JP4398326B2 - Reciprocating pump shaft seal - Google Patents

Description

  The present invention relates to a reciprocating pump shaft seal, and more particularly to a bellows shaft seal of a reciprocating pump that can be used for a high-pressure fluid such as liquefied gas.

  In general, a reciprocating pump (a pump represents a general device for compressing and transferring a fluid, and includes a pump for liquid, a compressor for gas, a compressor, etc. The same shall apply hereinafter). In some cases, the shaft is also referred to as a shaft.), And the fluid in the pump is sealed from the atmosphere. Usually, as a shaft seal of a reciprocating pump, V packing, lip seal, labyrinth type piston rod packing, segment type piston rod packing or the like is used. However, these seals are mechanisms that seal the fluid while allowing the shaft and cylinder to slide. Since there is a sliding portion in the portion that seals the fluid, the internal fluid is completely sealed from the atmosphere side. It ’s difficult. In particular, when the internal fluid is in a gaseous state and has a high pressure, the leakage cannot be completely prevented structurally. Oil seals and lubricated segment-type piston rod packings are excellent in preventing fluid leakage, but they require oil circulation, making the seal structure complicated and large. On the other hand, the bellows seal is a relatively simple seal that completely seals the internal fluid, and since it does not have a sliding portion, it can completely prevent leakage. However, due to its structure and material, if the pressure of the internal fluid is high, the bellows will be destroyed. Usually, the pressure of the internal fluid that can be used for the bellows seal is about 0.3 MPa. For this reason, various studies have been made. For example, Patent Document 1 discloses a method of using a special lip seal structure for a shaft seal mechanism of a high-pressure compressor. However, although it is effective when the internal fluid is a harmless gas such as air, it is difficult to use it for hydrogen or the like where a small amount of leakage is not allowed. Moreover, the volume of the space of the bellows portion of the bellows seal changes as the shaft reciprocates. For this reason, the fluid moves from the low temperature pump side to the normal temperature bellows seal side or vice versa, and there is also a defect that heat transfer, that is, heat inflow to the pump easily occurs. It was also a problem to keep the fluid cold by preventing the fluid in the axial direction and the accompanying heat transfer.

JP 2003-222077 A

  An object of the present invention is to develop a bellows seal that can be used for compressing a high-pressure internal fluid in a shaft seal of a reciprocating pump and suppresses heat transfer in the shaft seal portion.

  In a plurality of reciprocating pumps having a bellows seal, a first means for solving the above problem is to provide an auxiliary seal on the shaft sliding portion on the atmosphere side of the bellows seal of each pump, and between the auxiliary seal and the bellows. When the atmosphere side space of one pump is in the expansion process, the atmosphere side space of one of the pumps is in the contraction process. Yes, the total volume of the space on the atmosphere side of all the pumps that are conducting is constant during the reciprocation of the pump, and a second auxiliary seal is provided on the shaft sliding part on the pump side from the bellows seal of each pump. When the space between the two auxiliary seals and the bellows is the pump side space, the pump side spaces of each pump are connected by the conduction path, and when the pump side space of one pump is in the expansion process, Kutomo located in the pump side space contraction process of the other one of the pumps, the sum of the volume of the pump side space of all pumps are conducting is a shaft seal which is constant during reciprocation the course of the pump. Preferably, the shaft seal has a liquid sealed in the atmosphere side space.

  The second means is a plurality of reciprocating pumps having bellows seals, which are connected to the atmosphere side space of the bellows from the bellows seal of each pump to the atmosphere side space of the bellows, An auxiliary pump that compensates for the volume change of the space by the volume change of the cylinder, and a connecting path that connects the atmosphere side space of the bellows of each pump, and in the space on the atmosphere side of the bellows of each pump in the connecting path The shaft seal includes an isolation wall having elasticity for isolating fluid and a displacement measuring device for the isolation wall, and a liquid is sealed in the space on the atmosphere side of the bellows, the cylinder of the auxiliary pump, and the connection path.

