p. 1

voith turbo safeset torque-limiting couplings 1

[close]

p. 2

we are the experts in torque-limiting and connection couplings within voith turbo voith turbo the specialist for hydrodynamic drive coupling and braking systems for road rail and industrial applications as well as for ship propulsion systems is a group division of voith gmbh voith sets standards in the markets energy oil gas paper raw materials and transportation automotive founded in 1867 voith employs almost 40 000 people generates euro 5.2 billion in sales operates in about 50 countries around the world and is today one of the biggest family-owned companies in europe 2

[close]

p. 3

the history of voith turbo safeset the history of safeset began in 1972 at the kth royal institute of technology in stockholm where curt falk was studying for his doctorate in connection with that curt constructed a miniature rolling mill during construction he needed a quick and reliable solution for connecting and fixing the roll neck the result was that he developed an adjustable shrink connector now called hygrip which was later developed into a torque limiter the old method of torque limitation with shear pins was not reliable enough this was one of the reasons why curt started work on his own torque limiting coupling curt s idea for creating a more reliable coupling was based on a permanent connection with a safety function ­ later called safeset safeset is pressurized with oil causing it to expand and lock the hub by friction another unique function is its adjustable overload protection with simple resetting in order to develop the invention into a commercial product curt rented a workshop and took on the necessary staff to bring safeset to completion in 1978 curt falk took out a patent on the first safeset model in 1981 both patent and product were transferred to the company metallform safeset ab which could be called the origin of the present voith safeset company in hudiksvall in 1982 production of safeset product began in hudiksvall hudiksvall is a small town of some 16 000 inhabitants beautifully situated by the sea 270 km north of stockholm at first the number of employees was just five persons including curt in 1987 sales of the smartset design began this was a further development of the safeset principle and the first process improvement product in 1988 sales of autoset design began the first process improvement product with fully automatic resetting capability in 1992 the german voith group bought the company this resulted in rapid expansion especially on the international market the company changed its name to voith turbo safeset ab and the safeset product then became well-known in all the main industrialized countries of the world in 1997 a new factory in hudiksvall was built to meet the increased demand for the companies products 2000 saw the development of hycon a tapered sleeve coupling with a high friction coating hfc in 2011 the factory was again extended to include a new office section the facility now consists of a workshop area of 1 700 m2 and offices of 800 m2 the company has 80 employees in hudiksvall and a further 28 employees in subsidiaries throughout the world turnover is approx sek 200 million 3

[close]

p. 4

torque limitation and process improvement safeset smartset autoset safeset is a torque-limiting coupling that can be adapted to all manner of connection designs it has been the market leader in its product area for decades largely due to its unique features for instance integral to the safeset design is its adjustability while still retaining the constant release torque over time feature it only releases when the preset torque is exceeded and can be quickly reset safeset integrates a fixed hub or shaft connection and a safety coupling all in one machine component another big advantage is that it only has a few components that makes safeset both easy to use and easy to install and operate safeset consists of a twin-walled sleeve in which there is an initial clearance between the sleeve walls that is subsequently filled with pressurized oil by means of a pump when pressurized the safeset expands gradually thus creating a frictional connection the coupling is now capable of transmitting a torque proportional to the given pressure in the case of an overload event the safeset slips internally against the shaft a shear ring shears off the shear tubes allowing the pressurized oil to evacuate from the coupling which results in the return of the initial clearance in milliseconds the coupling releases its frictional grip and the coupling rotates freely on the integrated ball bearings after replacement of the shear tubes safeset can be quickly repressurized and thus resume its function as a torque limiter with the minimum amount of downtime of the drive line further developments of the safeset torque limiter is the process improvement coupling smartset and autoset they are both able to reduce short duration dynamic torque peaks during the start-up sequence or as a result of other process dynamics they will also release in the event of total system blockage that would have otherwise damaged components in the drive line 4

[close]

p. 5

safeset safeset is the most precise torque limiter available on the market it is used in multiple applications such as steel mills tunnel drilling machines crushers and many many more due to its · precise release point · no false releases due to fatigue · adjustable release torque smartset smartset is a development of the safeset with the additional ability to also slip without releasing to reduce short duration dynamic peak torques it is primarily used in compressor drives and refiners that are driven by synchronous motors but has other possible industrial applications due to its · ability to reduce transient torques at start-up · accurate and constant release torque · provides a backlash free connection autoset autoset handles short duration dynamic peak torques without releasing it is primarily used in steel industry and in particular levellers it is completely automatic and resets itself while still providing the following features · is preset to the required slip torque · can slip approximately 180 degrees without fully releasing · it then automatically resets itself to the initial preset torque level following the drive line stoppage 5

