CLUTCHES, BRAKES & COUPLINGS FEATURE
OVERCOMING pump
vibration V
ibration in pumps can be caused by a number of factors. This could
be related to poor installation, piping problems, or an out-of-balance rotor; or perhaps by structural issues or torsional resonances relating to the pump drive. The frequency of the torsional
resonance (a physical phenomenon which is present in all rotating systems) is controlled by the inertias and stiffnesses in the system, with torque spikes determining the amplitudes and resonant orders of vibration. Torsional resonance is therefore less likely to be a problem with an electric motor drive versus a diesel engine. Likewise, the same is true with a centrifugal pump versus a reciprocating pump. In both electrical and mechanical
pumps, poor misalignment of the drive and pump is a common issue and will result in vibration and reduced component
The CENTAMAX-SB is a highly reliable and robust design for the transmission of torques up to 24,000Nm
vibration
Coping with vibration in pumps: what are the causes, what are the consequences, and how can it be rectified? Centa Transmissions comments
life - unless the correct type of flexible coupling is specified.
COUPLING CHOICE The choice of flexible coupling is dictated by a number of issues, including operating torque, drive speed, the required stiffness and the ability of the coupling to cope with backlash and short-term spikes in operation. Coupling elements are
typically made from a special blend of rubber with a choice of torsionally soft or stiff compounds. Centa Transmissions calculates the torsional resonant frequencies and selects the correct stiffness for every pump application -
even the resonant frequencies induced by reciprocating pumps can be calculated. To rectify vibration problems, it is
PRECISE SOLUTION SUITS TEST STAND DESIGN
When it comes to e-mobility or emission reductions for combustion engines, there is increasing demand for dynamic and precise torque measurement solutions. So, Kistler has developed KiTorq, a torque measurement flange system for industrial test stands which can determine, for example, performance during the efficiency measurement of e-motors, gearboxes and pumps. This is characterised by a high dynamic with a limit frequency of 10kHz and an accuracy class of 0.05%. To make sure that the high-precision torque measurement flange system provides exact and reliable data, it is used with a shaft compensating coupling from Mayr. Based on the proven backlash-free and torsionally rigid ROBA-DS series, this helps minimise the disturbance variables which can occur due to alignment errors in the drive line. Due to existing radial, angular and axial shaft misalignments, bending torques and radial and axial forces occur on the measurement flange. However, the couplings compensate for transverse and axial forces as well as bending torques, enabling the company to realise even the smallest measurement uncertainties. Berk Buharali, product manager Torque Sensors at Kistler Instrumente, explained: “The couplings do
not only guarantee precise measurement results, but also provide the best possible protection for the measurement flange, the mechanically weakest link in the drive line.” “The connection of the ROBA-DS couplings and the measurement flanges to the shaft train is normally executed backlash-free via high-quality shrink disk hubs,” added Ralf Epple, product manager at Mayr. “Moreover, different coupling designs and flexible combination possibilities especially tailored to the requirements of the test stand enable the integration of measurement flanges in almost every test stand and drive constellation.” So, depending on the construction size, standard ROBA-DS couplings cover a speed range of 8,000 to 18,000rpm and are balanced to a balance quality of G 2.5 (reference speed 300rpm). With high-speed designs, in which the individual parts are machined to an extremely high accuracy
(quality IT5), and narrowed concentricity and axial run-out tolerances, speeds of up to 30,000rpm are possible. Here the balance quality of the coupling is G 2.5 at a reference speed of 5,000rpm. In addition, with the EAS-HSC and EAS-HSE series, Mayr power transmission has developed torque limiters
which are tailored to the extreme requirements of test stand technology. Mayr power transmission
www.mayr.com
essential that a robust coupling offering high torsional flexibility and resonance-free
operation is specified for drives susceptible to torsional vibration.
SOLUTIONS Centa Transmissions manufactures flexible couplings that do this, including the compact CENTAMAX-SB. This is a highly reliable and robust design for the transmission of torques up to 24,000Nm. Featuring high torsional flexibility, it dampens torsional vibrations and shocks while compensating for axial misalignments. Other options, which are subject to size and volume, include the compact and robust CENTAFLEX-CO for progressive torsional elasticity and the highly versatile ATEX approved CENTAFLEX-A, a torsionally soft coupling that can be doubled up into a long shaft (G-Shaft) that can overcome axial, radial and angular misalignment. Featuring a highly elastic rubber
element, the CENTAFLEX-A is an extremely versatile coupling. With a small outer diameter it can be used in many different configurations to provide a vibration- and noise-free high torque drive. It is also available with a silicon element for high ambient temperatures due to its superior thermal resistance. For deep well pumping situations, the CENTAX-V along with a cardan shaft is a torsionally flexible solution for a remote mounted engine, allowing large amounts of misalignment. These super strong couplings will support cardan shaft misalignments up to 3˚ without the need for additional bearing support. On conventional couplings, the driven and driving machines must be very finely aligned and cannot support the cyclic loads of cardan shaft joints. Bespoke coupling solutions for special
applications can also be created by the company, with one example being a pulley drive from the pump. In addition, spacers for fire pumps have been manufactured so engineers can carry out maintenance without disturbing the pipework. Centa also manufactures the CENTA-CP, a compact and versatile clutch coupling with flange bearing. Combining a torsional coupling and electromagnetic clutch coupling inside a flanged bearing housing, this allows the operator to start and stop the driven unit under load, protecting connected shafts and bearings against damaging reaction forces.
Centa Transmissions
www.centa-uk.co.uk
DESIGN SOLUTIONS | JULY/AUGUST 2018 29
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