  Since the shaft seal of the present invention has a bellows seal and completely seals the pump side and the atmosphere side, there is no leakage of the internal fluid to the atmosphere side. Further, the shaft seal of the present invention keeps the volume of the sealed space in the atmosphere side portion of the bellows seal constant with respect to the reciprocating motion of the shaft, eliminates the pressure change applied to the bellows due to the expansion and contraction of the bellows, and prevents the bellows from being destroyed. . Alternatively, the volume of the pump side portion of the bellows seal is kept constant with respect to the reciprocation of the shaft, the pressure of the pump side seal portion space due to the reciprocation of the shaft is kept constant, the pressure fluctuation is reduced, the bellows is deformed, Damage can also be prevented. Furthermore, heat transfer due to fluid movement between the periphery of the bellows seal and the pump portion can be suppressed, and a temperature change due to heat inflow can be prevented by operating the pump.

  The first means of the present invention will be described. The shaft seal of the reciprocating pump of the present invention is configured by combining a shaft seal of a pump having two or more bellows seals. The description will proceed according to FIG. 1, which is composed of a combination of two pump shaft seals, which is a basic structure. FIG. 1 is an explanatory view of a bellows seal of the present invention in which two bellows seals a and b having the same shape are connected by a conduction path.

  First, the atmosphere side space of the bellows seal will be described. In two reciprocating pumps having bellows seals, auxiliary seals 6a and 6b are provided on the shaft sliding portion on the atmosphere side, that is, the upper side in FIG. Spaces between the auxiliary seals 6a and 6b and the bellows 3a and 3b are referred to as atmosphere-side spaces 4a and 4b. The atmosphere-side spaces 4 a and 4 b are conducted through the movement path 8. The bellows seal “a” and the bellows seal “b” are bellows seals having the same shape. The reciprocating motion of the pump, that is, the shafts 1a and 1b, is controlled so that when the atmosphere side space 4a of the bellows seal of one a is in the expansion process, the atmosphere side space 4b of the bellows seal of the other b is in the contraction process. . As the bellows seal contracts or expands, for example, when the volume of the atmosphere side space 4a decreases, the volume of the atmosphere side space 4b increases. This decrease or increase in volume is proportional to the distance of contraction or extension of the bellows seal. Therefore, if the atmosphere side spaces 4a and 4b of the bellows seals a and b which are in opposite directions of contraction and extension are communicated with each other through the conduction path 8, the sum of the volumes of the atmosphere side spaces 4a and 4b is reduced. Constant during the reciprocating motion process.

  By adopting such a combined structure of the shaft seal, the space formed by the atmosphere side spaces 4a and 4b of the bellows seal is maintained at a constant volume regardless of the reciprocating motion of the pump, and the fluid inside thereof is compressed or expanded. There is nothing. That is, the space formed by the atmosphere side spaces 4a and 4b of the bellows seal does not cause pressure fluctuation with respect to the reciprocating motion of the pump. This means that at least due to pressure fluctuations in the space on the atmosphere side of the bellows seal, the bellows is not subjected to shear deformation due to pressures other than expansion and contraction due to reciprocation, and is not damaged. If an incompressible fluid is sealed in this space and the pressure in this space is made equal to the spaces 5a and 5b on the bellows pump side, the bellows will not be abnormally deformed or damaged even in a pump that handles high-pressure fluid. Even if an abnormal pressure is applied to the pump-side spaces 5a and 5b, if the air-side spaces 4a and 4b of the bellows 3a and 3b are incompressible liquid, the volume does not change depending on the pressure. It will not be damaged.

  In the above description, the bellows seal “a” and the bellows seal “b” are the same shape bellows seals, but it is not always necessary to have the same shape. On the other hand, a combination of a bellows seal having a structure in which the atmosphere side space 4b of the bellows seal of the b increases in accordance with the decrease amount of the atmosphere side space 4a that the bellows seal of the a decreases in the contraction process. In this case, the sum of the volumes of the atmosphere side spaces 4a and 4b is constant during the reciprocating process of the pump.

  Furthermore, the combination of the above-described bellows seals is not necessarily two, and may be three or more. Even in that case, each pump reciprocates in an interlocked manner, and the sum of the decreasing amount of the atmospheric side space that is decreasing and the sum of the increasing amount of the volume of the atmospheric side space that are increasing are always It is necessary to be equal. For example, there are two bellows seals that have an atmosphere side space volume that increases by half of the amount of decrease in the volume of the atmosphere side space of one bellows seal, and the reciprocating motion is opposite to the bellows seal, An example is a shaft seal having a structure in which they are conducted. Of course, each atmosphere side space needs to be conducted. Any form of conduction may be used. For example, all the atmosphere side spaces may be conducted by one conduction path, or each atmosphere side space may be conducted by another conduction path. There are infinite combinations of such bellows seals, but it is usually easy and easy to combine two, four and six pumps with the same shape of shaft seal. The reciprocating motion of each pump may be shifted every 1/2 cycle, 1/4 cycle, and 1/6 cycle with a reciprocating motion as one cycle like a normal pump.