[close]

p. 6

customized solutions tailor-made customer solutions to ensure the best possible functionality of the safeset products they are always specially adapted for the specific application intended this applies to all voith turbo safeset couplings ­ safeset smartset and autoset to identify the optimum solution for you as customer we often suggest a number of coupling types this forms a basis for discussion and facilitates the decision-making process as the advantages of the couplings are easy to compare next we adapt our existing couplings and prepare contract drawings our sales engineers are involved in the whole process they take responsibility for ensuring that both design and construction of the coupling fulfill the customer s needs and requirements with regard to application performance and design for example if the space available for the coupling is limited it will need to be adjusted in size to maintain the same high performance level we adjust the choice of steel grade and design in relation to your application 6

[close]

p. 7

benefits with a customized coupling you always get the optimum process-improved solution our products increase production the narrow tolerance range of our products allows you to achieve the highest possible performance from your equipment our products have short payback periods safeset couplings are reliable and are only release when the set torque is exceeded this minimizes operating stoppages and downtime and as a result increase production up-time our products improve processes our range allows you to improve the production process and downtime and as a result increase production up-time 7

[close]

p. 8

1 applications 8

[close]

p. 9

2 3 4 1 coal mining armored face conveyor safesets are installed on the low-speed side of the gearbox next to the chain drive to provide optimal protection against brief torque spikes that could break the chains 2 mineral crushers safesets are usually installed in combination with a flexible coupling which provide dampening and overload protection 3 rolling mills safesets are usually installed on the motor shaft or integrated in the drive line of the rolling mill to protect against overloads 4 straightening machines autosets are installed between the distribution gearbox and the cardan shafts or gear spindles to prevent roll slip protect the drive train and improve product quality 9

[close]

p. 10

1 10

[close]

p. 11

2 3 4 5 1 high-speed trains safesets are installed on each drive to provide protection against injury as a result of a drive line failure 2 car crushers safesets are installed in the drive line often in combination with fluid or flexible couplings to protect against overload 3 marine vessels safesets are installed in the main propulsion drives to protect the drive lines from damage as a result of grounding in shallow waters or floating debris that entangles the propeller 4 gas turbines safesets are integrated into the reduction gearboxes to protect the gear and the turbine from short circuit reversal torques coming from the generator 5 compressors smartset are installed on the motor shafts to reduce the damaging torsional excitations that occur during the start-up phase 11

[close]

p. 12

safeset the torque-limiting safety coupling features · fully adjustable release torque · selected release torque remains constant · precise point of release · back-lash free power transmission · compact low weight design · low moment of inertia a hollow steel sleeve is expanded by oil under pressure this produces a friction connection between a shaft and a hub at overload the coupling instantaneously releases the oil pres sure and interrupts the drive 12

[close]

p. 13

safeset being pressurized safeset following a release shaft oil charge port anti friction bearings on each side hollow steel sleeve seals on each side hub shear tube shear ring 13

[close]

p. 14

safeset function and design operation the set hydraulic pressure in the coupling generates a defined frictional force between the pressure sleeve and shaft this pressure determines the maximum torque which can be transmitted slip torque through the coupling if the operating torque exceeds the set slip torque the shaft rotates relative to the pressure sleeve the shear ring that is fixed to the shaft therefore also rotates relative to the pressure sleeve which in turn breaks the tops of the installed shear tubes as a result there is an instantaneous drop in the oil pressure which reduces the frictional force of the connection and releases the coupling resetting is a simple operation of replacing the broken shear tubes with new and repressurizing the coupling which can be done in minutes the permitted temperature range of the couplings is 20 to 60°c temperatures which exceed this range are possible with small design changes design the safeset coupling design consists of a twin-walled pressure sleeve which can be pressurized with oil up to 1 000 bar 14 500 psi with the shear tube ensuring the system is completely sealed larger safeset couplings have more than one shear tube which come in four standard sizes l 28 l 39 l 54 and l 63 the friction surfaces are specially treated to prevent any wear or pick-up during the initial slip phase of the coupling release once the coupling has released it rotates on bearing thus preventing any wear on the friction surfaces during normal operation the bearings remain static only following a release do they rotate which means the often referred to bearing life is a minor factor in terms of the operational dependability of the coupling to ensure the bearings do not overheat in a release condition the coupling has a small amount of lubrication oil poured in this equally ensures a constant friction coefficient across the friction surfaces and as a result the release torque is extremely precise safeset couplings are not influenced by material fatigue i.e s-n datas which ensures the release torque remains constant over time 14

[close]

p. 15

fatigue curve s-n curve calibration curve calibration diagram safeset torque pressure shear pin coupling 10 10 2 10 4 10 6 10 8 torque load cycle shear tube illustration typical release curve release diagram charge port shear tube torque time 15

[close]