JPS62312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shaft sealing device for a rotating shaft portion of a submersible actuator such as a submersible suction pump as a mud lifting device in a muddy water construction method.

BACKGROUND ART In muddy water construction methods such as reverse circulation drills, suction pumps submerged in water have been put into practical use to discharge excavated earth and sand to the ground together with water. These items are attached directly above the drilling bit and move deeper into the ground along with the drilling bit as drilling progresses. The problem here is that as the depth increases, the water pressure inside the borehole increases, and the pressure difference between the external pressure and the internal pressure of the submersible pump increases, requiring improved performance of the submersible pump's rotating shaft seal. be. Normally, suction pumps are installed on land, but the purpose of submerging them in water is to take advantage of the fact that the pump's performance is not limited to the suction head, and the entire head can be replaced with the discharge head. The aim is to increase the mud content and make it possible to pump water when the excavation depth increases. Therefore, a rotary shaft seal with very high performance is required for a submersible pump type shaft excavator.

Therefore, in order to enable use without increasing the rotary shaft sealing performance, a method has been devised in which a pressure medium is fed into the housing from the ground and circulated so that the working pressure is higher than the external pressure. Something similar to this was already published in 1973.
21521, JP-A-51-155005, JP-A-52-7644, JP-A-49-9003, JP-A-49-10307, etc. are disclosed. However, these have the disadvantage that means for feeding the pressure medium must be prepared separately.

By using hydraulic pressure as the rotational drive source without separately feeding this pressure medium, the drain oil of the hydraulic motor is branched from the middle and guided to the rotating shaft sealing chamber.
The head pressure up to the oil tank on the ground is applied to the shaft sealing chamber, and the difference in internal and external pressure is limited to the difference in specific gravity between the oil and the muddy water outside.This eliminates special pressure loading means and makes it possible to adjust the internal and external pressure difference adjustment mechanism. Japanese Patent Publication No. 52-9921 is disclosed as an attempt to simplify the method.

This device utilizes the pressure of drain oil from a hydraulic motor that rotates a cutter in an excavator. The rotational speed of the cutter varies depending on the soil quality, and therefore the amount of drain oil in the hydraulic motor also varies. For this reason, care was taken to keep the pressure constant by always applying only the head pressure even if the oil amount changes. Therefore, a pressure difference corresponding to the difference in specific gravity between the hydraulic oil and the mud water always occurs, and as the depth increases, this pressure difference increases, and the internal pressure is always lower than the external pressure. For this reason, if a mechanical seal is used that cannot avoid a small amount of leakage, or if the seal is damaged due to its lifespan during use, leakage will always occur from the high-pressure side to the low-pressure side. There is also a concern that trouble may occur with ground hydraulic equipment.

The present invention relates to an improvement on the above-mentioned Japanese Patent Publication No. 52-9921, and by using the drain pressure of the hydraulic motor as dynamic pressure rather than as head pressure, it is possible to achieve shaft sealing even when the excavation depth increases. When the part is rotating, the internal pressure is always higher than the external pressure, so that even if there is leakage from the shaft seal to the outside, the reverse does not occur. The object of the present invention is to provide an underwater shaft sealing device that prevents damage to a liquid chamber filled in a hydraulic drain containing a shafted sealing member such as a pairing.

In order to achieve this object, the present invention provides a space in which shaft seals of a submersible actuator driven by a hydraulic motor are arranged in two stages, upper and lower, and a liquid such as hydraulic oil is sealed between the upper and lower seals. At the same time, a pressure equalizer is installed to constantly balance the liquid inside the space and the external pressure, and the drain oil of the hydraulic motor flows into and fills the shaft-sealed space provided above the upper seal. The present invention is characterized in that a pressure loading means is provided in the middle of the drain piping to the tank so that the internal pressure of the shaft-sealed space is always higher than the external pressure even if the excavation depth changes.

Embodiments of the present invention will be specifically described below with reference to FIGS. 1 to 3.

