Hermetically sealed peripheral pump handles critical conveying tasks in wax production.
At Clariant Produkte (Germany), hermetically sealed peripheral pumps of the MPB series from Richter Chemie-Technik are installed in the montan wax production. In terms of process technology and also for environmental protection reasons, they are significantly better suited to the particular requirements of this production than other centrifugal pumps.
At the Gersthofen site, Clariant produces and processes synthetic and natural waxes, among other things. Synthetic waxes are preferably used in printing inks, coating systems, textiles or for coating citrus fruits. Natural Montan waxes are mainly used in care products (e.g. shoe polishes or car polishes) or in processing plastics.
Montan wax is extracted from bituminous lignite and processed into the end product via several process stages. "We have operating conditions here under which other pump designs fail very quickly," says Dipl.-Ing. Franz Kovanetz, the plant engineer at the Gersthofen-based montan wax plant, explains the reason why peripheral pumps of the MPB series from Richter Chemie-Technik are used in this process.
In the oxidation stage of the process, pumps have to convey the oxidant itself on the one hand and the oxidate still contaminated with oxidant on the other. In this process step, legislation requires the use of hermetically sealed pumps. Kovanetz: "In the past, all conventional magnetic coupling pumps have caused problems in this application. That means short service life due to deposits and damage due to cavitation." In addition, there is a requirement to maintain a certain temperature level at every point of the pump - after all, we are talking about handling molten wax. The pump must be heatable; in addition, the delivery volumes vary in relatively wide ranges - between 300 and 2000 l/h. Kovanetz continues: "At a pressure of over 4 bar, the pump must convey the foaming, corrosive medium without any problems. Centrifugal pumps often fail in this task; in the event of foaming of the medium, conventional centrifugal pumps cavitate and harmful vibrations occur."
At pressure of over 4 bar, the pump must convey the foaming, corrosive medium without any problems. Centrifugal pumps often fail in this task."
Dipl.-Ing. Franz Kovanetz, Plant Engineer at Clariant
This shows: The spectrum of requirements for the pumps operating here is extremely demanding. Kovanetz reluctantly recalls the past: "For a long time, there was not a single pump manufacturer who could offer a corrosion-resistant centrifugal pump with this broad delivery range. The 2000 l/h was not the problem, but rather the small flow rate of 300 l/h. Even with the required pressure of over 4 bar, some manufacturers waved them off. The centrifugal pumps with mechanical seals available 20 years ago had a service life of between one day and two weeks - a paradise for any pump manufacturer!"
With the help of a specially installed mechanical seal, Kovanetz and his team finally achieved a service life of about two years. Of course, the legislator's requirement for zero leakage proved to be a serious problem. At this time, they also tested the standard process pumps of the MNK series from Richter Chemie-Technik. But even these very robust pumps did not have a satisfactory service life for this application due to the extreme cavitation.
The breakthrough only came with the use of Richter peripheral pumps in optimum chemical design, as these are sealless and practically maintenance-free. Varying volumes can be efficiently realized by frequency control.
Reduced life cycle costs
What are the main advantages for Clariant of using these peripheral pumps? Franz Kovanetz: "On the one hand, there is a significantly longer service life, and the maintenance effort is also considerably lower." With the expected service life of four years, he assumes a cost advantage of several thousand euros per pump. What is very important to him is that the company has to contend with fewer malfunctions. "We can thus use employees more productively than for checking and repairing pumps." What the plant engineer is particularly pleased about is that the process is no longer interrupted so frequently: "Any interruption to a continuous process always means an impact on product quality. Only when a Konti unit is constantly operated does the product quality remain at a high level without fluctuations." Incidentally, all pumps are integrated into the process control system - there is also an automatic routine for cleaning the pump, for example.
How does the MPB peripheral pump achieve this long service life with low maintenance? Mainly through an innovative impeller sealing solution:
The sealing lips (patented) integrated into the impeller provide the sealing between the impeller and the housing wall of the silicon carbide ring channel, which is crucial for high efficiency. The sliding surfaces of the ring channel are highly polished - this ensures frictionless and low-wear sliding of the impeller sealing lips.
Another decisive advantage is the simple and fast assembly: The spring-loaded sealing lips make impeller ring channel adjustment accurate to a tenth of a millimetre unnecessary. Such narrow but hydraulically important gaps in conventional peripheral pumps often lead to premature wear - especially with temperature changes - and require a great deal of time for their precise installation and maintenance. The sealing lips of the Richter MPB impeller, however, compensate for the dimensional changes when exposed to temperature.
This is particularly important for Clariant: both the oxidant and the oxidate, which is still acidic, have temperatures well above 100 °C. "The Richter peripheral pump has very good temperature resistance; the pump also accepts minor temperature shocks without any problems," according to Franz Kovanetz's experience.
Conclusion
When conveying highly oxidizing substances and other corrosive media, Richter peripheral pumps are now standard at Clariant. Due to special technical details, these pumps have proven themselves and have the longest service life: An MPB installed in 2004 for test purposes is still running without problems in 2011.