RIGIFLEX®-HP for high speeds – Steel lamina coupling with high perfor-mance

RIGIFLEX® steel lamina couplings are used in all those applications which require a reliable and maintenance-free torque transmission with at the same time shaft misalignment. RIGIFLEX®-N has already gained a good reputation in the pump industry. This coupling system is in accordance with the standards of API 610 and can optionally be supplied in accordance with API 671 (API = American Petroleum Institute). The recently introduced new development RIGIFLEX®-HP, HP signifying high performance, now meets with such demands which could not be met to that extent by the classical RIGIFLEX®-N up to now.

First of all the use with very high speeds of up to 13.000 revolutions per mi-nute should be mentioned. This results in circumferential speeds of up to 200 m/s which require special attention with the selection and production of the coupling. For comparison only: For standard applications with flexible ROTEX® couplings the circumferential speed is approx. 40 m/s. Applications for RIGIFLEX®-HP are mainly in the drive of steam turbines using the process steam existing in chemical plants anyway as a source of energy to drive turbo compressors, fast-running pumps or generators. In addition, they are used for energy production on gas turbines or for liquefaction or decompression of industrial gases. Apart from that drives of large fans which are used, as an example, in underground mining or with wind tunnels use high-speed steel lamina couplings like RIGIFLEX®-HP.

Anyway, such kinds of applications require a highly accurate adaptation of the coupling to transmission mechanics. The drive train of a turbo compressor should usually have a torsionally flexible design and in addition meet with the API standards usual in the market. API 610 and 671 exclusively allow for the use of steel materials which means that elastomers must not be used. This standard can be met by designing the spacer as a torsion bar having the required torsional stiffness. Another challenge for KTR's design engineers is the position of center of gravity of the coupling as indicated by the customer. It should always be each within the range of the end face of shaft. The use of 3D designing systems as well as calculation and simulation software for the torsional vibration calculation supports the design engineers with such assignments.

In addition to theoretical considerations, a high accuracy in production from the part of KTR is absolutely vital in order to ensure the requested smooth running of the machines, even with coupling diameters of up to 650 mm and lengths of 1.5 m and more. The peak figures of the transmittable torques are 429,000 Nm. Anyway, lower figures are available as well. In total ten stand-ard sizes in two designs are available for the different applications. Two types of RIGIFLEX®-HP couplings are available, series C and series L, „C" signifying „compact" with the flange design and „L" signifying „large" for the hub design with big bore diameters. Anyway, it should be noted that standards do not exist with such applications. Each coupling selection is performed for the special application which means that every coupling is a tailor-made unique copy based on an intelligent construction kit system. As a consequence the coupling designs shown in the catalogue are each adapted to the individual demands of the customer.