Chemical Centrifugal Pumps

Some Typical Applications for a Chemical Centrifugal Pump

Pumping equipment relies on several different types of mechanical action for its functionality. Some models utilise a plunger or piston to draw in and then discharge a liquid, while others might emulate the peristaltic action of the intestine by compressing a flexible tube to keep its fluid contents in motion. A third variety employs the rotational force generated by a fan-like device with curved vanes, an impeller. Typically, the latter mechanism is responsible for the centrifugal pumps’ action widely used by the chemical industry in numerous applications.

Their operating principle differs markedly from the other types mentioned, which are examples of positive displacement devices. The user may choose from two casing designs that determine the performance characteristics. The appropriate choice will depend on the intended use. However, given the nature of the fluids to be handled, the most crucial requirement of these devices is that materials used in any components that may come into contact with those fluids must be highly resistant to their corrosive action.

The list of industries employing chemical centrifugal pumps for various applications is a lengthy one, and, not surprisingly, those companies that manufacture chemicals tend to occupy pole positions. These companies produce compounds such as ammonia, sulphuric acid, sodium hydroxide and numerous other corrosive or caustic materials essential to other manufacturers who incorporate them in a wide range of products intended for domestic, commercial and industrial use.

Aggressive liquids are also a common feature of the mining industry, where both corrosive and abrasive action can pose a constant threat to pipelines and pumping equipment. For companies faced with such challenges, a chemical centrifugal pump can be invaluable in many applications, such as transferring slurries and liquid waste from ore processing.

In addition to the essential resistant properties provided by materials such as stainless steel, Hastelloy-C and, more recently, thermosetting epoxy resins, these devices offer users another significant benefit. The reciprocating or compressive action of the positive displacement models results in a pulsed discharge stream that can be useful when it’s necessary to deliver successive, fixed volumes of a liquid. By contrast, the rotational energy produced by an impeller generates a continuous discharge of fluid at a given pressure and flow rate, making the chemical centrifugal pump the best choice for numerous applications.

While one may not associate the food and beverage industry with aggressive liquids, many of its everyday products are highly viscous, such as tomato ketchup, custard and pureed fruits. During the processing of these products, they are transported by pipelines. Accordingly, equipment must be kept free of any residual foodstuffs that may contain a potentially dangerous allergen or provide a breeding ground for bacteria when switching between products to comply with the exceptional hygiene standards demanded of the industry. For these reasons, the industry will often favour using a chemical centrifugal pump for those applications in which regular sterilisation of equipment with superheated steam after each use is essential.

While the pump is often an inline component of a pipeline system, it must perform when submerged in some circumstances. In inline use, seals act to prevent leakage of the contents into the external environment. However, when immersed in the liquid that requires pumping, it is equally essential to prevent fluid from leaking inwards in a region where it could penetrate the motor. Unfortunately, seals are subject to damage as a result of long-term wear and tear. Sealless technology offers a means to use a chemical centrifugal pump when submerged in applications such as draining sewage and chemical spillages.

In these units, there is no connection between the impeller and motor, so sealing is unnecessary. Instead, motive power is supplied indirectly by electromagnetic induction, allowing the drive unit to be housed in a solid casing with no need for any opening that would require a seal. A magnetic drive unit can be particularly beneficial when handling organic solvents, as these are often highly flammable. The motor is completely isolated from the impeller chamber in these chemical centrifugal pumps, so there is no risk that a stray spark could trigger a fire or explosion in such applications.

Prochem is recognised as a leading South African manufacturer and supplier of pumping equipment. Its world-class products include corrosion- and abrasion-resistant units manufactured locally from epoxy resin and the Finish Thomspon range of magnetic drive centrifugal pumps favoured by the chemical industry in numerous applications.

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