US20140245670A1

US20140245670A1 - Isolating device, method of replacing isolating structure part and method of controlling load of isolating structure

Info

Publication number: US20140245670A1
Application number: US13/782,280
Authority: US
Inventors: Sung Gook Cho; Chong Hak Kim; Kwang Ho Joo; Hyun Uk Kim; Sang Hoon Noh
Original assignee: JACE KOREA
Current assignee: JACE KOREA
Priority date: 2013-03-01
Filing date: 2013-03-01
Publication date: 2014-09-04
Also published as: WO2014133226A1

Abstract

Provided are an isolating device, a method of replacing an isolating structure part, and a method of controlling a load of the isolating structure part. The isolating device disposed between an upper structure and a lower structure includes an isolating structure part for performing an isolating function, and a height-adjustable part disposed on at least one of positions between the isolating structure part and the upper structure and between the isolating structure part and the lower structure, the height-adjustable part being adjusted in height by supplying or discharging fluid therein or therefrom.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an isolating system design using an isolating device that is capable of securing stability of a structure with respect to natural disasters, particularly, earthquake and increasing a life-cycle of the structure in a design of building structure such as nuclear power plant buildings.
2. Description of the Related Art
In case of key facilities such as nuclear power plant structures, the impacts of earthquake damage on the general public may he significantly high. Thus, performance of safety required in an isolating system should be very superior when compared to general structures.
Also, in case of nuclear power plant structures that are designed in recent years, a remaining period of about 100 years or more should be considered in design in consideration of a design life of about 60 years or more, a continuous operation, and a period for decommissioning. Thus, the integrity of an isolation system should also be maintained for about 100 years or more.
When an isolating device is damaged by external fatigue, earthquake, and the like, it is needed to replace the isolating device. When the isolating device is replaced, an isolating structure part that gives an isolating function in the isolating device may be mainly replaced.
Generally, when the isolating structure part is replaced, an upper structure may be jacked up to replace the isolating structure part. However, the above -described method may he required considerable time and expensive. In addition, the integrity of the upper structure may be put at risk.
The isolating structure part to which a relatively large load is applied may be relatively quickly deteriorated in isolating function than other isolating structure parts. However, a method of controlling a load of the isolating structure part is not proposed.
Japanese Patent Publication No. 2012-172314 discloses a feature in which a movable member that has a screw structure rotates to provide a working space thereby replacing an isolating device. However, it may take considerable space and time to rotate the movable member.

SUMMARY OF THE INVENTION

The present invention provides an isolating device in which an isolating structure part is easily replaced, and a load is easily controlled. The present invention also provides a method of replacing an isolating structure part and a method of controlling a load of the isolating structure part.
According to an aspect of the present invention, an isolating device disposed between an upper structure and a lower structure includes: an isolating structure part for performing an isolating function; and a height-adjustable part disposed on at least one of positions between the isolating structure part and the upper structure and between the isolating structure part and the lower structure, the height-adjustable part being adjusted in height by supplying or discharging fluid therein or therefrom.
The height-adjustable part may include: a deformable case providing a fluid space in which fluid is supplied; and a connector communicating with the fluid space and connected to an external fluid supply unit, the connector being exposed to the outside.
The isolating device may further include a horizontal deformation prevention part surrounding at least one portion of a side surface of the height-adjustable part to prevent the height-adjustable part from being deformed in a horizontal direction.
The height-adjustable part may be disposed between the lower structure and the isolating structure part, and the isolating structure part may be changed in load by supplying and discharging the fluid into and from the height-adjustable part.
The isolating device may further include a pressure gauge connected to the height-adjustable part to measure a pressure of the fluid within height-adjustable part.
The isolating device may further include a protection cover detachably connected to the upper structure and the lower structure, wherein the protection cover may be spaced apart from the isolating structure part to surround the isolating structure part.
The protection cover may be separated from at least one of the upper structure and the lower structure when earthquake greater than design criteria occurs.
The isolating structure part may include: a lead core; a stacked rubber bearing surrounding the lead core; a protection plate on upper and lower portions of the lead core and the stacked robber bearing; and a cap coupled to the protection plate, wherein the cap may be separated from the protection plate to define a passage through which the lead core is withdrawn.
According to another aspect of the present invention, a method of replacing an isolating structure part that performs an insulating function in an isolating device disposed between an upper structure and a lower structure, wherein the isolating device further includes a height-adjustable part disposed on at least one of positions between the isolating structure part and the upper structure and between the isolating structure part and the lower structure, the height-adjustable part being adjusted in height by injecting or discharging fluid therein or therefrom, includes: discharging the fluid from the height-adjustable part to decrease a height of the height-adjustable part and remove a load of the isolating structure part; removing the isolating structure part in the state where the height-adjustable part decreases in height to insert a new isolating structure part; and injecting the fluid into the height-adjustable part to increase the height of the height-adjustable part to apply a load to the new isolating structure part.
The isolating structure part may include: a lead core; a stacked rubber bearing surrounding the lead core; a protection plate on upper and lower portions of the lead core and the stacked robber bearing; and a cap coupled to the protection plate, wherein the cap may be separated from the protection plate to define a passage through which the lead core is withdrawn, and the new isolating structure part may be provided by inserting a new lead core into the stacked rubber bearing.
According to another aspect of the present invention, a method of controlling a load of an isolating structure part that performs an insulating function in an isolating device disposed between an upper structure and a lower structure, wherein the isolating device further includes a height-adjustable part disposed on at least one of positions between the isolating structure part and the upper structure and between the isolating structure part and the lower structure, the height-adjustable part being adjusted in height by injecting or discharging fluid therein or therefrom, includes: measuring a pressure of the fluid within the height-adjustable part; and supplying or discharging the fluid into or from the height-adjustable part on the basis of the measured pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

