JPS6160307B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mechanical seal suitable for use, for example, in a shaft seal of a canned water circulation pump in a thermal power plant.

In canned water circulation pumps at thermal power plants, the liquid to be sealed is at high pressure (200 to 300 kgf/cm ² ) and high temperature (350 to 400 kgf/cm 2 ).
℃), conventional mechanical seals are unreliable, and the sealing pressure has to be significantly increased to approximately 10Kgf/
I lowered it to cm ² and used ground packskin.
In products that use gland packing in this way, the pressure resistance conditions are limited, so it is necessary to reduce the pressure even when the tank is stopped.
It was necessary to keep the liquid supply pump running at all times to supply liquid (170°C) to the shaft seal, resulting in high operating costs. Particularly in recent years, as thermal power plants have become more popular with peak load stations and the number of stoppages has increased, improvements in shaft sealing devices have become an urgent issue for users.

The present invention was made in view of the above-mentioned circumstances, and
The purpose of this is to reduce operating costs by stopping the liquid supply pump that supplies liquid to the shaft seal at the same time as the canned water circulation pump stops, and to effectively seal high pressure and high temperature liquids. The present invention aims to provide a mechanical seal that can improve the reliability of the device.

Hereinafter, the present invention will be explained with reference to the drawings.

1 to 6 show an embodiment in which the present invention is applied to the shaft seal of a canned water circulation pump for a thermal power plant. In FIG. 1, X indicates the motor side of the pump, and Y indicates The impeller side of the pump is shown.
1 in the figure is a seal housing, and a rotating shaft 2 connected to the impeller of the pump is inserted through the center of this seal housing 1.
The mechanical seal of the present invention is installed in the annular space 3 between the seal housing 1 and the seal housing 1.

Below, this mechanical seal will be explained in detail.
5 is a stationary sealing ring, and 5 is a rotating sealing ring.
A and 5a are in sliding contact. Of the sealing rings 4 and 5, one sealing ring, for example, the stationary sealing ring 4, is connected to a plane A-A' perpendicular to the axis of the rotating shaft 2 passing through the center of gravity G as shown in FIG. It is made of tungsten carbide with a symmetrical shape. Also, the other sealing ring, that is, the rotating sealing ring 5
is made of silicon carbide. Further, on the outer periphery of the stationary sealing ring 4, a liquid guiding passage 7 is provided that conducts the cooling liquid B to the outer circumferential surface 4b of the stationary sealing ring 4.
A first metal retainer 6 made of an annular body 6a having a, 7b, and 7c formed thereon is fixed by shrink fit, for example. That is, this first metal retainer 6 is
In the annular body 6a, as shown in FIGS. 3 and 4, through holes 7a that penetrate in the axial direction are formed at appropriate intervals in the circumferential direction, and the through holes 7a are perpendicular to each of the through holes 7a. A through hole 7b penetrating in the radial direction is formed in the inner peripheral surface of the annular body 6a, and an annular groove 7c facing the outer peripheral surface 4b of the stationary sealing ring 4 and extending in the circumferential direction is formed on the inner peripheral surface of the annular body 6a. Through hole 7
b, and these through holes 7a,
7b and an annular groove 7c.
b, 7c are configured. Further, a pin hole 8 is formed in the first metal retainer 6 and extends through the pin hole 8 in the axial direction. As shown in FIG. 5, the stationary sealing ring 4 is secured to one holding member 9 via the first metal retainer 6 so as not to rotate.
is maintained. Further, a second metal retainer 1 made of an annular body 11a is provided on the outer periphery of the rotary sealing ring 5.
1 is fixed by shrink fitting, for example. The second metal retainer 11 has a concave portion 12 on a part of the outer peripheral surface of the annular body 11a over the entire width in the axial direction.
is formed in this concave portion 12, and a rotary sealing ring 5 is formed in this concave portion 12.
An engagement convex portion 13 of a piece 13a integrally extending and protruding from the other holding member 13 disposed on the impeller side.
a' is engaged as shown in FIG. Retained.

Further, a collar 14 is attached and fixed to the end face of the one holding member 9 on the motor side with a set screw 15, and a pin 16 that extends in the axial direction toward the motor side is screwed onto this collar 14. 16 is a spring retainer 1 disposed opposite to the collar 14;
The spring retainer 17 is loosely inserted into the pin hole 18 of No. 7, and the spring retainer 17 is formed with several spring holes 19 at appropriate intervals in the circumferential direction, and one end of the coil spring is accommodated in each spring hole 19 in a compressed state. 20 connects the stationary sealing ring 4 to the rotating sealing ring 5 via the collar 14 and one holding member 9.
Constant pressure on the side. The spring retainer 17 also includes one holding member 9 and a stationary sealing ring 4 along the inner surface of the seal housing 1.
A cylindrical adapter 21 that surrounds and extends to the sealed end surface 4a and has an open tip 21a is fixed by a set screw 22. The spring retainer 17 is fixed to a fixing member 24 by a mounting bolt 23, and the fixing member 24 is fixed to the seal housing 1 by a mounting bolt 25.

