Judgment and Treatment of Mechanical Seal Failure of Sealing Oil Pump DLXB820-R67

In thermal power plants, the generator sealing oil system is a key link to ensure hydrogen sealing. As the core equipment of the system, the reliability of the mechanical seal of the sealing oil pump DLXB820-R67 is directly related to the safe operation of the unit. However, due to long-term exposure to high pressure, high temperature and medium corrosion, the mechanical seal may fail. For engineers who maintain power plant equipment, timely detection and judgment of the sealing failure of the sealing oil pump is the first step to avoid major failures. Today we will share the typical manifestations and judgment methods of DLXB820-R67 mechanical seal failure, and tell you the coping strategies.

I. “Signal Light” of Mechanical Seal Failure of Sealing Oil Pump

The original intention of the design of the double-end mechanical seal is to achieve dual protection of high-risk media through two sets of sealing pairs and auxiliary seals of the dynamic ring and the static ring. However, when the following phenomena occur during the operation of the sealing oil pump DLXB820-R67, it often indicates potential problems in the sealing system:

1. Abnormal drop in the sealing liquid level

In the sealing oil system, the sealing liquid level of the balance tank is an important indicator for judging the sealing status. If the liquid level is observed to drop continuously and rapidly, it usually indicates that the lower end face seal ring is damaged, or foreign matter intrusion causes the seal surface to wear.

2. Excessive leakage

According to industry standards, the allowable leakage of mechanical seals usually does not exceed 10 mL/min. If the amount of liquid flowing out of the leakage hole of the sealing oil pump DLXB820-R67 significantly exceeds this value, the cause must be immediately investigated. For example, during the operation of the hydrogen side oil pump, if the leakage suddenly increases to more than 20 mL/min, it may mean that the pressure of the sealing liquid circulation system is unbalanced or the cooling water supply is insufficient.

3. Abnormal sealing liquid color

The color change of the sealing liquid is an intuitive signal to judge the wear of the sealing material. Under normal circumstances, the sealing liquid should be clear and transparent or slightly yellowish. If the liquid is observed to be turbid black or mixed with particles, it means that the graphite ring is seriously worn. In an actual case, the leakage liquid of a DLXB820-R67 sealing oil pump showed black floccules. After testing, it was found that the surface of the graphite ring had peeled off over a large area and needed to be replaced urgently.

4. System pressure fluctuations

The outlet pressure of the sealing oil pump DLXB820-R67 directly affects the hydrogen sealing effect. If the pressure fluctuations are frequent or the pressure value is lower than the design standard, it may indicate that there is a leak in the sealing system. For example, during a shutdown and maintenance, we found through the pressure sensor record that the outlet pressure of the sealing oil pump dropped by 15% within 10 minutes, and finally confirmed that the auxiliary sealing O-ring aging caused the gas leakage.

5. Abnormal vibration and noise

The normal operation vibration value of the sealing oil pump DLXB820-R67 should be controlled within the range of <0.05 mm on the air side and <0.10 mm on the hydrogen side. If abnormal vibration or explosion sound, metal friction sound and other noises occur during operation, it may be caused by seal wear or axial movement exceeding the standard.

II. Practical experience in judging failure

In actual work, judging the failure of the mechanical seal of the sealing oil pump DLXB820-R67 not only depends on instrument data, but also needs to be combined with on-site observation and experience. Here are a few key steps:

1. Check the sealing liquid circulation system first

Seal liquid impurity inspection: Remove the sealing liquid pipeline filter and check whether there is rust, scale or particulate accumulation. These impurities may be the source of seal surface wear.

Pressure and temperature monitoring: Use the pressure gauge and temperature sensor to confirm whether the pressure of the sealing liquid circulation system is stable and whether the temperature exceeds the design value. If the cooling water supply is insufficient, the sealing surface may fail due to high temperature.

2. Dynamic test of sealing performance

Short-term shutdown test: Under the premise of ensuring safety, shut down the sealing oil pump DLXB820-R67 for a short time and observe the balance of the oil pressure on the hydrogen side and the air side. If the oil pressure on the hydrogen side drops rapidly after shutdown, it means that there is a leak in the sealing system.

Manual cranking inspection: Through the cranking operation, feel the rotation resistance of the pump shaft. If the resistance increases or gets stuck, it may indicate that the seal has caused sleeve damage due to wear or dry friction.

3. Intuitive judgment after disassembly

Seal surface wear analysis: After disassembling the seal assembly, check the contact surface between the dynamic ring and the static ring. If scratches, cracks or large-area wear are found, the seal needs to be replaced.

Auxiliary seal status: Aging, deformation or tearing of auxiliary seals such as O-rings and bellows will also cause seal failure.

III. “Long-term strategy” to prevent failure

Clean the sealing liquid filter every quarter to prevent impurities from entering the sealing surface; check the cooling water system every six months to ensure that the flow and temperature meet the design requirements.

In the corrosive medium environment, use silicon carbide or ceramic sealing rings to improve corrosion resistance; for auxiliary seals such as O-rings, give priority to fluororubber or polytetrafluoroethylene materials to extend the service life.

Install online vibration monitors and leak detection sensors to track the operating status of the sealing oil pump in real time; set pressure and vibration thresholds through the DCS system, and trigger an alarm immediately if an abnormality occurs.

Although the mechanical seal of the sealing oil pump DLXB820-R67 is “hidden behind the scenes”, it is the “invisible guardian” to ensure the safe operation of the generator. Through careful observation, scientific judgment and standardized maintenance, not only can the hidden dangers of sealing failure be discovered in time, but also the life of the equipment can be maximized.

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E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

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