FIG. 1 is a cross-sectional view of an isolating device according to a first embodiment of the present invention;

FIG. 2 is a perspective view illustrating a coupled structure of a height-adjustable part and a horizontal deformation prevention part in the isolating device according to the first embodiment of the present invention;

FIGS. 3A to 3C are cross-sectional views for explaining replacement of an isolating structure part in the isolating device according to the first embodiment of the present invention;

FIG. 4 is a cross-sectional view illustrating a method of controlling a load of the isolating structure part in the isolating device according to the first embodiment of the present invention;

FIG. 5 is a cross-sectional view of an isolating device according to a second embodiment of the present invention;

FIGS. 6 and 7 are views of a protection cover in the isolating device according to the second embodiment of the present invention;

FIG, 8 is a view of an isolating structure part in an isolating device according to a third embodiment of the present invention; and

FIG. 9 is a view for explaining replacement of a lead core in the isolating device according to the third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Although an isolating device according to the present invention is applied to a nuclear power plant structure in following descriptions, the present invention is not limited thereto.
FIG. 1 is a cross-sectional view of an isolating device according to a first embodiment of the present invention, and FIG. 2 is a perspective view illustrating a coupled structure of a height-adjustable part and a horizontal deformation prevention part in the isolating device according to the first embodiment of the present invention.
An isolating device 1 is disposed between an upper structure 10 and a lower structure 20 to perform an isolating function when earthquake occurs. Each of the upper and lower structures 10 and 20 may include a concrete structure.
The isolating device 1 includes an upper isolating structure part 100, a lower isolating structure part 200, and a horizontal deformation prevention part 300. In addition, the isolating device 1 includes an upper plate 510, a lower plate 520, coupling members 531 and 532, a movement prevention member 533, and an intermediate metal plate 540.
The isolating structure part 100 has a square pillar shape. Also, a rubber plate 101 and a metal plate 102 are alternately stacked with each other to constitute the isolating structure part 100. The isolating structure part 100 prevents vibration of the lower structure 20 from being transferred into the upper structure 10 when earthquake occurs to protect the upper structure 10.
The height-adjustable part 200 is disposed below the isolating structure part 100. Also, a lower portion and a side surface of the height-adjustable part 200 are surrounded by the lower structure 20. The height-adjustable part 200 includes a case 210 that provides a fluid space for accommodating fluid, a connector 220 for supplying and discharging the fluid into and from the case 210, and an injection tube 230 connecting the case 210 to the connector 220.
The case 210 has a square plate shape on the whole. Also, the case 210 may vary in volume by supplying and discharging fluid. That is, if a large amount of fluid is injected into the case 210, the case 210 may increase in volume. On the other hand, if a small amount of fluid is injected into the case 210, the case 210 may decrease in volume. A lower side surface of the case 210 may have a pleated shape to enable the volume variation of the case 210.
When a large amount of fluid is injected, the pleated portion of the case 210 may be spread so that the case 210 increases in height. On the other hand, when a small amount of fluid is injected the pleated portion of the ease 210 may be contracted so that the case 210 decreases in height.
Liquid or gas may be used as the fluid for the present invention. Particularly, incompressible fluid having a small volume variation according to a temperature change may be used as the fluid. If a temperature at a site hr constructing nuclear power plant structures does not fall below zero, water may be used as the fluid, If the fluid is frozen, it may be very difficult to inject and discharge the fluid. In addition, the height-adjustable part 200 may undesirably vary in height to deteriorate the integrity of the structures 10 and 20. Thus, a material that is not frozen in consideration of a surrounding temperature may be used as the fluid. For example, silicon oil may be used as the fluid.
The case 210 may be formed of a flexible material such as rubber. The inside of the case 210 may be coated with another material such as a metal. The case 210 may be formed of various materials that endure a pressure applied thereto, have superior durability, and are flexible.