Further, the other holding member 13 that holds the rotary sealing ring 5 is fixed to the rotary shaft 2 with a key 26 interposed therebetween, so that it can be rotated together with the rotary shaft 2. The other holding member 13 includes a rotating sealing ring 5, a stationary sealing ring 4, and one holding member 9.
A cylindrical portion 13b is integrally provided along the inner circumferential surface of the rotary shaft 2 and extends toward the motor side surrounding the rotating shaft 2.

A coolant inflow passage 27 is formed in the seal housing 1, and this coolant inflow passage 27
The coolant B from the adapter 2 passes through the inlet 28 opened in the motor side portion of the adapter 21.
1, flows through the adapter 21 toward the open end 21a, and flows out into the seal housing 1 from the open end 21a. The coolant B that has flowed out into the seal housing 1 is then flowed out from the coolant outflow passage 29 of the seal housing 1 by the pump action caused by the rotation of the vane portion 13c formed on the outer periphery of the other holding member 13. It's becoming like that.

In addition, in this embodiment, the end surface 13 of the other holding member 13 is
The position where d contacts the rotary seal ring 5 is shifted toward the outer periphery as shown in _FIG . The pressing force _P2 from the other holding member 13 pushing the rotary sealing ring 5 shifts toward the outer circumference, and a moment M shown in FIG. 1 acts on the rotary sealing ring 5. The hydraulic pressure of the coolant B is offset by the moment M' generated by pressing the rotary seal ring 5 and the second metal retainer 11 toward the impeller, reducing the distortion of the rotary seal ring 5.
Liquid leakage at the sealed end surface 5a can be reduced.

In addition, in FIG. 1, 30 is an O-ring that is interposed between each member and acts as a seal. Further, in the figure, 30' is an O-ring interposed between the end surface 13d of the other holding member 13 and the back surface of the second metal retainer 11 to perform a sealing function, and 30'' is an O-ring of the other holding member 13. An O-ring is interposed between the outer circumferential surface of the cylindrical portion 13b and the inner circumferential surface of the rotary seal ring 5 and elastically supports the rotary seal ring 5. Reference numeral 31 refers to the rear surface of the rotary seal ring 5 on the motor side. (Atmospheric side) Cylindrical portion 13 of the other holding member 13 to communicate with X
This is a communication path formed in b, and this communication path 31 is
This prevents the rotary seal ring 5 from popping out in the event that air thermally expands at the rear surface of the rotary seal ring 5 or if high-pressure liquid leaks from the O-ring 30'.

In the mechanical seal configured as described above, the rotating seal ring 5 is rotated by the rotation of the rotating shaft 2.
rotates together with the other holding member 13, and the stationary sealing ring 4 is in a stationary state fixed to the seal housing 1 via one of the holding members 9, the spring retainer 17, and the fixing member 24, and the stationary sealing ring 4 4 and the rotary sealing ring 5 are in sliding contact at the sealing end surfaces 4a and 5a to perform a sealing action, so that the impeller side Y
Prevent liquid leakage. At this time, the static sealing ring 4 and the rotating sealing ring 5 generate sliding heat by sliding on the sealing end surfaces 4a and 5a, and as in this embodiment, the mechanical seal of the present invention is used in a canned water circulation pump of a thermal power plant. When applied to the shaft seal part of
300Kgf/cm ² ) and high temperature (350-400℃),
The temperature of each part of the mechanical seal increases, causing deformation and hindering the sealing action. Therefore, during operation of the canned water circulation pump, the coolant B is supplied to the coolant inlet passage 27 and the inlet 28 of the adapter 21.
The adapter 21 is introduced into the inner peripheral side of the adapter 21 through the adapter 21. The cooling liquid B introduced into the inner peripheral side of the adapter 21 damages each part of the mechanical seal, that is, one of the holding members 9 and the stationary sealing ring 4, in the process of flowing inside the adapter 21 toward the open end 21a side. The coolant is cooled from the outer circumferential surface side, further cooling the sealing end surfaces 4a, 5a and the rotary sealing ring 5, and flowing out from the coolant outflow passage 29 under the pump action caused by the rotation of the blade portion 13c of the other holding member 13. .

