Seals, typically either packing or a mechanical seal, are one of the components most often replaced in a slurry pump. Abrasive particles can easily wear through packing or clog mechanical seal components. In either case, seal life in a slurry environment can quickly be reduced down to weeks or even days. In operations where downtime can cost tens of thousands of dollars an hour, you can reap significant rewards by choosing not only the best sealing solution but also one that is easy and quick to replace.
In this post, we’ll focus on some of the best practices to speed up packing and seal replacement as much as possible when it is necessary.
When replacing packing, one of the biggest hassles is removing the lantern ring. Lantern rings can get off-axis and bind up in the stuffing box. Sometimes they get clogged and filled with particulate—making removal difficult and time consuming. Due to these difficulties, it is unfortunately a common practice to leave the lantern ring in place and only repack the rings above.
Here’s why we don’t recommend that approach:
So what to do about difficult lantern ring removal? It’s simple – don’t use a lantern ring.
Another way to make re-packing of a slurry pump easier and less time consuming is to purchase pre-cut rings. Most packing manufacturers now offer rings pre-cut for a small fee, which is easily recouped through eliminating the time and scrap required when cutting them yourself. You’ll know that the rings are the correct size, and the cuts were made accurately and with a sharp blade.
The biggest hassle with modern cartridge mechanical seals is installation. The single-piece cartridge seal is significantly easier to install than component seals, but this design still has its drawbacks. Installing a cartridge seal requires decoupling the power end and often moving pump/motor components. And since slurry pumps are often very large, this can become extremely time-consuming. The answer is to use the next step up in mechanical seal technology: advanced split seal design, such as that used in the Chesterton 442C Split Seal.
Over the past decade split seals have evolved to have fewer components, making installation a matter of minutes rather than hours. This seal design can also now achieve seal life equivalent to a non-split seal. Newer features also include fully split O-Rings and easy field-repair capabilities.
The only disadvantage in a slurry pump environment is that split seals do not typically have the features of a heavy-duty cartridge slurry seal, so setting up the appropriate environmental controls is paramount:
When flush isn’t an option, heavy-duty slurry seals have features such as non-clogging external springs, larger clearances to reduce clogging, and high-strength drives. These can often operate flushless under certain conditions, which can be improved with other environmental controls.
Although we have only talked about sealing considerations, there are many other ways to protect your assets and ease maintenance:
Stay tuned for more detailed posts on these topics!
Ron Frisard is Field Product Manager of Packing & Gaskets for A.W. Chesterton Company. He has worked for Chesterton for 27 years in all facets of valve and pump packing. Ron has presented at many conferences including the Electric Power Research Institute (EPRI), the American Society of Mechanical Engineers (ASME), and Valve World in Europe and America. Ron is also currently the Vice Chair for both the Packing and Gasketing divisions of the Fluid Sealing Association (FSA).
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