JPH0118244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lubricating device for a sealed turbine bearing, and particularly to a lubricating device that reliably supplies oil to the bearing even in an emergency.

In rotating machines, it is extremely important to supply lubricating oil to the bearings that support the rotor to ensure safe operation. An oil pump is required to send lubricating oil, and there are two types of oil pumps: those driven by a rotating shaft that is directly connected to the rotating shaft of the rotating machine, and those driven by an electric motor that are located separately. Even if the oil pump is directly connected to the rotating shaft, an electric motor-driven pump is required when the rotational speed drops when the rotating machine is stopped. Therefore, if the power to the electric motor is cut off due to some kind of accident, the rotating machine will be brought to an emergency stop, and the backup electric motor-driven oil pump will be operated using the backup power source prepared in advance, so that the rotating machine can be completely turned off. To ensure safe stopping of the machine, lubricating oil is supplied to the bearing until the machine stops. At this time, as a normal power source, a power source for general power is used as an AC power source, and as a backup power source, a battery or a power source of a generator driven by a diesel engine capable of rapid startup is used.

FIG. 1 shows a conventional turbine lubricating oil system. 1 is an oil tank (lubricant reservoir) in which lubricating oil is stored. The capacity of this oil tank 1 is set such that the lubricating oil remains in the tank for about 5 to 10 minutes so that the air bubbles that have gotten into the oil that has returned to the oil tank 1 have disappeared sufficiently before it is sucked into the main oil pump 2. It is set so that it can be done. The lubricating oil in the oil tank 1 is pumped to the bearing 6 of the turbine 7 by the main oil pump 2. Before reaching the bearing 6, the oil first passes through an oil cooler 4 and is cooled to an appropriate oil temperature. Next, the lubricating oil is passed through a lubricating oil filter 5 to remove dust from the lubricating oil to prevent dust from flowing into the bearing and causing damage. In this way, lubricating oil is sent to the bearing 6 of the turbine 7. If the discharge pressure of main oil pump 2 becomes too high,
In order to prevent the internal pressure of the lubricating oil piping and oil cooler 4 from rising above the design pressure, which is dangerous, a piping is provided that communicates with the discharge side of the main oil pump 2 and the inlet side of the oil tank 1. A safety valve 8 is installed at the That is, when the pressure rises above the design value, the safety valve 8 opens and oil is returned to the oil tank 1. Furthermore, it is important that the pressure of the lubricating oil sent to the bearing 6 is set higher than the atmospheric pressure of the bearing portion by a certain amount. This is because the flow rate flowing into the bearing section is
Since it is proportional to the square root of the pressure difference between the bearing atmospheric pressure and the oil supply pressure, if the oil supply pressure increases more than necessary, too much lubricating oil will flow, and if the oil supply pressure decreases too much, the required amount of lubricating oil will not flow. A pressure regulating valve 9 is therefore provided. When the pressure on the upstream side of the pressure regulating valve 9 increases, the valve is throttled, and when the pressure decreases, the valve is opened, and the pressure downstream of the pressure regulating valve 9, that is, the oil supply pressure to the bearing 6, is kept constant. Of course, the discharge pressure of the main oil pump 2 is
In the case of a turbine where the pressure is considered to be almost constant, an orifice may be used instead of the pressure regulating valve 9, or if the discharge pressure of the main oil pump 2 is at a sufficiently appropriate value as it is, nothing may be provided. be. The backup oil pump 3 is installed in parallel with the main oil pump 2, and when the main oil pump 2 stops for some reason, the pressure switch 10 detects the drop in discharge pressure and activates the start switch 11. Start the backup oil pump 3. The sudden stop of the main oil pump 2 is almost always due to the loss of power to the main oil pump 2, so the power source for the backup oil pump 3 is set to be a separate power source from the power source for the main oil pump 2. In steam turbines using steam or water, water turbines, or gas turbines using combustion gas, the turbine is sealed with labyrinth-type packing or mechanical seals, and the bearings are open to the atmosphere or are installed in bearing housings. The installed bearing has a slightly negative pressure below atmospheric pressure due to the air extractor. Therefore, the atmospheric pressure of the bearing portion remains approximately constant regardless of whether the main oil pump 2 is operating or stopped, or in other words, regardless of loss of the general power source. Therefore, the discharge pressure of the backup oil pump 3 should be equal to the discharge pressure of the main oil pump 2, or sufficient to deliver the minimum amount of oil necessary to prevent bearing seizure. .

If the above-mentioned conventional lubricating oil device is used in a turbine in an exhaust heat recovery plant that uses a medium whose leakage of fluorocarbons or the like to the outside should be prevented as much as possible, a serious problem will occur. This will be explained below.

