Rexnord® Omega™ and Thomas™ Couplings Reduce Pump Repairs at Tenneco Refinery
CASE STUDY
Tests at the Tenneco Oil Co. refinery in Chalmette, Louisiana, showed that pump repairs were reduced significantly when pump vibration was curtailed. To reduce vibration, the facility improved pump/motor alignment, instituted regular lubrication practices and replaced gear couplings with Rexnord Omega urethane elastomer couplings and Thomas disc-type couplings. In the tests, Omega couplings reduced coupling-related pump repairs by 79% and increased pump life by 406%, while Thomas couplings reduced coupling-related pump repairs by 58% and increased pump life by 142%.
In the search for a way to extend mean time between pump repairs, the refinery’s maintenance department installed Rexnord Omega couplings on 10 randomly selected motor/pump units up to 400 HP and 3600 RPM. Shortly afterward, Rexnord Thomas disc couplings were installed on eight applications that had higher horsepowers or speeds.
Measured vibration levels on the test units equipped with Rexnord Omega couplings were an average of 28% lower than the same units with gear couplings, according to Mike Polk, rotating equipment specialist at the refinery. At the end of one year, vibration levels were down an average of 49%, Polk says. Only one of the Omega couplings failed during the year-long test, the result of a seized pump bearing. In that case, the coupling’s elastomeric element sheared, protecting the motor. In the previous year, Polk notes, four gear-type couplings had failed.
The reduced vibration resulted in a corresponding reduction in coupling-related pump repairs, which were down 79% after one year of operation. In addition to an annual savings of more than $100,000 in repair costs on the test units alone, the cost of the Omega couplings is 30 to 50% less than gear couplings, Polk adds.
 Tests
at the Tenneco Chalmette
refinery showed that Rexnord Omega
couplings like this one on a
motor/pump unit reduced pump
vibration by 49%. The 150 HP
motor turns at approximately
3550 RPM, and the pump is
rated at 950GPM.
For heavy-duty applications with higher peak load requirements, Tenneco tested Thomas Series 71 disc couplings on eight motor/pump units operating above 3600 RPM. Despite two coupling failures caused by pump and alignment problems, the pumps with Thomas couplings showed average vibration levels 58% lower than the same units with gear couplings after six months of operation. Repairs were down 58% as well, according to Polk, resulting in a total annual savings of more than $80,000 for the test units. Maintenance costs are lower as well, since the Thomas couplings need no lubrication and can be inspected while operating by using a strobe light.
Most of the couplings were left in place following the test period. During the second year, the applications with Rexnord Omega couplings showed a 73% reduction in coupling-related pump repairs. Over the same period, the Thomas coupling applications exhibited a 53% reduction in coupling-related repairs. Polk concludes that these findings establish the ability of the couplings to perform over lengthy periods.
As a result of the tests, the Tenneco Maintenance Department recommended a change to the Rexnord Omega urethane elastomer couplings on all motor-driven pump applications up to 400 HP and 3600 RPM and installation of Thomas disc-type couplings on applications greater than 400 HP or at speeds above 3600 RPM.
NOTE: This application has been featured in articles appearing in Hydrocarbon Processing, Energy Progress, Machine Design, and Plant Engineering.
4-154-TennecoCS/12-10-03
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