JP2004251376A - End face contact type mechanical seal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an end face contact type mechanical seal having a long-time good shaft sealing function in rotary equipment such as a preceding stand-by operation type pump for submerged or aerial operation while effectively suppressing the heating of sealing rings even in aerial operation. <P>SOLUTION: The end face contact type mechanical seal has the first sealing ring 9 and the second sealing ring 10 relatively rotated in slide contact. The first sealing ring 9 is formed of a self-lubricating material and a ring surface 10a as the end face of the second sealing ring 10, with which the first sealing ring 9 has slide contact, is formed of a porous film 101 having a porosity of 4-20% which is formed of a material harder than the material for the first sealing ring 9 and whose pores have average diameters of 10-60 μm and communicate with each other. The porous film 101 is a chrome oxide film flame sprayed and a body portion 102 of the second sealing ring 10 excluding the porous film 101 is formed of titanium. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an end face contact type mechanical seal suitably used as a shaft sealing means in a rotary device such as a preceding standby operation type pump which may perform an in-air operation for a considerable time in addition to sealing a liquid. It is.
[0002]
[Prior art]
Generally, a mechanical seal used as a shaft sealing means of a rotating device has an end surface contact type configured to rotate relatively in a state where two sealing rings are in contact with each other, and a mechanical pressure or a dynamic pressure or two sealing rings therebetween. It is roughly classified into a non-contact type that is configured to rotate relatively in a non-contact state by generating static pressure.However, mainly, an end face contact where a sealing ring is in contact and liquid lubrication is required Non-contact type mechanical seals are used for rotating equipment that handles liquids such as pumps, and do not require lubrication between sealing rings because they are in non-contact state. Used for rotating equipment.
[0003]
By the way, depending on the application and use conditions of the rotating device, the case where the seal ring is operated without contacting the liquid while handling the liquid, or the case where it is necessary to seal the liquid while handling the gas There is. For example, in a preceding standby operation type pump such as a rainwater drainage pump, the pump shaft is driven in advance before starting pumping (precedence standby operation). It is in a state. In addition, even if the pump does not perform the preliminary standby operation, the pump may be operated in a state where the in-machine liquid region has a negative pressure (the outside air region has a higher pressure than the in-machine liquid) depending on its structure (impeller position, etc.) and use conditions. In such a case, the sealing ring is in a dry state.
[0004]
[Problems to be solved by the invention]
Therefore, the rotation of the preceding standby operation type pump or the like in which the submerged operation (when the sealing ring is in the liquid contact state) and the air operation (when the gas is sealed or the sealing ring is in the dry state) is performed as described above. Regardless of whether the mechanical seal of the end face contact type or the non-contact type is used as the shaft sealing means in the device, there are problems as described below, and it is a fact that it is difficult to take countermeasures.
[0005]
That is, when a non-contact type mechanical seal is used, since the space between the sealing rings is in a non-contact state, the leakage during the operation in the liquid is increased (for example, in a pump which allows a certain amount of leakage). However, the leakage exceeds the allowable range), and a good sealing function cannot be exhibited. Therefore, non-contact type mechanical seals are not preferable to be used for rotating equipment that handles liquids such as pumps, even if they require or must be operated in the air. In general, it is not practically used as a shaft sealing means for a pump or the like.
[0006]
On the other hand, when the end-face contact type mechanical seal is used, the seal ring is not lubricated during operation in the air, so that the seal ring may be abnormally worn or may be thermally damaged (heat cracked) due to heat generated by the seal ring. Therefore, a good sealing function cannot be exhibited for a long time, and there is a problem in durability. Traditionally, to solve this problem,
(A) One of the sealing rings is made of a material having a high self-lubricating property (self-lubricating material) such as carbon;
(B) reducing the contact pressure between the sealing rings by the spring (reducing the spring load);
(C) injecting water into the contact portion of the sealing ring;
However, none of them are effective solutions.
