JP2005315121A - Shaft seal structure for axial flow pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaft seal structure for an axial flow pump, capable of preventing dry sliding of shaft seal devices at both ends of a shaft to which an impeller rotated in both normal and reverse directions and capable of inverting a transport direction of liquid to be transported is fixed. <P>SOLUTION: The axial flow pump 1 is provided with the impeller 9 rotated in both normal and reverse directions and capable of inverting the transport direction of the liquid to be transported; the shaft 11 in which the impeller 9 is fixed to the middle and of which both ends are protruded out of a casing 3; and the shaft seal devices 15A, 15B for sealing the protruded portions of the shaft 11. A shaft seal device mounting pipe 13A in the inner side of the shaft seal device 15A is connected with a section 7B of the casing 3 in the opposite side to the shaft seal device 15A sandwiching the impeller 9, by means of a connecting pipe 19A, and a shaft seal device mounting pipe 13B in the inner side of the shaft seal device 15B is connected with a section 7A of the casing 3 in the opposite side to the shaft seal device 15B sandwiching the impeller 9, by means of a connecting pipe 19B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a shaft sealing structure of an axial flow pump in which an impeller can rotate in both forward and reverse directions to reverse the transport direction of a liquid to be fed.

A pump is used for transporting the liquid. When the transport direction of the liquid to be transported is reversed, the transport direction of the pump is changed by valve control to reverse the transport direction.
However, in order to change the structure of the transport pipeline of the pump by valve control, it is necessary to arrange many valves and pipes around the pump, and the structure of the pipe and a series of controls are complicated. .
In order to cope with such a problem, an axial flow pump is proposed in which an impeller is rotatable in both forward and reverse directions, and has two suction discharge ports capable of switching between suction and discharge of a liquid to be fed according to the rotation direction of the impeller. (See Patent Document 1). Such an axial flow pump is shown in FIGS.

  The axial flow pump 1 includes a tubular casing 3, an impeller 9 that can rotate in both forward and reverse directions within the casing 3, a shaft 11 with the impeller 9 fixed in the middle, two suction discharge ports 5A at both ends of the casing 3, 5B, provided with a drive device (not shown) for rotating the shaft 11 in both forward and reverse directions. Both ends of the shaft 11 pass through two shaft seal device attachment pipes 13 formed in the casing 3 and protrude to the outside, and are supported by bearings 17. A shaft seal device 15 attached to the end of the shaft seal device mounting tube 13 seals between the protruding portion of the shaft 11 and the casing 3. The shaft seal device 15 often uses a non-poured water mechanical seal.

  In the axial flow pump 1, when the impeller 9 rotates in the forward direction, the liquid to be fed is sucked from the suction / discharge port 5A, boosted in the casing 3, and discharged from the suction / discharge port 5B. When the impeller 9 rotates in the reverse direction, the transport direction of the liquid to be fed is reversed, and the liquid to be fed is sucked from the suction / discharge port 5B, pressurized in the casing 3, and discharged from the suction / discharge port 5A. A part of the liquid to be fed flowing in the casing 3 flows into the shaft seal device mounting pipe 13. The liquid to be fed which has flowed into the shaft seal device attachment tube 13 flows around the rotating shaft 11 while drawing a vortex. In the axial flow pump 1 that is transporting the liquid to be fed, the upstream side of the impeller 9 has a low pressure, and the downstream side of the impeller 9 has a high pressure.

Moreover, the liquid to be transported transported by the axial flow pump 1 may contain gas. Examples of the gas contained in the liquid to be delivered include gas originally contained in the liquid, air remaining in the piping of the axial flow pump 1, and some gas that has been accidentally mixed.
JP 2002-188598 A

