JP2019039415A - Seal system - Google Patents

Abstract

To provide a seal system which properly cools a double mechanical seal and a pump mechanism and makes a handling fluid of a pump unlikely to leak to the atmosphere side during normal operation and power failure.SOLUTION: A seal system includes: a double mechanical seal having pump side seal mechanisms 10, 12 and atmosphere side seal mechanisms 11, 13; a pump mechanism 19 which is driven by a rotary shaft 1; a first medium circulation line 30 which is connected to a first chamber 22a and a second chamber 22b and circulates a cooling medium serving as a fluid barrier, which is different from a handling fluid of a centrifugal pump, between the first chamber 22a and the second chamber 22b; a heat exchanger 21 and a cutoff valve 28 attached to the first medium circulation line 30; a second medium circulation line 31 which bypasses the cutoff valve 28; and a medium compression pump 45 and an on-off valve 23 attached to the second medium circulation line 31.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a seal system including a double mechanical seal provided in a seal housing, and in particular, a pump mechanism driven by a rotary shaft between a pump side seal mechanism and an atmosphere side seal mechanism constituting the double mechanical seal. The present invention relates to a seal system provided.

When refining fossil fuels such as oil and natural gas, it is necessary to remove impurities such as carbon dioxide (CO ₂ ) and sulfur (S). Sulfur is often recovered as hydrogen sulfide (H ₂ S) in the purification process, and the fluid handled by the pump used in the purification process may contain a lot of this hydrogen sulfide. Hydrogen sulfide is extremely toxic, and if it leaks into the atmosphere, it will cause serious damage to the human body. Therefore, in a pump that handles hydrogen sulfide, hydrogen sulfide should never leak to the outside. It is necessary to pay full attention to the design of the pump.

  The seal system shown in FIG. 2 includes a pump side seal mechanism (slip ring 110 and counter ring 112) and an atmosphere side seal mechanism (slip ring 111 and counter ring 113) in the seal housing 114 of the rotary shaft 101 of the centrifugal pump. A double mechanical seal. A pump mechanism 119 driven by the rotating shaft 101 is provided between the pump side seal mechanism and the atmosphere side seal mechanism. On both sides of the pump mechanism 119, a first chamber 122a and a second chamber 122b are formed. The first chamber 122a and the second chamber 122b are formed in the seal housing 114, the atmosphere-side seal mechanism is disposed in the first chamber 122a, and the atmosphere-side seal mechanism is disposed in the second chamber 122b. ing.

  The pump mechanism 119 pressurizes the fluid barrier / cooling medium from the first chamber 122a to the second chamber 122b so as to have a pressure Pb higher than the discharge pressure Ph of the pump impeller and supplies the fluid to the second chamber 122b. In the pressurized fluid barrier / cooling medium in the second chamber 122b, the medium pressurized by the pump impeller 103 leaks to the second chamber 122b through the slip ring 110 and the counter ring 112 of the pump side seal mechanism. Can be prevented.

  The seal system shown in FIG. 2 includes a recirculation system r disposed outside the seal housing 114. The recirculation system r is connected to the first chamber 122a and the second chamber 122b, and is configured to circulate the fluid barrier / cooling medium. The recirculation system r includes a heat exchanger 121, and the fluid barrier / cooling medium pressurized by the pump mechanism 119 reaches the heat exchanger 121 via the second chamber 122b, where it is cooled and cooled to the first chamber. A circulation path is provided to return to 122a and reach the pump mechanism 119 again.

  The fluid barrier / cooling medium is the handling fluid itself of the centrifugal pump, and is previously pressurized by the pump impeller 103 and injected into the seal system. When the fluid barrier / cooling medium in the seal system decreases due to leakage, the handling fluid of the centrifugal pump is pressurized by the pump impeller 103 and refilled in the seal system. Therefore, when the pump handling fluid contains a toxic or flammable fluid, there is a danger of high-pressure dangerous fluid in the immediate vicinity of the outside air and leakage to the outside.

