One-on-one consultation office for mechanical seal installation and fault diagnosis
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I work at a large petrochemical company with 2,000 employees, in the role of equipment engineer; I have been involved in the maintenance of pumps as well as in equipment management for over 6 years. Most of the mechanical seals used in our unit are from Dandong Klon and Liaoyang Pump Industry; a small number of the seals for reaction vessels are of Russian origin. Everyone is welcome to ask me questions regarding mechanical seals in the context of daily work (including seal installation, identification of leakage causes, etc.). I will do my best to provide answers. I am usually online on weekdays. PS: Please approach the discussions with an attitude of learning from and communicating with one another. No one is perfect; let’s learn from each other.* There is a difference in when one learns something, but everyone has their own area of expertise.
The mechanical seal used in our facility in low-temperature conditions showed no issues during installation, but leakage occurred after it had been in use for some time. Upon disassembly and inspection, a gap was found in the stationary ring. What could be the reason for this? One more thing to add is that no other symptoms were observed during use, such as excessive vibration or loud noise.
It’s probably a problem with the method used during the installation of the mechanical seal or with the quality of the product.
What is the temperature for your low-temperature operation? What material is the broken part of the mechanical seal?
-35-degree saline solution; the damaged static ring is made of silicon carbide
The mechanical seal did not provide adequate cooling; it failed when exposed to cold brine. Our shielded pumps also experienced bearing failure, with the sliding bearings being made of silicon carbide. But fewer asbestos sliding bearings explode. It is recommended to improve the seal flushing scheme, or replace the silicon carbide material with something such as cemented carbide.
If there is slight leakage in the mechanical seal, can it be resolved by adjusting the compression amount of the mechanical seal? How to adjust the compression level?
To prevent heat loss, this pump’s mechanical seal uses ethylene glycol as the sealing fluid, and it is necessary to regularly check the concentration of this fluid, with the main goal being to detect any leaks in the mechanical seal in a timely manner
The original poster mentioned canned pumps; I have a question about them. The shielded pumps in our factory are used for handling LNG, at temperatures around -140 degrees Celsius, and they are employed for loading LNG products. Recently, these pumps have started to fail after working fine the day before – the issue lies in the bearings located near the impeller, which wear out frequently. Could you explain what the reason is!
Regardless of whether there is a minor or severe leak, the mechanical seal must be removed and inspected to check the rotating and stationary rings as well as the compensation mechanism; remember to check the shaft shoulder pad as well. Tetrafluoride is prone to being crushed or corroded. Regarding the pressure rating, first determine whether your mechanical seal is modular or non-modular. For the former, no adjustment is needed; the thickness of the shutter itself determines the pressing amount. For the latter, a depth gauge is needed to make the measurement; after adjusting the pressure, the screw should be tightened. These days, containerized types are more common.
Firstly, the boiling point of LNG is around -169°; if I’m not mistaken, this is definitely lower than -140°. At this temperature, the LNG circulating inside the pump is in a gas-liquid mixture state, which makes it not an ideal fluid for flushing the bearings. In such cases, a vertical shielded pump or one equipped with an auxiliary impeller should be used. You’d better mention the type or model of your centrifugal pump, as well as its structure. Of course, it’s possible to find some time; I believe they won’t make such a basic mistake