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Twin screw pumps provide the right stuff for chemical batch processes



Twin screw positive displacement pumps provide performance solutions for many chemical batch processing applications that are difficult and complicated to achieve through the use of more common centrifugal pumps. Frequently, twin screw pumps are the “last resort” because they can solve many pumping challenges, but the technology is not widely known. is less. The twin screw pump itself can be more expensive compared to a centrifugal pump. However, when comparing the total cost of ownership for a system optimized for a twin screw pump against a system required to use a centrifugal pump, the twin screw pump quickly becomes a commercially attractive option. Twin screw pumps should be considered in any application where the process may involve risk of cavitation, some gas or vapor content, variations in flow, temperature, pressure, liquid characteristics or viscosity. Twin screw performance excels in chemical process and transfer applications that experience one or more of these variations, as well as any operating conditions that may be difficult or push the limits of other more common pumps. To get more news about Single Screw Pumps, you can visit hw-screwpump.com official website.
Twin screw designs in chemical processing applications are capable of flow rates up to 3,000 m3/h, differential pressures that exceed 100 bar, product temperatures up to 400°C, and product viscosities 1,000,000 cP, making them a very robust piece of machinery. They are capable of handling a variety of process conditions that exist in the chemical manufacturing and processing industry. Dry run, self-priming, wide capacity range, flushing and cleaning and excellent flow control are just some of them.

Variable frequency drives (VFD) are state of the art technology today and a very strong supporting technology for twin screw pumps. Using a VFD today allows users to leverage the full flexibility of the twin screw pump, since the pump capacity depends dominantly on speed and is not much affected by the differential pressure. Using the VFD now allows users to easily to utilize the full performance range from 10% up to 100% of the design speed and capacity range.

When evaluating total cost of ownership during start-up, operation, maintenance and shut down, a twin screw pump may well prove to be the most economical solution. Twin screw pumps are capable of handling multiple liquids or products over extended viscosity ranges during batch processing. They can also contend with a wide range of liquid characteristics - such as lubricating, non-lubricating, corrosive, and abrasive liquids - in addition to liquids containing entrained gas.

A centrifugal pump’s impeller creates an area of low pressure at the impeller’s eye. When pumping a fluid containing entrained gas, the gas will separate and collect at this point. This phenomenon, known as vapor locking, happens when gases at the eye restrict liquid flow through the impeller. The only way to correct vapor locking is to remove the gas. This involves stopping the pump, removing the air from the system, and repriming the pump.

Twin screw and rotary positive displacement pumps are volumetric machines and not limited in this aspect. Entrained gas entering the pumping cavity is displaced with the fluid discharged from the pump as the pump discharge is isolated from pump suction.

A second benefit offered by twin screw pumps is energy efficiency. Twin screw and other rotary positive displacement pumps’ volumetric efficiency increases as the viscosity increases. This is due to the internal clearances’ becoming more effective in sealing the pumping cavity. Due to their design, centrifugal pumps will experience a loss of capacity and efficiency as viscosity increases. Internal friction losses in a centrifugal pump will increase as the viscosity increases, resulting in reduced capacity, head development and efficiency. Centrifugal pump capacity will also vary as the system pressure changes, resulting in the need for additional controls such as control valves and variable speed drives.