John Crane's Type 5870 Flushless Seal Reduces Downtime for Abengoa Bioenergy

When demand is high, production must run at the height of efficiency. And while the myriad of tanks, pumps and mechanical seals that comprise an ethanol plant are expected to show signs of wear-and-tear due to their harsh environment, a one-day lifespan of a crucial piece of equipment has drastic effects on production.

According to Russell Konwinski, Maintenance Manager and an eight-year veteran of the Abengoa Bioenergy (formerly known as High Plains
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Corporation) ethanol fuel plant in York, Neb., the facility was experiencing great trouble with their prior seal's design longevity on their process pumps.

"Although most of our seals only lasted about 60 to 120 days before failing, one seal lasted a mere day before leaking," said Konwinski. "It was obvious that we needed something more reliable."

The scenario was further complicated by the actual product created at the facility - a yellow sticky corn mash containing about 30 to 35 percent solids. While double seals are typically the recommended solution for ethanol plants, the time and expense associated with the installation of a pressurized seal support system and the potential to dilute the process fluid with barrier water escaping the seal simply complicated the scenario.

Fortunately, John Crane had already recognized the need for a flushless single cartridge seal that would not require external seal water support or a barrier fluid system necessary with double mechanical seals. Although originally developed for the pulp and paper industry, the flushless seal has already been proven in a variety of process industries, water and wastewater plants, as well as food and beverage facilities. Konwinski and Russell Shockey, a pump technician for Abengoa Bioenergy for almost nine years, were introduced to the John Crane Type 5870 flushless single cartridge seal last spring. Since Abengoa Bioenergy was in the process of changing their pump styles at the time, Konwinski said it made sense to incorporate John Crane's Type 5870 solution during their already scheduled re-tooling. The factory preassembled single cartridge design allowed the complete pump system to be easily installed in a few h ours, quickly tested and placed in service for a trouble-free startup.

According to Tom Evans, Marketing Manager for John Crane, the Type 5870 Flushless Seal is designed to operate unsupported and was an obvious solution. The open-profile, abrasive-resistant sealing faces positioned near the impeller allow maximum cool running and clog-free performance and the large, dynamic o-ring prevents fibers or solids from causing seal hang-ups. Additionally, the 5870's single-coil spring allows for greater shaft motion due to cavitation, pulsations and other upset operating conditions. At the ethanol plant, the Type 5870 seal solution also provides savings as no external seal support system, tank reservoir or barrier fluid is needed. Further, the key selling point of the 5870 single seal is its flushless attribute and its robust design to accept pump cavitations, dry running and air bind operation. Since external seal water flush support burdens a system with extra liquid that must later be removed to create a final product, users of the John Crane 5870 single flushless seal are able to better maintain control and reduce cost with this flushless option. Evans stated that the flushless seal also will prove extremely beneficial in reducing water dependency. For example, when drought conditions exist and water prices increase, lowering water dependency truly lowers operating costs.

"Seals frequently fail due to sporadic or poor seal water flush conditions," said Evans. "If you can operate a seal that eliminates this weak link - your flush water supply - you can improve your process reliability."

Although no flushing is required, the 5870 does incorporate a quench connection for use if possible upset pump operating conditions occur and a grease or water quench media is needed to lubricate and cool the atmospheric side of the seal. After installing an initial seal in May 2002, two more were installed on larger pumps in July and November - all of which have incorporated the grease-style quench and are exceeding customer performance expectations.

According to John Finley, the local John Crane Sales Engineer, the seal has not only saved dollars in terms of decreased maintenance and downtime, but it has also reduced product cost since they aren't consistently ordering new seals. Abengoa benefits in not having to purchase another pump or resize existing pumps due to inherent problems. Upset operating conditions such as cavitation, dry running or air bind operation will cause a less robust seal to fail prematurely.

Shockey concurs. "Elimination of seal support is the key benefit," said Shockey. "Now we can install a seal and not have to support it with maintenance except for the grease quench."

From a cost standpoint, Konwinski said the seal quickly paid for itself. "The cost of a double seal, as well as the cost and manpower associated with a flush system quickly adds up," said Konwinski. "We are pleased with John Crane's solution and are happy to report that everything advertised about the product is true."

The Type 5870 Flushless Seal is designed to operate specifically in Goulds Pumps fitted with their TaperBoreTM PLUS seal chamber containing the Vane Particle Ejector (VPE) ring. This allows unsupported single seal operation in all light slurry applications. John Crane's 5870 open-profile, abrasive-resistant sealing faces positioned near the impeller allow cool running and clog-free performance.

Performance Capabilities:
Temperature: Up to 150°C/300°F
Pressure: Up to 21 bar g/300 psig
Particle Size: Up to 5,000 micron
Speed: Up to 11 m/s /2200 fpm
Axial Movement: ± 2mm/0.080"
Services: Up to 6 percent paper stock, ash slurries, corn slurries, beer wort, sugar juice, raw sewage, and slurries up to 20 percent by weight.