[0007]
That is, in the case of (A), although the heat generation of the sealing rings can be suppressed to some extent as compared with the case where both sealing rings are made of silicon carbide or the like having no self-lubricating property, the above-described problem occurs. The heat generation of the sealing ring cannot be suppressed to such an extent that the aerial operation can be performed without any problem. (Even if the sealing ring is made of carbon and silicon carbide, which is the best combination as the sealing ring material, the sealing ring slides. The moving surface rises to nearly 200 ° C.). Further, in the case of (B), the followability of the sealing ring is reduced or the contact pressure of the sealing ring is insufficient, which may cause a large amount of leakage. Therefore, even if heat generation of the provisional sealing ring can be suppressed. A good sealing function cannot be exhibited, and it cannot be used at all. On the other hand, in the case of (C), the liquid lubrication of the sealing ring can be effectively performed even in the air operation, and the heat generation of the sealing ring can be sufficiently suppressed. The initial cost and the running cost are increased, which is not practical in terms of cost. Further, the reliability of the mechanical seal is poor, for example, the failure of the water injection equipment is directly linked to the damage of the mechanical seal (heat loss of the sealing ring, etc.).
[0008]
The present invention has been made in view of such a point, and does not require a special mechanical seal structure as in (B) and requires special auxiliary equipment (water injection equipment) as in (C). Without any problem, the heat generated by the sealing ring can be effectively suppressed even in the aerial operation. It is an object of the present invention to provide an end face contact type mechanical seal capable of exhibiting a function.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an end face contact type mechanical seal configured to make the first sealing ring and the second sealing ring relatively slidably contact with each other. The first sealing ring is made of a porous film made of a material harder than the constituent material of the first sealing ring. The present invention proposes that a porous membrane having a porosity of 4 to 20% (more preferably 8 to 12%) in which pores of 60 μm (more preferably 15 to 40 μm) communicate with each other is provided. The porosity was determined according to JIS R7212 6.1.5.
[0010]
Thus, the end face contact type mechanical seal having the above-mentioned structure has a fluid to be sealed, which is an inner and outer peripheral area of the relative rotating portion, due to the relative rotational sliding action of the sealing end faces (sliding faces) which are the opposite end faces of the two sealing rings. This seals and seals between a region (inside the rotating device) and a non-sealed fluid region (outside the rotating device, generally an atmospheric region). However, there is a rotating device equipped with the mechanical seal. When operated in air (for example, when both sealed fluid regions are gas regions, the unsealed fluid region is a liquid region, but the sealed fluid region is a gas region having a higher pressure than the unsealed fluid region, or In the case where the sealed fluid region is at a negative pressure (the non-sealed fluid region is in the atmosphere region), the sealed end face slides dry, but the functions (1) to (3) described below are mainly exhibited. To be sealed And obtained by reducing the frictional resistance to the temperature rise of the surface as much as possible, capable of exhibiting good sealing function (shaft sealing function).
[0011]
(1) Sliding resistance reduction function
The sealing end face of the first sealing ring (hereinafter referred to as “first sealing end face”) is made of a self-lubricating material having low friction, and the sealing end face of the second sealing ring (hereinafter referred to as “second sealing end face”). ) Is formed of a porous film having a small contact area with the mating sealing end face (first sealing end face). The sliding resistance between the two sealing end faces is smaller than that in the case where one of the sealing rings is made of a self-lubricating material as described in (A).
[0012]
(2) Heat dissipation function
Since the second sealed end face is formed of a porous membrane having pores communicating with each other (hereinafter, referred to as “open pores”) instead of mutually independent pores (hereinafter, referred to as “independent pores”), the two sealed end faces are formed. The heat (sliding heat) generated between them causes rapid discharge (radiation) from the continuous ventilation hole. That is, in the case of independent pores, the air in the independent pores functions as a heat insulating layer and hinders heat radiation from the sealed end face. Since a series of communication passages extending to the outside of the sealing end face are formed, the air in the communication vent hole is caused to flow to a portion not closed by the mating sealing end face (first sealing end face) by thermal expansion due to sliding heat. Will be. That is, an airflow is formed in the communication passage toward the outside of the sealed end face. Such an air flow is also generated by the pressure difference during the in-air operation in which a pressure difference occurs between the sealed fluid region and the unsealed fluid region. In addition, such a differential pressure naturally occurs in a normal air operation for sealing a gas (the sealed fluid region is a gas region having a higher pressure than the unsealed fluid region), but also in a liquid operation for sealing a liquid, When the sealed fluid region (liquid region) has a negative pressure (for example, when the inside of the pump casing is not yet filled with water during the operation of the pump), a dry sliding state occurs in which the differential pressure is generated (the present invention). In this case, such a state is not a submerged operation but an aerial operation. Further, for example, in the aerial operation performed prior to pumping in the preparatory standby operation type pump, since the in-machine region (in the pump casing) is at atmospheric pressure, both sealed fluid regions are at atmospheric pressure, and the differential pressure is generated. Absent.
