MATERIALS HANDLING
Composite blends have self-lubricating benefits, but wear quickly and sacrifice useful life at the fast rotational speeds of centrifugal pumps, leading to failure. Solids handling: most chemicals contain some level of suspended solids or particulates that come from either the process or supply tanks. Te solids will rub against the pump’s casing and other internal components, causing wear. Both centrifugal and gear pumps rely on internal circulation paths, which can be clogged by solids and cause failure. In the case of centrifugal pumps, the solids are thrown around at such high velocities that pitting and premature wear will occur even quicker. For gear pumps, the result of solids handling is the same as dry run: failure. Solids cause gear pumps to lock and fail. At best, solids wear down contacting gear components, resulting in reduced pump capacity.
NPSH imbalance/cavitation: every pump consumes net positive suction head (NPSH). If a pump consumes more NPSH than the system provides, vapour forms and cavitation will result. Cavitation is the violent implosion of entrained vapour bubbles that sends shock waves and vibrations through the fluid. Depending on the intensity and frequency of the cavitation, the pump’s internals degrade, leading to breakdowns, leaks and costly downtime and repairs or replacement. Gear pumps fail fast with vapour and thin liquids because of the galling of internal parts and failed bushings. Centrifugal pumps rely on converting velocity head to pressure head, which is not possible with compressible entrained vapour. In short, both centrifugal and gear pumps fail when operating under sustained cavitation and poor NPSH applications. Inflexible operating range: pumps
are typically built to operate at a single specified design point. Meanwhile, these pumps are installed in dynamic systems that operate across a wide range of operating points. Tis is impactful to centrifugal pumps, which have a Best Efficiency Point (BEP), or the single operating point where they are most efficient. Maintaining operation close to BEP is critical to a centrifugal pump’s reliability because a centrifugal pump that operates outside of its BEP will see amplified loads that result in excess stress on the bushings and shaft. Tis stress leads to deflection, rubbing contact, premature wear, leak-path
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development and compromised product containment. Unlike centrifugal pumps, positive displacement (PD) pumps do not require BEP-reliant operation because they function consistently with changing environmental and liquid conditions. In this way, centrifugal pumps have a narrow operating range, whereas PD pumps offer flexibility to operate across the full system range.
THE SOLUTION Sliding vane pumps have proven their standing as a first-choice alternative to centrifugal and gear pumps in chemical- transfer applications because they are simple to use, reliable and flexible. Tey don’t require tuning to a single BEP; the vanes self-compensate for wear, sustaining like-new performance throughout the system’s operational life; and they can easily handle pumping conditions that feature varying system pressure, zero NPSHa, liquid/vapour mix, suspended solids and regular dry-run operation. Te latest advancement in seal-less magnetic drive technology is the Magnes series magnetic-drive sliding vane pumps from Blackmer. Offering a combination of functionality, reliability and flexibility, these magnetic-drive sliding vane pumps deliver performance in severe-duty liquid
transfer for high-value chemical-processing applications. Magnetic-drive sliding vane pumps solve legacy pain points with technically superior functionality that’s designed for chemical and severe-duty applications. Tey eliminate sensitivity to intermittent, extended and unexpected dry-run conditions. Te dry-run capability is orders of magnitude better than competing technologies that rely on bushings made from sensitive ceramics, temporary coatings or soft composites. In contrast to pumps that boast of cumulative allowances, sliding vane pumps have an indefinite dry-run range. Imagine the flexibility of being unaffected by poor operating conditions and operator error. Consider the increased functionality of self- priming, suction-lift, product-recovery and line-stripping operations. Unlike most competing technologies that self-destruct when confronted with contaminants, magnetic-drive sliding vane pumps can effectively process liquids with suspended-solids levels of up to 20%. Performing as a zero-NPSHr solution, magnetic-drive sliding vane pumps are ideal for challenging pump inlet conditions, offering sustained performance with liquids featuring up to 20% vapour or air content. Unlike alternate options that must be
tuned to a single BEP, magnetic-drive sliding
Chemical transfer capabilities pump comparison
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