What are the Limitations of Helical Rotor Pumps?October 16, 2018
Helical rotor pumps are efficient. They feature an all-important discrete pocket pumping capability, transport semi-solid fluids that would defeat other pumps, and they're clearly packed with superior flowrate-managing characteristics. However, even though the above features are desirable, essential even, the technology does have its limitations, just like any other equipment type. Anyway, having talked so often about benefits, here's a brief look at those limitations.
Thermally Sensitive Elastomers
Don't underestimate the strength inherent in a modern engineering plastic or rubber. These materials resist extraordinary abrasive forces, plus they keep right on functioning when hot fluids require pumping. Still, elastomeric compounds can swell and cause obstructions. And, since helical rotor pumps do use elastomeric stators, their outer surfaces can expand towards the rotor, so much so that the expanding rubber attenuates flow.
When a standard rotating pump is upgraded, it's a simple matter to insert the new model. The pumping chambers line up, the volute and pump vanes deliver the required clearance, and the system is ready to go as soon as the bolts and gaskets are compression-fitted. For progressive cavity devices, things aren't so simple. If the equipment is to provide its shear-free, packet conveying feature, then the clearance between the rotor metal and stator elastomer must be configured just-so. Again, a swelling stator or heavily abraded metal rotor will compromise those dimensional tolerances.
Slower Rotational Velocity
Casual observers, should they be permitted access into a plant room, aren't going to see a helical rotor spinning so fast that it blurs before the eyes. Realistically, the clearance dimensions, rotor length, and fluid medium all introduce system friction. Helical rotor pumps are efficient, they're loaded with highly desirable pumping attributes, and they comport themselves very well, but they're not designed to be hyper-fast.
Dealing with Unique Challengesm
A regular rotating pump uses a two-chamber build. The dry electrical motor uses a common drive shaft to create positive displacement in the wet pumping chamber. If the windings become damaged, they smell. If the pump vanes break, then they require replacing. Helical pumps suffer from torn stators and extreme abrasive effects. They're coupled to prime movers, and that coupling can also accumulate damage. In other words, this pump format should only ever be repaired by experts, engineers who're very familiar with this technology.
Again, and this point is worth repeating, helical rotor pumps are special, and they're uniquely qualified when it comes to certain challenging fluid conveyance scenarios. Still, they do have limitations. That uniqueness factor, for instance, can be a drawback, unless the equipment is supported by an engineering group who knows this pumping principle inside and out.
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