RU2591979C1 - Valve emergency shutoff automatic device for main pipeline - Google Patents

Abstract

FIELD: valves production.

SUBSTANCE: present invention is intended for transportation of gases via main gas lines. Valve emergency shutoff automatic device comprises two control chambers that are connected with the gas line and communicate via calibration orifices. Outlet chamber that is connected with the hydraulic drive of the gas line shutoff device is divided by a bursting disc into two cavities. There are ballast and emergency tanks connected to the gas line via check valves. Moving rod with a conical head is located near the disc. Control chambers are separated by the first bellows arranged coaxially inside the cylindrical casing and its rigidly fixed lower cover. Upper free end of the bellows is tightly closed by a plate with calibration orifices and a central rod fixed on it; this rod has a possibility of axial movement in case of longitudinal deformation of the bellows. Central part of the rod is fixed on the plate tightly closing the lower free end of the second bellows that is rigidly fixed on the partition with a central orifice installed in the housing. Average diameters of the first D₁ and the second D₂ bellows are not equal. Total section area of the calibration orifices is calculated using an algebraic relation.

EFFECT: invention is designed to improve the operating reliability of the machine and extend its longevity.

1 cl, 2 tbl, 2 dwg

Description

The invention relates to the field of valve engineering and can be used in the transportation of gases through gas pipelines (MG). The emergency shut-off valve (AZK) provides automatic shut-off of the emergency section of the MG in case of its possible rupture, accompanied by the leakage of a large volume of gas. The use of gas stations increases the safety of MG operation, reduces gas losses when it is damaged, and prevents the possibility of large-scale catastrophes due to the explosion of a large volume of gas-air mixture. The gas station is installed at the locations of the ball valves to shut off the MG and ensures the automatic closing of these valves and thereby blocking the emergency section of the gas pipeline.

Known automatic devices for emergency shutdown of the gas pipeline when it is damaged, including a gas distribution device for controlling the drive of the shut-off element in the gas pipeline, sensors that record the rate of pressure drop, and cylinders connected to the gas pipeline through openings of small cross-section [1, 2].

Also known are automatic pipelines emergency shutdowns when it is damaged, containing switchgears that respond to changes in gas flow rates [3, 4].

The main disadvantage of these devices is the presence of a movable pair (seat-valve) in the gas supply line to the hydraulic cylinder of the shut-off element (ball valve) of the gas pipeline. A feature of the operation of gas stations is that for a long time (tens of months) the machine is in the “cocked” state (the valve is locked). In this case, a slow flow of gas through the shut-off element is possible due to its insufficient tightness or due to the formation of microcracks during long-term operation. This can lead to a false response of the gas station during the flow of a certain "critical" volume of gas. On the other hand, if the saddle-valve pair is well ground, then the diffusion of materials of the movable pair is possible, which leads to its "sintering" and to a loss of mobility, and therefore to inoperability of the filling stations.

A well-known emergency shutdown machine MG when it is damaged [5], characterized in that the spool of the switchgear is made in the form of a spring-loaded first piston installed in the lower end of the housing, at the upper end of which a second piston is installed, connected with the hydraulic damper piston located in the bore of the housing a spring connected through a plate to the first piston. The first piston is supported on a thin metal membrane sandwiched between the lower end of the housing and the flange mounted on this end to ensure that the membrane ruptures in the lower position of the first piston.

A significant advantage of this filling station is that the distributor valve provides access to the MG shut-off actuator only when the membrane ruptures, which eliminates gas leakage to the shut-off actuator. The main disadvantage is the complexity of the design, which includes three pistons, several ring seals, a complex system for regulating the annular channel of the hydraulic damper, which requires disassembling the machine to configure it, as well as the additional use of a hydraulic system with non-freezing liquid. This leads to the complexity of the manufacturing technology and configuration of the machine, as well as its operation, which, ultimately, is reflected in the main indicator - reliability.

Closest to the technical solution to the claimed invention is an emergency shut-off valve on gas pipelines [6], which contains a distributor with a spool installed in its body in the form of a piston, the first and second control chambers connected to the MG. A gas shutoff valve (ball valve) is installed in the gas pipeline connected with the hydraulic drive. The control cavity of the hydraulic actuator is connected to the exit chamber of the filling station and the membrane. The piston is installed in the housing between the first and second control chambers on two oppositely directed upper and lower rods. These rods are fixed with the possibility of their axial movement in the sealing sleeves located in the lower cover of the housing and in the partition between the second control chamber and the output chamber. The output chamber is divided into two cavities by a metal membrane sandwiched between the upper end of the housing and the lid, and is connected to the control cavity of the drive of the shut-off member.

