Photo courtesy of Piller Industrieventilatoren GmbH
In several industry sectors, the use of vapor compressors is increasing – mainly to replace turbo compressors due to purchase and maintenance costs. Vapor compressors are used in processes where process-related high temperature differences are required. Through a serial connection of one or more vapor compressors, an increase of temperature can be achieved. In the milk industry, vapor compressors are widespread.
The essential steps in the production of milk powder are evaporation and drying. After heat treatment the milk is handled to the evaporator, which is basically fed by a vapor compressor (blower), working on the principle of a heat pump. The vapor compression under vacuum increases the heat of the milk and thereby the concentration of dry milk substance, which is separated as milk powder in the final drying sub-process. The provided energy is used efficiently through multiple recovery. Vapor with low temperature level is taken from the process, compressed, and returned as hot vapor with high temperature level to the process again.
Problem and challenge
Vapor compressors make substantial demands on the sealing systems, mainly in consideration to vapor tightness and to keeping the vacuum inside the system. Inlet and outlet temperature of the vapor compressor are 151.52°F and 160.16°F (66.4°C and 71.2°C). The system pressure is 3.36 PSI (0.23 bar) absolute. The seal medium is water vapor. The shaft diameter is 4.72” (120 mm). The shaft rotates with 3,000 revolutions. For the small space between the blower housing and shaft bearing, the seal has to have a small axial installation length, a maximum of 4.13” (105 mm). All seal components must have FDA compliance due to their use in the food industry.
EagleBurgmann Espey solution
To fulfill the application requirements of vapor tightness, FDA compliance and keeping the vacuum inside the system, Espey designed the carbon floating ring seal type Espey WD500, type WDSA, with split housing for easy assembly and maintenance. The seal is fitted with 5 overlapped mortised resin-impregnated seal rings with gas-tight joints. To achieve vapor tightness, the seal has a barrier gas port that is fed with water vapor taken from the process. To conduct condensed vapor, the seal is designed with a leakage port. The seal guarantees long-term operation time.
For more information on EagleBurgmann Espey products, please contact us at firstname.lastname@example.org.