Centrifugal Pumps: To Seal or Not to Seal
The most common pump used to transfer corrosive fluids is, hands down, a centrifugal pump. These energy-efficient pumps provide smooth fluid flow, are available in standard flooded suction or self-priming designs, and offer a large variety of sizes to handle applications from a few gallons (or liters) per minute, to hundreds and even thousands of gallons (or liters) per minute.
Standard centrifugal pumps usually incorporate a mechanical seal to prevent leakage where the internal rotating impeller shaft protrudes through the stationary pump housing. This is similar to how the water pump in an automobile uses a mechanical seal to prevent coolant leakage from the pump. With this design, mechanically sealed pumps often have a lower initial purchase price compared to other types of pumps and can handle some solids as well as fluids.
The downside of a mechanically sealed pump, however, is that if the pump is operated without liquid (known as dry running), the friction causes the seal faces to rapidly heat up, causing wear and eventually failure. As such mechanically sealed pumps cannot run dry without damage unless equipped with a seal flush system and have a higher life cycle cost. Plus, they are more complex to specify for corrosive fluids due to many variations of seal types and construction materials.
The best way to completely eliminate the issues created by mechanical seals is to eliminate the mechanical seal and opt for a sealless, mag-drive centrifugal pump. Unlike a mechanically sealed centrifugal pump, a sealless mag-drive pump has no physical connection between the motor shaft and the impeller. Plus, the life cycle cost is generally lower compared to a mechanically sealed pump due to the lower maintenance cost (no seals to replace), ease of installation (no water/ drain lines for seals that require a flush fluid), and increased productivity (less downtime).
These differences in mechanically sealed versus sealed mag-drive centrifugal pumps is a key differentiator when choosing the best pump for your specific applications.
About Finish Thompson
Finish Thompson Inc. designs and manufactures pumps for the safe transfer of a wide variety of corrosive liquids. Products include centrifugal sealless magnetic drive pumps with run-dry capability, mechanically sealed pumps, drum and barrel pumps, vertical mag-drive pumps, multi-stage pumps, and the FTI Air line of air operated double diaphragm (AODD) pumps. For durable solutions for your applications, contact Finish Thompson Inc.