  By the way, in FIG. 2, the pump mechanism 119 works to pressurize the fluid barrier / cooling medium and send it from the first chamber 122a to the second chamber 122b, so that a large amount of heat is generated in the vicinity of the pump mechanism 119. If the heat is left as it is, there is a risk of interference between constituent devices due to thermal expansion, deformation of members due thereto, or plastic deformation of the sealing material such as the O-rings 134 and 135, thereby impairing the sealing function. Therefore, the heat exchanger 121 is provided in the seal system to actively cool the fluid barrier / cooling medium.

  However, since the driving force in which the fluid barrier / cooling medium circulates through the seal system is generated by the pump mechanism 119, when the centrifugal pump stops due to a power failure or the like, the pump mechanism 119 also stops simultaneously. As a result, the heat generated in the operation until just before the stop is not dissipated, and there is a possibility that the temperature of peripheral devices of the pump mechanism 119 rises to an unacceptable temperature.

  The carrier sleeves 108 and 108 ′ shown in FIG. 2 are pushed away from each other by a spring 109 provided between them, and the ends of the carrier sleeves 108 and 108 ′ cause the slip rings 110 and 111 to face the opposing rings 112 and 113. Is pressed against each. During operation of the centrifugal pump, the carrier sleeve 108 is pushed to the atmosphere side by the pressure Pb in the second chamber 122b. On the other hand, the pressure Pa in the first chamber 122a is applied to the carrier sleeve 108 '. Therefore, as a whole, the combination of the carrier sleeves 108 and 108 ′ causes a Pb−Pa differential pressure to be applied from the pump side to the atmosphere side. For this reason, the pressure on the seal surfaces of the slip ring 111 and the counter ring 113 on the atmosphere side is higher than that at the time of operation stop and the sealing effect is increased, but the pressure on the seal surfaces of the slip ring 110 on the pump side and the counter ring 112 is on the operation side. It becomes lower than when it stops, and the sealing effect decreases.

  Conversely, when the pressure in the first chamber 122a becomes higher than the pressure in the second chamber 122b, the combined pressure of Pa-Pb is applied from the atmosphere side to the pump side in the combination of the carrier sleeves 108 and 108 '. For this reason, the pressure on the sealing surfaces of the slip ring 111 and the counter ring 113 on the atmosphere side becomes lower than when the operation is stopped, the sealing effect is reduced, and the fluid barrier / cooling medium is likely to leak.

British Patent No. 1441653 International Publication No. WO2008 / 090994 Pamphlet

  As described above, in the technique shown in FIG. 2, the pump impeller 103 pressurizes the fluid itself handled by the centrifugal pump and supplies it to the seal system, and the leak prevention fluid (fluid barrier / cooling medium) of the seal system. It is used as. The pressure of the fluid barrier / cooling medium applied to the atmosphere side sealing mechanism is equivalent to the discharge pressure of the centrifugal pump when the operation is stopped. That is, when the pump handling fluid contains a toxic or flammable fluid, there is a danger of high-pressure dangerous fluid in the immediate vicinity of the outside air and leakage to the outside.

  Furthermore, when the operation of the pump mechanism 119 is stopped due to a power failure or the like, the temperature of the device must be avoided, but the seal system of FIG. 2 has insufficient measures. That is, considering the case where the pump handling fluid contains toxic or flammable fluid, the technique shown in FIG. 2 cannot be used as it is, and harmful pump handling fluid leaks to the outside from the sliding surface of the mechanical seal. It is necessary to consider so that it does not come out.

  Therefore, the present invention properly cools the double mechanical seal and the pump mechanism during normal operation and power failure even when the pump handling fluid contains toxic or flammable fluid, and the pump handling fluid leaks to the atmosphere side. It is an object to provide a seal system without fear.

