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Why Are Your Mechanical Seals Failing?

(Hint: It May Not Be Your Water Treatment Program's Fault)
Mechanical contractors and facilities managers know full well the challenges mechanical seals present. Critical to the functioning of your water management system, but sometimes considered to be the weakest links, they can fail for a variety of reasons, making it tough to diagnose the problem. And of course, the longer it takes to diagnose the problem, the longer the system itself is out of service.

It can become a vicious cycle of failed mechanical seals/system shutdown/system repair that you can’t find your way out of. Read on to learn more about the various causes for seal failure AND the steps you can take to prevent them.

WHY MECHANICAL SEALS FAIL
  • Installation issues. Sometimes the seal is doomed from the start, like when the wrong type of seal or seal material is chosen for the specific application; if the installer uses too much force during the process, or if the pump is installed incorrectly or the installer shortcuts the procedure.
  • Operations issues. Failing to operate the pump properly is another major source of failure. Short-cutting the startup process or running the pump without water are common errors leading to seal damage.
  • Contaminants in the fluid. Like any other component of a fluid-handling system, mechanical seals are susceptible to corrosion damage. If contaminants or corrosive materials begin forming in the gap between the stationary housing and the rotating shaft, the build-up can damage the seal and cause it to leak. 
  • Age. Like anything else, seals will wear down over time. The older the mechanical seal, the higher the probability of a failure.
THE IMPACT OF CORROSION INHIBITORS

Your system may need corrosion inhibitors, but how do you balance that against protecting your mechanical seals from damage? Industry studies indicate this isn’t a problem as long as the corrosion treatments follow the manufacturer’s guidelines. A study by the National Association of Corrosion Engineers (NACE) task group T-7G-6 determined that sodium nitrate-based inhibitors could be used safely in concentrations at least as high as 4000 ppm NaN02 without causing measurable degradation in a mechanical seal. This implies that inhibitors can be used safely as long as the manufacturer’s directions are followed.

The best practice for controlling corrosion is to follow a two-pronged approach. First, treat the water with a corrosion inhibitor designed for your system. Inhibitors can block the chemical reactions that cause corrosive material to form and coat surfaces, preventing corrosive material from taking hold. Second, install side stream filtration to remove seal-damaging contaminants from the water.    

WHAT NEXT?

If you’re facing mechanical seal failure, make sure you’ve taken all the potential causes into account: mishandling of seal components, incorrect seal assembly, improper seal design and materials, improper equipment start-up and operational practices, fluid contaminants, or poor equipment condition. There are many reasons why mechanical seals might fail, but the majority of these can be minimized or prevented with proper planning and oversight. If you’d like to learn more, please feel free to contact us for additional details.