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Maximizing Steam Turbine/Compressor Performance With Precise
Torque Monitoring At The Coupling
CASE STUDY
Maximizing Steam Turbine/Compressor Performance With Precise Torque Monitoring At The Coupling
FLORENCE, KY – All turbo machinery is subject to degradation that, over time, will affect the system’s effi ciency and operational performance. Precise monitoring of turbo machinery performance with continuous torque-monitoring systems can be used to identify gradual effi ciency loss, allowing a more focused maintenance scope to be developed to return the system to its optimum operation and effi ciency.
Torque monitoring based on heat balance, energy balance, and other methods utilizes numerous parameters such as
pressure, temperature, fl ow rate, gas composition, etc., which require precise instrumentation to properly measure with low uncertainty. [Kurz, R., Brun, K., and Legrand, D., 1999, “Field Performance Testing of Gas Turbine Driven Centrifugal Compressors,” Proceedings of the 28th Turbomachinery Symposium,
Turbomachinery Laboratory, Texas A&M University, College Station, Texas, pp. 216-220.] However, phase displacement technology can be used to accurately measure torque directly at the coupling to within 1% of full-scale torque, a combination of all electrical and mechanical sources of error. This accuracy provides the lowest amount of uncertainty when computing effi ciency, compared to alternative methods.
A system of this type was recently installed on a cracked-gas compressor train at Qenos Olefi ns in Australia to determine the causes of a power limitation. The Kop-Flex Powerlign system utilizes phase displacement technology for long-term reliability, eliminating need for re-calibration. Two rings with pickup teeth are installed on a torsionally soft spacer, and intermeshed at a central location. Two monopole sensors 180 degrees apart are mounted on the coupling guard. As the coupling rotates, the ferromagnetic teeth create an AC voltage waveform in the sensor coil, which is digitally processed using known calibration parameters. Because of the intermeshed
Daniel PhillipsManager, Field Service EngineeringKop-Flex, Inc., Regal Power Transmission Solutions7565 Harmans Road Hanover, MD 21076Offi ce +1 410 787 8515 Mobile +1 443 831 1782
Email: [email protected]
Photograph 1- Completed Mechanical Installation
pickup teeth, the system is referred to as a single channel phase displacement system, producing two independent torque measurements (Figure 1). The Powerlign system will output torque, power, speed, and temperature, which can be easily integrated with any DCS system (Figure 2).
At the Olefi ns plant the operating cycle of the steam-driven, cracked-gas compressor train is 7-8 years. During this cycle the plant reaches production limitations because this compressor train encounters a power limit. To determine the cause of the power limit as “turbine fouling” or “compressor fouling” or a combination of both was not confi dently possible with the instrumentation installed. The cause had long been the subject of an engineering debate between the Machinery group, Process Engineering group and Operations department. One option to add more power by upgrading the turbine power rating from 7.5 MW to 9 MW was investigated. This required a capital investment of
Figure 1- Two Independent Torque Signals
Trevor Mayne Machinery EngineerQenos Olefi ns AustraliaOffi ce – 61-9-258-7516 Email [email protected]
Mark EllulQenos I & E SpecialistQenos Olefi ns Australia
Regal Power Transmission Solutions7120 New Buffi ngton RoadFlorence, KY 41042Customer Service: 800-626-2120Fax: 800-262-3292Technical Service: 800-626-2093
www.RegalPTS.com
APPLICATION CONSIDERATIONSThe proper selection and application of power transmission products and components, including the related area of product safety, is the responsibility of the customer. Operating and performance requirements and potential associated issues will vary appreciably depending upon the use and application of such products and components. The scope of the technical and application information included in this publication is necessarily limited. Unusual operating environments and conditions, lubrication requirements, loading supports, and other factors can materially affect the application and operating results of the products and components and the customer should carefully review its requirements. Any technical advice or review furnished by Regal-Beloit America, Inc. and its affi liates with respect to the use of products and components is given in good faith and without charge, and Regal assumes no obligation or liability for the advice given, or results obtained, all such advice and review being given and accepted at customer’s risk.For a copy of our Standard Terms and Conditions of Sale, Disclaimers of Warranty, Limitation of Liability and Remedy, please contact Customer Service at 1-800-626-2120. These terms and conditions of sale, disclaimers and limitations of liability apply to any person who may buy, acquire or use a Regal Beloit America Inc. product referred to herein, including any person who buys from a licensed distributor of these branded products.
Kop-Flex is a trademarks of Regal-Beloit Corporation or one of its affi liated companies.©2015 Regal-Beloit Corporation, All Rights Reserved. MCWR1520E • Form# 9633E
Figure 2- Sample Output from Powerlign
$2 million. The plant elected to defer this investment and instead installed a torque meter at the major 8-year shutdown.
The installation involved replacing the existing coupling spacer and fl exible halves with a “drop-in” torque meter and integral fl exible elements (Figure 3). The torque meter assembly was dynamically balanced to API standards so it was not necessary for the user to return any coupling components for the retrofi t. The coupling guard was modifi ed so that the two variable-reluctance sensors could be installed, completing the mechanical installation (Photographs 1-3).
On restarting the plant and having completed a number of compressor effi ciency improvements, the torque meter clearly showed the 7.5 MW turbine did not require an uprate and that the major power losses were coming from the compressor. The torque meter also allowed online tuning of the seal gas system of the compressor to establish the lowest power draw from the recycles that the seal system introduces. An additional 200 KW of power was reduced from the turbine load with the manual adjustments made on the seal gas system.
The torque meter is now being used to monitor turbine steam fouling issues and process related compressor fouling so that the corrective online washing can be activated as soon as issues arise.
Photograph 2- Smart Spacer Retrofi t
The historical data collected from the torque meter will also provide a basis of mechanical loading through the drive drain of the cracked-gas compressor over time. This data will be used to determine if increases in the maximum continuous operating speed rating of the compressor and the turbine can be accomplished at minimal costs. This would achieve increases in the operating envelope of the compressor.
The value of the torque meter has justifi ed the installation of a second system for the Olefi ns plant’s second steam cracking plant turbine/compressor train in October 2012.
For more information, an interactive page-fl ip version of Regal Power Transmission Solutions’ Industrial Coupling Catalog is online at RegalPTScatalogs.com. Printed copies can be ordered at http://www.RegalPTS.com.
Figure 3- Existing Coupling Arrangement (Top), Retrofi tted with Smart Spacer (Bottom)
Photograph 3- Sensor Installation in Coupling Guard