An exhaust heat recovery plant is a plant that uses steam or high-temperature gas to discharge heat at a relatively high temperature.
A boiler is used in the exhaust chimney, and the heat is recovered and used effectively using a heat medium such as fluorocarbons. The heat carrier, such as fluorocarbons, which has been recovered and vaporized, is led to a turbine to drive the turbine, and in the condenser, it is cooled by a cooling medium (often water such as seawater or fresh water) and liquefied, and then the waste heat recovery boiler Return to

FIG. 2 is an example of an exhaust heat recovery plant that uses fluorocarbons to drive a turbine. The freon vapor passes through the flow rate control valve 14, performs work within the turbine 7A, and drives the turbine 7A. The exhaust gas is cooled and condensed in a condenser 15. The condensation of this fluorocarbon lowers the turbine exhaust pressure, and due to the pressure difference with the turbine inlet pressure, the fluorocarbon flows through the turbine 7A. Cooling is performed using cooling water supplied by a cooling water pump 16. The fluorocarbon liquid absorbs heat in the heat exchanger 19 by the fluorocarbon pump 17, evaporates into steam, and is guided to the flow rate control valve 14. The flow control valve 14 is opened and closed by the speed controller 13 depending on the deviation of the turbine speed from the required value. This controls the turbine speed. In this example of a plant, heat is recovered from a heat source such as exhaust gas using oil, and then the heated oil and fluorocarbon are further heat exchanged in a heat exchanger 19. After heat exchange, the oil whose temperature has dropped is sent to the exhaust heat recovery boiler 20 by the oil pump 18, where it absorbs heat from the heat source, and when the temperature rises, the heat exchanger 19 heats the fluorocarbon to generate fluorocarbon vapor. . The reason why fluorocarbons are used as the working medium for operating the turbine 7A is that the boiling point of fluorocarbons is relatively low.
This is because, for example, exhaust heat from factory chimneys can be used to create steam (which becomes vacuum steam at 200°C to 300°C), making it possible to effectively utilize the exhaust heat. In this turbine 7A, a seal 22 prevents freon leakage from inside the turbine, and a bearing 6 is placed outside of the seal 22.

This seal 22 includes a mechanical seal and a labyrinth type seal. Mechanical seals have less leakage, but when the shaft diameter exceeds 100mm, even mechanical seals cannot sufficiently prevent leaks. The seal problem is caused by the fact that the rotating rotor is outside the turbine casing, which is a stationary body, so it is necessary to completely surround the rotor with the turbine cover 21.
By sealing, the problem of fluorocarbon leakage can be fundamentally solved.

In this case, if the cooling water pump 16 stops for some reason, the cooling water will be lost, so the condenser 15
The fluorocarbons cannot be condensed, so the pressure inside the turbine increases, and since the turbine cover 21 is hermetically sealed, the pressure inside the turbine cover 21 also increases through the seal 22. If this happens, the turbine 7A will have to be stopped urgently, but the turbine 7
Until A completely stops, lubricating oil must be supplied to the bearing 6 at a pressure higher than the pressure inside the turbine casing.

The most common reason for the cooling water pump 16 to stop is usually that the power to the motor driving the cooling water pump 16 is cut off due to a ground fault or the like. In the conventional example, this power source is also common to the power source of the main oil pump 2, so the back-up oil pump 3
will be activated to send lubricant. For the reasons mentioned above, the discharge pressure of this oil pump 3 is lower than that of the main oil pump 2.
The discharge pressure must be the sum of the internal pressure of the turbine cover 21 and the oil supply pressure.

As a countermeasure against this problem, it is possible to set the discharge pressure of the backup oil pump 3 to be high in advance. However, in this case, the lubricating oil piping up to the bearing must be matched to the discharge pressure of the backup oil pump 3, and must be completely separate from the piping connected to the discharge port of the main oil pump 2. because,
As shown in Figure 1, the piping connected to the main oil pump 2 outlet is designed to prevent excessive pressure rise.
This is because a safety valve, pressure regulating valve 9, etc. are included. In this way, providing two lines of oil piping means
In addition to increasing piping costs, the disadvantage is that the bearing must be sized to accommodate two oil supply lines. In addition, when the backup oil pump 3 is started, the backup oil pump 3 is stopped and the oil is immediately sent into the bearing 6.
There is an inconvenience that the piping must be filled with oil even during standby. Furthermore, if a cavity remains in this piping, there is a problem in that oil supply is delayed and air bubbles are sent to the bearing 6 at the same time as oil.

