydraulic pump (section of the hydraulic line from the point of connection of the hydropneumatic compensator to the entrance to the hydraulic pump).

ΔP _in - pressure loss at the inlet to the flow rate driver (in the hydraulic line section from the point of connection of the hydropneumatic compensator to the inlet of the flow rate equal to q _l × ℓ _in , where ℓ _in - the length of the section);

- потери напора, создаваемого побудителем расхода на единицу длины гидравлической магистрали, где ℓ_м - длина гидравлической магистрали; $$q_l=\frac{P_n^f}{{\ell }_m}$$

- loss of pressure created by the flow driver per unit length of the hydraulic line, where ℓ _m is the length of the hydraulic line;

P _a - atmospheric pressure hermetically isolated from the environment;

P _with - pressure stabilization.

We will consider the practical implementation of the proposed method by the example of a hydraulic thermal control system of one of the objects, which has a system of living quarters that are tightly isolated from the external environment and connected to each other.

The thermal control system of this facility is a closed hydraulic line, combining heat exchange units, valves and sensor equipment located in inhabited premises. The motive fluid flow rate in the hydraulic line is a hydraulic pump, the compensation of temperature changes in the volume of the working fluid is provided by a hydropneumatic compensator.

A simplified hydraulic diagram of the thermal control system of the object is shown in figure 1, where are indicated:

1 - hydraulic line;

2 - hydropneumatic compensator;

3 - a liquid cavity of a hydropneumatic compensator;

4 - gas cavity of a hydropneumatic compensator;

5 - drain valve;

6, 7 - pressure sensors;

8 - differential pressure sensor (pressure gauge of a hydraulic pump);

9 - a hydraulic pump (flow inducer).

In order to simplify the hydraulic circuit, heat transfer units, regulatory bodies, most of the fittings and sensor equipment are not shown in the diagram, while the total hydraulic resistance of these elements is considered uniformly distributed along the length of the hydraulic line, which is generally fair for the system under consideration.

As can be seen from figure 1, the fluid cavity of the hydropneumatic compensator 3 is connected to the hydraulic line 1 at the inlet to the hydraulic pump 9, which is a characteristic case for high-pressure hydraulic thermal control systems of such objects. The boundaries of the characteristic sections of the hydraulic line and, accordingly, the design scheme are assigned lettering. Point B indicates the conditional leak point (leak point), which is located at a distance ℓ from the point of connection of the hydropneumatic compensator to the hydraulic line.

We plot the pressure distribution in the hydraulic line during operation of the hydraulic pump 9. Conditionally open the line at point E and turn it along the X axis (points E and E ₁ ). On the y-axis, we will plot the pressure. Then the nominal (until the depressurization of the hydraulic line) diagram will take the form shown in figure 2, where are indicated:

- фактический напор гидравлического насоса; $$P_n^f$$

- the actual pressure of the hydraulic pump;

ℓ - the distance to the location of the leaky section of the hydraulic line (point B) along the movement of the working fluid from the point of connection of the hydropneumatic compensator (point A) to the hydraulic line;

ℓ _m - the length of the hydraulic line;

ℓ _in - the length of the hydraulic line from the point of connection of the hydropneumatic compensator (point A) to the entrance to the hydraulic pump (point B);

P _a ≈1 kgf / cm ² - the pressure of the atmosphere is hermetically isolated from the external environment of the room. Thus the static pressure in the hydraulic line (connection point a hydropneumatic compensator point A) above accept (for clarity) than atmospheric pressure habitable space P _a. Therefore, when a leak appears at point B, the working fluid of the hydraulic line will flow into the living room with varying degrees of intensity, which will be determined by the geometric dimensions of the leak and the pressure drop between the pressure of the working fluid at this point and the atmosphere pressure of the living room.

The loss of the working fluid from the hydraulic line 1 will be compensated by displacing the corresponding amount of liquid from the fluid cavity of the hydropneumatic compensator 3, which will be accompanied by a decrease in the volume of the fluid cavity 3 and a corresponding increase in the volume of the gas cavity 4 of the hydropneumatic compensator 2. As a result of the increase in the volume of the gas cavity of the hydropneumatic compensator 4, the gas pressure environment in it, and therefore in the hydraulic line 1 will begin to decline. This will be recorded by pressure sensors 6 and 7, broadcast to a computer complex (VK) and transmitted via telemetry to the facility operation control center.

