Written by James Crowell, Field Service Engineer
As with all mixing equipment a seal needs to exist to keep product inside the mixing chamber. Our equipment addresses this with two types of seals, single mechanical, and double mechanical seals. A single mechanical seal is simply two seals faces pressed together by spring tension. A double mechanical seal has two sets of seal faces, one set to prevent product from leaking, and one set to retain the barrier/buffer fluid used for lubricating and removing heat. Unfortunately, the seal is typically the weakest link in the system, however most seal failures can be prevented with proper treatment and a little preventative maintenance.
Single Seal Failure: Two of the most common reasons why single mechanical seals prematurely fail:
- running machine without product in the chamber
- poor cleaning, leading to left behind product that hardens and becomes abrasive
Single mechanical seals are lubricated and cooled with the product being run through the machine. It is imperative that the unit is not run without product in the chamber. It will only take a matter of seconds for a dry running seal to overheat and fail! The second most important part of maintaining a single seal is to make sure it is thoroughly cleaned after each run. Residual product being left behind can dry and harden and become abrasive, and this can lead to premature wear. If the product is sticky enough it can lead to breaking the actual seal faces the next time you turn the unit on. Typical CIP cleaning cycles will remove residual product and help prevent seal failure.
Double Seal Failure: Double mechanical seals are lubricated by both product and a barrier/buffer fluid such as water, or glycol. The barrier/buffer fluid is regulated by a Safeunit which allows for adjustment of pressure and flow. With the double mechanical seal, the most important step is to make sure the barrier/buffer fluid is on prior to starting the unit. If the double mechanical seal is run without the barrier/buffer fluid, the seal will overheat and fail.
To help prevent double seal failure, we offer an alarm that is tied into your controls that, unless the barrier/buffer fluid is on, it will not allow the unit to run. This is very effective at helping prevent premature failure. Along with removing heat and lubricating the seals, the barrier/buffer fluid also helps remove residual product and keeps the seal faces clean. This coupled with a typical CIP cycle will help keep the seals clean and help prevent premature failure.
If you would like to learn more about how to prevent premature seal failure, please contact Admix and we can arrange on site training for your maintenance staff. This training includes a classroom session to review all aspects of your mixer, including seals, as well as assembly/disassembly training on your actual piece of equipment.