  One aspect of the present invention is a seal system for sealing a rotary shaft of a centrifugal pump, a double mechanical seal having a pump-side seal mechanism and an atmosphere-side seal mechanism, the pump-side seal mechanism, and the atmosphere-side seal mechanism A pump mechanism driven by the rotating shaft, a first chamber defined by at least the atmosphere-side seal mechanism and the pump mechanism, and at least the pump-side seal mechanism and the pump mechanism. A second barrier chamber, a fluid barrier / cooling medium connected to the first chamber and the second chamber and different from a handling fluid of the centrifugal pump between the first chamber and the second chamber. A first medium circulation line to be circulated, a heat exchanger and a shutoff valve attached to the first medium circulation line, The second medium circulation line connected to the first medium circulation line and bypassing the shutoff valve, and a medium pressurizing pump and an opening / closing valve attached to the second medium circulation line are provided. .

A preferred embodiment of the present invention further includes a seal housing that accommodates the double mechanical seal, wherein the first medium circulation line and the second medium circulation line are disposed outside the seal housing.
In a preferred aspect of the present invention, a power failure detector for detecting a power failure of the centrifugal pump, a power failure detection signal output from the power failure detector, the shutoff valve is closed, the open / close valve is opened, and the medium pressurization is performed. A system controller for starting the pump is further provided.

In a preferred aspect of the present invention, a first connection point where one end of the second medium circulation line is connected to the first medium circulation line is located between the shut-off valve and the heat exchanger, The second connection point where the other end of the second medium circulation line is connected to the first medium circulation line is located between the shut-off valve and the second chamber.
The preferable aspect of this invention is further equipped with the power supply for supplying electric power to the said medium pressurization pump, The said medium pressurization pump is provided with the electric motor as a motor.
In a preferred aspect of the present invention, the fluid barrier / cooling medium is oil, and the pressurized medium pump is an oil pump.

  According to the present invention, when the pump handling fluid contains toxic or flammable fluid, the double mechanical seal and the pump mechanism are appropriately cooled both during normal operation and when the centrifugal pump and the pump mechanism are stopped. It is possible to provide a seal system that is free from leakage on the side.

It is a figure which shows one Embodiment of the sealing system provided with the double mechanical seal. It is a figure which shows the conventional sealing system provided with the double mechanical seal.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of a seal system including a double mechanical seal. The double mechanical seal has a function of sealing a gap between the rotary shaft 1 and the partition wall 2 that partitions the high pressure side h and the low pressure side n.

  In FIG. 1, on the high-pressure side h, the pump impeller 3 of the centrifugal pump is fixed to the rotary shaft 1, and the shaft sleeve 4 extends over the axial length of the double mechanical seal. The shaft sleeve 4 is fixed to the outer peripheral surface of the rotating shaft 1. An O-ring 24 is provided between the shaft sleeve 4 and the rotating shaft 1, and seals so that the fluid handled by the centrifugal pump does not leak from the gap between the shaft sleeve 4 and the rotating shaft 1. Centrifugal pump handling fluids include toxic and flammable fluids.

  The pump impeller 3 and the seal housing 14 are partitioned by the partition wall 2. A part of the rotary shaft 1 and the pump impeller 3 extends through a through hole 2 a formed in the partition wall 2. The partition wall 2 has a radial hole 2b communicating with the through hole 2a. During operation of the centrifugal pump, the radial hole 2 b is filled with a handling fluid pressurized by the pump impeller 3. A pressure detector 53 is connected to the radial hole 2 b, and the discharge pressure Ph of the pump impeller 3 is measured by the pressure detector 53.

  A cylindrical ring 5 having an inner peripheral surface in contact with the outer peripheral surface of the shaft sleeve 4 is provided substantially at the center of the shaft sleeve 4. A hollow cylindrical body 6 is fixed to the ring 5. The axial length of the ring 5 is shorter than the axial lengths of the axial sleeve 4 and the hollow cylindrical body 6. The hollow cylindrical body 6 has axially extending portions on both sides of the outer peripheral portion thereof, and the axial length of the inner peripheral portion of the hollow cylindrical body 6 is the same as the axial length of the ring 5, It faces the outer periphery of the ring 5. The shaft sleeve 4, the ring 5, and the hollow cylindrical body 6 are arranged coaxially. A thread groove 7 is formed on the outer peripheral surface of the hollow cylindrical body 6.