  In FIG. 1, the bellows 3a and 3b are bent lines for simplification of description, but any material and structure that can serve as a bellows may be used in any form. The bellows preferably has a structure in which the increase / decrease amount of the volume of the atmosphere side spaces 4a, 4b changes in proportion to the expansion / contraction distance of the bellows. The optimum material and structure may be selected in consideration of the nature of the internal fluid of the pump, the pressure and temperature of the internal fluid, and the ease of manufacturing the shaft seal. Generally, corrugated bellows that are used as metal bellows, and a corrugated bellows that is made by cutting fluororesin, or a thermoplastic resin that is molded to reverse the curvature. It is easy to use things on a continuous curve. The bellows having the structure described above is a suitable bellows seal material of the present invention because the amount of increase / decrease in the volume of the atmosphere side space changes in proportion to the expansion / contraction distance of the bellows.

  The auxiliary shaft seals 6a and 6b may be seals of any structure. For example, gland packing, V packing, lip seal, lip seal with spring, rod packing, O-ring, etc. are convenient and convenient. The auxiliary shaft seals 6a and 6b are not required to have a particularly directional seal for fluid sealing, and usually a gland packing, an O-ring, a rod packing, etc. are easily used.

  Next, the pump side space will be described. If it demonstrates according to FIG. 1, the sum of the volume of the pump side space 5a and 5b of the bellows seal | sticker currently conducted by the conduction path 9 will be kept constant in the same way as the method of keeping the volume of the atmosphere side space constant. The shaft seal eliminates pressure changes in the pump side spaces 5a and 5b due to expansion and contraction of the bellows. That is, the second auxiliary seals 7a and 7b are provided in the shaft sliding portion on the pump side of the bellows seals of the two pumps, and the space between the second auxiliary seals 7a and 7b and the bellows 3a and 3b of the respective pumps. Is the pump-side spaces 5a and 5b. The pump-side spaces 5a and 5b are conducted through the conduction path 9. Due to the characteristics of the bellows seal, when the atmosphere side spaces 4a and 4b move to compensate each other as described above, in the pump side spaces 5a and 5b, the pump side space 5a of the bellows seal of a is in the process of expansion. In some cases, the pump side space 5b of the bellows seal of the other b is in the contraction process, and the sum of the volumes of the pump side spaces 5a and 5b of the two pumps conducted by the conduction path 9 is constant during the reciprocation of the pump. It becomes a certain shaft seal. In the shaft seal of the present invention, the pressure change in the pump side space due to expansion and contraction of the bellows is eliminated, and at least deformation and breakage due to pressure fluctuations due to expansion and contraction of the bellows are eliminated. The second auxiliary seals 7a and 7b may be the same as the auxiliary seals 6a and 6b. However, since it is in contact with the fluid inside the pump, normal care should be taken regarding the seal selection material and the like. Although the explanation was made in the case of two pumps, the pump side of all the bellows seals that are conducting even with a combination of three or more shaft seals or shaft seals with different shapes, as described in the atmosphere side space above. The total volume of the space may be constant during the reciprocating motion of the pump.

  The atmosphere side space means and the pump side space means can be provided on the shaft seal in an overlapping manner, but it can also be provided as a shaft seal incorporated one by one, and damage due to pressure fluctuations in the spaces on both sides of the bellows is reduced. Also, since the pressure in the atmosphere side space is usually small, if a suitable fluid is sealed in the atmosphere side space and the pressure is the same as that in the pump side space, the pressure difference on both sides of the bellows will disappear, and there is no risk of damage to the bellows. It becomes even smaller. As the sealing fluid, a liquid such as a lubricating oil having a good sealing property is suitable.

