What are the causes of steam leakage from the turbine seal?
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In 2005, our factory upgraded and installed new high-pressure centrifugal ammonium pump systems, driven by turbines. These turbines were manufactured by Elliott Company in the United States. However, after operating for some time, leaks occurred in the steam seals at the front and back of the turbines (four carbon ring seals). The steam that leaked in entered the turbine lubricating oil through the turbine oil seals, resulting in severe emulsification of the lubricating oil； After disassembling the turbine, the gap between the carbon ring and the shaft was measured to be around 0.20 mm, which matches the values specified in the reference data. The gap between the spare carbon ring and the shaft was also measured at around 0.20 mm. Could anyone help analyze the cause of the steam seal leakage?
Is it a back-pressure turbine? There is usually an axis seal steam condenser; check to see if the vacuum level is sufficient
For the back-pressure turbine, there is severe steam leakage from the shaft seal, and the pressure in the shaft seal condenser is positive (the power steam is the steam at the turbine exit, at 2.1 MPa); it’s not clear what the cause of this is Is it due to severe steam leakage from the turbine shaft seal? Is it still due to the inability to create a vacuum in the shaft seal condenser?
The clearance issue – is the clearance you’ve chosen too large? ? ?
The evacuator needs to be checked: first, the steam pressure; second, the nozzle size; third, the position of the nozzle can be adjusted; fourth, it is also necessary to check whether the evacuation condenser is leaking. 5. Check whether the pipeline being pumped is unobstructed. At the same time, the gap between the carbon rings is further reduced.
Typical seals generally include vacuum sealing and pressure-sealing, along with gear seals, all of which prevent the medium from leaking into the environment or entering the bearings and contaminating the lubricant. If the tooth seal gap is normal, it is almost always a problem with the pumping seal.
Adjust the gap between the carbon ring and the shaft, and check whether the gear seal gap is normal. Adjust the gap to be as small as possible, ideally between 0.05mm and 0.1mm, to ensure coaxiality.
Whether it is a back-pressure turbine or a condensing turbine, when there is significant steam leakage from the turbine shaft seals, the steam will inevitably heat the bearing housing, causing the bearing temperature to rise to the level at which an alarm is triggered. Additionally, the steam can penetrate into the bearing housing along the axis direction, resulting in the emulsification of the lubricating oil. Without shutting down the system, an air duct (DN10-15) can be installed between the shaft seal and the bearing housing; clean air is blown through this duct to prevent steam from entering the bearing housing, thereby also protecting the bearings from overheating. The effect is quite good; tests on steam turbines have shown that it can reduce bearing temperatures by 8–10°C, and it also solves the problem of lubricant emulsification.
I’ve learned that in general designs, isn’t this wire always included?