  The ring 5 and the hollow cylindrical body 6 have a threaded hole penetrating in the radial direction, and the ring 5 and the hollow cylindrical body 6 are fixed by a screw 32 inserted into the threaded hole. The tip of the screw 32 is engaged with the recess 33 of the shaft sleeve 4. The hollow cylinder 6 is fixed by screws 32 so as not to rotate and displace axially with respect to the ring 5.

  Two carrier sleeves 8 and 8 ′ are fitted in an annular recess formed by the shaft sleeve 4, the ring 5 and the hollow cylindrical body 6. These carrier sleeves 8, 8 ′ are arranged on both sides of the ring 5. An O-ring 34 is disposed between the outer surface of the carrier sleeve 8, 8 ′ and the inner surface of the hollow cylindrical body 6, and an O-ring 35 is disposed between the inner surface of the carrier sleeve 8, 8 ′ and the outer surface of the shaft sleeve 4. Has been placed. The carrier sleeves 8, 8 ′ can be displaced in the axial direction of the rotary shaft 1, but are fixed so as not to rotate by an axial projection 36 that contacts the screw 32.

  A spring 9 is arranged between the carrier sleeves 8, 8 '. The spring 9 acts to push the carrier sleeves 8, 8 'apart. Slip rings 10 and 11 are attached to the surfaces of the carrier sleeves 8 and 8 'apart from the ring 5, respectively. By the spring 9, the slip rings 10 and 11 are pressed against the opposing rings 12 and 13, respectively. The facing rings 12 and 13 are fixed to the pump side cover 14a and the atmosphere side cover 14b of the seal housing 14, respectively. Reference numeral 14 generally indicates the seal housing. The combination of the slip ring 10 and the counter ring 12 constitutes a pump side seal mechanism of a double mechanical seal, and the combination of the slip ring 11 and the counter ring 13 forms an atmosphere side seal mechanism of a double mechanical seal.

  Slip rings 10 and 11 and opposing rings 12 and 13 constituting a double mechanical seal are accommodated in a seal housing 14. More specifically, the seal housing 14 has a hollow cylindrical portion 38 surrounding the double mechanical seal at the center thereof. A thread groove 15 is formed on the inner surface of the hollow cylindrical portion 38. The screw groove 15 is opposed to the screw groove 7 through a minute radial gap, and the lead directions of the screw grooves 15 are opposite to each other. The screw groove 7 is a male screw that rotates together with the rotary shaft 1, and the screw groove 15 is a stationary female screw. The screw groove 15 surrounds the screw groove 7. The screw groove 7 and the screw groove 15 constitute a pump mechanism 19 driven by the rotary shaft 1. The pump mechanism 19 is located between the pump-side seal mechanism (lip ring 10 and counter ring 12) of a double mechanical seal and the atmosphere-side seal mechanism (slip ring 11 and counter ring 13).

  On both sides of the pump mechanism 19, there are an annular first chamber 22a and an annular second chamber 22b. The first chamber 22 a is a room facing the low pressure side n, and is a room defined by the pump mechanism 19, the carrier sleeve 8 ′, the slip ring 11, the counter ring 13, the atmosphere side cover 14 b, and the hollow cylindrical portion 38. The hollow cylindrical portion 38 has an inlet 16 connected to a first medium circulation line 30 described later, and the first chamber 22 a is connected to the inlet 16.