  The shaft seal of the present invention is structured such that the fluid in the pump side space only flows between the pump side spaces where the respective bellows seals are conducted in accordance with the reciprocating motion of the pump, and the pump passes through the auxiliary shaft seal structurally. It is thought that it does not flow between the sides. This indicates that the heat of the pump-side fluid does not directly enter the bellows-side space together with the fluid. However, with the reciprocation of the shaft, heat transfer due to conduction between the fluid and the shaft is inevitable. Therefore, as shown in FIG. 2, it is desirable to provide a heat insulating structure on the pump side from the bellows seal of the shaft, preferably on the pump side from the conduction path 9, to suppress movement due to heat conduction through the shaft. For example, the shaft of the sliding part with the second auxiliary seal is made into a heat insulating structure as a heat insulating material such as a foamable material or a sintered metal. Alternatively, it is preferable that the shaft of the sliding portion with the second auxiliary seal or the cylinder wall on the pump side has a hollow structure, and further the inside thereof is evacuated to enhance the heat insulation and to be the shaft of the heat insulation structure. The length of the heat insulating structure is not particularly limited, but is preferably longer than the reciprocating distance of the shaft. As a more preferred embodiment, there is a method in which the cylinder wall with respect to the sliding surface of the shaft of the heat insulating structure is also heat insulating. Thereby, the heat transfer from the cylinder wall side can also be prevented. In addition, although the heat transfer of the heat insulation structure of the present invention has been described as the movement from the pump side to the shaft seal side, conversely, the heat transfer structure is also effective for the heat transfer from the shaft seal side to the pump side. In particular, when the pump transfer fluid is a low-temperature liquefied gas or the like, an effective heat-insulating pump shaft seal is obtained.

  Further preferred embodiments will be described. Normally, the atmosphere side space is filled with air, but a shaft seal in which a liquid is sealed is a preferred embodiment. The liquid has a higher viscosity than air and has a function of improving the sealing performance of the auxiliary seal. The liquid is preferably a liquid that has good fluidity and easily flows through the conduction path. However, it is preferable that the auxiliary shaft seal has a viscosity capable of exhibiting a sealing property and improves the lubricity of the sliding portion. For example, it is preferable to use normal lubricating oil in consideration of compatibility with the temperature, pressure, and the material of the sealing material such as bellows. In particular, in the above-described shaft seal in which the pressure in the atmosphere-side space is increased, a shaft seal in which a liquid is sealed in the atmosphere-side space is a very preferable embodiment.

  The second means of the present invention will be described. First, the auxiliary pump will be described. FIG. 3 is an explanatory view of the form and function of an auxiliary pump of one bellows seal used in this means. In a reciprocating pump having a bellows seal, the space 1a on the atmosphere side of the bellows seal communicates with the space 4a 'on the atmosphere side of the bellows 3a. For example, a shaft seal having an auxiliary pump that compensates for the decrease by a change in the volume of the cylinder 15a, for example, an increase. Here, the structure in which the change in the volume of the cylinder 15a compensates for the change in the volume of the space 4a ′ on the atmosphere side of the bellows 3a is the sum of the volume of the space 4a ′ on the atmosphere side and the volume of the cylinder 15a communicating therewith. The volume should just be substantially constant. It is more realistic that the elastic isolation wall 13 to be described later can be elastically deformed and has a volume change that slightly fluctuates within a range where it is not damaged, and is also suitable for detection of bellows fracture described later. That is, in this means, the state in which the volume change as described above occurs in the total volume of the atmosphere side space 4a ′ and the cylinder 15a with the reciprocating motion of the pump shaft is the volume of the atmosphere side space 4a ′ of the bellows 3a. It is called a structure that compensates for changes. This is a volume change that can be dealt with by deformation of the bellows 3a.

  In FIG. 3, there is an auxiliary pump connected to the bellows seal immediately above the bellows seal and having the same shaft as the pump shaft 1a. In the auxiliary pump, the cylinder 15a communicates with the space 4a 'on the atmosphere side of the bellows 3a. The piston 16a of the auxiliary pump is provided on the shaft 1a and interlocks with the shaft 1a. In the present invention, it should be noted that the cross-sectional area of the space 4a ′ on the atmosphere side of the bellows is substantially equal to the cross-sectional area of the cylinder 15a, and the volume change of the space 4a ′ on the air side accompanying the reciprocation of the bellows is the volume of the cylinder 15a. It is a structure that can be supplemented with changes. Specifically, for example, as shown in FIG. 3, when the thickness of the shaft 1a does not change between the bellows seal and the auxiliary pump, the diameter of the cylinder 15a may be made substantially equal to the effective diameter of the bellows 3a. The effective diameter of the bellows 3a is a substantially cylindrical shape (a bellows-like cylinder) formed by the horizontal surfaces of the upper and lower ends of the bellows 3a and a bellows-like circumferential portion of the bellows 3a, for example, a stack of frustoconical plates. Is the length corresponding to the diameter of the circle. In other words, the effective diameter is an imaginary diameter for taking the bellows-like cylinder as a cylinder and taking out the volume. This effective diameter does not change with respect to the piston 16a of the auxiliary pump, that is, the reciprocating motion of the shaft 1a, and the expansion / contraction of the bellows 3a that is interlocked.