The upper stem has a cone-shaped head and is installed in close proximity to the membrane to ensure its rupture. The first and second control chambers are interconnected through calibrated through holes in the piston. The first control chamber is connected to a ballast tank connected to the MG through a check valve. The submembrane cavity of the outlet chamber is connected to the emergency gas supply capacity and is also connected to the MG through a check valve.

The advantage of this design of the gas station is that it eliminates false positives in the operational mode of operation and thereby increase the reliability of the gas station. The main disadvantage of the gas station, selected as a prototype of the present invention, is the difficulty of ensuring the tightness of the moving elements of the gas station - two rods moving in the sealing sleeves, and a piston moving in the body of the gas station. Pilot testing of this design of the filling station at Tomsktransgaz LLC showed that in winter conditions (at temperatures below -40 ° C) when using rubber rings in the sealing sleeves and piston, the tightness of the movable joints may be broken [7, 8]. This leads to the need for periodic replacement of the sealing rings (with disassembly and subsequent tuning of the filling stations) and to a decrease in the reliability of its operation.

The technical result of the present invention is the development of gas stations, providing increased reliability and long-term operation due to the exclusion of movable joints requiring sealing, as well as providing ease of setup and operation of gas stations.

The technical result of the invention is achieved by the fact that an emergency shut-off valve for the main gas pipeline tap has been developed, comprising a housing with upper and lower covers, two control chambers connected to the gas pipeline communicating with each other through calibrated openings connected to the hydraulic drive of the gas pipeline shut-off element, divided into two cavities bursting diaphragm, ballast and emergency tanks connected to the gas pipeline through non-return valves, and a movable stem with a conical head, located laid near the membrane. The control chambers are divided by the first bellows, placed coaxially inside the cylindrical body and rigidly fixed on its lower cover, the upper free end of the bellows is hermetically sealed by a plate with calibrated holes and with a central rod fixed on it with the possibility of axial movement with longitudinal deformation of the bellows. The central part of the rod is mounted on a plate that tightly closes the lower free end of the second bellows, rigidly mounted on a partition with a central hole installed in the housing, while the average diameters of the first D ₁ and second D ₂ bellows correspond to the inequality

and the total cross-sectional area of the calibrated holes is determined by the ratio

where k ₁ , k ₂ are the stiffnesses of the first and second bellows, respectively;

- аварийное значение скорости спада давления в газопроводе; $${\left|\frac{dp}{dt}\right|}_{\mathrm{to}R}$$

- emergency value of the pressure drop rate in the gas pipeline;

V is the volume of the ballast capacity;

p ₀ - pressure in the gas pipeline before the accident;

φ is the flow coefficient of calibrated holes;

- функция показателя адиабаты газа; $$R\left(\gamma \right)={\left(\frac{2}{\gamma +\mathrm{one}}\right)}^{\frac{\gamma +\mathrm{one}}{2\left(\gamma -\mathrm{one}\right)}}\sqrt{\gamma }$$

- gas adiabatic exponent function;

- показатель адиабаты газа; $$\gamma =\frac{c_p}{c_V}$$

- indicator of gas adiabat;

c _p , c _V — specific isobaric and isochoric heat capacities of the gas;

R is the gas constant of the gas;

T is the absolute temperature of the gas.

The invention is illustrated in FIG. 1, which shows a diagram of the inventive gas stations.

The machine consists of a cylindrical body 1, closed by upper 2 and lower 3 covers, in which the first control chamber (A), the second control chamber (B) and the exit chamber containing the lower (C) and upper (D) cavities are placed. In the housing 1, the lower 4 and upper 5 bellows of different diameters are coaxially placed. The bellows 4 is rigidly fixed to the bottom cover 3, and the bellows 5 is rigidly fixed to the partition 6 in the housing 1. The free ends of the bellows 4, 5 are hermetically closed by plates 7, 8, respectively. A calibrated through-hole 9 is made in the plate 7. A rod 10 is coaxially mounted on the plates 7, 8, the conical head 11 is made in the upper part of the plate. A thin metal membrane 12 is clamped between the upper end of the housing 1 and the cover 2. During longitudinal deformation (stretching the bellows 4 and compression of the bellows 5) the rod 10 can move upward in the axial direction, while the conical head of the rod 11 provides a rupture of the membrane 12.

