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Diesel Generator Sealing Oil System Analysis

Generator Sealing Oil System Analysis

The oil required for the generator seal tile (ring) refers to the turbine bearing lubricant. Most people are used to calling the seal oil according to the purpose. The sealing oil system is a system for supplying oil to the generator sealing bush, and the oil pressure is higher than a certain amount of hydrogen pressure in the generator to prevent the hydrogen in the generator from leaking outward along the gap between the rotating shaft and the sealing tile. It also prevents the oil from being too high and causes the generator to enter the oil in large quantities.

Sealing oil system technical parameters summary:
Sealing tile oil inlet temperature: 25～50°C- l7
Sealing tile oil temperature: ≤70°C
The sealing tile oil pressure is greater than the internal hydrogen pressure: 0.056±0.02MPa
Oil demand of sealing tile: steam end 92L/min; excitation end 92L/min

Generator seal oil systems are available in dual flow and single flow ring systems. The single-flow ring seal oil system equipment is divided into several units. Namely: sealed oil supply control device (including vacuum oil tank and vacuum pump); enlarged tank and float tank (for hydrogen side oil return); air extraction tank installed in generator bearing lubricating oil return line and its exhaust fan.

Sealing oil system main equipment

Enlarged slot

The steam end of the generator and the hydrogen side of the excitation end (bounded by the sealing tile) each have a drain pipe connected to the expansion tank, and the oil discharged from the seal ring is expanded in the tank so that the oil containing hydrogen can separate the hydrogen. There is a horizontal partition in the enlarged tank, and the enlarged tank is divided into two compartments, and the U-shaped pipe is connected through the outer side, so as to prevent the gas from being in the sealed oil drain pipe due to the fan pressure difference between the two ends of the generator. Loop in. Inside the enlarged tank, there is a pipeline connected with the oil water detecting alarm, and an alarm signal is issued when the oil level in the enlarged tank rises above a predetermined value.

Float tank
The hydrogen side oil returns to the float tank after expanding the tank. The function of the tank is to further separate the hydrogen in the oil. The float tank is equipped with a float valve that automatically controls the oil level. In order to keep the oil level in the tank within a certain range. A manual bypass valve and a liquid level inspection window are installed outside the float tank to allow manual operation of the oil level if necessary. Under low hydrogen pressure (O.05MPa or less) operating state, the float valve in the float tank moves slowly, which will cause oil draining. At this time, the bypass door should be opened properly and the oil level should be closely monitored. The float oil level The value of the hydrogen pressure required to return to normal is measured by actual conditions.

Air extraction slot
The air-side sealing oil of the generator is mixed with the bearing lubricating oil and discharged into the air extraction tank. The gas in the oil is separated and discharged to the outside atmosphere through the exhaust fan, and the lubricating oil flows back to the main tank of the steam turbine through the pipeline.

Sealing oil control device
The main equipment in the sealing oil control device has two main AC oil pumps, one for standby, one for standby, which are all driven by AC motor, so it is also called AC oil pump; one recirculating oil pump and one accident oil pump, when the main oil pump fails The pump is put into operation. It is driven by a DC motor, so it is also called DC oil pump; a pressure difference valve is used to automatically adjust the oil pressure of the sealing tile, so that the pressure automatically tracks the gas pressure in the generator and stabilizes the oil-air pressure difference. Within the scope of the need. When the oil-air pressure difference needs to be changed, it is only necessary to adjust the compression spring of the differential pressure control valve.

Vacuum device
The equipment in the vacuum unit mainly refers to a vacuum tank, a vacuum pump and a recirculation pump, which are oil purifying devices in a single-flow annular seal oil system. The vacuum pump works uninterruptedly to maintain the vacuum in the vacuum tank. At the same time, air and water (steam) are extracted and discharged. In order to accelerate the release of air and water from the oil, a plurality of nozzles are arranged inside the vacuum tank, and the oil that is added to the vacuum tank is passed through the nozzle at the end of the replenishing pipe, and the recirculating oil is diffused through the nozzle at the end of the recirculation pipe to accelerate the gas and water. Separated from oil. The recirculation pump is a single-stage centrifugal pump that uses a line to create a partial circulation loop of oil in the vacuum tank for better oil purification. In order to ensure the hydrogen purity of the generator, the gas in the sealing oil must be minimized. Generally, the lower limit of the degree of vacuum is set to -88 KPa.g, and an alarm signal is issued when the lower limit value (refer to a decrease in vacuum) is exceeded.

