FR2524959A1 - METHOD AND DEVICE FOR CLOSING A SAFETY ASSISTED VALVE - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR CLOSING A SAFETY ASSISTED VALVE AND TO A DEVICE IMPLEMENTING THIS PROCESS. SUCH A VALVE INCLUDES IN PARTICULAR A SUPPLY NOZZLE 3 IN COMMUNICATION WITH A PRESSURIZED ENCLOSURE, A VALVE 5, MEANS 7 ELASTICALLY APPLYING THE VALVE 5 ON THE NOZZLE 3 WHICH ALLOWS THE TAKING OFF OF THE VALVE 5 WHEN THE PRESSURE IN THE ENCLOSURE IS GREATER THAN A PREDETERMINED SET PRESSURE, AND ASSISTANCE MEANS 7 COMMANDS THAT CAN APPLY THE VALVE 5 ON THE NOZZLE 3. IN THE PROCESS, ACCORDING TO THE INVENTION, THE ASSISTANCE MEANS 7 ARE ACTIVATED TO CLOSE THE VALVE WHEN THE PRESSURE IS PRESSED IN THE ENCLOSURE BECOMES LOWER THAN A CLOSING PRESSURE, AND FOR A LIMITED PERIOD IN TIME. IN ADDITION, THE ACTION EXERCISED BY THE ASSISTANCE MEANS 7 IS ABOLISHED WHEN THE PRESSURE IN THE ENCLOSURE Rises BEYOND THE CLOSING PRESSURE. THE INVENTION WILL FOUND FULLY ITS APPLICATION IN THE OPERATION OF COOLING CIRCUITS, IN NUCLEAR POWER PLANTS.

Description

252495

1 -

  The invention relates to a method for closing a sou-

  pope assisted by safety and to a device implementing this

  It will notably find its application in the field of the circulation of fluid under pressure, more particularly the circuits under high pressure, for example the cooling circuits in

nuclear power plants.

  In industry, it is known to equip a pressure vessel with a safety valve which protects the enclosure against any overpressure This valve is tared to open from a determined pressure Gold, when the valve is in the open position, the valve undergoes, in addition to the static pressure of the fluid present in the enclosure that escapes, the dynamic pressure of this fluid and thus the reclosing of the valve may require a much greater effort than the effort required to contain the static pressure alone To overcome this difficulty, there are so-called assisted valves that have an external assistance such as a cylinder

  which ensures the reclosing of the valve.

  Currently, the efforts generated by this assistance

  are almost always applied: these efforts are sup-

  awarded only when the pressure in the chamber exceeds a certain threshold and are re-established when the pressure in the chamber becomes lower than this threshold This quasi-permanent locking of the valve is dangerous for the operation of the circuit Indeed, the valve has resilient means sufficient to maintain the valve in the closed position, and the external assistance is only useful for the

  In addition, a mechanical failure of external assistance

  may cause the valve to lock in the closed position.

  In this type of operation, the opening and closing speeds of the safety valve are relatively slow because of the inertia of the moving element acting on the valve which comprises the elastic means and the external assistance means. can have serious consequences, for example in the case of a cooling circuit, where it is essential to quickly close the valve

  to limit the escape of the fluid outside the circuit.

  The main object of the present invention is to provide a method of closing a power assisted valve in which the assistance means have a time-limited action. This amounts to eliminating the quasi-permanent locking and thus makes it impossible to

  valve lock in closed position.

  Another object of the present invention is to propose a method which provides flexibility of operation and which reduces the

  response time on opening and closing.

  Other objects and advantages of the present invention appear

  will be described in the following description, which is given only

  indicative and not intended to limit it.

  The method of closing a safety assisted valve, in particular used in pressurized fluid circuits, comprising in particular a supply nozzle in communication with a pressure vessel, a valve, the means elastically applying the valve

  on the nozzle which allow the release of the flap, that is to say the

  the opening of the valve, when the pressure in the chamber is greater than a predetermined setting pressure, and controlled assistance means that can apply the valve to the nozzle, is characterized in that it actuates the assistance means to close the valve when the pressure in the chamber becomes less than a pressure

  said closure, and for a limited period of time.