After a corresponding analysis of the information received by the VC, the latter generates a message about the depressurization of the system to the central console of the facility, turns off the hydraulic pump 9 and transmits a status message about depressurization to the Operation Center. After the alarm is triggered on the central control panel of the facility, the operators using a special device (not shown in Fig. 1) open the drain valve 5 and communicate the gas cavity of the hydropneumatic compensator 4 with the atmosphere of the room, equalizing the pressure in the hydraulic line 1 and in the room. As a result, the flow of the working fluid from the hydraulic line 1 is stopped. The atmospheric pressure of the room will be selected as the initial value in the process of further search for the place of leakage.

The diagram of the hydraulic pressure line after the fluid pressure reduction in the gas cavity hydropneumatic compensator with an initial value equal to P _a, to the level of stabilization _to P shown in Figure 3.

расходуется:As can be seen from the plot (figure 3), the pressure of the hydraulic pump $$P_n^f$$

consumed:

- to overcome the hydraulic resistance of the plot B-V (part of the pressure head BK);

- to overcome the hydraulic resistance of section B-E (E ₁ ) (a component of the head EM);

- to overcome the hydraulic resistance of the plot E (E ₁ ) -A (part of the pressure EM (E ₁ M ₁ ))

- to overcome the hydraulic resistance of the plot AB (pressure loss at the inlet to the hydraulic pump ΔP _I ).

According to the diagram in figure 3 it is easy to determine the pressure component ΔP _BK :

$$\Delta P_{B\mathrm{TO}}\left(P_n^f-\Delta P_{\mathrm{at}x}\right)-\left(P_a-P_c\right),gde\left(2\right)$$

ΔP _BK - the pressure spent on the determination of the hydraulic resistance of the BB section of the hydraulic line;

- фактический напор, создаваемый гидравлическим насосом; $$P_n^f$$

- the actual pressure created by the hydraulic pump;

ΔP _in - pressure loss at the inlet to the hydraulic pump in the section of the hydraulic line from the point of connection of the hydropneumatic compensator (point A) to the entrance to the hydraulic pump (point B);

P _a is the atmospheric pressure of the room;

P _with - pressure stabilization.

In turn, the pressure ΔP _BK spent on overcoming the hydraulic resistance of the BB section of the hydraulic line can be expressed as

$$\Delta P_{B\mathrm{TO}}=\left({\ell }_{B-\mathrm{AT}}\right)\times q_{l}gde\left(3\right)$$

ℓ _B-V = (ℓ-ℓ _in ) - the length of the section of the hydraulic line from the point of leakage (point C) to the exit to the hydraulic pump (point B);

- потери напора, создаваемого гидравлическим насосом на единицу длины гидравлической магистрали, где ℓ_м - длина гидравлической магистрали. $$q_l=\frac{P_n^f}{{\ell }_m}$$

- loss of pressure created by the hydraulic pump per unit length of the hydraulic line, where ℓ _m is the length of the hydraulic line.

Then, taking into account (2) and (3), we find the linear coordinate of the location of the leaky section of the hydraulic line:

$$\ell =\frac{\left(P_n^f-\Delta P_{\mathrm{at}x}\right)-\left(P_a-P_c\right)}{q}-{\ell }_{\mathrm{at}x},gde\left(\mathrm{one}\right)$$

ℓ _in - the length of the section of the entrance to the hydraulic pump (section

hydraulic line from the point of connection of the hydropneumatic compensator to the entrance to the hydraulic pump). Directly search for leaks in the hydraulic line is as follows.

, создаваемый гидравлическим насосом 9, по показаниям датчика перепада давления 8.At the time planned for work, the operator connects to the drain valve 5 an onboard vacuum pump with an electric drive controlled by a VK (not shown in Fig. 1), and starts a leak search program in VK. According to this program, the hydraulic pump 9 is turned on and a gradual stepwise decrease in the pressure of the medium in the gas cavity of the hydropneumatic compensator 4 is provided by the corresponding on / off of the vacuum pump with continuous monitoring and registration of pressure at each stage. At the same time, the actual pressure is recorded $$P_n^f$$

created by the hydraulic pump 9, according to the readings of the differential pressure sensor 8.