  If the diameter of the cylinder 15a of the auxiliary pump above the space 4a 'on the atmosphere side of the bellows 3a is made substantially the same as the effective diameter of the bellows 3a, the volume of the space divided by the piston 16a of the auxiliary pump and the bellows 3a That is, the sum of the volume of the space 4a ′ on the atmosphere side of the bellows 3a and the volume of the cylinder 15a can be kept substantially constant regardless of the reciprocation of the shaft. In other words, the pressure in the space 4a 'on the atmosphere side of the bellows 3a hardly changes even if the shaft reciprocates. That is, a pressure change does not occur in the space 4a 'on the atmosphere side of the bellows 3a due to the reciprocation of the shaft, and the bellows is not damaged. Therefore, if the bellows structure withstands the pressure difference between the pressure inside the pump, more precisely the pressure in the pump-side space 5a and the pressure in the space 4a 'on the atmosphere side of the bellows 3a, the bellows 3a is capable of reciprocating the shaft. It is not damaged by the pressure difference due to the pressure change in the space 4a 'on the atmosphere side of the bellows 3a. When the difference between the pressure in the pump side space 5a and the pressure in the space 4 on the atmosphere side of the bellows 3a is large, the fluid is sealed in the space 4a ′ on the atmosphere side of the bellows 3a and pressurized, and the pressure difference between both sides of the bellows 3a It is desirable to reduce the value.

  In FIG. 3, the shaft side of the bellows 3a is connected to the atmosphere side, but a structure in which the cylinder wall side of the bellows 3a is connected to the atmosphere side is also conceivable. In this case, the area obtained by subtracting the cross-sectional area of the shaft from the cross-sectional area of the cylinder 16a of the auxiliary pump, that is, the effective cross-sectional area of the cylinder of the auxiliary pump is substantially equal to the effective cross-sectional area of the space connected to the atmosphere side of the bellows seal. What is necessary is just to make it equal. The effective cross-sectional area of the space connected to the atmosphere side of the bellows seal is the average cross-sectional area of the bellows-shaped bellows-shaped cylinder calculated from the cross-sectional area of the cylinder of the bellows seal portion, considering the effective diameter of the bellows as the diameter. Is the area minus. In this way, even if the shaft 1a reciprocates and the volume of the space 4a ′ on the atmosphere side of the bellows 3a changes, the cylinder 15a of the auxiliary pump compensates for this volume change, and the space on the atmosphere side of the bellows 3a. The pressure change of 4a 'does not occur. Therefore, the same effect as described above can be obtained.

  Furthermore, it is preferable to enclose a liquid such as lubricating oil in the space 4a 'on the atmosphere side of the bellows 3a and the cylinder 15a of the auxiliary pump as described above. Further, it is more preferable that the pressure in the space 4a 'on the atmosphere side of the bellows 3a and the pressure in the auxiliary pump cylinder 15a is the same as the space 5a' on the pump side of the bellows. Further, if the pressure measuring device 12 is attached to the space 4a 'on the atmosphere side of the bellows 3a or the cylinder 15a of the auxiliary pump, it is convenient that the abnormality of the shaft seal of the present invention can be found quickly.

