on the chain gang
is a necessity for chain systems but what happens in sensitive
applications, such as food production, where lubricant may be undesirable?
trying to determine the life expectancy of a chain in service have used
a calculation to estimate the life of power transmission chains with some
degree of accuracy.
of mechanical handling conveyor chains though, has always been more difficult
to predict, as they are more dependant on the quality of maintenance they
receive particularly lubrication.
trends in the manufacturing industry have been to reduce the level of
maintenance staff with the inevitable detrimental effect on the quality
and maintenance of the chains and therefore chain life.
As a rule
of thumb, to achieve an acceptable life from mechanical handling chain
operating under poor lubrication conditions, the load-carrying capacity
is reduced by a factor of five over a well-lubricated chain. The present
situation has given impetus to the development of lubrication-free chains.
factors were: the environmental and safety pressures to remove hazardous
substances such as excess lubricant from escalators following
the Kings Cross fire; lower maintenance costs; and longer life.
wear is a major cause of escalators being taken out of service for overhaul
and is probably the most costly single item to replace on a heavy duty
public service escalator, in terms of both material and labour. One innovation
was to adapt and built on the polymer bushed chain concept, originally
developed by the London Underground Escalator Engineering Department and
one of the UKs leading tribology consultants.
extensive trials and testing, in an effort to obtain a cleaner operating
environment below the escalator, not only to reduce fire risk but to ensure
that every link was effectively lubricated.
have been available for many years, but the criteria was to achieve endurance
and reliability when operating at typical bearing pressures of around
20N/mm˛, without the benefit of a rotating bearing effect. A typical escalator
step chain is designed to last for a minimum of 20 years. The production
techniques developed by the chain manufacturer have been a key factor
in the successful use of polymer bush chains in the past few years. Performance
monitoring results, by independent inspectors, are predicting chain life
well in excess of 20 years, with the additional commercial benefit of
considerably reduced maintenance costs.
problem was that the chain had to fit into the existing space envelope
on the escalator. The addition of any non-lube component between the pin
and bush had the inevitable effect of increasing the bush outside diameter
and reducing the strength of the chain.
research a material was found that was thought to be suitable and the
size problem overcome. The chain shown in the diagram is the result of
this development, with the design being used on many escalator installations.
The key to
the design is the polymer bush fitted between the steel pin and bush and
the material used in the manufacture of the pin. The wear life of the
lube-free chain compared with the standard greased chain is considerable.
of the polymer bush fitted to the escalator chain has led to the same
principle being applied to other industries with very different conditions.
can be said to be an ideal environment for a minimal lubrication chain.
Non-lube transmission chains have been available for some years, fitted
with plastic bushes between the pins and the bushes, but have always been
restricted in their performance. One restriction is the extreme difficulty
of fitting a polymer bush into a transmission chain and still offering
a chain that complies with the BS, ISO or ANSI standards. Another was
the very limited load capacity of the bush insert.
proved to be the Renold Syno chain. It has a special oil-impregnated bush
which serves to lubricate both the pin and roller with a USDA-approved
food quality lubricant. The chains are now in service in many applications
where lubrication is difficult, impossible or undesirable, notably the
food industry (where lubricant contamination is a major concern with conventional
chain types), electronics, paper, packaging, clothes and textiles.
of course, applications where non-lube chains cannot, at present, be used;
for the time being, the operator will still be required to lubricate chains
as before in these places. But even in these difficult applications, chains
can be treated and maintained with special lubricants tailored for specific
industries. In most cases there is no excuse for allowing chains to fail
prematurely due to lack of a suitable lubricant.
inventor of the bush roller chain, has led the world in chain technology
for more than a century. Renold Chain is part of a diverse, worldwide
engineering group that specialises in power transmission products. For
further information, contact: Andrew Freeman, marketing manager, Renold
Renold House, Styal House, Wythenshawe, Manchester M22 5WL. Telephone:
0161 437 5221. Facsimile: 0161 437 7782. E-mail: email@example.com
website is at: http://www.renold.com
major biscuit manufacturer was having serious problems with short chain
life on the infeed conveyor of a flow wrap machine. The installed chains
needed replacement after as little as three months, due to difficulties
experienced in lubricating the chain.
the product was building up on and around the chain parts and effectively
blocking the penetration of oil into the chain. The oil-wet product debris
then attracted more debris by adhesion, which compounded the problem.
design provided only a small amount of tension adjustment for the chain
and so the rapid wear caused by lubrication starvation severely restricted
the chain life. The adapted transmission chain used on the conveyor also
suffered from misalignment, which had led to abrasion against the conveyor
some small modifications to the track layout and the fitting of an attachment
variation of Renold Syno chain to replace the original chain. This new
Syno chain remains fitted and continues operating without problems after
nine months a threefold increase in life.
has required no tension adjustments to allow for wear. The biscuit manufacturer
is delighted with the new chain development and the savings enjoyed.
include: reduction of downtime; saving of maintenance time for tension
adjustements; saving of lubrications costs; extension of chain life; and
saving of chain replacement costs.
including the chain, is washed down on a regular basis with hot water.
This has not affected the self-lubricating feature of the chain. The Renold
Syno chain now features in the customers plans for future replacement
and is already used in several new applications.
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