When the axial flow pump 1 transports a liquid to be fed containing gas such as sludge in a sewage treatment plant, the gas flows in a vortex around the shaft 11 together with the liquid to be fed in the shaft seal device mounting pipe 13. In the shaft seal device mounting pipe 13 on the upstream side of the impeller 9 that is low pressure, gas tends to collect on the outer periphery of the shaft 11. If gas collects on the outer periphery of the shaft 11, the sliding surface of the shaft seal device 15 tends to be dry sliding, which causes damage to the shaft seal device 15. Moreover, since the axial flow pump 1 can reverse the transport direction of the liquid to be fed, the shaft sealing devices 15 at both end portions of the shaft 11 are liable to be damaged due to dry sliding. If the shaft seal device 15 is damaged, the liquid to be delivered leaks from the shaft seal device attachment tube 13.
The present invention solves the above problem, and an object of the present invention is to provide a shaft that protrudes outside the casing in an axial pump that can reverse the transport direction of the liquid to be fed by rotating the impeller in both forward and reverse directions. It is to provide a shaft seal structure of an axial flow pump capable of preventing the shaft seal devices at the protruding portions at both ends from being dry-sliding.

  The present invention adopts the following configuration in order to solve the problem. The shaft seal structure of the axial flow pump according to the present invention includes an impeller that can rotate in both forward and reverse directions in a casing to reverse the transport direction of the liquid to be fed, and one that sucks the liquid to be fed according to the direction of rotation of the impeller In an axial flow pump comprising two suction discharge ports for discharging, a shaft having an impeller fixed in the middle and projecting both ends projecting out of the casing, and a shaft seal device for sealing the projecting portion of the shaft, And a connecting pipe for mutually connecting the casing located on the opposite side of the shaft seal device with the impeller interposed therebetween.

  According to the present invention, the liquid to be fed is pressurized by the impeller rotating by the axial flow pump, and the upstream side of the impeller has a low pressure and the downstream side has a high pressure. Therefore, the inner side of the shaft seal device and the casing located on the opposite side of the shaft seal device with the impeller interposed therebetween are low pressure and the other is high pressure, and the liquid to be fed through the connecting pipe from the high pressure side to the low pressure side. Flows. The flow of the liquid to be fed from the high pressure side to the low pressure side prevents gas from collecting on the outer periphery of the shaft in the vicinity of the shaft seal device, thereby preventing dry sliding of the shaft seal device. Regardless of the transport direction of the liquid to be transported, the liquid to be transported that passes through the connecting pipe flows inside the shaft seal device and pushes the gas from the outer periphery of the shaft in the vicinity of the shaft seal device. Movement is prevented.

  Since the present invention has the shaft seal structure of the axial flow pump as described above, dry sliding of the shaft seal device of the axial flow pump is prevented even when the liquid to be fed contains gas.

  The best mode for carrying out the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of a digestion tank in a sewage treatment plant, FIG. 1 (i) is a longitudinal sectional view of the digestion tank, FIG. 1 (ii) is a cross-sectional view taken along line AA in FIG. FIG. 3 is a top view of an axial flow pump having a shaft sealing structure according to the present invention, FIG. 3 is a side view of an axial flow pump having a shaft sealing structure according to the present invention, and FIG. 4 is an axial flow for transporting a liquid to be fed in the positive direction. FIG. 4 (i) is an explanatory view of the flow of the liquid to be fed in the forward direction in the digestion tank, FIG. 4 (ii) is an explanatory view of the flow of the liquid to be fed in the forward direction in the axial flow pump, FIG. 5 is a state diagram of the axial flow pump for transporting the liquid to be fed in the reverse direction, FIG. 5 (i) is an explanatory view of the flow of the liquid to be fed in the reverse direction in the digester, and FIG. 5 (ii) is the axial flow. It is explanatory drawing of the flow of the to-be-delivered liquid of the reverse direction in a pump.

A digestion tank 21 shown in FIGS. 1 (i) and (ii) is installed in a sewage treatment plant, and sludge containing gas is stored in the digestion tank 21, and this sludge is stored in an axial flow pump 1 described later. It is a liquid to be delivered.
Two pipes 23A and 23B are inserted into the digestion tank 21 from the outside, one end of the pipe 23A opens slightly below the sludge liquid level in the digestion tank 21, and the other end of the pipe 23A is an axial flow pump. 1 is connected to the suction / discharge port 5A, one end of the pipe 23B opens slightly above the bottom surface of the digestion tank 21, and the other end of the pipe 23B is connected to the suction / discharge port 5B of the axial flow pump 1. .