The injection tube 230 and the connector 220 are disposed on a side of the case 210 to inject and discharge the fluid. The injection tube 230 horizontally extends from a side surface of the case 210 and then vertically extends. The connector 220 connected to the outside is disposed on an end of the injection tube 230. The connector 220 is exposed to the outside. Also, the connector 220 is connected to an external injection device to inject or discharge the fluid into or from the case 210. The connector 220 may have various shapes if the connector 230 normally closes the injection tube 230 and connects the injection tube 220 to the outside as necessary.
In another embodiment, the connector 220 may he maintained in an always opened state. Also, an ON/OFF valve may be provided at the injection tube 230. In this case, the connection and disconnection of the connector 220 to an external fluid injection device may be performed in a state where the valve is in an OFF state.
The horizontal deformation prevention part 300 has a square hand shape to surround the side surface of the height-adjustable part 200. The horizontal deformation prevention part 300 may be formed of a metal, e.g., a stainless steel. An injection tube accommodation part 310 for accommodating the injection tube 230 is disposed in the horizontal deformation prevention part 300. The injection tube 230 is accommodated within the injection tube accommodation part 310 to prevent the injection tube 230 and the horizontal deformation prevention part 300 from interfering with each other. An upper side surface of the horizontal deformation prevention part 300 faces a lower portion of the isolating structure part 10 to restrain horizontal movement of the isolating structure part 100.
The horizontal deformation prevention part 300 prevents the height-adjustable part 200 from being deformed. When the fluid is supplied into the height-adjustable part 200, the horizontal deformation prevention part 300 prevents the height-adjustable part 200 from being horizontally deformed to effectively increase a height of the height-adjustable part 200.
The upper plate 510, the lower plate 520, the coupling members 531 and 532, and the movement prevention member 533 fix the isolating structure part 100 and the horizontal deformation prevention part 300, and particularly, restrain horizontal movement of the isolating structure part 100 and the horizontal deformation prevention part 300. In the first embodiment, the lower plate 520 may have an empty middle portion to accommodate the height-adjustable part 200 and the horizontal deformation prevention part 300.
The intermediate metal plate 540 is disposed between the isolating structure part 100 and the height-adjustable part 200. The intermediate metal plate 540 and a top surface of the lower structure 20 are overlapped in height. Also, the intermediate metal plate 540 resists a shear force due to an earthquake load and uniformly transfers a vertical load into the fluid of the height-adjustable part 200. Also, the intermediate metal plate 540 prevents the isolating structure part 100 from rotating.
Hereinafter, replacement of an isolating structure part in the isolating device according to the first embodiment of the present invention will be described with reference to FIGS. 3A to 3C.
Referring to FIG. 3A, the connector 220 of the height-adjustable part 200 is connected to an external device to discharge fluid within the height-adjustable part 200. Thus, the case 210 decreases in volume to decrease a height of the case 210, thereby decreasing a height of the height-adjustable part 200.
When the height-adjustable part 200 decreases in height, the load of the isolating structure part 100 is removed. Thus, the isolating structure part 100 and the upper plate 510 are spaced apart from each other while the isolating structure part 100 moves downward.
Thereafter, as shown in FIG. 3B, the upper plate 510, the coupling member 531, and the movement prevention member 533 are removed, and then the isolating structure part 100 is removed.
Thereafter, as shown in FIG. 3C, a new isolating structure part 100′ is inserted. Then, the upper plate 510 is introduced and fixed, and fluid is supplied into the case 210. When the fluid is supplied into the case 210, the height-adjustable part 200 increases in height. As a result, the lower structure 20, the height-adjustable part 200, the intermediate metal plate 540, the isolating structure part 100′, the upper plate 510, and the upper structure 10 are closely attached to each other to perform an isolating function by the new isolating structure part 100′.
The above-described replacement method of the isolating structure part may be variously changed.
For example, the isolating structure part 100 may be replaced without removing the upper plate 510, the coupling member 531, and the movement prevention member 533. For this, the upper plate 510 and/or the horizontal deformation prevention part 30 may be deformed. Alternatively only the movement prevention member 533 may be removed without removing the upper plate 510 and the coupling member 531 to replace the isolating structure part 100.