  The control device of a power-assisted valve, comprising in particular a supply nozzle in communication with a pressure vessel, a valve, means elastically applying the valve on the nozzle which allow the release of the valve, when the pressure in the valve enclosure is greater than a predetermined set pressure, and controlled assistance means that can apply the valve to the nozzle, is characterized in that it applies the valve on the nozzle to close the valve when the pressure in the enclosure becomes less than a so-called closing pressure and during a

limited period of time.

  The invention will be better understood if one refers to the description

  below, as well as to the attached drawings which form part of it

  grante. Figure 1 illustrates a schematic representation

  of a safety valve to which the closing process relates.

  FIG. 2 illustrates a preferred embodiment of

  device implementing the method according to the invention.

  FIG. 1 schematizes a safety-assisted valve. This valve 1 comprises in particular an exhaust chamber 2 in which

  opens a nozzle 3 in communication with an enclosure not shown.

  3 - This exhaust chamber 2 is open on the outside in 4 On the opening of the nozzle 3 is applied a valve 5 via

  These means 6 are calibrated and allow the determination of

  when the pressure in the chamber is greater than a predetermined setting pressure, these means 6 will be advantageously

consist of a spring.

  Assistance means 7 ordered from outside the

  valve can apply the valve 5 to the nozzle 3 to force its closure.

  setting and possibly locking.

  Such assisted valve is known to those skilled in the art and

  will not be described in more detail.

  In the method of closing an assisted valve according to

  the invention, the means of assistance 7 are actuated to close the sou-

  pope when the pressure in the enclosure becomes less than a pres-

  so-called closure, and for a limited period of time.

  Moreover, the action exerted by the S assisting means is eliminated when the pressure in the chamber rises above the closing pressure. In this method, the means of assistance are actuated for a limited period of time, and thus these means can not

  ensure the permanent maintenance of the closure of the valve.

  their, when the pressure in the enclosure becomes greater than a certain threshold said closure pressure, these means of assistance

  can not be applied to the flap. In particular, if the pressure

  in the enclosure rises above the closing pressure during the time interval where the assistance means force the

  flapper on the nozzle, this action is immediately interrupted.

  In a device implementing this method, the pressure

  the closure will preferably be different and less than

  Thus, the assistance means 7 can not in any case maintain in the chamber a pressure greater than the pressure

tare.

  The means of assistance 7 will advantageously be constitua

  by a jack, more particularly a pneumatic or hydraulic cylinder.

  The supply pressure of this jack can be advantageously a

  function of the pressure in the enclosure, olus Precisely be a fraction

  This has the advantage of always being able to

  Det the cla whatever the pressure in the chamber, and rluç 4 - especially it allows to use the same cylinder for different

tare pressures.

  In the embodiment of the assisted tan illustrated in FIG. 1, the assistance cylinder comprises a piston 8 equipped with a rod 9, and a fixed cylindrical body 10 comprising in particular a bottom 11 and two orifices, one 12 of which side of the bottom 11, the other 13 on the side of the rod 9 The valve 5 is integral with a central axis 14 on which

  the action of the elastic means 6, for example a spring, is exerted.

  The rod 9 and the central axis 14 are advantageously arranged along the same axis The assistance cylinder 7 is in the retracted position when the piston 8 abuts the bottom 11 In this position, the rod 9 is disengaged from the axis central 14 a distance sufficient not to hinder the detachment of the valve 5 when the pressure in the chamber becomes greater than the calibration pressure In the device according to the invention, when the assistance is not controlled, the cylinder 7 is

in retracted position.

  When the assistance means are controlled, the pressurized operating fluid is introduced through the orifice 12, which causes the displacement of the piston 8 and the rod 9. In its displacement, the rod 9 comes to bear on the central axis 14 and comes to force the valve 5 in

  stop on the nozzle 2 Once the application period has been completed, a

  unrepresented return stroke returns the piston 8 to the bottom 11 of the ves-

  rin to release the rod 9 of the central axis 14 The valve 5 and the central axis

  tral 14 subjected to the action of spring 6 which is greater than the exertion

  on the valve 5 by the pressure in the enclosure will remain applied

against the nozzle 2 to seal it.

