Pumps For High Purity Chemical Production

Louise Smyth

Tom Zuckett introduces the ideal technology for chemical manufacturers who can’t tolerate any deviation from established specifications in their processes.

Their names sound like sinister creations that would spring from the evil mind of a mad scientist in a futuristic novel or movie:

  • Hexafluorochloride
  • Dexamethasone
  • Germanium
  • Cadmium Telluride.

In reality, they are among the many chemical ingredients that are indispensable foundational components in the manufacture of such commodities as pharmaceuticals, semiconductors and solar panels.

The main concern for the manufacturers of these so-called “high-purity” chemicals is not trying to pronounce their names or remembering how to spell them, but ensuring that they are produced in a manner that guarantees the highest level of purity. When these chemicals are not manufactured according to strict specifications for purity, nightmarish scenarios can result that are worthy of a science-fiction novel for both the manufacturer and the end user.

There is one type of pumping technology – solid-body plastic, air-operated double-diaphragm (AODD) pumps – that possesses the design, construction and operational characteristics that are necessary to guarantee the high-purity manufacture of chemicals, while also offering the ultimate level of energy efficiency and reliability.

The Challenge Of Pumping High Purity Chemicals

The universal chemical market consists of thousands of products that are used in hundreds of industries. At the most basic level are the low-grade chemicals that are used in making simple plastics or swimming-pool cleaners and sanitisers. As you move up the chemical food chain, you eventually arrive at the high-purity chemicals. These products are used in precise manufacturing processes where there can be no variance in the makeup of the chemical or slippage in its overall quality.

Costs

On top of the need for pristine purity is the fact that these chemicals are very expensive to produce. Therefore, if a batch is deemed not to meet expected quality levels, it can cost hundreds of thousands of dollars in lost revenue for the manufacturer – as well as putting a blemish on the manufacturer’s reputation. Additionally, because of the high stakes that are involved in the production of high-value commodities, their manufacturers will strictly audit the production processes of the chemical companies to make sure that the chemical is produced according to established specs. Anything that can cause the chemical to become out-of-spec would be grounds for the end user to consider finding another supplier.

Handling Dangers

Another concern for chemical manufacturers is that many of their products can be highly toxic and dangerous to handle. This means that any time high-purity chemicals are handled there is an inherent risk involved. The risk stems from the fact that the release of these chemicals can lead to severe health consequences for humans and animals, as well as damage to the environment.

With all that said, keeping dangerous high-purity chemicals fully contained is often easier said than done. Since many can also be highly corrosive, the pumping equipment used to transfer them is prone to chemical attack if the materials of construction are not compatible with the acid, caustic or solvent. Materials of construction are not the only factor to consider when determining if a pump should be used to handle dangerous chemicals.

Overcoming Pump Design Issues

Another area to focus on is the actual design features of the pump. For example, if the design incorporates mechanical seals or packing, they may be prone to leaking.

Attempts have been made to eliminate the shortcomings of pumps that feature mechanical seals through the implementation of magnetic couplings or double barrier seals. While these methods of containment do outperform mechanical seals, they do possess some disadvantages that reduce their effectiveness.

The viscosity range of liquids that are transferred by pumps with magnetic couplings is limited by the amount of transferable torque that can be created. The use of pumps with double seals or barrier liquids can be impractical due to their high cost and the elevated level of maintenance required.

Some common pump styles that have traditionally been used to handle high-purity chemicals include:

  • Lobe
  • Gear
  • Centrifugal models

While they may be constructed of chemically compatible materials, their design features mechanical seals, the performance of which can be compromised over time, raising the possibility that leaks will occur.

In terms of actual performance, these competitive pump styles also have limits when it comes to the reliable, energy-efficient transfer of high-purity chemicals. Gear pumps, for instance, move liquids through the meshing of gears.

Over time as the gears wear, the pump’s volumetric consistency is reduced, resulting in fluctuating flow rates and increased energy usage. The operation of both gear and centrifugal pumps can also create turbulence in the pumped liquid, which can lead to shearing that will damage or alter the liquid’s chemical properties and move it out of spec. Lobe pumps, since they are not true PD pumps, can be subject to product slippage, which will make attaining consistent flow problematic and result in compromised production rates.

In total, pneumatically driven AODD pumps possess many attributes that most electronically driven pumps do not, including portable design, seal-less operation, dry-run and deadhead capabilities, good suction-lift capability, ability to handle a wide product viscosity range, ability to handle small particulates, control without need of a variable frequency drive (VFD), easy grounding, and simple operation, maintenance and repair.

The Benefits Of The AODD Pump

Although other PD-pump technologies have shortcomings when handling high-purity chemicals, the AODD pump does not come with such concerns. Specifically, solid-body plastic AODD pumps that are CNC-machined are the preferred choice over their injection-moulded cousins. The CNC-based design enables tight tolerances, reduced vibration, lower risk of leakage, and greater stability and durability. In general, solid-body AODD pumps are stronger and have a longer life cycle with less required and easier maintenance.

Injection-moulded plastic pumps, on the other hand, can have small cavities or crevices in the body where liquids can accumulate and potential leak paths can be created. During their operation, injection-moulded pumps can also vibrate or bounce more than solid-body models, which can loosen pipework and increase the chances that a leak path will form.

Solid-body plastic AODD pumps can also be constructed of high-quality materials such as polytetrafluoroethylene (PTFE) that are specifically compatible with the chemicals that are being handled, which eliminates corrosion and leak concerns. The overall design and operation of AODD pumps gives them dry-run capability and good controllability, while they are seal-less. Their compressible drive medium permits gentle delivery with attenuated pressure peaks. Start-up is simple and the space required is considerably less than in the case of piston-actuated diaphragm pumps or screw pumps

Almatec Maschinenbau is the inventor of plastic solid-body AODD pumps and offers an extensive product range. In the handling and transfer of high-purity chemicals, Almatec recommends its E-Series AODD Pumps. E-Series pumps offer a range of features and benefits for manufacturers and users of high-purity chemicals.

In Conclusion

Admittedly, there is a science-fiction “out there” feeling to many of today’s high-purity chemicals with fertile, inquisitive minds needed to develop them and find their uses. What is firmly rooted in reality, however, is the need to manufacture and handle them in accordance with a strict set of specifications that cannot be compromised.

That’s why guaranteeing their purity and quality is job Number 1 for their manufacturers. Those concerns can be overcome through the use of pumping equipment that has been designed to achieve reliable production of high-purity chemicals. Although other pump technologies can claim to do this, it’s the plastic solid-body AODD pumps, specifically the E-Series model from Almatec, that can turn those claims into reality.

Tom Zuckett is with Almatec