It is an object of the present invention to improve the above-mentioned drawbacks and provide a lubricating oil device having the ability to increase oil supply pressure using the simplest system.

The features of the present invention include a system for circulating lubricant through the bearings, a main pump device provided in this system, a lubricant reservoir provided in the suction side system of the main pump device, and a lubricant reservoir provided in the discharge side system of the main pump device. In a lubricant circulation system for a sealed turbine bearing comprising a check valve and a pressure regulating valve, an auxiliary pump device provided in a bypass system that bypasses the main pump device, and a non-return check provided in a discharge side system of the auxiliary pump device. A lubricating device for a sealed turbine bearing comprising a valve, a detection device that drives an auxiliary pump device when the power is cut off, a bypass system that bypasses the pressure regulating valve, and a bypass valve that is installed in the bypass system and operates when the power is cut off. be.

Next, one embodiment of the present invention will be described with reference to FIG. 31 is an oil tank provided in the suction side piping 51 of the main oil pump 32 serving as the main pump device; 33 is a check valve provided in the discharge side piping 52 of the main oil pump 32; 34
is an oil cooler that cools lubricating oil, 35
36 is a bearing that supports the sealed turbine 37; 38 is a pressure regulating valve that keeps the oil supply pressure to the bearing 36 constant; 39
Reference numeral 40 indicates a safety valve provided in a pipe 53 that communicates the discharge side of the main oil pump 32 with the inlet side of the oil tank 31; 40 indicates a condenser for the turbine 37; pump 59
Cooling water is sent by. 41 is the main oil pump 32
This is a gear-type backup oil pump that serves as an auxiliary pump device installed in a piping 54 that bypasses the main oil pump 32.
It has a capacity equivalent to or the minimum capacity necessary to prevent seizure of the bearing 36. 42 is a check valve provided in the discharge side pipe 54 of the backup oil pump 41, and 43 is a turbine 3 provided in the condenser 40.
Pressure switch for detecting the exhaust rising pressure of No. 7, 44
When the pressure of the turbine 37 suddenly increases, the pressure regulating valve 38 is fully closed, so a bypass valve that operates to open and close is provided in the piping 55 that bypasses the pressure regulating valve 38.
Reference numeral 45 denotes a pressure relief valve that opens and closes, and is installed in a test pipe 56 that connects the discharge side and suction side of the backup oil pump 41. This pressure relief valve 45 and the safety valve 39 are set to operate at the same pressure. . 46 is a stop valve provided in the test pipe 56;
Reference numeral 7 denotes a pressure switch that detects the reduced discharge pressure of the main oil pump 32. A starting switch 48 is opened and closed by a signal from this pressure switch 47 or pressure switch 43, thereby starting the backup oil pump 41.
operate. 49 is an air valve that is activated by a signal from the pressure switch 43, and when the air valve 49 is activated, a bypass valve 44 and a stop valve 46 connected to this system 57 are activated.
operate. 50 is a high pressure relief valve provided in a pipe 58 that bypasses the bearing 36. That is, it corresponds to the conventional safety valve (8 in FIG. 1).

Next, backup oil pump 41 due to power cutoff
This section explains how to start the .

First, the power source is the same, main oil pump 32 and condenser 4
If the cooling water pumps 59 of 0 stop at the same time,
The discharge pressure of the main oil pump 32 decreases, and the condenser 40
pressure increases. This pressure change is detected by the pressure switch 47 or pressure switch 43, and the air valve 4
9 is opened, the bypass valve 44 of the pipe 55 is opened, and the stop valve 46 of the test pipe 56 is closed.
At the same time, the backup oil pump 41 is operated via the start switch 48 to supply lubricating oil to the bearing 36 of the turbine 37 via the pipe 55.

Further, the main oil pump 32 and the cooling water pump 59 are powered by separate power supplies, and when only the cooling water pump 59 is stopped, the pressure in the condenser 40 increases. This pressure increase is detected by the pressure switch 43, and the air valve 49, the bypass valve 44, the stop valve 46, and the backup oil pump 41 are operated in the same manner as described above, and the main oil pump 3
2 as well as the bearing 36.

Further, if the main oil pump 32 and the cooling water pump 59 are powered by separate power supplies and only the main oil pump 32 is stopped, the discharge pressure of the main oil pump 32 will decrease. This pressure drop is detected by the pressure switch 47, and the air valve 49, bypass valve 44, stop valve 46, and backup oil pump 41 are operated to supply oil to the bearing 36 in the same manner as described above.

