Regenerative turbine pumps excel in multiple processing applications

There is no shortage of pumping technology when it comes to fluid processing applications. A quick review of available and capable pump technology spans across the spectrum, ranging from air-operated double-diaphragm (AODD) and peristaltic pumps, to centrifugal pumps, to internal gear and sliding vane pumps. While each technology stands out for its array of benefits in a particular application, there are some that excel in several.

The versatility of the pump technology plays a major role in its ability to process an array of different substances. One specific substance – autogas – has become more popular as the world looks to greener fuel sources. Autogas, also known as liquified petroleum gas (LPG), is a mixture of butane and propane, with a composition that allows it to be transported and stored as a liquid and burned as a gas.

Autogas, however, comes with its share of processing challenges, such as needing pump technology capable of handling low viscosities and vapor pressure well above normal atmospheric pressure. Without the proper pump technology, autogas processing can lead to slippage or cavitation.

Side-channel and sliding vane pumps are two standouts from the list of pumping technologies that are known for their performance when handling a variety of fluids. But there is another pump technology that shines because of its versatility. That technology is the regenerative turbine, a rotodynamic variant designed to handle clean liquids at or near their boiling points, such as LPG or autogas, carbon dioxide and boiler-feed water, among other substances.

This article will examine the versatile nature of regenerative turbine pumps.

The basics of regenerative turbine pumps

Regenerative turbine pumps have close parallels to positive displacement pumps. Regenerative turbine pumps provide multi-stage performance from a single-stage impeller. This allows the pump to create high differential pressures at low flow rates.

Regenerative turbine pumps use a rotating, non-contact, free-wheeling impeller disc that has around 60 small cells on its periphery. When the liquid enters the suction port, the impeller contains and accelerates it around the narrow hydraulic channel in which the impeller operates. The growing angular velocity as the impeller rotates increases the kinetic energy in the liquid as it progresses around the channel, building energy and pressure.

The pump technology name stems from its function – the continuous regeneration of small liquid cells creates the differential pressure capability of the pump. Other names for this style of pump include peripheral pumps, centrifugal regenerative pumps and regenerative pumps, among many others. Regardless of the name, this technology is categorized in the rotodynamic family of pumps.

Regenerative turbine pumps have the versatility to transfer liquids at high pressure and low flow, while also processing entrained vapors in liquids at or near their boiling point. These conditions limit many pump technologies, causing performance issues, cavitation, vibration and noise. But regenerative turbine pumps don’t falter under those conditions.

Specifically, regenerative turbine pumps can handle viscosities of 0.1 to 50 centistokes with differential pressures up to 300 psi (20 bar) and have a maximum allowable working pressure of up to 493 psi (34 bar) to enable handling liquids with high vapor pressures.

Typical regenerative turbine pumps generate flow rates up to 52.8 gallons per minute (200 liters per minute), though some variations can operate with flow rates above that amount. Some newer iterations of this technology can reach peak flow rates as high as – and potentially higher than – 158.5 gallons per minute (600 liters per minute).

This pump technology thrives because of its design. The spiral motion, as well as its speed, diminishes the chances for cavitation and pulsation by smoothing the fluid and collapsing any vapor bubbles immediately when they form. Vibration and noise problems seldom occur because the pump operates with a smooth flow and a hydraulically balanced design.

Regenerative turbine pumps are ideal for LPG or autogas applications. The technology also functions optimally in other applications where low viscosity fluids exist, such as aerosols and refrigerants. Other applications include ammonia, vaporizer feed and cylinder filling, as well as boiler-feed water.

Stacking up with sliding vane pumps

We frequently see regenerative turbine pumps in similar applications to sliding vane pumps, and although sliding vane pumps have some advantages, the main one being slightly higher hydraulic efficiency which allows faster priming, regenerative turbines stack up in other ways.

Their design is such that regenerative turbine pumps are able to operate continuously without impact on their operating life and can run at the maximum differential pressure (up to 200 psi/14 bar or higher) for this entire time without damage or shortened life.

Regenerative turbine pumps have few moving parts and no contact between moving parts. This means long service life between repairs so operators don’t have to worry about taking the pumps offline to replace wear parts on a frequent basis. Without as many moving parts, operators of regenerative turbine pumps spend less time shutting down the pump for scheduled maintenance and don’t have to stock as many components for eventual replacement.

The major wear parts on regenerative turbine pumps – the impeller and the mechanical seal – can be repaired or replaced without taking the entire pump out of service. In most cases, these parts can be replaced within an hour and do not require the operator to disconnect it from the pipework. Additionally, depending on the pump design, this maintenance can occur without disconnecting the motor, thereby maintaining alignment and negating the need for an additional trade on-site.

Similarities with side-channel pumps

Side-channel pumps share many parallels with regenerative turbine pumps, such as performing well under poor suction conditions and the ability to self-prime. That’s because side-channel pumps share a similar construction with regenerative turbine pumps. Both technologies use an impeller with cells that capture liquid and energize it before transferring it outside of the pump apparatus.

The differences between these two pumps, however, come down to the size and ease of maintenance. Due to their design, side-channel pumps have a larger footprint. They feature multiple pumping stages and are considerably larger than their single-stage counterparts.

Let’s take an LPG installation. In this application, a side-channel pump might require four to eight stages to meet the duty parameters.

With regenerative turbine pumps, which are single-stage, operators can obtain similar performance as a four- or five-stage side-channel pump. Regenerative turbine pumps also can function at two-pole speeds, compared with side-channel pumps, which typically function at four-pole speeds.

Regenerative turbine pumps have a compact footprint and simple design with up to 25 components and no special clearances to manage or special tools required. Also, a simple design means operators don’t need a veteran engineer to maintain them, allowing any technically savvy associate with moderate experience to keep the technology running. 

Conclusion

Regenerative turbine pumps operate optimally with a vast range of liquids under varying conditions in multiple applications. The common deterrents – cavitation, vibration, entrained vapor – don’t have the same effect on regenerative turbine pumps. Operators can expect longevity from this technology, as well as long intervals between maintenance.

The value of regenerative turbine pumps is clear. They have the versatility to pump many types of liquids. Operators don’t have to replace several components on the pump or remove it from service for several hours. In most cases, the pumps can be repaired or rebuilt without removing them from the pipework or even the motor. As the technology continues to improve in the future, it will become a more common choice among operators in a wide range of applications.

---

Stephen Basclain is the business development manager for Ebsray. He can be reached at Stephen.Basclain@psgdover.com. Ebsray designs and manufactures regenerative turbine and positive displacement pump technologies, including sliding vane, gear and lobe pumps. Ebsray is a brand of PSG, a Dover company.