The processes described with reference to FIGS. 3A to 3C may be performed to inspect the isolating structure part 100 without the replacement of the isolating structure part 100. In case of the inspection of the isolating structure part 100, if it is determined that the isolating structure part 100 has appropriate performance, the isolating structure part 100 may be reused.
In the present invention, the term “replacement” may include replacement of only a portion of the isolating structure part 100.
To replace the isolating structure part 100, the load of the isolating structure part 100 should be removed, and also the some constituting parts should be spaced apart from each other to provide a working space. According to the present invention, the fluid within the height-adjustable part 200 may be discharged to quickly and simply remove the load of the isolating structure part 100 and space apart some constituting parts from each other. Thus, the isolating structure part 100 may be efficiently replaced in a short time.
If severe earthquake occurs, the isolating structure part 100 may be damaged. Thereafter, the damaged isolating structure part 100 may not perform appropriate isolating function in subsequent aftershock. The inappropriate isolating function of isolating structure part 100 is a highly sensitive issue at the nuclear power plant structure in which safety is particularly important. According to the present invention, the isolating structure part 100 may he quickly replaced by fewer workers to safely protect the nuclear power plant structure.
A method of controlling a load of the isolating structure part in the isolating device according to the first embodiment of the present invention will be described with reference to FIG. 4.
In this specification, the term “load” represents a vertical confining pressure that is applied to the isolating device or the isolating structure part.
Several tens to several hundreds of isolating devices are disposed on a lower portion of the nuclear power plant building. Here if isolating devices to which a load of the building is not applied or a very small load is applied exist, a load may be concentrated into other isolating devices. As a result, it may be difficult to adequately perform the isolating function, and also the isolating devices may be shortened in life-cycle. However, it may be difficult to inspect whether the adequate load is applied to each of existing isolating devices.
According to the present invention, as shown in FIG. 4, an pressure gauge may be connected to the connector 220 to easily determine a load applied to a corresponding isolating device by using the measured pressure. If fluid is further injected into an isolating device having a low pressure, a height-adjustable part 200 may increase in height and thus be closely attached to an isolating structure part 100 to increase a load applied to the isolating device. On the other hand, if a portion of fluid is discharged from an isolating device having a high pressure, a height-adjustable part 200 may decrease in height, and thus a degree of attachment therebetween may he reduced to decrease a load applied to the isolating device.
Thus, according to the present invention, a load applied to each of the isolating devices may be easily grasped to easily control the load.
According to another embodiment of the present invention, an pressure gauge 240 may be installed to a height-adjustable part 200. Here, a digital pressure gauge may be attached to each of a plurality of height-adjustable parts 200 to receive measured pressures through wireless or wired communication. Furthermore, a fluid tank, a fluid supply unit, and a fluid control unit may be connected to each of the height-adjustable parts 200 to remotely or automatically supply fluid according to the measured pressure values.
As described above, according to the present invention, the load applied to each of the isolating devices 100 may he easily grasped and efficiently controlled for a short time. Thus, the isolating function of the isolating structure part 100 may be effectively managed to effectively protect the nuclear power plant structure when earthquake occurs.
FIGS. 5, 6, and 7 are views of an isolating device according to a second embodiment of the present invention.
In the second embodiment, a protection cover 400 surrounds an insolating structure part 100.
Since an isolating device 1 is exposed to the outside, but is not installed within a building, the isolating device 1 may be unexpectedly damaged due to fire, rainwater, collision by movement of equipment (ladder) for maintaining and managing, and the like. Furthermore, the isolating device 1 should be protected against physical/chemical impacts such as radioactivity.
The protection cover 400 is divided into four portions to respectively surround four sides of the isolating device 100. Each portion includes a first portion 410 coupled to a lower structure 20, a second portion 420 that is bent and extends from the first portion 410 to protect the isolating structure part 100, and a third portion 430 that is bent and extends from the second portion 420 and is coupled to an upper structure 10.