[0013]
(3) Wear powder discharge function
Since the porous film constituting the second sealed end face is harder than the constituent material (self-lubricating material) of the first sealed end face, the wear due to sliding of the sealed end face occurs exclusively at the first sealed end face. The abrasion powder is quickly discharged from between the sealing end faces with the relative movement (relative rotation) of the second sealing end face (the surface of the porous membrane), which is the uneven surface, with respect to the first sealing end face. Therefore, there is no occurrence of abnormal wear due to the relative rotation sliding contact between the sealing end faces with the wear powder interposed therebetween, and the wear powder does not adhere and accumulate between the sealing end faces and burn.
[0014]
On the other hand, when the rotating device is operated in liquid (for example, when both sealed fluid regions are liquid regions, the unsealed fluid region is a gas region, but the sealed fluid region is a liquid having a higher pressure than the unsealed fluid region. In the case where the sealed end surface is a liquid region, or the unsealed fluid region is a liquid region, and the sealed fluid region has a lower pressure than the unsealed fluid region due to pressure fluctuation, the sealed end face is in a liquid contact state and the gap between the sealed end faces is Since it is liquid lubricated, a good sealing end face sealing function is exhibited as in a general end face contact type mechanical seal in which the second sealing end face is not formed of a porous film. That is, since the second sealed end face is formed of the porous film having the communicating holes, the liquid to be sealed leaks from the communicating holes, but such leakage is caused by the average pore diameter and the pore size of the porous film. By setting the rate in a predetermined range as described later, the rate can be kept within an allowable range, and a large amount of leakage unlike the case where a non-contact type mechanical seal is used does not occur. The lubricating property of the sealing end face by the liquid is greatly improved by the liquid holding function (a kind of oil pot function) by the concave portions (pores) on the surface of the porous film.
[0015]
By the way, when the average pore diameter of the porous membrane is less than 10 μm or the porosity is less than 4%, the heat radiation function of (2) is not sufficiently exhibited, and the contact area with the first sealed end face is not increased. Is not so much reduced as compared with the case where the second sealing end face is not made of a porous structure, and even if the first sealing ring is made of a self-lubricating material, the function (1) of reducing the sliding resistance is not sufficiently exhibited. Further, when the average pore diameter is less than 10 μm, the function of (3) for discharging abrasion powder is not sufficiently performed. In particular, the functions (1) and (2) are more effectively exhibited when the average pore diameter is 15 μm or more, and the functions (1) and (2) are more effective when the porosity is 8% or more. It is exhibited in.
[0016]
Further, when the average pore diameter exceeds 60 μm or when the porosity exceeds 20%, the strength of the porous membrane is reduced, and leakage from the communication passages (communication holes group) increases, and Good sealing function during operation cannot be expected. Further, when the average pore diameter exceeds 60 μm, the wear powder on the first sealing end surface easily enters the pores, and the function (3) of discharging the wear powder is not exhibited. In particular, considering the function of maintaining the strength of the porous film and the function of discharging abrasion powder, it is more preferable to set the average pore diameter to 40 μm or less and the porosity to 12% or less.
[0017]
In the present invention, for the above reasons, the average pore diameter of the porous membrane is set to 10 to 60 μm (more preferably, 15 to 40 μm), and the porosity of the porous membrane is set to 4 to 20% (more preferably, 8 to 12%). ). In addition, the thickness of the porous film does not hinder each function exhibited by setting the average pore diameter and the porosity within the above ranges, and the base material (the main body of the second sealing ring excluding the porous film) It is set appropriately on condition that a predetermined strength can be secured without easily peeling off from (part), but it is generally preferably 0.2 to 1.0 mm.
