The service star

The progressive cavity pumps of the CC series from Vogelsang. Easier, quicker, more efficient

In 1970, Helmut Vogelsang revolutionized the pump market by inventing a rotary lobe pump with elastomeric coating on the conveying elements. In the agricultural sector, the wastewater segment, in industry and in biogas plants, this conveying technology – known all around the world simply as the “Vogelsang pump” – successfully fought off competition from the ubiquitous progressive cavity pump in every field. In the mid-1990s, the company also managed to speed up the process of changing spare parts: The QuickService concept made it possible to replace all the key components on the spot, without dismounting the pump, in less than half the time required previously.

At the end of 2014, Vogelsang surprised the specialist world yet again with an apparently contradictory product: a completely innovative, incomparably easy to maintain progressive cavity pump. The reason? Changing conditions in biogas production resulted directly in new demands and requirements from plant operators regarding the pump technology. However, established providers were only taking some of these changes into account, and reluctantly. As an experienced partner to the biogas sector, Vogelsang saw this as a call to action.

New customer requirements led our experts to first thinking about developing our own progressive cavity pump

Following its successful implementation in the agricultural sector, it was the many positive characteristics and advantages of the rotary lobe pump that caused the “Vogelsang pump” to be discovered by new users in other areas, such as wastewater technology, industry and biogas technology. 

Developments in the German biogas sector resulted in ever-more viscous and therefore challenging and problematic suspensions in the digesters. Due to the addition of high dry matter content and fibrous solid matter, such as dung or grass silage, some pump types were increasingly reaching their limits – particularly as the suspensions also contain high levels of abrasive components and foreign matter. For this reason, other pumps seemed like a possible solution under certain circumstances, especially the progressive cavity pump, given that the conveying elements boast long running times in other areas. However, when they visited customers on-site, our biogas experts realized that there were no progressive cavity pumps available that were specifically adapted to the precise requirements and needs of biogas plants. Even if the conveying elements could guarantee a satisfactory operational time, users were frequently unsatisfied with the overall performance in everyday operations. So our biogas experts started thinking about developing our own progressive cavity pump. The final decision was not taken lightly. A Vogelsang progressive cavity pump would have to meet both the company’s own quality standards and the specific requirements of applications in biogas plants. The experts soon began to doubt whether a costeffective solution could be found for such a familiar and long-established concept as the progressive cavity pump. After all, since the patent was first registered in 1931, numerous companies had specialized in precisely these pumps. On the other hand, Vogelsang itself had played a major role in further developing and improving the rotary lobe pump concept with the IQ series, adding many useful details and making service and maintenance work and handling considerably easier.

So the experts began the necessary analyses as to exactly which characteristics of the progressive cavity pump convince customers to choose this pump, and which characteristics specifically put them off? Which improvements are users looking for, especially in the biogas sector? In conversations, customers would time and again draw attention to the complexity of changing parts. This took up a lot of space and time and very little had changed over the years when it came to ease of maintenance. Even newly launched product concepts inspired little enthusiasm among biogas plant operators, who saw no progress in the situation. In the autumn of 2014, these circumstances led progressive cavity pump experts to demand in print: “Progressive cavity pumps have to become easier to maintain!” Users also frequently complained about clogging in the suction housing and insufficiently sturdy cardan shafts or coupling rods for transferring the motor’s drive power to the rotor.

What operators want: The QuickService progressive cavity pump

In discussions, operators and plant employees frequently referred to the rotary lobe pump or the RotaCut from Vogelsang and asked why we didn’t build a progressive cavity pump in a similar way. And so the development department at Vogelsang set itself precisely this challenge. Numerous ideas and some very complicated designs were devised and then discarded again. Other ideas, such as the angled flange on the discharge side, were instant hits. But one thing struck the development staff as strange: If such an uncomplicated design could so decisively simplify servicing and maintenance, why had none of the specialists thought of it before? Were they maybe missing something?

Meanwhile, the advantages were convincing. Unlike in conventional progressive cavity pumps, it was no longer necessary to dismount parts of the discharge-side pipe, thanks to the new design. This not only simplifies the pipeline construction, it also means less space is needed for servicing and maintenance work. But far more importantly, the rotor and stator pumping elements can easily be removed and replaced as a single unit. The pump itself can be put back into operation while the replaced unit is reconditioned. This is an impressive advantage in systems where pumps are not kept redundantly in reserve but where long standstills are unacceptable. And the concept doesn’t only apply to small, manageable pumps.