  The second chamber 22 b is a room facing the high pressure side h, and is a room defined by the pump mechanism 19, the carrier sleeve 8, the slip ring 10, the counter ring 12, the pump side cover 14 a, and the hollow cylindrical portion 38. The hollow cylindrical portion 38 has an outlet 17 connected to the first medium circulation line 30, and the second chamber 22 b is connected to the outlet 17. The outlet 17 communicates with the inlet 16 via the first medium circulation line 30.

  The sealing system is a combination of the medium circulation line 30 connected to the first chamber 22a and the second chamber 22b, the second medium circulation line 31 connected to the first medium circulation line 30, a throttle valve and a check valve. The throttle / check valve 18, the shut-off valve 28 that closes when the second medium circulation line 31 is used, the heat exchanger 21 that cools the fluid barrier / cooling medium, and usually the fluid barrier / cooling The medium is pressurized and stored, and in the event of an emergency, an accumulator 40 that pressurizes the fluid barrier / cooling medium in the first medium circulation line 30 by opening the on-off valve 27 is provided. Both ends of the second medium circulation line 31 are connected to the first medium circulation line 30, and the second medium circulation line 31 extends by bypassing the shutoff valve 28.

  A diaphragm (partition) (not shown) is disposed inside the accumulator 40, and a gas such as nitrogen gas is sealed therein. The fluid barrier / cooling medium accumulated in the accumulator 40 is pressurized by the pressure of the gas. Accordingly, the accumulator 40 has a function of pressurizing and storing the fluid barrier / cooling medium.

  One end of the first medium circulation line 30 is connected to the inlet 16, and the other end of the first medium circulation line 30 is connected to the outlet 17. The throttle / check valve 18, the heat exchanger 21, and the shutoff valve 28 are attached to the first medium circulation line 30. The heat exchanger 21 is located between the shut-off valve 28 and the first chamber 22a, and the throttle / check valve 18 is located between the shut-off valve 28 and the second chamber 22b. The accumulator 40 is connected to a branch line 41 extending from the first medium circulation line 30, and the on-off valve 27 is attached to the branch line 41. The accumulator 40 is connected to the first medium circulation line 30 via the branch line 41. The branch line 41 and the accumulator 40 are located between the heat exchanger 21 and the first chamber 22a.

  One end of the second medium circulation line 31 is connected to the first medium circulation line 30 at the first connection point 20a, and the other end of the second medium circulation line 31 is connected to the first medium circulation line 30 at the second connection point 20b. ing. The first connection point 20a is located between the heat exchanger 21 and the shutoff valve 28, and the second connection point 20b is located between the second chamber 22b and the shutoff valve 28. In the present embodiment, the second connection point 20 b is located between the outlet 17 and the throttle / check valve 18.

  Further, the sealing system includes a medium reservoir 44 that stores a fluid barrier / cooling medium, a medium pressurization pump 45 that pressurizes the fluid barrier / cooling medium supplied from the medium reservoir 44, and a first connection point 20a and a medium pressurization. The on-off valve 23 disposed between the pump 45, the check valve 26 disposed between the medium pressurizing pump 45 and the second connection point 20b, and the medium pressurizing pump 45 and the check valve 26. A pressure regulating valve 47 and a pressure detector 48 are provided between them. The pressure detector 48 is located downstream of the pressure adjustment valve 47. The medium reservoir 44, the medium pressurization pump 45, the on-off valve 23, the pressure adjustment valve 47, the pressure detector 48, and the check valve 26 are attached to the second medium circulation line 31. The first medium circulation line 30 and the second medium circulation line 31 are disposed outside the seal housing 14. The first medium circulation line 30 and the second medium circulation line 31 are filled with a fluid barrier / cooling medium.

  The seal system further includes a power failure detector 61 for detecting a power failure, and a system controller 62 that controls operations of the shut-off valve 28, the on-off valve 23, the on-off valve 27, and the medium pressurizing pump 45 described above. When the power failure detector 61 detects a power failure, the power failure detector 61 issues a power failure detection signal and sends this power failure detection signal to the system controller 62. The system controller 62 is configured to receive the power failure detection signal, close the shut-off valve 28, open the on-off valve 23, and start the medium pressurizing pump 45. As the shut-off valve 28, the on-off valve 23, and the on-off valve 27, an electromagnetic valve, an electric valve, a pneumatic drive valve, a hydraulic drive valve, or the like can be used.