[0018]
As the constituent material of the first sealing ring, a material having a high self-lubricating property such as carbon or fluororesin is selected. In general, it is preferable to use carbon in combination with a sprayed film described later. Further, the porous film is generally formed by spraying a material (sprayed material) harder than a self-lubricating material such as carbon on the main body portion of the second sealing ring (the second sealing ring portion excluding the porous film). However, the thermal spraying method is preferably plasma spraying in order to obtain a thermal sprayed film (porous film) having the above-described properties. Chromium oxide, alumina, tungsten carbide, zirconia, or the like is used as the thermal spraying material (a constituent material of the porous film), and the thermal spraying film (porous film) of the continuous vent can be easily formed. In light of this, it is generally preferred to use chromium oxide. In addition, as a constituent material (base material) of the main body portion of the second sealing ring, the main body portion is a portion that does not directly affect the sealing function, so that any material that can form a sprayed film that does not easily peel off may be used. Although there is no particular limitation, it is preferable to use a metal material having high thermal conductivity in order to enhance the heat dissipation of the sealing ring. In addition, it is preferable to use a metal material also from the viewpoint of ease of processing of the second sealing ring (especially, when the second sealing ring has a divided structure divided in the circumferential direction, in the case of silicon carbide, etc. Although it is difficult to form a structure, a metal material can be easily formed into such a divided structure, and a complicated sealed ring shape can be easily obtained.) As the metal material constituting the main body, for example, titanium, Hastelloy, stainless steel, copper alloy, etc. can be used. In particular, when the porous film is a chromium oxide sprayed film (plasma sprayed film). It is preferable to use titanium, which has a small thermal expansion difference (linear expansion coefficient difference) from the porous film and hardly peels off the porous film.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration of the present invention will be specifically described based on the embodiments shown in FIGS.
[0020]
FIG. 1 shows an example of a vertical mixed-flow pump (preceding standby type pump) 1 such as an irrigation pump that is operated in a standby mode. The pump 1 has a discharge elbow (discharge port) 2a and a suction port at upper and lower ends. A vertically long pump casing 2 having a bell (suction port) 2b, and a pump casing 2 extending upward from a portion near the top of the suction bell 2b through the center of the pump casing 2 and A pump shaft 4 connected to the prime mover 3 installed, an impeller 5 provided at a lower end of the pump shaft 4 disposed near the upper part of the suction bell 2b, and a pump shaft 4 provided at a peripheral wall portion of the discharge elbow 2a. Is provided with an end face contact type mechanical seal 6 which is a shaft sealing device interposed between a cylindrical shaft sealing portion 2 c penetrating through the pump shaft 4.
[0021]
According to the present invention, the end face contact type mechanical seal 6 is configured as shown in FIGS. 2 to 4 or 4 to 7. Hereinafter, the end face contact type mechanical seal 6 according to the present invention shown in FIGS. 2 to 4 is referred to as a “first seal 6a”, and the end face contact type mechanical seal 6 according to the present invention shown in FIGS. Seal 6b ". Further, in the following description, each component means a component of both seals 6a and 6b unless otherwise specified.
[0022]
As shown in FIG. 2 to FIG. 4 or FIG. 4 to FIG. 7, each of the seals 6 a and 6 b includes a seal case 7 attached to a shaft sealing portion 2 c which is a portion through which a rotary shaft of the pump casing 2 passes, and a spring retainer attached to the seal case 7. A stationary seal ring 9 as a first seal ring held movably in the axial direction (up and down direction) and relatively non-rotatable via the pump 8 and a pump shaft 4 disposed above the stationary seal ring 9 and serving as a rotary shaft. The rotating seal ring 10 as a fixed second seal ring, and the seal case 7 and the spring retainer 8 are interposed between the seal case 7 and the spring retainer 8 to urge the stationary seal ring 9 upward to press and contact the rotary seal ring 10. An inner peripheral area of the relative rotary sliding contact portion provided with the spring 11 by the relative rotary sliding contact action of the first and second sealed end surfaces 9a, 10a as sliding surfaces of the sealing rings 9, 10. Sealed fluid area (pump casing The communicating area) S and the non-sealed fluid region (atmospheric region outside the pump casing 2) A which is the outer peripheral side region is configured to shield sealed within 2.
[0023]
As shown in FIG. 2 or FIG. 5, the seal case 7 is an annular body having an L-shaped cross section having an inner peripheral portion having a larger diameter than the pump shaft 4. It is attached to the upper end of the sealing portion 2c via an O-ring 12.
[0024]
The spring retainer 8 includes a retainer main body 8a and a pressing body 8b as shown in FIG. 2 or FIG. The retainer main body 8a is inserted and held in the inner peripheral portion of the seal case 7 via an O-ring 13 so as to be movable in the vertical direction, and rotates relative to the seal case 7 by a drive pin 14 protruding from the seal case 7. It is blocked by the engagement action. The pressing body 8b is an annular body attached to the upper end of the retainer main body 8a by an appropriate number of bolts 15 (only one is shown), and has an inner peripheral surface formed as a conical cam surface with a constricted lower surface. .
