Plastic Pumps vs. Plastic-Lined Pumps for Chemical Applications

Posted: 4/7/2014

Owing to their well-earned reputations for consistent performance, sealless magnetic drive pumps are increasingly being employed in chemical process applications. Given their characteristics, magnetic drive pumps have made steady inroads into industries traditionally served by conventional mechanical seal pumps. Both the Chemical and Pharmaceutical industries are increasingly using plastic-lined sealless magnetic drive pumps to pump highly toxic and corrosive substances. And whether it's a centrifugal pump or a self-priming pump, generally speaking a chemical pump that's suitable for pumping corrosive liquids is subject to strict standards when in terms of safety, atmospheric leaks and of course, service life. These high requirements are the reasons for the trend towards sealless in particularly, magnetic drive pumps.

Plastic-lined pumps have become more and more popular in chemical process applications that present challenging conditions where, for instance, zero environmental leakage is a necessity. But are they the best pump choice for such applications? Or are there pumping applications that would be bettered served by a polypropylene or kynar plastic pump rather than a plastic-lined pump? Both pump types offer a higher than metallic degree of corrosion resistance, temperature capability, resistance to permeation and abrasion. But there are several crucial differences that should be considered when deciding between the two pump types.

First and foremost among these differences has to be the simple fact that plastic magnetic drive pumps are simply less expensive than comparable plastic- lined pumps. On the other hand lined-pumps offer the advantages of the superior pressure handling capabilities of their metal shells. That said; the majority of chemical pumping applications won't require the pressure handling capabilities lined pumps offer. It's also worth noting that many plastic-lined pumps have coating between 1/8 and 3/16 thick, that's about the same thickness as a plastic pump; but every plastic pump from the same model line will absolutely feature that thickness whereas plastic-lined pumps from the same model lines will inevitably have more variance.

Plastic-lined pumps are also typically coated in particular expensive ETFE or PFA plastics. Both are superior to Polypropylene and Kynar in terms of their ability to handle a wider range of chemicals, higher concentrations of those chemicals and at higher temperatures. However, the overwhelming majority of chemical processes don't require higher resistances tan those offered by Polypropylene or Kynar pumps. For obvious reasons, lined pumps also weigh more than plastic pumps, which adds to their expense in the form of increased freight costs.

Lined pumps have established a dependable service record over the last few decades that points to their suitability for chemical handling, they are particularly capable where corrosive and hazardous liquid wastes or chemicals have to be contained and pumped or in situations where fire or other accidents are a concern. But they aren't for every application and their use could actually be considered overkill for smaller flow chemical pumping applications under 200GPM where a plastic pump would be better suited to the task.

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