A coupling hole 411 is defined in the first portion 410. A coupling plate 440 and a coupling protrusion 441 are disposed on the lower structure 20. The coupling protrusion 440 is inserted into the coupling hole 411. Then, as shown in FIG. 7, the coupling protrusion 440 rotate to fix the protection cover 400 to the lower structure 20.
The third portion 430 is fixed to the upper structure 10 by using sealant. In another embodiment, the third portion 430 may he fixed to the upper structure 10 by using a magnet or fixed to the upper structure 10 by using the same method as that of the first portion 410.
The protection cover 400 may be formed of a stainless steel material. Also, the protection cover 400 may be provided in a multi-layered shape. If the protection cover 400 is provided in the multi-layered shape, the uppermost layer that is exposed to the outside may be formed of a material such as a stainless steel plate having thermal resistance, water resistance, and hardness, and the lowermost layer may he formed of a material having radioactivity resistance such as lead.
Since the protection cover 400 according to the second embodiment is spaced apart from the isolating structure part 100, the protection cover 400 does not have an influence on an isolating function of the isolating structure part 100. Also, the protection cover 400 may be easily separated when the isolating device 1 is inspected and replaced. If earthquake greater than design criteria occurs, the protection cover 400 may he separated from an upper structure 10 and/or a lower structure 20. Thus, the protection cover 400 does not have an influence on the isolating function of the isolating structure part 100.
An isolating device according to a third embodiment will be described with reference to FIGS. 8 and 9.
Only the isolating structure part 110 is illustrated in FIGS. 8 and 9. Other parts may have the same structure as those of the first embodiment, and also the protection cover according to the second embodiment may be adopted for the current embodiment. However, a height-adjustable part 200 and a horizontal deformation prevention part 300 may be deformed in shape adequate for the isolating structure part 110 having a cylindrical shape.
The isolating structure part 110 has a cylindrical shape on the whole. The isolating structure part 110 includes a lead core 111 having a cylindrical shape, a stacked rubber bearing 112 that surrounds the lead core 111, an upper protection plate 113, and a lower protection plate 114. Each of the upper and lower protection plates 113 and 114 may include a rubber plate.
In the third embodiment, the lead core 111 of the isolating structure part 110 may function as a damper for absorbing an earthquake force. The stacked rubber bearing 112 may perform a vertical load resistance function, a horizontal deformation function, and a restoration function.
However, when earthquake occurs, the lead core 111 may he more damaged than the stacked rubber hearing 112. Thus, if the integrity of only the lead core 111 is deteriorated, the stacked rubber hearing 112 may be reused to save the replacing cost, and only the lead core 111 may be replaced.
In the isolating structure part 110 according to the third embodiment, caps 116 and 117 are respectively disposed on the upper and lower protection plates 113 and 114 so that the lead core 111 is easily replaced. The caps 116 and 117 may be removed from the protection plates 113 and 114 by a screw 118 disposed on each of the caps 116 and 117 and a screw 115 disposed on each of the protection plates 113 and 114. When the caps 116 and 117 are removed, the lead core 111 may be replaced through a space in which each of the caps 116 and 117 is disposed. When the lead core 111 is removed, the lead core 111 is pushed into a space that is formed by removing the upper cap 116 and then withdrawn through a space that is formed by removing the lower cap 117.
When the caps 116 and 117 are mounted again after the lead core 111 is replaced, the isolating structure part 110 in which only the lead core 111 is replaced, and the normal isolating function is performed may be provided. A lubricating agent such as grease may be filled into an empty space between the new lead core 111 and the stacked rubber bearing 112. A lubricating agent injection hole may be formed in the caps 116 and 117 and/or the protection plates 113 and 114 to supply the lubricating agent.
According to the present invention, the isolating device in which the isolating structure part is easily replaced, and the load is easily controlled may be provided. In addition, the prevent invention may provide the method of efficiently replacing the isolating structure part for a short time and a method of controlling a load of the isolating structure part.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. Therefore, future modifications to the embodiments of the present invention cannot depart from the technical scope of the present invention.