[0025]
As shown in FIGS. 2 to 4 or FIGS. 4 to 6, the stationary sealing ring 9 is an annular body divided into two parts in the circumferential direction. The circumferential end faces 9b, 9b are fixed to the spring retainer 8 in a form (annular form) in which they abut. Tightening of the stationary sealing ring 9 and fixing of the stationary sealing ring 9 to the spring retainer 8 are performed by tightening the pressing body 8b to the retainer main body 8a with bolts 14. By removing the bolt 14, the stationary sealing ring 9 can be easily attached and detached. It has become. The stationary sealing ring 9 is made of a self-lubricating material such as carbon, and its upper end surface (the tip end surface of the annular portion 9b projecting upward from the pressing body 8b) is smooth and perpendicular to the axis. It is formed on the first sealed end surface 9a which is an annular surface. An O-ring 16 for secondary sealing between the retainer body 8a and the stationary sealing ring 9 is engaged and held at the upper end of the retainer body 8a. As shown in FIG. 2 or FIG. 5, a cylindrical vapor leakage diffusion preventing body 26 surrounding the outer peripheral portions of both sealing end faces 9a and 10a is attached to the pressing body 8b.
[0026]
As shown in FIG. 2, the rotary seal ring 10 of the first seal 6a is an annular body having a non-divided structure, and is fixed and held on the pump shaft 4 via a fixing ring 17 and a retainer 18. The fixing ring 17 is divided into two parts in the circumferential direction. The fixing ring 17 is fastened in a ring shape to hold the pump shaft 4 and is detachably fixed to the pump shaft 4 by tightening a fixing screw 19. The retainer 18 is fixed to the pump shaft 4 by fittingly holding the pump shaft 4 via an O-ring 20 and engaging an engaging pin 21 provided on the fixing ring 17. The rotary seal ring 10 is fitted to and held by annular recesses formed at the lower end portion of the retainer 18 via O-rings 22 and 23, and is engaged with an engagement pin 24 provided on the retainer 18 so that the rotary seal ring 10 Fixedly held.
[0027]
As shown in FIGS. 5 and 7, the rotary seal ring 10 of the second seal 6b is an annular body divided into two in the circumferential direction similarly to the stationary seal ring 9, and the divided portions 10b, 10b are bolted by bolts 10d. The split end faces 10c, 10c are fixed to the pump shaft 4 by being fastened to abut against each other and connected to the fixing ring 17a. As shown in FIG. 5, the fixing ring 17a is disposed above the rotary seal ring 10 and is fixed to the pump shaft 4. The drive pin 21a provided on the fixed ring 17a allows the pump shaft 4 of the rotary seal ring 10 to be fixed. Fixed (prevention of relative rotation). The fixing ring 17a is, similarly to the fixing ring 17 of the first seal 6a, divided into two in the circumferential direction. The divided portion is fastened to a ring shape holding the pump shaft 4 and the fixing screw 19a is fastened. Thereby, it is detachably fixed to the pump shaft 4. Further, an O-ring 20 a for secondary sealing between the rotary shaft 10 and the pump shaft 4 is provided on the inner peripheral portion of the rotary seal ring 10.
[0028]
As shown in FIGS. 2 and 3 or FIGS. 5 and 6, the rotary sealing ring 10 is a smooth annular surface orthogonal to the axis at the lower end surface thereof, and the first sealing end surface 9a is in sliding contact with the second sealing surface. The sealing end face 10a is formed, and the second sealing end face 10a is formed of a porous film 101 that is harder than the constituent material (self-lubricating material such as carbon) of the stationary sealing ring 9, and the porous film 101 The main body portion 102 of the second sealing ring 10 except for the above is made of a metal material such as titanium.
[0029]
The porous film 101 is formed by spraying (preferably, plasma spraying) chromium oxide or the like on a concave portion (which has been subjected to serration processing) formed on the lower end surface of the main body portion 102. The porous membrane 101 has pores (communication pores) communicating with each other. As described above, the average pore diameter, the porosity, and the film thickness of the membrane 101 are each 10 to 60 μm (more preferably, 15 to 60 μm). ４０40 μm), 4 to 20% (more preferably 8 to 12%) and 0.2 to 1.0 mm. In addition, as shown in FIG. 3 or FIG. 6, the porous film 101 is formed so as to slightly protrude from the inner and outer edges of the first sealed end face 9a in the radial direction.