In building 1, three cameras are formed - two control and one output. The first control chamber (A) is the inner cavity of the bellows 4. The second control chamber (B) is limited by the outer surface of the bellows 4, the inner wall of the housing 1 and the partition 6. The output chamber contains a lower (submembrane) cavity (C) and an upper cavity (D) . The cavity (C) is limited by the inner wall of the housing 1, the plate 8 and the bursting disc 12. The cavity (D) is limited by the bursting disc 12 and the upper cover 2.

The first control chamber (A) is connected through a nozzle 13 to a ballast tank 14, which is connected through a non-return valve 15 to the main gas pipeline 16. The second control chamber (B) is directly connected to the gas pipeline 16 through a nozzle 17. The submembrane (lower) cavity of the outlet chamber (C ) through the nozzle 18 is connected to the emergency gas supply capacity 19 and through the check valve 20 with the main gas line 16. The control cavity of the hydraulic actuator 21 of the ball valve 22 is connected through the nozzle 23 to the upper cavity of the outlet chamber (D).

The emergency shutdown valve operates as follows. Operationalization

When the filling station is connected to the gas main 16, the gas through the check valves 15, 20 fills the containers 14, 19 and through the fittings 13, 17, 18 enters the control chambers (A), (B) and into the cavity (C) of the output chamber. The pressure in the chambers (A), (B), (C) is equalized and equal to the pressure in the gas line 16. The gravity of the rod 10 is balanced by the elastic force of the bellows 4 and 5.

Operational Operation

When the filling station is in operation, when the pressure in the gas line 16 is constantly or slowly changing (increases or decreases due to the connection of gas consumers or due to the uneven operation of compressor stations), the pressure in the chambers (A), (B), (C) is also constantly or slowly changes, but remains the same for each of the chambers due to the slow flow of gas through calibrated holes 9 in the plate 7 separating the first and second control chambers. In this case, the rod 10 is in its original state and its conical head 11 does not touch the bursting disc 12.

Emergency operation

When the gas pipeline 16 ruptures, the pressure in it begins to drop sharply, and the pressure release rate is several times higher than in the case of pressure fluctuations in the operational mode. In this case, the check valves 15, 20 are closed, isolating the tanks 14, 19 from the gas pipeline 16, thereby ensuring that they maintain a constant pressure p ₀ corresponding to the pressure in the gas pipeline 16 before the accident.

The pressure in the second control chamber (B), directly connected through the fitting 17 to the gas pipe 16, also begins to drop sharply in accordance with the pressure drop in the MG. As a result of this, a force F appears, acting from below on the plate 7, rigidly connected to the bellows 4:

F = [p ₀ -p (t)] (S ₁ -S ₂ ),

where S ₁ , S ₂ are the effective areas of the first and second bellows, respectively;

p (t) is the pressure in the second control chamber.

Under the action of the force F, the bellows 4 is deformed in the longitudinal direction, the plate 7 together with the rod 10 moves upward, overcoming the elastic force of the bellows 5. In this case, the conical head 11 of the rod 10 breaks through the membrane 12. Gas from the tank 19 passes through the nozzle 18 into the upper cavity (D ) the output chamber and through the fitting 23 enters the control cavity of the hydraulic actuator 21, ensuring the closure of the ball valve 22.

Setting the gas station is carried out by selecting the diameters of the calibrated holes 9 in the plate 7 and the free volume of the ballast tank 14.

The positive effect of the invention is to increase the reliability of its operation is as follows.

1. The use as a flexible sealing device of the first bellows 4, placed coaxially inside the cylindrical body and rigidly mounted on its lower cover 3, allows axial movement of the rod 10, mounted on the plate 7, hermetically closing the upper part of the bellows 4. This does not require a movable joints requiring sealing, which completely eliminates the uncontrolled flow of gas between the control chambers (A) and (B) in addition to calibrated holes 9 in the plate 7.

2. The presence of calibrated holes 9 in the plate 7 allows varying the number and diameter of these holes, as well as the free volume of the ballast capacity, to select the desired response mode of the filling station in relation to the specific characteristics of the MG (gas flow, working pressure, emergency value of the pressure relief rate).

3. The use of a second bellows 5, fixing the central part of the rod 10, provides a reliable separation of the chambers (B) and (C) without a movable joint requiring sealing.