First, FIG. 1 is an overall side view showing a state in which a pit is being excavated by a pit excavating machine according to the present invention. Reference numeral 1 denotes a base installed on the ground, and a rotary table 2, which is an excavation torque supply device, is fixed on the base 1. A Kelly bar 3 is engaged with the center of the rotary table 2 in a shape that allows it to receive excavation torque as the rotary table 2 rotates. It is configured to drive a drill pipe 4, a crossover sub 5, a stabilizer 6, a submersible pump unit 7 with a stabilizer, and a bit 8 which are connected to the lower end of the Kelly bar 2 in this order.
A swivel joint 9 is connected to the upper part of the kely bar 3, and a hydraulic rotary joint 10 is connected to the upper part of the swivel joint 9, and water is supplied from a hydraulic pump unit 11 installed on the ground through a hydraulic hose 12. The pressure oil is led to the submersible pump unit 7. Suspension 9a is attached to swivel joint 9, and crane 1
2 hangs drill strings up to bit 8, including swivel joint 9. There is a suction port in the center of the lower end of the bit 8, through which earth and sand excavated by the submersible pump unit 7 is sucked up together with water, passes through the inner cylinder of each drill string, and is then passed through the delivery hose 13 attached to the swivel joint 9. It is discharged to the settling tank 14 via the water. The supernatant liquid is then sucked up by the submersible pump 15 and returned to the borehole, and by repeating this process, the borehole is excavated.

Next, the drive system of the submersible pump unit 7 will be explained with reference to FIG. The oil tank 16 of the hydraulic pump unit 11 installed on the ground is divided into two tanks, and hydraulic oil is supplied from the first tank 16a through a film 17 by a hydraulic pump 19 driven by an electric motor 18. It gets sucked up.
Then, by tilting the control valve 20 from the illustrated neutral state to the "hydraulic motor forward rotation" side, the hydraulic fluid is guided to the piping that rotates the hydraulic motor 21 in the forward direction, and the hydraulic fluid is guided to the piping that rotates the hydraulic motor 21 in the forward direction. From the port, the flow passes through the internal conduit to the internal conduit on the rotation side located in the center, and flows through the swivel joint 9.
It is guided to the Kerry bar 3 through the internal conduit on the rotating side. Here, even if the drill string rotates, there is no flow from the hydraulic pump unit 11 to the rotary joint 1.
The rotary joint 10 is provided with a rotation stopper 10a on the fixed side to prevent the hydraulic hose from turning around. The water is then guided from the kelly bar 3 to the hydraulic motor 21 of the submersible pump unit 7 via the external piping of the drill pipe 4, crossover sub 5, and stabilizer 6. The hydraulic oil that has been worked by the hydraulic motor 21 then returns to the second oil tank 16b along the same route. Then, it passes through the filter 29 and returns to the first oil tank 16.
flows into a. A line filter 22 equipped with a clogging detector and a bypass circuit in case of clogging, and an oil cooler 23 which is activated only when the oil temperature rises are installed in the middle of this return piping. The hydraulic pump 19 is configured such that its discharge amount can be varied by an electric regulator 24. Further, the pressure setting of the discharge pressure is performed by the relief valve 25. Drain oil from the hydraulic motor 21 passes through a drain pipe 26, passes through a line filter 27 with a clogging detector and a bypass circuit in case of clogging, and a sequence valve 28 before reaching the third oil tank 16.
flows into c. The hydraulic oil overflowing from the third oil tank 16c flows into the first oil tank 16a. Second oil tank 16b and third oil tank 16c
The reason why the manner in which the hydraulic oil flows into the first oil tank 16a is different is due to the difference in the amount of each hydraulic fluid flowing into the first oil tank 16a. In other words, the drain oil amount to the third oil tank 16c is 2 to 5 times the discharge amount of the hydraulic pump 19.
%, whereas the second oil tank is about 16%.
The amount of oil returned to b is 95 to 95% of the discharge amount of the hydraulic pump 19.
This is a very large amount of about 98%, so if muddy water is mixed in the oil, it may flow into the first oil tank 16a without settling in the oil tank 16b, and this point was taken into consideration. . Capacitance-type muddy water mixing detectors 30 and 31 attached to the oil tanks 16b and 16c, respectively, detect the capacitance of the hydraulic oil and the capacitance when muddy water is mixed into the tank. It detects the change and stops driving the hydraulic pump. Similarly, if the line filters 22, 27 become clogged, it is detected electrically and an alarm is sounded. This is because the inside of the borehole is filled with muddy water, so if the piping inside the borehole or the underwater shaft sealing device is severely damaged and muddy water gets mixed in, it is important to catch the problem as soon as possible and take measures before it becomes a serious problem. It has been made possible to do so.