[0030]
Thus, in the preliminary standby operation type pump 1, the preliminary standby operation is performed before the start of pumping. In other words, the pump shaft 4 is driven in advance in a state where the water level does not reach the suction port 2b or the impeller 5a, so that when pumping (drainage) such as large water becomes necessary, it can be dealt with immediately. Keep it. In such a preliminary standby operation, the pump casing 2 is not filled with water, and the sealed end faces 9a and 10a are brought into relative rotary sliding contact with each other in a dry state where no liquid comes into contact.
[0031]
However, the first sealed end face 9a is made of a self-lubricating material such as carbon, and the second sealed end face 10a is made of the porous film 101 having the above-described form (average pore diameter, porosity) having continuous air holes. Therefore, even in the aerial operation (preceding standby operation) in which the sealing end surfaces 9a and 10a are not lubricated with liquid, the sliding resistance reduction function, the heat radiation function and the abrasion powder discharge function of the above (1) to (3) enable the sealing. The temperature rise of the end faces 9a and 10a is suppressed as much as possible. Further, although the first sealing end face 9a is worn, the sealing end faces 9a and 10a do not cause a pitching phenomenon (so-called tearing phenomenon), and the life of the sealing end faces 9a and 10a is improved. As a result, although the first seal 6a or the second seal 6b is an end-face contact type mechanical seal that is not suitable for the aerial operation, the aerial operation is performed for a considerable time (for example, one hour). It can be suitably used as shaft sealing means of the preceding standby operation type pump 1.
[0032]
When the operation shifts from the preliminary standby operation to the pumping operation, that is, when the inside of the pump casing 2 is full and the submerged operation in which the liquid lubrication is performed by the pumping of the sealed end faces 9a and 10a is started, the second sealed end face 10a communicates. By setting the average pore diameter and the porosity of the porous film 101 in the above-described ranges despite the fact that the porous film 101 is formed of the porous film 101 having pores, as described above, leakage from the sealing end faces 9a and 10a can be prevented. The allowable range (especially, the pump inherently allows a considerable amount of leakage, and the allowable range is large), and a good shaft sealing function can be exhibited.
[0033]
It should be noted that the present invention is not limited to the above-described embodiments, and can be appropriately improved and changed without departing from the basic principle of the present invention. For example, the rotary seal ring 10 may be a first seal ring made of a self-lubricating material such as carbon, and the stationary seal ring 9 may be a second seal ring on which the porous film 102 is formed. Further, both the first and second sealing rings may have a non-divided structure. In addition, the end face contact type mechanical seal according to the present invention can be used for various types of rotation required to perform both submerged operation and air operation (dry condition or negative pressure condition) in addition to the preceding standby operation type pump. It can be suitably used as shaft sealing means for equipment.
[0034]
【Example】
As an example, an end-face contact type mechanical seal (hereinafter, referred to as an "example seal"), which is the first seal 6a and has a size attachable to the vertical mixed flow pump 1 having the pump shaft 4 having a diameter of 115 mm, was manufactured. In the example seal, the stationary sealing ring (first sealing ring) 9 is made of carbon, the main body part 102 of the rotary sealing ring (second sealing ring) 10 is made of titanium, and the porous membrane 101 is used as the main body part 102. And a chromium oxide sprayed film (film thickness: 0.4 mm) formed by plasma spraying chromium oxide.
[0035]
In addition, as a comparative example, the rotary seal ring 10 was a single material component having no porous film 102, that is, the rotary seal ring 10 was a dense silicon carbide sintered material (density: 3.13 g / cm 3). ³ ) Except that the seal was the same as that of the example seal (hereinafter referred to as “comparative example seal”).
[0036]
Then, the following first to fourth seal tests were performed using the example seal and the comparative example seal. In the following description, all pressures refer to gauge pressures based on atmospheric pressure.