Vacuum tank
In normal operation (here, the AC main seal oil pump is put into operation for normal operation), the bearing oil is continuously replenished into the vacuum tank, and the air and water contained in the lubricating oil are separated in the vacuum tank through the vacuum pump. And the vacuum line is discharged outside the plant, so that the oil entering the sealing tile can be purified to prevent the air and water from polluting the hydrogen in the generator. A floating ball valve is arranged in the vacuum oil tank, and the floating ball of the floating ball valve is lifted and lowered with the oil level, thereby adjusting the opening degree of the floating ball valve, so that the filling speed is controlled, and the oil level in the vacuum oil tank is also controlled. The liquid level of the vacuum tank is the normal oil level in the middle position of the liquid level observation window, and the high and low liquid level alarm signals are issued upwards or downwards at about 100 mm. The normal oil level is within the upper and lower 6Omm range. The oil level is low and the oil pump is easy to "cavitation". As a result, the output pressure and flow will drop, even without flow output.
The reason for the low oil level of the vacuum tank is that the float valve fails to operate; the second is that the nozzle at the outlet end of the float valve (in the vacuum tank) is blocked by dirt. In both cases, the vacuum tank must be taken out of service and the vacuum pump stopped. After the recirculation pump and the main seal oil pump (replace the oil supplied by the accident seal oil pump) to destroy the vacuum, drain the oil and then open the manhole cover of the vacuum tank for maintenance. In addition, due to the abnormal increase of the gap of the sealing tile, the oil level of the vacuum oil tank may always be low. At this time, the total oil quantity of the sealing tile can be measured, and the measurement result can be compared with the original record to determine whether the sealing gasket gap is not Normally increased. If confirmed, a new sealing tile must be used to solve the problem.
The sealing oil system mainly includes: a normal operation circuit, an accident running circuit, and an emergency sealing oil circuit (ie, a third sealing oil source).
Normal operation circuit: bearing lubricating oil supply pipe → vacuum oil tank → main seal oil pump → oil filter → differential pressure valve → generator sealing tile → hydrogen side oil discharge (empty side oil discharge without expansion groove and float oil tank directly return air Pull out the trough) → enlarge the trough → float tank → air extraction trough → bearing lube drain pipe → turbine main tank.
The accident running circuit does not pass the vacuum oil tank: bearing lubricating oil supply pipe → accident sealing oil pump (DC oil pump) → oil filter → differential pressure valve → generator sealing tile → hydrogen side oil discharge (empty side oil discharge without expansion groove and The float tank directly returns to the air extraction tank) → enlarge the tank → float tank → air extraction tank → bearing lubricant drain pipe → turbine main tank. Emergency sealing oil circuit: the bearing lubricating oil supply pipe directly passes through the differential pressure valve to the sealing tile. When the main sealing oil pump and the DC oil pump are both disabled, the bearing lubricating oil directly seals the hydrogen in the generator as a sealing oil source. At this time, the hydrogen pressure in the generator must be reduced to 0.05 MPa.
As long as the generator shaft rotates or there is gas in the machine that needs to be sealed, the seal oil system needs to supply oil to the seal. When the generator shaft rotates, the sealing oil pressure is higher than the internal hydrogen pressure O.05～0.O7MPa.g; when the generator shaft is stationary, the sealing oil pressure is higher than the internal hydrogen pressure of 0.036～0.056MPa.g.
When the generator is in an air state, such as the sealing tile needs to supply oil, it is economical to supply oil to the sealing tile according to the operation mode of the third oil supply circuit.
When the accidental sealing oil pump (DC pump) is put into operation, since the sealing oil cannot be purified without passing through the vacuum oil tank, the air and moisture contained in the oil may diffuse into the generator with the hydrogen side returning oil, resulting in a decrease in hydrogen purity. Strengthen the monitoring of hydrogen purity. When the purity of hydrogen is significantly reduced, the exhaust valve at the upper part of the expansion tank should be operated every 8 hours for sewage discharge, and then high-purity hydrogen gas is supplied into the generator through the hydrogen main pipe.

AOT ELECTRONIC TECHNOLOGY CO.,LTD which has 15 years experience in diesel generator spare parts manufacturing. We provide full kinds of generator spare parts for engine replacement and other related electric products such as automatic transfer switch, electric Relay etc. Welcome to contact us for more information.

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