Centrifugal Pumps Special Dry-Running Centrifugal Pumps Save Time, Money, and Problems

“The hermetically sealed centrifugal pump outperforms magnetic-drive pumps with respect to mode of operation and reliable contents of solids and gases in the pumping medium” — the verdict of PROCESS on a new magnetic-drive pump. That was over two and a half years ago, so its now time to find out how the dry-running horizontal pump has fared in day-to-day service.

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EagleBurgmann Germany GmbH & Co. KG

Maag Pump Systems AG

Italvacuum, Srl

Paul Bungartz GmbH & Co. KG

The onsite situation is “hot” in the truest sense of the word: in one of its many applications, the acid that the MPCH_DryRun is handling has a temperature of 240 °C. The liquid, which contains gas and some nitric acid, has a low system pressure of 30 mbar. This means that standard pumps with a closed impeller often suffered from stoppages. Dry running, which is essentially the key feature of these special horizontal pumps from specialist pump manufacturer Bungartz (“it keeps running even when dry”), leads to considerable damage to the sliding bearings in conventional pumps.

To avoid such failures as well as the mounting costs due to material damage and lost time, the management team took the decision last autumn to replace the existing magnetic-drive pump with a MPCH_DryRun fitted with an open impeller. Whereas the originally installed pump failed at least once per quarter, the DryRun has been operating without problems since it was commissioned in October 2009.

“Even the high product temperature of 240 °C in this application is not unusual for our pump,” explains Frank Bungartz, the third-generation managing director of the Düsseldorf-based pump specialists, “the DryRun can handle pumping media temperatures of up to 400 °C without problems.” This is made possible by the barrier integrated between the product and bearing chambers. It minimises heat transfer to the bearing supports. Thus in the aforementioned application, the bearing temperature is only 51 °C at the pump end and 25 °C at the motor end (further example, see diagram). The highly effective thermal shielding means that the DryRun can operate even with extremely hot media, such as liquid melts.

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