Further, each drill pipe 4 is provided with external piping as described above, and when each drill pipe is connected, these external pipings are connected by self-sealing joints 32 and 33.

In addition, when the control valve 20 is moved from the neutral state to the "hydraulic motor reverse rotation" side, the piping exiting the control valve 20 of the hydraulic pump unit 11 is changed to "forward" and "return" compared to the case of normal rotation. ' is reversed.

Next, the configuration of the submersible pump unit 7 will be specifically explained based on FIG.

The submersible pump unit 7 is installed directly above the bit 8, and the pump suction port diameter and discharge port diameter are the same so that the excavated earth and sand will not clog the pump. The pump is a centrifugal pump, and an impeller 37 inside a casing 36 is driven by a hydraulic motor 21 via a shaft 38. The shaft 38 is connected to the shaft of the hydraulic motor 21 by a chain coupling 39. The shaft 38 is supported by a bearing 41 attached to a housing 40 and a bearing 43 attached to a housing 42. There is a case 44 between the hydraulic motor 21 and the housing 40, and they are separated by O-rings 45, 4.
6 and are bolted together in a sealed manner. Covers 47 for attaching chain coupling rings 39 to the left and right sides of the case 44 are attached by bolts via O-rings. Since the shaft of the hydraulic motor 21 is not provided with a seal, drain oil flows into the case 44. A plurality of through holes 49 are formed in the upper part of the housing 40 so that the drain oil filled in the shaft-sealed space C in the case 44 and the housing 40 can easily circulate therein. A discharge port (not shown) is provided at the bottom of the housing 40 so that oil filled therein can be drained. Housing 40 and housing 42
They are connected by bolts with an O-ring 50 in between. An air vent hole 51 is provided at the upper part of the space A formed by the housing 42, and the hole 51 is closed with a plug 52. bearing 4
3, an upper rotary seal 55 and a lower rotary shaft seal 5 are provided between the housing 42 and the sleeve 54 which rotates integrally with the shaft 38 by a key 53.
6 is installed. The space between the upper rotary shaft seal 55 and the lower rotary shaft seal 56 communicates with the space A of the housing 42. A bellows type pressure equalizer 57 and a cover 58 are attached to the housing 42 so as to be exposed inside the excavation hole. The inner diameter of the cover 58 is approximately equal to the outer diameter of the bellows type pressure equalizer 57 when it is pressurized to its maximum level, with a slight gap. Therefore, when the bellows type pressure equalizer 57 expands and contracts, the inner diameter portion of the cover 58 guides it, so that it can be installed laterally. In addition, the bellows of the bellows type pressure equalizer 57 are not spiral-shaped but are formed by a collection of rings, and the lower part of the cover 58 has a plurality of discharge ports 58a, so that mud does not flow into the bellows part. It has a structure that does not easily interfere with the expansion and contraction of the bellows because it is difficult to adhere to and is easy to discharge. This is necessary to ensure smooth expansion and contraction due to the thermal expansion of the hydraulic oil filled in the space A of the housing 42 and the balance between the internal pressure and external pressure of the space A. Then cover 58 with a margin for the amount of expansion and contraction of the bellows.
The length of is determined. A discharge port is provided at the bottom of the space A of the housing 42 and is closed with a plug 59.