As shown in FIGS. 2 and 3, the axial flow pump 1 includes a tubular casing 3, an impeller 9 that can rotate in both forward and reverse directions in the casing 3, a shaft 11 in which the impeller 9 is fixed in the middle, and a casing 3. Two suction / discharge ports 5A and 5B at both ends and a drive device (not shown) for rotating the shaft 11 in both forward and reverse directions are provided.
A shaft seal device mounting tube 13A is formed in a section 7A between the suction / discharge port 5A and the impeller 9 of the casing 3, and a shaft seal device mounting tube is formed in the section 7B between the suction / discharge port 5B and the impeller 9. 13B is formed. One end of the shaft 11 passes through the shaft seal device mounting tube 13A and protrudes outside the casing 3, and the other end also passes through the shaft seal device mounting tube 13B and protrudes outside the casing 3, and is supported by the bearings 17 respectively. Yes. A shaft sealing device 15A is attached to the end of the shaft sealing device mounting tube 13A, a shaft sealing device 15B is attached to the end of the shaft sealing device mounting tube 13B, and the shaft sealing devices 15A and 15B are connected to the shaft 11. The space between the protruding portion and the casing 3 is sealed. The shaft seal devices 15A and 15B are non-poured water mechanical seals.

The shaft seal device mounting tube 13A located inside the shaft seal device 15A and the section 7B of the casing 3 are connected by a connecting tube 19A, and the shaft seal device mounting tube 13B located inside the shaft seal device 15B. The section 7A of the casing 3 is connected by a connecting pipe 19B.
When the impeller 9 rotates in the forward direction, the axial flow pump 1 discharges the liquid to be delivered sucked from the suction / discharge port 5A from the suction / discharge port 5B, and when the impeller 9 rotates in the reverse direction, it sucks from the suction / discharge port 5B. The delivered liquid is discharged from the suction discharge port 5A so that the sludge in the digestion tank 21 can be stirred.

Next, the operation will be described.
First, the case where the impeller 9 of the axial flow pump 1 rotates in the forward direction will be described with reference to FIGS. 4 (i) and (ii). When the impeller 9 rotates in the forward direction in the casing 3, sludge above the digestion tank 21 is sucked into the pipe 23A and flows into the section 7A of the casing 3 through the suction discharge port 5A. The sludge that flows into the section 7A is increased in pressure by the impeller 9 and becomes a high pressure, flows into the section 7B, is discharged from the section 7B to the pipe 23B through the suction discharge port 5B, and is discharged from the pipe 23B to the lower side of the digestion tank 21. The Initially, a part of the sludge that flows into the section 7A flows into the shaft seal device mounting pipe 13A, and a part of the sludge that flows into the section 7B flows into the shaft seal device mounting pipe 13B. The section 7A located on the upstream side of the impeller 9 and the shaft seal device mounting pipe 13A are low pressure, and the section 7B located on the downstream side of the impeller 9 and the shaft seal device mounting pipe 13B are high pressure.

  Since the connecting pipe 19A connects the shaft seal device mounting tube 13A and the section 7B, the high-pressure sludge in the section 7B flows into the shaft seal device mounting pipe 13A through the connecting pipe 19A. It flows out from the sealing device attachment tube 13A to the section 7A. Even if the gas contained in the sludge is collected on the outer periphery of the shaft 11 rotated by the shaft seal device mounting pipe 13A, the gas flows into the section 7A together with the sludge flowing out from the shaft seal device mounting pipe 13A to the section 7A. The gas does not collect on the outer periphery of the shaft 11 of the shaft seal device attachment tube 13A.

  Since the connecting pipe 19B connects the shaft seal device mounting pipe 13B and the section 7A, the high-pressure sludge in the shaft seal device mounting pipe 13B flows out into the section 7A through the connecting pipe 19B, and the section 7B. The sludge flows into the shaft seal device attachment pipe 13B. Even if the gas contained in the sludge is about to collect on the outer periphery of the shaft 11 rotated by the shaft seal device attachment pipe 13B, the gas is separated from the shaft seal device attachment pipe 13B through the connecting pipe 19B and into the section 7A. 7A will not flow out and gas will not collect on the outer periphery of the shaft 11 of the shaft seal device attachment tube 13B.