  The second means of the present invention will be described with reference to FIG. 4 based on the function of the auxiliary pump. FIG. 4 is an example of this means, and the space 4a ′, 4b ′ on the atmosphere side of the bellows of the two reciprocating pumps having the shaft seal provided with the auxiliary pump described in FIG. 3 is connected by the connecting paths 8a, 8b. It is a shaft seal that is connected, provided with an elastic isolation wall 13 in the connection path, and provided with a displacement measuring device 14 on the isolation wall. In the shaft seal provided with the auxiliary pump as described above, the pressure in the space 4a ', 4b' on the atmosphere side of the bellows 3a hardly changes with the reciprocating motion of the pump, but the bellows is deformed or broken due to some abnormality When you wake up, you need to discover it immediately. As a countermeasure, there is a method in which the pressure measuring device 12 is attached in the space 4a ', 4b' on the atmosphere side of the bellows 3a or the cylinder 16a of the auxiliary pump. However, when a plurality of pumps are used as a set, the space 4 on the atmosphere side of the bellows is connected by the connection paths 8a and 8b without providing the pressure measuring device 12 to the shaft seal of each pump. If an isolation wall 13 that can be elastically deformed is provided in the road and a displacement measurement device 14 is provided on the isolation wall, the measured value of the displacement measurement device 14 can be changed with respect to changes in the space 4 on the atmosphere side such as bellows destruction. It can be discovered immediately. The material of the elastic isolation wall 13 is not particularly limited. What is necessary is just to select suitably from rubber | gum, a metal, a plastics, etc. in consideration of the property, temperature, pressure, etc. of the sealing fluid.

  Also in this case, an incompressible liquid such as lubricating oil is sealed in the spaces 4a ′ and 4b ′ on the atmosphere side of the bellows 3a and 3b, the auxiliary pump cylinders 16a and 16b, and the connection paths 8a and 8b as described above. . Further, it is more preferable as described above if the pressure in the space 4 on the atmosphere side of the bellows 3a, 3b and the pressure in the auxiliary pump cylinders 16a, 16b are the same as the pump side spaces 5a ', 5b' of the bellows.

  On the pump side of the bellows seal, similarly to the first means, second auxiliary seals 7a and 7b are provided on the shaft sliding portion on the pump side of the bellows seal of each pump, and the second auxiliary seal 7a of each pump is provided. , 7b and the bellows 3a, 3b are pump-side spaces 5a ′, 5b ′, and the pump-side spaces 5a ′, 5b ′ are made conductive by the conduction path 9. Due to the characteristics of the bellows seal, when the space 4a ′, 4b ′ on the atmosphere side compensates for the reciprocation of the bellows by the bellows seal a and the bellows seal b as described above, the pump side space 5a ′. , 5b ′, when the pump side space 5a ′ of the bellows seal of one a is in the expansion process, the pump side space 5b ′ of the bellows seal of the other b is in the contraction process and is conducted by the conduction path 9. A shaft seal in which the sum of the volumes of the pump-side spaces 5a 'and 5b' of the two pumps is constant during the reciprocating motion of the pump. For this reason, the pressure applied to both sides of the bellows 3a, 3b is always constant. When the pressure applied to both sides of the bellows 3a and 3b is equal, the deformation stress due to the fluid is not applied to the bellows even during the pump operation. Therefore, there is no fear that the bellows is damaged due to the pressure change of the fluid based on the reciprocating motion of the pump.

  As mentioned above, it is desirable that the pressure of the fluid on both sides of the bellows be equal. However, in such a state, even if the bellows is broken for some reason, it is difficult to immediately detect it. In such a case, as described above, with respect to the bellows seal on the a side in FIG. 4, the volume change of the auxiliary cylinder 15a that compensates for the volume change of the space 4a ′ on the atmosphere side of the bellows is not a complete compensation amount. The volume change of the auxiliary cylinder 15a is slightly reduced. The amount of change in the total volume of the space 4 a ′ on the atmosphere side of the bellows and the volume of the auxiliary cylinder 15 a due to the reciprocating motion of the pump is within the allowable amount of elastic deformation of the isolation wall 13.

  As for the bellows seal on the b side in FIG. 4, as with the bellows seal on the a side, the volume change of the auxiliary cylinder 15 b that compensates for the volume change of the space 4 b ′ on the atmosphere side of the bellows is the same volume as the auxiliary cylinder 15 a. Keep it as low as possible. By doing so, the pressure applied to both sides of the bellows 3a, 3b is equalized while the isolation wall 13 vibrates due to elastic deformation as the pump reciprocates. If the vibration of the isolation wall 13 is measured by the displacement measuring device 14, when the bellows is normal, the vibration is regular. On the other hand, if the bellows 3a is broken for some reason, for example, the fluid present in the space 4a ′ on the atmospheric side of the bellows and the auxiliary cylinder 15a due to the reciprocating movement of the pump passes through the broken bellows 3a and the space 5a on the pump side of the bellows. The amount of fluid that flows in and out and deforms the isolation wall 13 changes. Thereby, a change occurs in the vibration of the isolation wall 13. If this change in vibration is detected by the displacement measuring device 14, an abnormality of the bellows 3a can be detected immediately. The breakage of the bellows 3b can be similarly detected. For the above reasons, if described on the a side in FIG. 4, the volume change of the auxiliary cylinder 15 a that compensates for the volume change of the space 4 a ′ on the atmosphere side of the bellows is not a complete compensation amount. The volume change is slightly reduced. The same applies to the b side in FIG. The amount of change in the total volume of the space 4 a ′ on the atmosphere side of the bellows and the volume of the auxiliary cylinder 15 a due to the reciprocating movement of the pump is preferably within an allowable amount of elastic deformation of the isolation wall 13.

