delay the length of time it takes
for the bolt to loosen, but it will
not permanently prevent
it. The main reason is
that the split washer
does not solve the
gapping issue, the
free space remaining
between the threads
of the nut and the bolt.
On a typical
threaded assembly there
is just 15% efficient metal
to metal contact between
the threads. Everything else
is empty space that enables
plenty of side to side movement
Threaded bolts that
self-loosen during the
machine’s operation
can cause all manner
of problems from
increased maintenance
and downtime to
quality issues and lost
for the bolt. Additionally, being metal
itself, a spring washer can cause
damage to contact faces and corrode
in place.
For the Australian mining
operation, this problem was
exacerbated by the size of the bolts.
The bigger the bolts, the bigger the
gap between threads which leads
to more vibrational impact on the
assembly. This realisation resulted in
the company changing to adhesive
thread locking with Henkel’s Loctite
270.
This is a high strength formulation
that completely fills all gaps between
the thread and prevents any
movement of the bolt within the nut.
Secured this way, the assembly is
completely vibration-proof but can
still be easily dismantled with hand
tools for repair and maintenance.
Additionally, the liquid thread locker
seals the threads against humidity
and dust, preventing corrosion and
surface erosion.
This simple adjustment to working
practice has not only underpinned
productivity but contributed to a
safer working environment. It is
economical too as one 50ml bottle
of liquid thread locker is sufficient
to secure around 850 M10 bolts but,
unlike spring washers, can be used
on any bolt size.
To demonstrate how a threaded
assembly can self-loosen with
devastating effect, Henkel has created
a powerful video which shows two
identical loads, suspended 40m in the
air, vibrating at the same rate. The
fixture on one crane is locked with
an adhesive thread locker to prevent
vibrational loosening, the other is
unsecured. The result is sobering. !
production
FEBRUARY 2021 | WWW.EUREKAMAGAZINE.CO.UK 29
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