Over the years, the pumping technology of choice in many fluid-transfer applications — from oil and gas and chemical production to liquid terminals that are supplied by pipelines, barges, rail cars and trucks — has been the centrifugal pump. Their method of operation — fluid enters the pump impeller along or near the rotating axis and is accelerated by the impeller, flowing radially outward into the volute discharge port — makes them well-designed for high-volume transfer applications. Centrifugal pumps also perform relatively well with water-like fluids that must be transferred through piping networks with variable flow rates.To get more news about Single Screw Pumps, you can visit hw-screwpump.com official website.

Still, a different technology — positive displacement twin and triple screw pumps — can be a more versatile, reliable and efficient alternative than centrifugal pumps in the fluid-handling operations that are critical to many industries. This article illustrates how effective screw pumps can be as an alternative to their centrifugal cousins.
Making a move
The main challenge in making the screw pump a more prevalent option in liquid-handling applications is convincing operators to move away from a technology that is conceded to be the default one for numerous jobs. Generally speaking, the bulk of the fluids handled in industrial applications have low viscosities and must be transferred at very high flow rates, which plays to the operational strength of centrifugal pumps.
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In many cases, for instance, oil and gas and chemical processing systems have been designed around the pumping technology rather than the other way around. Engineers are first familiar with centrifugal pumps and, because of this firsthand knowledge, will attempt to work within the centrifugal pump’s operational limits. They know how centrifugal pumps operate and their benefits, and they are confident the pumps are the best technology to help them meet their goals.
To illustrate this mindset, in some cases a design engineer — instead of considering a different pumping technology — will blend or heat raw crude oil to manipulate the process and get the viscosity of the fluid down to less than 300 centistokes (cSt), which makes it easier for the centrifugal pump to handle. In this instance, they are reconditioning the fluid to fit the pumping technology — irrespective of the cost impact.

In other words, when measures like this are taken to satisfy the needs of the pump, the popularity of centrifugal pumps in liquid-transfer applications becomes something of a self-fulfilling prophecy.

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No matter how a liquid might be reconditioned, operators must still take care to ensure the centrifugal pump is operating on its Best Efficiency Point (BEP). The BEP is the point at which the pump works at its highest level of efficiency. Centrifugal pumps rarely operate at their BEPs.
However, when the operation of the pump moves outside the BEP window, uneven pressure will be applied to the impeller, which will cause the pump’s shaft to “deflect” because of an increase in radial thrust. When deflection occurs, higher loads are placed on the bearings and mechanical seal, which will cause damage to the pump’s casing, back plate and impeller. Ensuring operation at the BEP can be a time-intensive task since the pump must be monitored constantly and adjusted, which consumes man hours and money.

Additionally, meeting production rates and quotas has always been top priority in liquid-transfer operations, but as operating costs have continued to rise, a call for increased operational efficiency in terms of the energy required and consumed during pumping operations has been issued. In this area, centrifugal pumps can also fall short.