Therefore, as described above, in the present invention, the stationary sealing ring 4 is formed of tungsten carbide, and the rotating sealing ring 5 is formed of silicon carbide, so that these sealing rings 4 and 5 are made of a combination of hard materials. , has sufficient pressure resistance against high-pressure liquid from the impeller side Y. Therefore, the liquid supply pump that supplies cooling liquid B to the shaft seal can be stopped at the same time as the canned water circulation pump is stopped, reducing operating costs. At the same time, the sealing end faces 4a, 5 of each sealing ring 4, 5
Sufficient wear resistance performance can be ensured in a. Furthermore, since the stationary sealing ring 4 is formed in a symmetrical shape with respect to the plane A-A' perpendicular to the axis of the rotating shaft 2, the pressure on the stationary sealing ring 4 is balanced on the left and right sides, causing pressure imbalance. In addition, deformation due to temperature is balanced on the left and right sides, the sealing end face 4a is less distorted against changes in pressure and temperature, and high-pressure and high-temperature liquids can be effectively sealed. Further, the stationary sealing ring 4
A first metal retainer 6 is fixed to the outer periphery of the stationary sealing ring 4, and the first metal retainer 6 has liquid guide passages 7a, 7b, and 7c that conduct the cooling liquid B to the outer peripheral surface 4b of the stationary sealing ring 4. Since the cooling liquid B flowing through these liquid guide passages 7a, 7b, and 7c
As a result, the outer circumferential surface 4b of the stationary sealing ring 4 can be sufficiently cooled. Furthermore, the first metal retainer 6
The stationary sealing ring 4 is held by one holding member 9 via, for example, a pin 10, and the rotating sealing ring 5 is held by the other holding member via a second metal retainer 11 fixed to the outer periphery of the rotating sealing ring 5. 13
For example, the pin hole 8 is held in the hard material 4, 5, which is inherently weak against impact, because it is held by the engaging protrusion 13a'.
without providing stress concentration parts such as or concave parts 12,
Highly reliable retention is possible.

In the above embodiment, the rotary sealing ring 5 may be formed of tungsten carbide having a symmetrical shape with respect to a plane perpendicular to the axis of the rotating shaft 2, and the stationary sealing ring 4 may be formed of silicon carbide. Further, the present inventors have discovered that the object of the present invention can be achieved in the same manner as in the above embodiment even if both the stationary seal ring 4 and the rotating seal ring 5 are made of the same material, tungsten carbide (or silicon carbide). In this case, it has been confirmed by
The most effective combination of materials for the stationary sealing ring 4 and the rotating sealing ring 5 is tungsten carbide and silicon carbide, and the combination of tungsten carbide and silicon carbide produces good results in this order. Ta.

[Brief explanation of the drawing]

The drawings show an embodiment in which the present invention is applied to a shaft seal of a canned water circulation pump for a thermal power plant, in which FIG. 1 is a longitudinal sectional view, FIG.
The figure is a longitudinal sectional view showing the first metal retainer fixed to the outer periphery of the stationary sealing ring, and Figure 4 is the − of Figure 3.
FIG. 5 is a sectional view taken along the - line in FIG. 1, and FIG. 6 is a sectional view taken along the - line in FIG. 1. 1... Seal housing, 2... Rotating shaft, 4...
... Stationary sealing ring (one sealing ring), 5... Rotating sealing ring (other sealing ring), 6... First metal retainer,
7a, 7b, 7c...Liquid guiding passage, 8...Pin hole,
9... One holding member, 10... Pin, 11...
Second metal retainer, 12... recessed portion, 13... other holding member, 13a'... engaging convex portion, 20... coil spring in compressed state, 27... coolant inflow passage, 29... coolant Outflow passage, B...Cooling liquid,
X: Motor side of canned water circulation pump, Y: Impeller side of canned water circulation pump.

Claims (1)

[Claims] 1. In a mechanical seal in which a stationary sealing ring and a rotating sealing ring are brought into sliding contact at their sealing end faces, each sealing ring is formed of tungsten carbide or silicon carbide, and one sealing ring is formed in a plane perpendicular to the axis of the rotating shaft. Formed into a symmetrical shape,
and a first metal retainer having a liquid guide passage formed therein for conducting a cooling liquid to the outer peripheral surface of the seal ring is fixed to the outer periphery of the one seal ring, and the one seal ring is connected to one side through the first metal retainer. and a second sealing ring fixed to the outer periphery of the other sealing ring.
A mechanical seal characterized in that the other sealing ring is held by the other holding member via a metal retainer.