Claims

1. An isolating device disposed between an upper structure and a lower structure, the isolating device comprising:

an isolating structure part for performing an isolating function; and

a height-adjustable part disposed on at least one of positions between the isolating structure part and the upper structure and between the isolating structure part and the lower structure, the height-adjustable part being adjusted in height by supplying or discharging fluid therein or therefrom.

2. The isolating device of claim 1, wherein the height-adjustable part comprises:

a deformable case providing a fluid space in which fluid is supplied; and

a connector communicating with the fluid space and connected to an external fluid supply unit, the connector being exposed to the outside.

3. The isolating device of claim 1, further comprising a horizontal deformation prevention part surrounding at least one portion of a side surface of the height-adjustable part to prevent the height-adjustable part from being deformed in a horizontal direction.

4. The isolating device of claim 1, wherein the height-adjustable part is disposed between the lower structure and the isolating structure part, and

the isolating structure part is changed in load by supplying and discharging the fluid into and from the height-adjustable part.

5. The isolating device of claim 1, further comprising an pressure gauge connected to the height-adjustable part to measure a pressure of the fluid within height-adjustable part.

6. The isolating device of claim 1, further comprising a protection cover detachably connected to the upper structure and the lower structure,

wherein the protection cover is spaced apart from the isolating structure part to surround the isolating structure part.

7. The isolating device of claim 6, wherein the protection cover is separated from at least one of the upper structure and the lower structure when earthquake greater than design criteria occurs.

8. The isolating device of claim 1, wherein the isolating structure part comprises:

a lead core;

a stacked rubber bearing surrounding the lead core;

a protection plate on upper and lower portions of the lead core and stacked robber bearing; and

a cap coupled to the protection plate,

wherein the cap is separated from the protection plate to define a passage through which the lead core is withdrawn.

9. A method of replacing an isolating structure part that performs an insulating function in an isolating device disposed between an upper structure and a lower structure, wherein the isolating device further comprises a height-adjustable part disposed on at least one of positions between the isolating structure part and the upper structure and between the isolating structure part and the lower structure, the height-adjustable part being adjusted in height by supplying or discharging fluid therein or therefrom, the method comprising:

discharging the fluid from the height-adjustable part to decrease a height of the height-adjustable part and remove a load of the isolating structure part;

removing the isolating structure part in the state where the height-adjustable part decreases in height to insert a new isolating structure part; and

injecting the fluid into the height-adjustable part to increase the height of the height-adjustable part to apply a load to the new isolating structure part.

10. The method of claim 9, wherein the isolating structure part comprises:

a lead core;

a stacked rubber bearing surrounding the lead core;

a protection plate on upper and lower portions of the lead core and the stacked robber bearing; and

a cap coupled to the protection plate,

wherein the cap is separated from the protection plate to define a passage through which the lead core is withdrawn, and

the new isolating structure part is provided by inserting a new lead core into the stacked rubber bearing.

11. A method of controlling a load of an isolating structure part that performs an insulating function in an isolating device disposed between an upper structure and a lower structure, wherein the isolating device further comprises a height-adjustable part disposed on at least one of positions between the isolating structure part and the upper structure and between the isolating structure part and the lower structure, the height-adjustable part being adjusted in height by injecting or discharging fluid therein or therefrom, the method comprising:

measuring a pressure of the fluid within the height-adjustable part; and

supplying or discharging the fluid into or from the height-adjustable part on the basis of the measured pressure.