  The seal system includes a pressure detector 53 that measures the discharge pressure Ph of the pump impeller 3 and a pressure detector 51 that measures the pressure Pb in the second chamber 22b. The pressure detectors 53 and 51 are connected to the system controller 62.

  A seal system with a double mechanical seal provided within the seal housing 14 uses a fluid barrier and cooling medium. This fluid barrier / cooling medium is a medium having no relation to the fluid handled by the centrifugal pump and has no toxicity or danger. In one embodiment, the fluid barrier and cooling medium is oil and the medium pressurization pump 45 is an oil pump. In the present embodiment, the medium pressurizing pump 45 includes an electric motor as its prime mover.

  The operation of the sealing system having the above-described configuration is as described below. The inside of the first medium circulation line 30 is filled with a fluid barrier / cooling medium having a pressure equal to or higher than the discharge pressure Ph of the pump impeller 3 of the centrifugal pump. During normal operation, the on-off valve 23 is closed and the shut-off valve 28 is open. When the rotating shaft 1 rotates in the normal operation, the pump mechanism 19 sucks and pressurizes the fluid barrier / cooling medium in the first chamber 22a and discharges it to the second chamber 22b. The fluid barrier / cooling medium pressurized by the operation of the pump mechanism 19 returns to the first chamber 22 a through the first medium circulation line 30.

  The pressure Pb in the second chamber 22 b is higher than the discharge pressure Ph of the pump impeller 3 by the throttle / check valve 18 attached to the first medium circulation line 30. While the fluid barrier / cooling medium flows through the first medium circulation line 30 from the throttle / check valve 18 to the inlet 16, the pressure of the fluid barrier / cooling medium is reduced due to pressure loss, and the fluid barrier / cooling medium in the first chamber 22a is also reduced. The pressure of the cooling medium is Pa lower than Pb. Since the pressure Pb in the second chamber 22b is higher than the discharge pressure Ph of the pump impeller 3, the centrifugal pump enters the second chamber 22b from the seal surfaces of the slip ring 10 and the counter ring 12 constituting the pump-side seal mechanism. The handling fluid does not enter.

  The carrier sleeve 8 is pushed from the pump side to the atmosphere side by the pressure Pb in the second chamber 22b. Since the pressure Pa in the first chamber 22a is applied to the carrier sleeve 8 ', the combination of the carrier sleeves 8 and 8' applies a differential pressure of Pb-Pa as a whole from the pump side to the atmosphere side. For this reason, the pressure applied to the seal surfaces of the slip ring 11 and the counter ring 13 constituting the atmosphere-side sealing mechanism becomes higher than when the pump mechanism 19 is stopped, and the sealing effect is increased, and the pump handling fluid leaks to the atmosphere side. Is reliably prevented.

  When the fluid barrier / cooling medium flows through the first medium circulation line 30, the fluid barrier / cooling medium is cooled by the heat exchanger 21 provided in the first medium circulation line 30. The cooled fluid barrier / cooling medium returns to the first chamber 22 a through the first medium circulation line 30 and the inlet 16. In this way, during operation of the centrifugal pump, the fluid barrier / cooling medium passes between the first chamber 22a and the second chamber 22b through the first medium circulation line 30 while being cooled by the heat exchanger 21. Circulate. Since the cooled fluid barrier / cooling medium cools the pump mechanism 19, the pump mechanism 19 and peripheral devices (for example, the O-rings 34 and 35) do not become high temperature.

