Types of Chemical Handling Pumps and Their Use

Chemical Handling Pumps

The history of pumping equipment is lengthy. Most of it has been devoted to developing new and more efficient ways to transport water. With the arrival of the internal combustion engine, the technology was adapted to circulate the viscous oils required to lubricate its moving parts. As new industries emerged and began to expand, the growing need to work with more aggressive liquids fuelled the demand for chemical handling pumps with the ability to withstand their corrosive effects.

These devices are of several different types, and each has its particular applications. However, they all possess one feature in common. Unlike the earlier cast iron and bronze units used to transport water and lubricating oil, these must be made from more robust materials with improved anti-corrosive properties. The first material to meet this requirement was stainless steel. While it remains in use today, it’s not suitable in all situations.

To deal with the more aggressive liquids, metallurgists addressed the needs of chemical handling pump manufacturers and the industries they supply by developing a range of so-called superalloys. They are essentially alloys of iron with cobalt and nickel but may also include other refractory metals. They are known for their superior strength and exceptional resistance to abrasion, oxidation and corrosion, even at extremely high temperatures. Many non-moving components of these devices are generally made of plastics, such as polypropylene, as these are also largely unaffected by chemical corrosion.


Exploring the Moving Parts of Chemical Handling Pumps

Given the potential danger to workers, it is essential to avoid leaks. Conventional gland packing seals are unsuitable for chemical handling pumps. Instead, these models have mechanical spring-loaded seals. Alternatively, some models are now powered by electromagnetic induction motors and are sealless. All the moving parts are encased in the airtight housing. Thus, the absence of a drive shaft eliminates any need to fit vulnerable seals. This design also has advantages when transferring organic liquids, which are often highly inflammable. Isolating the motor from the pump chamber and its contents ensures that no stray spark from the armature can come into contact with the vapour and cause a fire or explosion.

Of the various types of chemical handling pumps used in industry, the most common rely on the centrifugal force for their operation. They employ one or more fan-like impellers, depending on the power required. The rotating impellers draw liquid into the housing, forcing it against the sides and accelerating it towards the outlet. They are highly efficient, easy to use and, due to their straightforward design, they are generally cheaper than other, more complex models. However, as they lack the suction power of other pump types, they will work best when used to transfer low viscosity fluids at relatively low pressures.


Choosing the right handling pumps

Other chemical handling pumps rely on a principle known as positive displacement and are more efficient than the centrifugal models. They are of several different designs, employing gears, screws, rotating vanes, diaphragms or reciprocating pistons and plungers to transport liquids. They are more versatile than the centrifugal models as they are suitable for transporting high viscosity fluids at high pressures. They are also a good choice for moving fluids with low vapour pressure as these tend to flow more slowly, creating added resistance.

While positive displacement can create a continuous flow, chemical handling pumps with pistons or plungers can be adapted to deliver liquids in the form of discreet, measured volumes. These are known as metering or dosing pumps and have numerous applications across various industries. For example, water treatment plants employ dosing pumps for several tasks. These include pH adjustment, the addition of flocculants to improve sedimentation and filtration and to dose the domestic supply with chlorine to suppress bacterial growth.

Since the industrial revolution, our society has become increasingly dependent on harsh chemicals, and the chemical handling pumps necessary to transport and measure them. For example, most farmers rely on nitrogen-based artificial fertilizers and the vast quantities of highly corrosive sulphuric acid required for their manufacture. The mining, oil and gas industries all depend heavily on equipment that can withstand the corrosive effects of aggressive liquids and are resistant to mechanical damage from abrasive slurries.

Choosing the right pump for the job is crucial. A mistake could lead to lost production, unnecessary replacement costs and even threaten worker safety. Consult the specialists at Prochem for professional guidance with your selection and to learn more about the company’s world-class chemical handling pumps.

Ebara Products - Chemical Handling Pumps

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