  FIG. 5 shows a schematic sectional view of an example of a pump having a bellows seal of the present invention. This pump is a liquefied gas pump which has a supply liquid tank 36 in the lower part and is operated by hydraulic pressure on the shaft operating pistons 20a and 20b provided in the upper part. The two pumps have the same shape but operate with the suction and discharge processes reversed. The pump of the present embodiment is the pump of the second means. The seal of the pump on the left side of the figure corresponds to a in FIG. 4, and the pump on the right side corresponds to b in FIG.

  If it demonstrates with the pump of the left side corresponding to a, the piston of a pump exists in a bottom dead center (state in which the piston fell most). There is a bellows seal at the center of the shaft of the pump, and the bellows is in its most extended state. Immediately above this is an auxiliary pump that connects the cylinder 4 and the space 4a 'on the atmosphere side of the bellows 3a. The piston of the auxiliary pump is at the lowest point and the cylinder volume is almost zero. The piston is provided with a piston ring to serve as an auxiliary seal. The shaft thickness of the bellows seal portion and the shaft thickness of the auxiliary pump portion are the same, and the effective diameter of the bellows is equal to the cylinder diameter of the auxiliary pump. In this way, the change in the volume of the space 4a on the atmosphere side of the bellows accompanying the reciprocation of the shaft can be compensated by the change in the cylinder volume of the auxiliary pump. Note that a low-viscosity lubricating oil such as spindle oil is sealed in a space formed by the space 4a 'on the atmosphere side of the bellows and the cylinder of the auxiliary pump.

  The cylinder wall 10a and the shaft below the bellows seal have a heat insulating structure. Specifically, the cylinder wall 10a and the shaft are hollow and the inside is in a vacuum state. A second auxiliary seal 7a is provided at the heat insulating structure portion of the shaft and the sliding portion of the cylinder wall, and the pump side space below the bellows seal is used as an isolation space.

  The right pump has the same structure as the left pump described above, but the piston of the pump is at the top dead center, the bellows is in the most contracted state, and the piston of the auxiliary pump is in the highest point. Then, the right and left pumps always operate in a reverse reciprocating state.

  The spaces of both pumps communicate with each other at three locations. A conduction path 21 that communicates the space above the piston of the auxiliary pump, a conduction path 9 that communicates the space on the pump side of the bellows, and a conduction path 35 that communicates the space above the piston of the pump body. The spaces communicated by the three conduction paths are isolated by a sealing mechanism such as a piston ring or the second auxiliary seal 7a, and the space volume of each pump varies with the reciprocation of the pump shaft. The shafts work in reverse to compensate for their respective volumes. Therefore, the fluid in each space does not change its volume and pressure by flowing through the conduction paths 21, 9, and 35.

  Between the connecting paths 8a and 8b that connect the space formed by the cylinder of the auxiliary pump of the two pumps and the space on the atmosphere side of the bellows, a thin metal plate isolation film 13 is provided, and the spaces do not conduct each other. Not. However, the space created by the cylinder of the auxiliary pump of each pump and the space on the atmosphere side of the bellows, as described above, the space on the atmosphere side of the bellows and the cylinder of the auxiliary pump compensate for the volume change as the shaft reciprocates. The volume and pressure hardly change with the reciprocating motion of the shaft. That is, normally, the shape of the isolation film 13 does not change. However, if there is some abnormality in one of the pumps and there is a pressure change in the space on the atmosphere side of the bellows, the shape of the isolation film 13 changes. This can be measured by a displacement measuring device or the like attached to the isolation film 13 to detect an abnormality in the pump bellows seal at an early stage.