The impeller 37 also has thin back blades 37a, 3.
7b is attached. This was installed with the aim of reducing the pressure on the back side of the impeller 37.
The impeller 37 is fitted into the shaft 38 via a key 60 so as to rotate together, and is prevented from coming off by an impeller nut 61. Further, a plate 62 is attached to the housing 42 connected to the casing 36.
2 and the impeller 37 form a labyrinth seal 62a. This can prevent large fluids from entering the space B formed between the boss portion of the impeller 37 and the housing 42. Also, the housing 42 is directed toward this space B.
A fixed blade 42a is provided at . This is installed for the purpose of preventing wear around the space B caused by the earth and sand flowing in through the back blade 37a of the impeller 37 swirling in the space B. However, since it is also necessary to cool down the lower rotary shaft seal 56, a through hole 63 leading to the outside is opened to guide the pumped liquid from the back blade 37a.
This means that the total head of submersible pumps for construction is usually about 10~
20 m, the internal pressure of the casing 36 is always 1 to 2 kg/ ^cm2 higher than the external pressure, and even if the back blade 37a and labyrinth 62a are effective, the pressure in space B is 0.3 to 1.3 kg/cm2. Since the pressure is higher than the external pressure by about ^cm2 , the pumped liquid is circulated through the through hole 63.

Since the present invention is configured as described above, the pressure in the space A shown in FIG. is 0.3~1.3
This means Kg/cm ² . Therefore, if a leak occurs in the seal in this part, the pumped liquid will flow into the space A. For this reason, the bellows type pressure equalizer 57 gradually swells, and eventually the shape of the bellows collapses and it tightly sticks to the inner wall of the cover 58. However, if the upper rotating shaft seal 55 is not damaged, there is no risk of trouble occurring in the rotating shaft sealing section. After one excavation hole has been dug, it is lifted to the ground, so if the bellows type pressure equalizer 57 is inspected at this time, abnormalities can be discovered. Also, consider the sealing pressure of the upper rotary shaft seal 55. If we consider the head pressure of the hydraulic oil as disclosed in Japanese Patent Publication No. 52-9921, the seal pressure can be considered as the difference in specific gravity between the specific gravity of muddy water, 1.1, and the specific gravity of hydraulic oil, 0.85. The sealing pressure is 2.5Kg/cm ² . However, since the aim of the present invention is to make the drain pressure of the hydraulic oil, that is, the pressure in the shaft seal space C, higher than the pressure in space A, the pumped liquid in space A is higher than that in space B at a depth of 100 m. Considering the worst case scenario, the drain pressure should be increased to 2.8 to 3.8 kg/cm ² . As mentioned above, the drain oil returns to the oil tank in an amount of 2 to 5% of the discharge amount of the hydraulic pump.
Therefore, in the case of a submersible pump that rotates at a nearly constant rotation rate during operation, the amount of drain oil is also almost constant, and from this it is easy to determine the piping resistance.
Setting the drain pressure is easy because the drain pressure can be determined by arbitrarily selecting the pipe size. When using a seal mechanism, consider the amount of drain oil at the lowest discharge amount, and install an orifice such as a variable restrictor in the circuit 26 in the middle so that the piping resistance due to the amount of oil at this time exceeds this (as shown in the figure). ) or the sequence valve 2 is installed in the intermediate circuit 26 as shown in Figure 3.
8 and setting its pressure to 2.8 to 3.8 Kg/cm ² , the minimum working oil pressure inside the housings 40 and 42 can be set to 2.8 to 3.8 Kg/cm 2 regardless of the flow rate.
Can be made into ^cm2 . Needless to say, this value is based on the assumption of excavation depth and submersible pump capacity.