[0037]
That is, in the first seal test, the pump 4 was operated in the air with no load, and the pump casing 2 was opened to the atmosphere (the sealed fluid region S was maintained at 0 MPa). State), the pump shaft 4 was driven. In the second to fourth seal tests, the pump casing 2 is filled with nitrogen gas after closing the discharge port 2a and the suction port 2b and the pressure inside the pump casing 2 (the pressure in the sealed fluid region S). ) Is maintained at a constant pressure, and the pump 1 is operated in the air (the rotation speed of the pump shaft 4 is the same as in the first seal test). The pressure was maintained at 0.1 MPa in the seal test, 0.2 MPa in the third seal test, and 0.3 MPa in the fourth seal test. Then, in each seal test, the sliding surface temperature was measured at regular intervals during a period of 180 minutes from the start of driving of the pump shaft 4, and the relationship between the sliding surface temperature and the elapsed time was obtained. The results are as shown in FIG. 8 for the example seal and as shown in FIG. 9 for the comparative example seal. 8 and 9, “□” indicates that the pressure in the pump casing 2 is 0 MPa, “Δ” indicates that the pressure is 0.1 MPa, and “Δ” indicates that the pressure is 0.2 MPa. .3 MPa is indicated by “で”.
[0038]
As understood from FIGS. 8 and 9, in the seal of the example, the sliding surface temperature is significantly lower than that of the seal of the comparative example in both the air operation and the liquid operation. After the end of each seal test, an annular mark on the second sealed end face (the sealed end face of the rotary seal ring 10) 10a was visually observed, but no visible annular mark and scratches were observed in the seals of the examples. Was. On the other hand, in the comparative example seal, a clear abrasion was recognized even when a record groove-shaped annular mark that was clearly observed was formed or the annular mark was not formed to such an extent that the annular mark was clearly observed. Further, after gently wiping the second sealed end face 10a with a cloth once, it was also checked whether or not wear powder (mainly carbon powder) was attached to the sealed end face 10a. Although it was not recognized at all or was very small even if it was attached, abrasion powder was significantly attached to the seal of the comparative example.
[0039]
【The invention's effect】
As can be easily understood from the above description, according to the present invention, the undesired change of the seal structure as in the above (B) and the cost and seal reliability as in the above (C) are considered. An end-contact type that can exhibit a good and stable sealing function and is durable in rotating equipment such as a pre-standby operation type pump that performs both in-air operation and submerged operation without the need for problematic equipment. A mechanical seal can be provided.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional front view showing an example of a vertical mixed-flow pump (preceding standby operation type pump) equipped with a first seal or a second seal.
FIG. 2 is an enlarged detailed view of a main part of FIG. 1 and is a longitudinal sectional front view showing a first seal.
FIG. 3 is an enlarged view of a main part of FIG. 2;
FIG. 4 is a cross-sectional plan view taken along the line IV-IV of FIG. 2 or FIG. 5;
FIG. 5 is an enlarged detailed view of a main part of FIG. 1 and is a longitudinal sectional front view showing a second seal.
FIG. 6 is an enlarged view of a main part of FIG. 5;
FIG. 7 is a cross-sectional bottom view taken along the line VII-VII of FIG. 5;
FIG. 8 is a graph showing a relationship between sliding surface temperature and elapsed time in the seal of the example.
FIG. 9 is a graph showing the relationship between sliding surface temperature and elapsed time in a comparative example seal.
[Explanation of symbols]
4 ... Pump shaft (rotating shaft), 6, 6a, 6b ... End face contact type mechanical seal, 7 ... Seal case, 9 ... Stationary sealing ring (first sealing ring), 9a ... First sealing end face (sealing of stationary sealing ring) End face), 10 ... Rotating sealing ring (second sealing ring), 10a ... Second sealing end face (the sealing end face of the rotating sealing ring, the annular face on which the second sealing ring slides), 101 ... Porous film (sprayed) Membrane), 102... Body part of rotary seal ring (body part of second seal ring excluding porous membrane).

Claims (5)

In an end face contact type mechanical seal configured so that the first seal ring and the second seal ring are in sliding contact with each other, the first seal ring is formed of a self-lubricating material, and the end face of the second seal ring is formed. The annular surface on which the first sealing ring is in sliding contact is formed by a porous film made of a material harder than the constituent material of the first sealing ring, and has a porosity of 4 to 20% in which pores having an average pore diameter of 10 to 60 μm communicate with each other. An end surface contact type mechanical seal characterized by comprising a porous membrane as described above. The end surface contact type mechanical seal according to claim 1, wherein the average pore diameter is 15 to 40 m. The end face contact type mechanical seal according to claim 1 or 2, wherein the porosity is 8 to 12%. The end face contact type mechanical seal according to claim 1, wherein the self-lubricating material is carbon, and the porous film is a sprayed film of chromium oxide. The end face contact type mechanical seal according to claim 4, wherein a main body portion of the second sealing ring excluding the porous membrane is made of titanium.

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