Next, the increase in the discharge pressure of the backup oil pump 41 will be explained. This backup oil pump 41
A gear type pump is used, which has a small change in discharge pressure even when a large pressure change occurs, and has the pump characteristics shown in Fig. 4. As is clear from this figure, the discharge pressure, that is, the pressure of the turbine 37 (see Figure 3) increases, and the pressure of the pipe 52 opening to the bearing 36 increases from the normal discharge pressure A to the maximum emergency pressure B. The bearing 36 can also be lubricated without substantially reducing its flow rate C. This pump characteristic can also be obtained with piston pumps.

In this embodiment, a gear type pump is used, but if a centrifugal type pump is used, the pump characteristics will be as shown in FIG. As is clear from this figure, there is no problem at normal discharge pressure A during normal operation, but when the pressure of the turbine 37 increases, the discharge flow rate C' decreases and becomes zero before reaching the emergency maximum pressure B. Therefore, when using this centrifugal pump, it is necessary to consider these effects and use one with a large capacity.

Next, returning to FIG. 3, the backup oil pump 41
The test operation will be explained. Since the backup oil pump 41 must operate reliably in an emergency, it is necessary to periodically test it during normal operation. Now, when the backup oil pump 41 is driven while the main oil pump 32 is in operation, oil flows through the test pipe 56 and is returned to the suction side of the backup oil pump 41 through the pressure relief valve 45.

Note that when the discharge pressure of the main oil pump 32 rises above a predetermined level, the safety valve 39 opens and oil is returned to the oil tank 31 from the piping 53 to absorb the pressure.

Similarly, when the pressure in the turbine 37 rises abnormally and the pressure inside the pipe 52 between the bearing 36 and the pressure regulating valve 38 rises, the high pressure relief valve 50 opens and the oil tank 31 absorbs the pressure to ensure safety. do.

Further, in this embodiment, the backup oil pump 41 is operated by detecting the discharge pressure of the main oil pump 32 and the pressure of the condenser, but it is of course possible to directly detect power cutoff in addition to detecting these pressures. It is.
As mentioned above, in the case of the safety valve 8 (Fig. 1) of the prior art, the pressure of the oil supplied to the bearing 6 is determined by the pressure regulating valve 9, so even if the pressure of the safety valve 8 is increased, it will not cause an abnormality. Sometimes, the atmospheric pressure in the bearing increases and the supply stops, so even if the pressure in the safety valve 8 is increased, it is meaningless.

In the present invention, the bypass valve 44 shown in FIG. 3 opens in the event of an abnormality to allow high-pressure oil to flow bypassing the pressure regulating valve 38.
Since it is set to 0, the flow to the oil tank can be blocked even in the event of an abnormality. When the pressure rises above the abnormal pressure, the high pressure relief valve 50 is activated. That is, the high pressure relief valve 50 is useful in conjunction with the function of the bypass valve 44.

According to the present invention, the bearings of the emergency turbine can be reliably lubricated without increasing equipment costs, and the effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a conventional turbine bearing lubrication device, FIG. 2 is a system diagram explaining an exhaust heat recovery plant, and FIG. 3 is a system diagram showing an embodiment of the sealed turbine bearing device of the present invention. FIG. 4 is a performance characteristic diagram of a gear type pump, and FIG. 5 is a performance characteristic diagram of a centrifugal pump. 31...Oil tank, 32...Main oil pump, 33
... Check valve, 36 ... Bearing, 37 ... Turbine,
38...Pressure regulating valve, 41...Backup oil pump, 42...Check valve, 43...Pressure switch,
44...Bypass valve, 45...Pressure relief valve, 46
... Stop valve, 47 ... Pressure switch, 49 ... Start switch, 50 ... High pressure relief valve, 54, 55 ...
...Piping, 56...Test piping, 58...Piping.

Claims (1)

[Claims] 1. A system that circulates lubricant to the bearings, a main pump device installed in this system, a lubricant reservoir installed in the suction side system of this main pump device, and a lubricant reservoir installed in the discharge side system of the main pump device. A sealed turbine bearing comprising a pressure regulating valve, an auxiliary pump device provided in a bypass system that bypasses the main pump device, and a detection device that drives the auxiliary pump device when the power source for driving the main pump device is cut off. In this lubricating system, a bypass system is provided in parallel with the pressure regulating valve to bypass the pressure regulating valve, and a bypass valve that opens when the turbine internal pressure rises is provided in the bypass system, and the bearing side of the pressure regulating valve is provided with a bypass system that bypasses the pressure regulating valve. between the system and the lubricant reservoir,
A lubricating device for a sealed turbine bearing, characterized by being equipped with a high pressure relief valve.