Urea, the world’s leading type of nitrogen fertilizer, is produced by high-pressure synthesis from liquid ammonia (NH₃) and a gas/water mixture with carbon dioxide (CO₂) under high pressure (up to max. 180 bar) and elevated temperatures (up to max. 446°F) in a synthesis tower.  Synthetic ammonia carbamate is then produced and obtained as white granules and a finished product.

In 2002, a major Slovakian company in the chemical industry who produces urea came to Espey Burgmann for assistance in guaranteeing seal function under these high pressure conditions.

The Need

The high process pressures required for the company’s fertilizer manufacture are attained by multi-stage radial, integrally-geared compressors, in this case, an eight-stage compressor designed by MAN Diesel & Turbo SE.  All of the eight compressor stages needed a chamber seal with barrier gas and leakage protection. In no way could the highly compressed CO₂ leak from the process room. Other seal requirements included easy assembly, compact design and vibration prevention during start and spin-out phases. 

The Solution

Espey Burgmann’s solution was to use WKA 802 HD chamber seals for each stage of the eight-stage compressor with barrier gas protection and a leakage drain.  The seal rings were one-piece made of coal-graphite and antimony proofed with a titanium bandage.

The WKA 802 HD series shaft seals are completely preassembled units designed for high-pressure applications (250 bar) and are typically utilized in steam turbines, turbo compressors and compactors.  The seal is one part, and consists of two components: a carbon ring and a binding into which the carbon ring is shrunk.  This design principle gives it its dimensional stability.  A damping element prevents the sealing ring from swinging up during machine operation without pressure.

The seal housing is a modular system in which the individual sealing parts such as the chamber, the intermediate chamber and the sealing gas chamber are combined, one behind the other, depending on the operating conditions.

Other advantages include:

• Ease of assembly and service
• Long life cycle (low wear)
• Maintenance free
• Dry running warranty
• Compensation of radial and axial shaft movements
• Axially short

Since 2002, the WKA 802 HD seals utilized for this application have been running without failure, a true testament to the reliability of Espey Burgmann products.

For more information on Espey Burgmann seals, please contact us at ebnow@eagleburgmannseals.com.