materials/solids processing
27
The planetary gears create more contact points The smaller size means that planetary gearboxes
which means that the system is capable of maintaining offer solutions where other types are inoperative, for
the power without slipping. While this kind of torque example they have been used to power aerators for
is possible with other gear systems, they will be up to Yorkshire Water’s Rawcliffe Sewage Treatment Works.
twice the size and require a far larger motor to run The concept that ‘small and light’ can also mean
them. ‘strong’ isn’t unique to water processing; other sectors
The torque distribution of these systems means that including F1 technologies are realising this and using
they are more resistant to shock loading and provide it to their advantage. These light weight and compact
rigidity. gearboxes offer a solution to operators of large pumps
Many gear systems are unreliable when used in a with limited space.
system with requirements similar to that of peristaltic The planetary design offers flexibility for solutions
pumps. Yorkshire Water’s Rawcliffe Sewage Treatment to any non-standard application. For example Brevini
Works has the ability to process water at a flow rate of was the only company able to design a solution for
23,600m3/day. However, until they installed planetary Thames Water that complied with their ‘no engineering’
gearboxes this maximum rate was impossible due to rule when an old gearbox broke, saving both down time
constant breakages. Brevini’s gearboxes have been and money.
successfully integrated into many water plants as, This flexibility is a great advantage for peristaltic
with features such as twin taper roller bearings and pump users as each pump needs specific requirements,
extremely high torque rates, they are capable of for example the planetary system is able to run
surviving in conditions where other transmissions fail. clockwise and anti-clockwise and any standard motor
The utilisation of the twin taper roller bearings, can be direct mounted.
which can withstand extremely high radial loads, in Peristaltic pumps continue to be preferable to water
the output of the gearbox allows the gearbox to be authorities. The introduction of a planetary gearbox
integrated into the casing by some OEM manufacturers. system such as the range offered by Brevini ensures
The gearbox is fitted with a double seal arrangement that these pumps will run more efficiently with less
which can accommodate higher pressures thus maintenance. Brevini has the widest range of planetary
ensuring that, when the hose needs replacing, the gearbox solutions in the world. The products are widely
lubricant in the pump does not enter the gearbox. available and provide compact, solutions that offer
The lifetime of a planetary gearbox can be up savings in running costs.
to 100 000 hours when it is in continuous use. The
only routine maintenance required is oil changes,
Obsolete gearboxes
though even here less oil is required than with other Meanwhile also in the UK, Anglian Water PLC sewage
conventional gearboxes. treatment works (STW) in Benfleet has replaced its
To ensure that the gearboxes will perform, their obsolete gearboxes for Brevini’s planetary gearboxes.
load capacity is calculated with a hertzian pressure When the old ‘varatio strateline’ gearboxes began to fail
and breaking strain in accordance with ISO DP6336 on two half bridge scrapers Anglian Water found that
in relation to theoretical life. This offers engineers a Brevini were the only company able to meet all the
benchmark for how long the system will operate. In the requirements for a new gearbox. Brevini was able to
unforeseen circumstance of a breakdown the modular offer a low-cost solution providing compact and highly
construction of these planetary systems means that efficient gearboxes without the need to replace or re-
parts are held in stock. This reduces lead times from engineer the half bridge scraper.
weeks to a matter of hours. When a half bridge scraper stopped working and
Planetary gearboxes are capable of high reduction another was found sounding distressed at Benfleet STW,
rates meaning that a smaller input gear is required Anglian Water had to make a decision whether to repair
than with other transmission types. Brevini’s planetary the existing, dated gearboxes or to re-engineer the half
gearbox’s are capable of reduction rates of 3-10:1. bridge scraper to accommodate a new gear box. Both of
The addition of further stages can result in very high these options were expensive and would have resulted
reduction (ratios can reach 15 000:1) whilst keeping in a lengthy downtime.
the system relatively small. Using its range of planetary gearboxes Brevini could
Many users of large peristaltic pumps find that design a drop-in solution that provided cheaper running
conventional gearboxes are far too cumbersome to be costs and minimal maintenance throughout its long life
used effectively. These large gears require massive span.
support structures to house them. Planetary gearboxes Any standard motor can be directly mounted onto
as made by Brevini can be up to half the size and the gear units so the gearboxes can be installed straight
60per cent lighter than conventional ‘worm and wheel’ into any existing system. v
gears. This smaller size means that a smaller support
structure can be used which is ultimately easier to Jon Snaith is General Manager, Brevini UK,
handle. Warrington, Cheshire, UK. www.brevini.co.uk
www.engineerlive.com
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