  Therefore, when the impeller 9 rotates in the forward direction, a sludge flow from the shaft seal device mounting tube 13A to the section 7A and a sludge flow from the shaft seal device mounting tube 13B to the section 7A are formed. The sludge flow prevents the gas from collecting on the outer periphery of the shaft 11 by the shaft seal device mounting pipes 13A and 13B, and also prevents the shaft seal devices 15A and 15B from becoming dry sliding.

  Next, the case where the impeller 9 of the axial flow pump 1 rotates in the reverse direction will be described with reference to FIGS. 5 (i) and (ii). When the impeller 9 rotates in the reverse direction in the casing 3, sludge below the digestion tank 21 flows into the section 7B of the casing 3 from the pipe 23B through the suction / discharge port 5B, and is pressurized by the impeller 9 to the section 7A. It flows in and is discharged from the pipe 23A to the upper side of the digestion tank 21 through the suction discharge port 5A. First, a part of the sludge flows from the section 7B into the shaft seal device mounting pipe 13B, and flows from the section 7A into the shaft seal device mounting pipe 13A. The section 7B on the upstream side of the impeller 9 and the shaft seal device mounting pipe 13B are at low pressure, and the section 7A on the downstream side of the impeller 9 and the shaft seal device mounting pipe 13A are at high pressure.

  The connecting pipe 19B connects the shaft seal device mounting pipe 13B and the section 7A, and high-pressure sludge flows from the section 7A through the connecting pipe 19B into the shaft seal device mounting pipe 13B, and further into the section 7B. leak. The connecting pipe 19A connects the shaft seal device mounting pipe 13A and the section 7B, and the high-pressure sludge flows out from the shaft seal device mounting pipe 13A through the connecting pipe 19A and into the section 7B. Sludge flows into the shaft seal device attachment tube 13A.

Even if the gas contained in the sludge is collected on the outer periphery of the shaft 11 rotated by the shaft seal device mounting pipes 13A and 13B, the gas flows along with the sludge flowing through the shaft seal device mounting tubes 13A and 13B. Gas does not collect on the outer periphery of the shaft 11 of the apparatus mounting pipes 13A and 13B.
Therefore, when the impeller 9 rotates in the reverse direction, a flow of sludge that passes through the shaft seal attachment tubes 13A and 13B is formed, and the flow of these sludge pushes gas from the shaft seal attachment tubes 13A and 13B, and the shaft seal. Dry sliding of the devices 15A and 15B is prevented.

It is a block diagram of the digester tank of a sewage treatment plant, FIG.1 (i) is a longitudinal cross-sectional view of a digester tank, FIG.1 (ii) is an AA line cross-sectional view of FIG.1 (i). It is a top view of an axial flow pump provided with the shaft seal structure concerning the present invention. It is a side view of an axial flow pump provided with a shaft seal structure concerning the present invention. FIG. 4 (i) is an explanatory diagram of the flow of the liquid to be fed in the positive direction in the digestion tank, and FIG. 4 (ii) is a diagram of the positive flow in the axial flow pump. It is explanatory drawing of the flow of the to-be-delivered liquid of a direction. FIG. 5 (i) is an explanatory view of the flow of the liquid to be fed in the reverse direction in the digestion tank, and FIG. 5 (ii) is the reverse diagram of the axial flow pump. It is explanatory drawing of the flow of the to-be-delivered liquid of a direction. It is a top view of a conventional axial flow pump. It is a side view of a conventional axial flow pump.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Axial flow pump 3 Casing 5A, 5B Suction discharge port 7A, 7B Section 9 Impeller 11 Shaft 13A, 13B Shaft seal attachment pipe 15A, 15B Shaft seal 17A, 17B Bearing 19A, 19B Connecting pipe 21 Digestion tank 23A, 23B Pipe

Claims (1)

An impeller that can rotate in both forward and reverse directions in the casing and reverse the transport direction of the liquid to be transported, two suction discharge ports that one sucks the liquid to be transported according to the rotation direction of the impeller, and the other, and an impeller that is fixed in the middle In an axial flow pump comprising: a shaft whose both ends protrude outside the casing; and a shaft seal device that seals a protruding portion of the shaft.
A shaft seal structure for an axial flow pump, comprising a connecting pipe that connects the inside of the shaft seal device and a casing located on the opposite side of the shaft seal device with an impeller interposed therebetween.

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