Another method is to take advantage of the fact that drill pipes 4 must be added as the excavation depth becomes deeper, and pipes are added each time they are connected. A seal joint 33 may be used. In this way, the size of the self-sealing joint 33 is selected in consideration of pressure loss, and as the excavation depth increases, the pressure difference due to the difference in specific gravity of oil and mud increases, so this increment is By compensating for the pressure loss, the seal pressure can be kept almost constant even if the excavation depth changes. Furthermore, if the desired pressure loss cannot be obtained due to a small amount of drain oil, the return piping from the hydraulic motor 21 may be branched in the middle to allow the required amount of oil to flow to the drain piping.

As described above, an orifice such as a variable restrictor,
By using pressure loading means such as the sequence valve 28 and the self-sealing joint 33 that takes pressure loss into account, the pressure within the shaft-sealed space C can always be set to a higher value than the external pressure.

These seal pressures were taken into consideration during rotation, but seals are usually more severe during rotation or sliding than when they are stationary, and even if seals have a considerable seal pressure when stationary, they are more severe during rotation or sliding. The general concept is that even a small amount of sealing pressure may not last if the sealing pressure is increased. Therefore, the best effects can be obtained by applying the present invention to shaft seals during rotation and sliding, which are particularly problematic.

As described above, according to the underwater shaft sealing device of the present invention, the drain oil of the hydraulic motor is filled in the shafted sealed part, and even if the pressure here is greater than the external pressure through the shaft seal, the depth of excavation is always greater. A pressure loading means is provided in the middle of the drain piping so that the height is increased, and the shaft seals are arranged in two stages, upper and lower, and a space chamber filled with a liquid such as hydraulic oil is formed between the upper and lower seals. A pressure equalizer is installed to balance the internal and external pressures in the room, so if a mechanical seal is used that cannot avoid slight leakage, or if the seal breaks due to its lifespan during use, only a small gap will be created. Although the hydraulic oil filled in the sealed part will inevitably leak to the outside, muddy water will never enter the sealed part from the outside, which will prevent problems from occurring with bearings, hydraulic motors, etc. can be completely avoided.
Therefore, the internal pressure can always be made higher than the external pressure without providing a separate pump or other means for feeding and circulating the pressure medium into the shaft-sealed part, so high sealing performance is not required. Furthermore, even if a leak occurs in a seal that is in direct contact with external pressure, it is possible to prevent immediate damage to the liquid chamber filled in the hydraulic drain where the sealed body such as the bearing is located.

[Brief explanation of the drawing]

FIG. 1 is an overall side view of a pit excavator that is an embodiment of the underwater shaft sealing device of the present invention, and FIG.
FIG. 3 is an enlarged sectional view of the submersible pump unit shown in the figure, and is a hydraulic circuit diagram for explaining the drive of the submersible pump unit and the principle of the shaft sealing device of the present invention. 7... Submersible pump unit, 8... Bit, 21...
Hydraulic motor, 26...Drain piping, 28...Sequence valve, 33...Self seal joint, 36...
Casing, 37... Impeller, 38... Shaft,
40, 42...housing, 44...case, 49...
Through hole, 54... Sleeve, 55... Upper rotating shaft seal, 56... Lower rotating shaft seal, 57... Bellows type pressure equalizer, 58... Cover, A... Space in housing 42, B... Between impeller 37 and housing 42 The space formed, C... shaft-sealed space.

Claims (1)

[Claims] 1 The shaft seals of the submersible actuator driven by a hydraulic motor are arranged in two stages, upper and lower, and a space chamber filled with a liquid such as hydraulic oil is formed between the upper and lower seals, and the internal pressure within the space chamber is A pressure equalizer is installed so that the external pressure is always balanced, and the drain oil of the hydraulic motor flows into and fills the shaft-sealed space provided above the upper seal. 1. An underwater shaft sealing device characterized in that a pressure loading means is provided so that the internal pressure of the shaft-sealed space is always higher than the external pressure even if the pressure changes.