4. To select the diameters of the bellows 4, 5, we consider the nature of the pressure change in the control chambers of the filling station. In case of emergency pressure relief in the MG, the pressure in it decreases from the initial value p ₀ according to the law p (t). Accordingly, the pressure decreases in the second control chamber (B) directly connected to the gas pipeline. At the same time, the total force acts on the bellows system:

where S ₁ , S ₂ - effective area of the first and second bellows;

Δр (t)> 0 is the pressure difference acting on the bottom of each bellows.

The effective area is calculated by the outer D _n and inner D _{in the} diameter of the bellows:

- средний диаметр сильфона.Where $$D=\frac{\mathrm{one}}{2}\left(D_n+D_{\mathrm{at}}\right)$$

- the average diameter of the bellows.

The axial movement of the bellows system is determined by the formula [9]:

where k ₁ , k ₂ are the stiffnesses of the first and second bellows, respectively.

The rigidity of the bellows is determined by the formula [9]:

where E, µ is the elastic modulus and Poisson's ratio of the material of the bellows;

h is the wall thickness of the bellows;

n is the number of working bellows corrugations;

A is a coefficient depending on the ratio D _n / D _in and the radius of the corrugation r.

To ensure the functioning of the filling stations, it is necessary that the bellows system together with the rod fixed on it move up towards the bursting disc. Moreover, from (3) follows the inequality:

i.e

Taking into account (2), we obtain the required ratio between the average diameters of the bellows:

Introducing the coefficient of reliability ε = 2 [9], from (5) we obtain the ratio included in the claims:

When k ₁ = k ₂ from (6) it follows:

D ₁ > 2D ₂ .

Thus, the average diameter of the first bellows is more than twice the average diameter of the second bellows with the same rigidity.

5. To determine the total cross-sectional area S _{Σ of the} calibrated holes 9 in the plate 7, we consider the process of gas outflow from the first control chamber (A) to the second (B) after the MG break. In this case, the pressure in the chamber (B), equal to the pressure in the gas pipeline, begins to decrease from the initial value of p ₀ with an average speed of | dp / dt | _cr , depending on the length of the MG section between adjacent ball valves.

The pressure in the ballast tank 14 and in the associated chamber (A), the volume of which is much less than the volume of the ballast tank, will begin to decrease in accordance with equation [10]:

where p ₀ is the pressure in the pipeline before the accident;

t is the time;

τ is the relaxation time of the ballast capacity.

The value of τ is determined by the relation [10]:

where V is the volume of the ballast capacity;

φ is the flow coefficient of calibrated holes;

S _Σ is the total cross-sectional area of the calibrated holes;

- функция показателя адиабаты газа; $$R\left(\gamma \right)={\left(\frac{2}{\gamma +\mathrm{one}}\right)}^{\frac{\gamma +\mathrm{one}}{2\left(\gamma -\mathrm{one}\right)}}\sqrt{\gamma }$$

- gas adiabatic exponent function;

- показатель адиабаты газа; $$\gamma =\frac{c_p}{c_V}$$

- indicator of gas adiabat;

c _p , c _V — specific isobaric and isochoric heat capacities of the gas;

R is the gas constant of the gas;

T is the absolute temperature of the gas.

It follows from (7) that over time t = τ, the pressure in the ballast capacity decreases to

The change in pressure is equal to:

Δp = p ₀ -0.368p ₀ = 0.632p ₀ .

The average rate of pressure drop can be estimated by the formula

Substituting the expression for τ (8) in (9), we obtain:

To operate the gas station in emergency mode, it is necessary that the pressure in the first control chamber (A) is much higher than the pressure in the second chamber (B). In this case, the pressure differential on the plate 7 will allow to move the rod 10 towards the bursting membrane 12, overcoming the elasticity of the bellows 4, 5.

Therefore, the pressure drop rate in the ballast tank should be much less than the emergency value of the pressure drop rate in the gas pipeline:

Substituting expression (10) in (11), we obtain:

From (11) follows the relation for determining S _Σ :

Calculations of the dynamics of gas stations, given by the method of [11], showed that reliable movement of the rod is provided at

In view of (14), the relation for determining S _Σ takes the form:

Implementation example

Let us consider the operating characteristics of a gas station, the circuit of which is shown in FIG. 1, in case of emergency rupture of the main gas pipeline. The parameters of MG and gas stations are shown in tables 1, 2.

The values of the diameters of the bellows and the total area of the calibrated holes are calculated by the formulas (6), (15) for the parameters of MG and AZK given in the tables.

The dynamics of the differential pressure acting on the bellows system in the direction from bottom to top (towards the bursting disc) is shown in FIG. 2 for two values of gas temperature (T = + 40 ° C - solid lines, T = -40 ° C - dashed lines) and for three values of the total cross-sectional area of calibrated holes (S _Σ = 3.1 mm ² ; S _Σ = 4.9 mm ² ; S _Σ = 7.1 mm ² ).

