Though you may consider mechanical seals to be quite small mechanisms in slurry-pumping systems, they can be the vital bridge between success and failure. Poor or incorrect seal selection can lead to serious damage to the pumping system. Ultimately, if you want to get the most from your slurry pumps, the choice of mechanical seals is essential. Fluid-handling experts at Controlled Liquid Equipment offer some tips for extending the longevity of these components.
Increasing slurry-pump trustworthiness begins with an understanding of the challenges involved in transferring highly abrasive fluids such as manure, cement, and starch. These pumps certainly have their work cut out for them. Therefore, when selecting a mechanical seal for slurry service:
Robust design characteristics
Heavy slurry usually involves a high solid content. A seal design that can withstand erosive impacts while protecting the seal faces is a must. Specially designed seals for slurry applications typically feature durable construction materials, hardened faces, and heavy-duty springs to ensure the seal faces have the correct pressure setting to seal the system.
When pumping a slurry mixture, process pressure will naturally drive the particle-filled fluid into the sealing interface, causing abrasion and accelerated wear. A restriction bushing isolates the mechanical seal from the harsh process so that the seal is mostly sealing the cleaner, cooler flush fluid.
A proper flushing plan will keep abrasives away from the seal faces. Seal flushing also keeps things moving in the stuffing box to prevent solids stagnation and build-up. As with any pumping application, you should always avoid dry running conditions.
Choosing the proper seal for a slurry pump is just part of the equation. It’s also imperative to select the right pump for the job and to maintain it properly. As with other pumping systems, poor equipment conditions caused by bad bearings, cavitation, excessive impeller loads, and misaligned shafts can lead to excessive vibration and shock to the mechanical seal. A slurry pump running under these conditions will generate more heat and more opportunity for abrasives to enter the sealing interface.
Lubricating Film Matters
According to fluid-handling experts, regardless of your pumping application, a lubricating film at the sealing interface is always needed. A film that is too thick will increase leakage and may allow particulate between the mechanical seal faces, increasing wear from abrasion. Conversely, a film that is too thin will generate heat and degrade materials. Keeping the sealing interface cool and clean will promote longer seal life. Controlled Liquid Equipment are a seal division and deals with many of the top Blue Chip companies all around South-Africa. Here at Controlled Liquid Equipment, we manufacture and supply mechanical seals and gland packing to suit customer designs. We supply a wide variety of pumps, valves and seals to suit our client’s needs.