  By the way, at the time of a power failure, the pump impeller 3 of the centrifugal pump stops and the pump mechanism 19 also stops. Therefore, when the power failure detector 61 detects a power failure, the power failure detector 61 sends a power failure detection signal to the system controller 62. The system controller 62 closes the shutoff valve 28 attached to the first medium circulation line 30, opens the on-off valve 23, and starts the medium pressurizing pump 45. Since the medium pressurizing pump 45 needs to be operated at the time of a power failure, it is connected to a power source 58 different from the power source for operating the centrifugal pump. The power source 58 supplies power to the medium pressurizing pump 45 to operate the medium pressurizing pump 45. The power source 58 can be composed of a battery, a diesel engine drive generator, or the like.

  The medium pressurizing pump 45 pressurizes the fluid barrier / cooling medium supplied from the medium reservoir 44. The pressurized fluid barrier / cooling medium passes through the pressure regulating valve 47 and the check valve 26 and flows into the first medium circulation line 30 at the second connection point 20b. The fluid barrier / cooling medium further flows into the second chamber 22b through the outlet 17. The medium pressurizing pump 45 is configured to pressurize the fluid barrier / cooling medium to a pressure higher than the discharge pressure Ph of the pump impeller 3. Since the shut-off valve 28 is already closed, the fluid barrier / cooling medium does not flow toward the throttle / check valve 18.

  The fluid barrier / cooling medium in the second chamber 22b sent from the medium pressurizing pump 45 passes through the gap between the screw groove 7 and the screw groove 15 of the pump mechanism 19 and reaches the first chamber 22a. Here, the difference between the pressure Pb in the second chamber 22 b and the pressure Pa in the first chamber 22 a is determined by the discharge flow rate of the medium pressurizing pump 45 and the resistance applied to the fluid passing through the stopped pump mechanism 19. . The discharge pressure of the medium pressurizing pump 45 is adjusted by the pressure adjusting valve 47 so that the outlet side pressure of the check valve 26 measured by the pressure detector 51 is higher than the pressure Ph measured by the pressure detector 53. Is done. The discharge pressure of the medium pressurizing pump 45 is measured by the pressure detector 48, and the pressure adjustment valve 47 operates based on the pressure measurement value sent from the pressure detector 48.

  The fluid barrier and cooling medium further enters the first medium circulation line 30 from the first chamber 22a through the inlet 16. The fluid barrier / cooling medium flows through the first medium circulation line 30, is cooled by the heat exchanger 21, enters the second medium circulation line 31 at the first connection point 20 a, and returns to the medium reservoir 44 through the opening / closing valve 23. The cooled fluid barrier / cooling medium in the medium reservoir 44 is sent again to the second chamber 22 b by the medium pressurizing pump 45.

  The cooled fluid barrier / cooling medium in the second chamber 22 b flows to the first chamber 22 a via the pump mechanism 19 and is cooled again by the heat exchanger 21. Since the fluid barrier / cooling medium also contacts the double mechanical seals (slip rings 10 and 11 and opposing rings 12 and 13) provided in the seal housing 14, the entire heat of the double mechanical seal can be taken away. Become. In addition, the fluid barrier / cooling medium can quickly cool the double mechanical seal and its periphery, thereby preventing interference between components due to thermal expansion, and plastic deformation of elastic seals such as O-rings 34 and 35. And the sealing function can be maintained. As a result, the safety of the centrifugal pump is increased.

  The medium pressurizing pump 45 sends the fluid barrier / cooling medium cooled by the heat exchanger 21 to the second chamber 22b at a pressure higher than the discharge pressure Ph of the pump impeller 3, so that the fluid handled by the centrifugal pump can be reduced. Intrusion into the second chamber 22b can be avoided. Furthermore, since the fluid barrier / cooling medium pressurized by the medium pressurizing pump 45 flows from the second chamber 22b through the pump mechanism 19 to the first chamber 22a, the pressure of the first chamber 22a is the pressure of the second chamber 22b. Will be lower. As a result, since the differential pressure of Pb-Pa is applied to the combination of the carrier sleeves 8 and 8 'as a whole from the pump side to the atmosphere side, the operation of the sealing surfaces of the slip ring 11 and the counter ring 13 on the atmosphere side is stopped. Even if it is time, the state which maintained the sealing effect similar to the time of operation continues. The difference between the pressure Pb in the second chamber 22b and the pressure Pa in the first chamber 22a is determined by the discharge flow rate of the medium pressurizing pump 45 and the resistance applied to the fluid passing through the stopped pump mechanism 19, so that the difference The flow rate of the medium pressurizing pump 45 is selected so that the pressure Pb-Pa is appropriate.