As soon as stabilization of pressure P _s in the hydraulic line is recorded and recorded at one of the stages (for a specified time, the measured pressure does not go beyond the measurement error), VK turns off the hydraulic pump 9, determines the measured pressure loss per unit length of the hydraulic line and pressure loss at the entrance to the hydraulic pump, after which, based on the measured values of the parameters, it determines the linear coordinate (length of the section ℓ) of the leakage site.

The process of finding the place of leaks is controlled by the operators of the facility in a special format of the system Laptop.

Thus, the following exemplary algorithm for finding the leakage site of a site is implemented in VC, the main operations of which are:

- start the search program;

- measurement and registration of the initial pressure of the atmosphere of the room;

- inclusion of the hydraulic pump with measurement and registration of the current created pressure;

- stepwise decrease (with a given step) of pressure in the gas cavity of the hydropneumatic compensator and holding for a predetermined time at each level with continuous recording of pressure;

- fixation and registration of stabilization pressure;

- determination (calculation) of losses of the measured pressure of the hydraulic pump per unit length of the hydraulic line;

- determination (calculation) of pressure loss at the inlet to the hydraulic pump;

Note. The linear dimensions of the contour (length) and its individual sections are embedded in the VK search program.

- calculation according to relation (1) with the determination of the linear coordinate of the leak point;

- documenting the received parameters and outputting information to the system Operator Laptop, transmitting information to the facility’s Operation Center through telemetry tools.

Thus, the proposed method allows you to:

- promptly determine the location (linear coordinate) of the leaky section of the hydraulic line without resorting to time-consuming operations, for example, to divide the hydraulic line into separate sections;

- almost completely automate the process of finding a leak point with displaying the results in a special format for the operator’s system Laptop (the hydraulic circuit of the temperature control system is displayed with an indication of the leak point and other information - linear coordinates, number, room area, etc.).

In addition, the method:

- does not require the development and manufacture of special equipment;

- safe for operators, as the search for leaks is carried out at a pressure in the hydraulic line less than the pressure of the atmosphere hermetically isolated from the external environment of the inhabited room.

Claims (1)

A method for determining the location of an unpressurized section of a closed hydraulic line equipped with a flow inducer and a hydropneumatic compensator for temperature changes in the volume of the working fluid, including the operation of reducing the pressure of the medium in the gas cavity of the hydropneumatic compensator to the level of stabilization of this pressure within the measurement error, characterized in that after the fact of depressurization is established previously set the pressure in the gas cavity of the hydropneumatic compensator medium equal to the measured pressure of the atmosphere hermetically isolated from the external environment of the room P _a , and the reduction of this pressure to the mentioned level of stabilization is carried out with the flow activator switched on, while the actual pressure is measured $$P_n^f,$$

created by the aforementioned flow driver, fix and record the stabilization pressure P _c , determine the measured pressure loss per unit length of the hydraulic line q _l and the pressure loss at the inlet of the flow driver ΔP _in , then determine the location of the leaky section of the hydraulic pipe from the relation
$$\ell =\frac{\left(P_n^f-\Delta P_{\mathrm{at}x}\right)-\left(P_a-P_c\right)}{q_l}-{\ell }_{\mathrm{at}x},$$

where ℓ is the distance to the location of the leaky section of the hydraulic line in the direction of movement of the working fluid from the point of connection of the hydropneumatic compensator to the hydraulic line;
$$P_n^f$$

- the actual pressure created by the stimulator of the flow of the working fluid;
ℓ _in - the length of the section of the entrance to the hydraulic pump (section of the hydraulic line from the point of connection of the hydropneumatic compensator to the entrance to the hydraulic pump);
ΔP _in - pressure loss at the inlet to the flow rate driver (in the hydraulic line section from the point of connection of the hydropneumatic compensator to the inlet of the flow rate equal to q _l × ℓ _in , where ℓ _in - the length of the section);
$$q_l=\frac{P_n^f}{{\ell }_m}$$

- pressure loss created by the flow driver per unit length of the hydraulic line, where ℓ _m is the length of the hydraulic line;
P _a - atmospheric pressure hermetically isolated from the environment;
P _c - pressure stabilization.

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