  Furthermore, since the fluid pressure above and below the sliding portions of the second auxiliary seals 7a and 7b of each pump does not change with respect to the axial reciprocation, the fluid flows up and down through the second auxiliary seals 7a and 7b. There is nothing. Therefore, no heat is diffused by the movement of the fluid in the second auxiliary seals 7a and 7b. Further, since the shaft and the cylinder wall in the vicinity of the second auxiliary seals 7a and 7b have a heat insulating structure, there is little heat transfer by conduction through the shaft and the cylinder wall. For this reason, the heat transfer to the upper part through the seal part of handling fluid can fully be prevented.

  The shaft seal of the present invention is suitable for various reciprocating pumps, particularly for reciprocating pumps that reliably prevent leakage of internal fluids and handle internal fluids that require high pressure and heat insulation, without providing a complicated sealing mechanism. Yes.

FIG. 1 is an explanatory view of a shaft seal of the first means of the present invention. FIG. 2 is an explanatory view of a shaft seal according to a preferred embodiment of the first means of the present invention. FIG. 3 is an explanatory diagram relating to the auxiliary pump for the shaft seal of the second means of the present invention. FIG. 4 is an explanatory view of the shaft seal of the second means of the present invention. FIG. 5 is a sectional view for explaining the shaft seal according to the embodiment of the present invention.

Explanation of symbols

a: Bellows seal with bellows extended b: Bellows seal with bellows contracted 1a: Shaft 1b: Shaft 2a: Cylinder wall 2b: Cylinder wall 3a: Bellows 3b: Bellows 4: Space 4a on the air side of the bellows seal : Atmosphere side space 4a ': Atmosphere side space 4b of bellows seal: Atmosphere side space 4b': Atmosphere side space 5a of bellows seal: Pump side space 5a ': Pump side space 5b of bellows seal: Pump side space 5b ': Space on pump side of bellows seal 6a: Auxiliary shaft seal 6b: Auxiliary shaft seal 7a: Second auxiliary shaft seal 7b: Second auxiliary shaft seal 8: Conduction path (atmosphere side)
8a: Connection path 8b: Connection path 9: Conduction path (pump side)
10a: heat insulating structure 10b: heat insulating structure 11: conduction path 12: pressure measuring device 13: isolation wall 14: displacement measuring device 15a: auxiliary pump cylinder 15b: auxiliary pump cylinder 16a: auxiliary pump piston 16b: auxiliary pump piston 20a: pump operation Piston 20b: Pump operating piston 21: Conduction path 30: Fluid inlet 31: Fluid outlet 32b: Suction valve 33b: Discharge valve 34b: Pump piston 35: Conduction path 36: Fluid tank

Claims (3)

  In a plurality of reciprocating pumps having a bellows seal, an auxiliary seal is provided on the shaft sliding portion on the atmosphere side from the bellows seal of each pump, and the space between the auxiliary seal and the bellows is an atmosphere side space, and the atmosphere of each pump When the side space is conducted by a conduction path and the atmosphere side space of one pump is in the expansion process, the atmosphere side space of at least one other pump is in the contraction process, and the atmosphere side spaces of all the pumps that are conducting The total volume of the pump is constant during the reciprocating motion of the pump, and a second auxiliary seal is provided on the shaft sliding part on the pump side from the bellows seal of each pump, and the space between the second auxiliary seal and the bellows is provided on the pump side. And when the pump side space of each pump is in the expansion process, the pump side space of at least one other pump is Located contraction process, shaft seal sum of the volume of the pump side space of all pumps are conducting is constant during reciprocation the course of the pump.   The shaft seal according to claim 1, wherein a liquid is sealed in the atmosphere side space.   In a plurality of reciprocating pumps having bellows seals, the space on the atmosphere side of the bellows is connected to the atmosphere side shaft from the bellows seal of each pump, and the volume change of the space on the atmosphere side of the bellows due to the reciprocation of the shaft is cylinder A supplementary pump that compensates for the change in volume of the pump, and a connection path that connects the space on the atmosphere side of the bellows of each pump, and an elasticity that isolates the fluid in the space on the atmosphere side of the bellows of each pump in the connection path. The shaft seal which has the isolation wall which has and the displacement measuring apparatus of an isolation wall, and enclosed the liquid in the space of the atmosphere side of a bellows, the cylinder of an auxiliary pump, and a connection path.

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