Leakage issues with the mechanical seals of individual butadiene pumps
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This post was last edited by Jiangshang Shanren on 2017-12-6 at 13:21. The pumps used in the butadiene plant where I work are mostly centrifugal pumps. Compared to shielded pumps, centrifugal pumps have their advantages: they require fewer stringent conditions regarding the medium used, and their maintenance as well as the replacement of spare parts are more cost-effective. Butadiene material has its own characteristics; it tends to polymerize at high temperatures. Therefore, during the pumping process, polymers can easily cause wear to the mechanical seal of the pump, leading to leaks. Solution: Besides replacing the new seal, I’ve heard of using nitrogen lines for purging and water flushing systems at the seal location, but I’ve never seen it in person. Does anyone know how to reduce seal wear, or are there any viable solutions that allow avoiding frequent seal replacements?
Just state the problem; in the future, avoid using terms like “guru” or “pleading earnestly”.
First, introduce your sealing and flushing solution or the previous diagram, so that everyone can help you.
I study engineering, so I’m not very familiar with equipment. Our centrifugal pumps are equipped with only one set of end-face sealing devices, and do not have a sealing flush system
For materials with particles, those that are wear-resistant should be chosen; regarding the flushing method, there should be an in and an out flow, such as 54
The medium should be free of particles, but a small amount of polymer is generated upon transport through the impeller due to high temperatures. Is it feasible in terms of process design and budget to add flushing equipment to an existing pump system? Where can I find relevant information? Thank you
One of the reasons why mechanical seals can provide sealing is the presence of a liquid film in the friction pair between the stationary and rotating rings; this liquid film is usually the process fluid. Your process fluid is butadiene, and butadiene generates heat during rotational friction, which makes it more likely to polymerize into particles that affect the lifespan of the mechanical seal. If this mechanism is understood, one will know how to solve this problem; one method is to apply cooling water or coolant from the outside to lower the temperature of the mechanical seal. For double-end face seals, lubricants such as white oil are used in between; this changes the liquid film in the friction pair from the process fluid to an external liquid that does not polymerize. If the process medium is not sensitive to the lubricant, applying pressure to the lubricant can yield even better results. At present, the technology for mechanical seals under such normal operating conditions is already well-developed in China; mechanical seals modified in this way generally have a service life of two years.
Please take a look at our pump sealing system: the left side should be the cooling system, while the right side is the white oil sealing system. I would like to ask how white oil circulates in end-face sealing? This pump is the one whose mechanical seal needs to be replaced most frequently.
In the mechanical seal system, there is a component inside that is designed to resemble an impeller and rotates along with the shaft; white oil circulates within it. Judging from the overall external structure of your mechanical seal, its design is already quite reasonable; it has a self-circulating cooling fluid, so I don’t think any further changes to the process are necessary. If the service life is not long, I personally suspect there are issues in the following areas: First, your seal oil tank is equipped with a pressure injection pump, which means that the seal oil needs to be pressurized. Since the photos in the diagram are not shown, it’s not clear whether your sealant tank is already under pressure and whether that pressure has reached the designed value. II. Since butane is prone to polymerization, the cooling heat exchanger at the outlet of the mechanical seal can easily get clogged with polymers; it is necessary to clean it thoroughly to ensure that the flushing line remains unobstructed and that the temperature of the mechanical seal can be reduced. II. During each repair for seal leakage, it is necessary to check whether the leakage is indeed caused by wear of the stationary and rotating rings; improper material of the O-rings or blockages in the springs can also lead to leakage. If the material of the O-ring is not suitable, upgrade it; if the spring is clogged with polymer, replace multiple springs with a single one. III. Feel the flushing inlet of the pump and the outlet pipe of the seal oil system; if the temperature is indeed above 70 degrees as you described, then the external process needs to be modified in order to reduce this temperature.