It didn’t take long for the specialists in the development department to realize that replacing parts would be even easier and, above all, quicker if the connection between the drive and rotor could be detached from the stator output. Thanks to the innovative construction, this connection is now easily accessible once the rotor/stator unit is swung out. In addition to standard mechanical engineering solutions, such as a multi-tooth or feather key connection, it soon occurred to the engineers to look into a friction-locked cone joint. They were familiar with the concept from other projects, where it had proven useful. The key advantage is that the drive shaft and the rotor do not need to be positioned precisely to one another. In addition, the connection is self-centering, thanks to the taper. It can simply be tensioned or released using a threaded rod via the through bore in the rotor. With this connection, there is no need for laborious removal of small pins in a tight suction housing or other complicated tasks.

No need to disconnect the protective sleeve from the cardan shaft

And this design has another advantage: It is also possible to fulfill the customer’s wish for a well-protected and long-lasting cardan shaft. Detailed studies have shown that robust cardan joint shafts are also a suitable means of transferring forces in challenging applications, provided they are protected reliably against the contaminated medium. However, if this protection has to be dismounted every time you take out the rotor, there is an increased risk that it will be incorrectly reinstalled, causing contamination to reach the cardan shaft. A narrow suction housing also means that the protection is rubbed off. With a friction-locked cone joint, there is no need to dismount the protective sleeve, either when changing the rotor or during a sealing change. Furthermore, the engineers designed a generous suction housing. The idea was that this would prevent rubbing against the protective sleeve, as well as significantly reducing the risk of clogging in the suction housing. And tests proved they were fully justified in their assumptions.

Progressive cavity pump of CC series: a new kind of sealing change

The developers also envisaged the connection between the motor and cardan shaft as a friction-locked cone joint. The pump is driven by a parallel shaftgeared motor with a hollow shaft. This may sound complicated and elaborate, but in practice it makes life easier for users. Thanks to this design, the cardan shaft or even the entire rotating unit can be dismounted in one piece. And more importantly for practical purposes, the shaft seal can be replaced from the outside without opening the pump.

Award for excellent work

The developers’ painstaking work and perseverance with the development was amply rewarded. The new pump proved itself superlatively in tests on its dedicated test bench and in the field. In May 2014, the patent was registered. That same year, the new design from Vogelsang won over the jury of an innovation competition. As part of EnergyDecentral 2014, the unique concept of the CC series was awarded the silver medal. 

The market had a far more important reward in store: The new concept inspired strong interest from customers, especially in the biogas sector, for which it had been developed. Established competitors on the market soon followed with similar concepts. However, thanks to its patent protection, the original from Vogelsang remains unsurpassed. And to ensure that it stays that way, the CC series is being constantly developed further, as you would expect from Vogelsang. Today, Vogelsang offers single-stage and two-stage geometries in four series with volume flows of up to 300 m3/h.

The most interesting thing about the CC series, however, is not the large range of different models, it’s the fact that Vogelsang developed it itself. Because the entire construction is made in-house, it is also possible to combine pumps and cutters to create compact system solutions. These include the CC-Cut, the direct combination of a CC series progressive cavity pump and a RotaCut to form an exceptionally compact pump system. Or the PreMix liquid feeding system for biogas plants. In the PreMix, a CC series progressive cavity pump is combined with a RotaCut RCX and a flange for connection to a screw conveyor for solid matter. In this way, the PreMix brings together four steps in a single compact system, mashing different substrates with a liquid suspension to create a homogeneous suspension, while simultaneously chopping up and treating the suspension. Any heavy material in the suspension is separated out right at the beginning. Biogas plant operators who ferment a wide variety of different substrates are particularly impressed by the PreMix. Variants of the RedUnit are also based on a progressive cavity pump from the CC series. Here the progressive cavity pump is combined with an XRipper twin-shaft shredder and/or a RotaCut, which makes it possible to turn solid matter into a pumpable medium in the tightest of spaces.

The original from Vogelsang remains unsurpassed.
Today, Vogelsang offers single-stage and two-stage geometries in four series with volume flows of up to 300 m3/h.

There are few manufacturers who can boast such wide-ranging knowledge and experience of the individual components and their possible combinations, while also being in a position to offer the corresponding control technology. And so it is these combined products that are opening up new applications and markets to Vogelsang, ensuring the company’s position at the front of the pack. In upcoming issues of THINK RED! we will be presenting some exciting application examples.

Overview of the characteristics and advantages of CC progressive cavity pumps

Specifically developed to pump highly viscous and abrasive media

  • Generously dimensioned cardan shaft
  • Robust protective sleeve to protect the cardan shaft
  • Rotor and/or stator can be changed without disassembling the protective sleeve
  • Large suction housing with continuous free passage
  • Suitable for delivery rates of up to 300 m3/h

Fast and easy servicing

  • Stator/rotor element swings out
  • Stator and rotor can be replaced as a unit or individually
  • Sealing can be changed without opening the pump
  • Minimum space requirements for service work

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