As follows from FIG. 2, when the MG breaks, the pressure drop Δp (t) increases, which reaches its maximum value after t≈50 s after the gas pipeline rupture. With the calculated value of S _Σ = 3.1 mm ^{2, the} differential pressure ensures reliable movement of the rod and the response of the gas station. With an increase in the total cross-sectional area of the calibrated holes (S _Σ = 4.9 mm ² ; S _Σ = 7.1 mm ² ), the pressure drop decreases, which can lead to a decrease in the reliability of the filling stations.

Thus, the inventive automatic emergency shut-off valve of the main gas pipeline ensures the achievement of the technical result of the invention - improving the reliability of the gas station, its long-term operation, ease of setup.

LITERATURE

1. Andreev G.S. Stop valves of gas pipelines. L .: Nedra, 1968 .-- S. 73-76.

2. RF patent №2138720, IPC F16K 17/34. Gas pipeline emergency shutdown machine / Nemterenko Yu.A.; publ. BI No. 27, 1999

3. RF patent No. 2101595, IPC F16K 17/04. A device for emergency shutdown of a hydraulic system pipeline / Rudenko A.P., Kushnir K.V .; publ. BI No. 1, 1998

4. A.S. USSR No. 189271, IPC F16K 17/34. An automatic machine for controlling the shutdown of a gas pipeline in case of its damage / Gubin B.L., Shabashov S.Z .; publ. BI No. 18, 1961

5. RF patent No. 2029191, IPC F16K 17/34, G05D 16/10. Automatic circuit breaker of a gas pipeline when it is damaged / Polyakov VB, Rybin P.A., Shabashov S.Z., Kunchenkov V.Ya .; publ. BI No. 4, 1992

6. RF patent No. 2208730, IPC F16K 17/34. Emergency shut-off valve on gas pipelines / Arkhipov V.A., Zubrilin A.S., Kotov V.D., Sobolevsky V.I., Shifanov A.V., Shrager G.R .; publ. BI No. 20, 2003

7. Kotov V.D. A device for disconnecting sections of the Champions League MG at their break // Gas industry. 2002, No. 8. - S. 58-59.

8. Tolmachev V.E. Automatic emergency shut-off valve on the main gas pipeline // Gas industry. 2002, No. 9. - S. 48.

9. Directory of the machine builder in 6 volumes, T. 6. - M .: Mashgiz, 1955. - S. 213-214.

10. Sorkin R.E. Gas thermodynamics of solid propellant rocket engines. M .: Nauka, 1967 .-- 368 p.

11. Arkhipov V.A., Zubrilin A.S., Kotov V.D., Tkachenko A.S., Tretyakov N.S., Shrager G.R. Automatic shutdown of sections of the main gas pipeline // Izv. universities. Oil and gas. 2003, No. 2. - S. 94-101.

Claims (1)

An emergency shut-off valve for the main gas pipeline crane, comprising a housing with upper and lower covers, two control chambers connected to the gas pipeline, communicating with each other through calibrated holes, an output chamber connected to the hydraulic actuator of the gas shut-off element, divided into two cavities by a bursting membrane, ballast and emergency containers, connected to the gas pipeline through check valves, and a movable rod with a conical head located near the membrane, characterized in that the control chambers separated by the first bellows, placed coaxially inside the cylindrical body and rigidly fixed on its bottom cover, the upper free end of the bellows is hermetically sealed by a plate with calibrated holes and with a central rod fixed to it with the possibility of axial movement with longitudinal deformation of the bellows, the central part of the rod is fixed to the plate hermetically closing the lower free end of the second bellows, rigidly fixed to the partition with a Central hole installed in the housing, while m the average diameters of the first D ₁ and second D ₂ bellows correspond to the inequality

and the total cross-sectional area of the calibrated holes is determined by the ratio

where k ₁ , k ₂ are the stiffnesses of the first and second bellows, respectively;

- emergency value of the pressure drop rate in the gas pipeline;
V is the volume of the ballast capacity;
p ₀ - pressure in the gas pipeline before the accident;
φ is the flow coefficient of calibrated holes;

- gas adiabatic exponent function;

- indicator of gas adiabat;
c _p , c _V — specific isobaric and isochoric heat capacities of the gas;
R is the gas constant of the gas;
T is the absolute temperature of the gas.

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