  As described above, according to the present invention, when the pump handling fluid contains a toxic or flammable fluid, the double mechanical seal and the pump mechanism 19 can be appropriately used both during normal operation and when the centrifugal pump and the pump mechanism 19 are stopped. It is possible to provide a sealing system that is cooled and has no risk of leakage to the atmosphere side. It goes without saying that the present invention is not limited to the above-described embodiment, and includes various embodiments implemented within the scope of the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Bulkhead 3 Pump impeller 4 Shaft sleeve 5 Ring 6 Hollow cylindrical body 7 Screw groove 8, 8 'Carrier sleeve 9 Spring 10, 11 Slip ring 12, 13 Opposing ring 14 Seal housing 14a Pump side cover 14b Atmospheric side cover 15 Screw groove 16 Inlet 17 Outlet 18 Throttle and check valve 19 Pump mechanism 20a First connection point 20b Second connection point 21 Heat exchanger 22a First chamber 22b Second chamber 23 Open / close valve 24 O-ring 26 Check valve 27 Open / close Valve 28 Shut-off valve 30 First medium circulation line 31 Second medium circulation line 32 Screw 33 Recess 34, 35 O-ring 36 Axial protrusion 38 Hollow cylindrical portion 40 Accumulator 44 Medium reservoir 45 Medium pressure pump 47 Pressure adjustment valve 48 Pressure detection 51 Pressure detector 53 Pressure detector 58 Power supply 61 Power failure detector 62 Sys System controller

Claims (6)

A sealing system for sealing a rotary shaft of a centrifugal pump,
A double mechanical seal having a pump-side seal mechanism and an atmosphere-side seal mechanism;
A pump mechanism disposed between the pump-side seal mechanism and the atmosphere-side seal mechanism and driven by the rotating shaft;
A first chamber defined by at least the atmosphere-side sealing mechanism and the pump mechanism;
A second chamber defined by at least the pump-side seal mechanism and the pump mechanism;
A first medium circulation line that is connected to the first chamber and the second chamber and circulates between the first chamber and the second chamber with a fluid barrier / cooling medium that is different from a handling fluid of the centrifugal pump; ,
A heat exchanger and a shut-off valve attached to the first medium circulation line;
The second medium circulation line having both ends connected to the first medium circulation line and bypassing the shutoff valve;
A seal system comprising a medium pressurizing pump and an on-off valve attached to the second medium circulation line. A seal housing that houses the double mechanical seal;
The seal system according to claim 1, wherein the first medium circulation line and the second medium circulation line are disposed outside the seal housing. A power failure detector for detecting a power failure of the centrifugal pump;
The system controller according to claim 1, further comprising a system controller that receives a power failure detection signal output from the power failure detector, closes the shut-off valve, opens the on-off valve, and starts the medium pressurizing pump. The sealing system described in. A first connection point at which one end of the second medium circulation line is connected to the first medium circulation line is located between the shut-off valve and the heat exchanger;
The second connection point where the other end of the second medium circulation line is connected to the first medium circulation line is located between the shut-off valve and the second chamber. The sealing system as described in any one of thru | or 3. A power source for supplying power to the medium pressurizing pump;
The seal system according to claim 1, wherein the medium pressurizing pump includes an electric motor as a prime mover.   The seal system according to any one of claims 1 to 5, wherein the fluid barrier / cooling medium is oil, and the pressurized medium pump is an oil pump.

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