  Figure 2 illustrates a device implementing the procedure

  According to the invention, this device comprises in particular an enclosure 15 to be protected, an assisted valve 1 a control cabinet 16 and a pressure sensor 17 connected to the enclosure 15. This pressure sensor 17 will advantageously be placed on the wall of the enclosure. enclosure 15, to be immune from the dynamic effects due to the flow of fluid through the

safety valve.

  The method according to the invention will be better understood if one

  refers to a cycle of operation As long as the pressure in the

  is less than the set pressure, the valve is held in the closed position by elastic means 6, and the service cylinder

  7 is in the retracted position However, as soon as the pressure in the

  When the pressure reaches the closing pressure, the pressure sensor 17 sets

  the control cabinet 16 under tension.

  If the pressure in the enclosure exceeds the set pressure, the forces due to the static pressure exerted on the valve are greater than the forces generated by the elastic means 6 and the clafet takes off from the nozzle. displacement, the movable element is only composed by the valve 5 and the central axis 14 The escape of the fluid through the safety valve results in a lowering of the pressure in the enclosure When the latter has fallen back to the level of

  the closing pressure, the chamber can be closed again.

  The pressure transmitter 17 transmits the information to the control cabinet 16 which actuates the assistance means 7 for a limited period of time.

  the time to force the closing of the valve.

  If, during this period of time, the pressure in the

  If the remaining time is less than the closing pressure, the delay simultaneously cuts off the power supply to the control cabinet 16.

  during this time interval, the pressure in the enclosure

  is greater than the closing pressure, the information is transmitted by the pressure sensor 17 to the control cabinet 16 which suppresses

  immediately the action of the assistance means 7 on the valve 5 In--

  the timer is removed and the control cabinet 16 remains

under pressure.

  Proper functioning of a valve assisted according to the in-

  It has been obtained with a time of application of the assistance means of the order of a few seconds. This time delay will advantageously be achieved by means of electrical devices doubled by safety by pneumatic devices. The embodiment which has just been described described is given only as an indication, and other implementations of the present invention within the reach of those skilled in the art, could be

  adopted without departing from its scope.

Claims (8)

  1 Method of closing an assisted safety valve,   especially used in pressurized fluid circuits, including   In particular, a nozzle (3) for supply in communication with a pressure vessel, a valve (5), means (6) resiliently applying the valve (5) to the nozzle (3) which allow the valve to detach ( 5), that is to say the opening of the valve, when the pressure in the chamber is greater than a set pressure   predetermined, and controlled assistance means (7) which can   quer the valve (5) on the nozzle (3), characterized in that one actuates the assistance means (7) to close the valve when the pressure in the chamber becomes less than a so-called closing pressure,   and for a limited period of time.   2 Method of closing a valve assisted according to the   1, characterized in that the action exerted by the assistance means (7) is suppressed when the pressure in the chamber rises   beyond the closing pressure.   3 Control device for a power assisted valve, comprising in particular a nozzle (3) for supply in communication with a   pressure vessel, a valve (5), means (6) applying elasticity   the valve (5) on the nozzle (3) which allow the release of the valve (5), that is to say the opening of the valve, when the   pressure in the chamber is greater than a pres-   determined, and controlled assistance means (7) that can apply the valve (5) to the nozzle (3), characterized in that it applies the valve (5) on the nozzle (3) to close the valve when the pressure in the chamber becomes less than a so-called   closure, and for a limited period of time.   4 Control device of a valve assisted according to claim 3, characterized in that it stops its action on the valve (5) when the pressure in the chamber goes back beyond the closing pressure.   Control device of a valve assisted according to one   of claims 3 or 4, characterized in that the pressure of   closing is less than the set pressure.   6 Valve control device assisted by one   claims 3, 4 or 5, whose assistance means (7) are   constituted in particular by a jack, characterized by the fact that   Actuator control pressure is a function of the pressure in the enclosure to protect.   7 Control device for a power assisted valve according to   claim 6, the assistance cylinder of which has a repositioned position   towed in which it is released from the valve (5), and does not hinder its movement, characterized in that when the assistance is   not controlled, the cylinder is in the retracted position.   8 control device of a power assisted valve according to claim 3, comprising in particular a pressure sensor (17),   characterized in that the pressure sensor (17) is arranged di- right on the speaker.   9 control device of a power assisted valve according to claim 3, characterized in that the application time   is of the order of a few seconds.