Acoustic emission technology from Kittiwake Holroyd is
enabling Bridge of Weir Leather to make informed predictive
maintenance decisions in three key areas: bearing analysis,
rotating equipment and compressed air and vacuum leaks,
resulting in downtime reductions of 10 to 15%

Bridge of Weir Leather Company is a
privately-owned Scottish company. It
produces upholstery leather, which is
exported to 60+ countries worldwide, most
of which is destined for the automotive
industry. Growth prompted a review of
machine performance. The company
examined its processes in detail, identifying
any bottle-necks in production, investing in
capital machinery to increase capacity, and
increasing the number of shifts worked. It
became obvious that a more proactive
approach to maintenance was need.

Bridge of Weir Leather had relied on a
more ‘traditional’ approach. Steven Lang,
engineering manager, explains: “We adopted
the philosophy that we’d do our best to
prevent failure but if we weren’t successful,
then we had sufficient capacity to cope with
a small amount of downtime. However, with
escalated demand for our product, we could
no longer rely on that buffer.”
Bridge of Weir Leather started to research
various condition monitoring approaches
including thermal imaging and vibration. A
key challenge was
that a lot of the
equipment is slow
rotating – down
to 10rpm mark
which, says
Lang, vibration
monitoring
wasn’t able to
cope with: “About
90% of the
factory couldn’t
be
monitored
using vibration. There’s no way we could
justify a £4-5k spend to address only 10% of
our maintenance problems.”

Solution
Acoustic emission was also investigated and
Kittiwake Holroyd’s handheld MHC-Memo
Pro demonstrated that it provided the
solution needed. Able to monitor an
unlimited number of machines on a periodic
basis, the device stores Standard and Super
Slo modes within its walk around routes.

“The MHC-Memo Pro is able to give a
reading for everything that we can find to
take a sample of – one minute on machinery
that’s spinning at thousands of rpm and then
on something spinning at 20rpm,” says Lang.

The functionality of this single piece of
equipment and its ease of use works well for
Bridge of Weir Leather. The company uses it
for predictive maintenance in three main
areas: bearing analysis, rotating equipment
and compressed air and vacuum leaks. As
the mechanical condition of machinery
deteriorates, energy loss processes such as
impacts, friction and crushing generate
sound wave activity that spans a broad range
of frequencies. By detecting only the high
frequency part of this signal with special
acoustic emission (AE) sensors, it is possible
to detect miniscule amounts of activity, for
example a slight rub, a brief impact or the
crushing of a single particle in the lubricant.

“It’s so simple to use. Its Distress parameter
removes the need for machine specific
interpretations. If Distress is greater than 10,
then we know there is a problem. However
the real value stems from collating historical
data and trending,” says Lang. “By devising
routes and analysing results over time, we
can better understand the machinery and
create real intelligence on how the bearings
react to changes in operation, how issues
develop and – critically – how long it will last
until complete failure.”
Bridge of Weir Leather has created weekly
routes to follow around the plant, taking and
logging regular samples to build a picture of
machinery health. The MHC-Memo Pro can
hold up to six routes at a time, each having
up to 435 measurement points within a site,
area, machine and point hierarchy. Once
downloaded, all readings are stored in a
machine database in the supplied Analysis
Pro software, which has features such as Trend
Plots, Alarm Levels, Exception Reports,
Missed Points List and User Notes. Routes
can be replaced and the process re-enacted.

Results
The company estimates that in some areas,
use of the MHC-Memo Pro has assisted in
significantly improving machine uptime.

“We are making calculated and informed
decisions now,” explains Lang. “Rather than
changing a bearing or a motor prematurely,
we know how much longer we can safely run
the machine before failure. We operate three
or four major shutdowns a year and need to
know if any critical machinery won’t last
between these intervals. Before the adoption
of the MHC-Memo Pro, we’d have to make a
decision between changing it between shut
downs and impacting production, or leaving
it and running the risk of unscheduled
downtime. Now, historical data informs our
maintenance planning, enabling us to make a
confident judgment.”
“One of the greatest successes has been in
identifying compressed air leaks,” adds Lang.

“Any leaks obviously compromise efficiency
and we now set aside time during shut down
for engineers to identify them. Over 40 have
been found that we’d have otherwise been
unaware of. In addition, our vacuum dryer
was a significant cause of unscheduled
downtime; even the machine manufacturers
struggled to recommend an effective way to
detect leaks. The MHC-Memo Pro makes
this process quick and easy. The set up time
after replacing the seals on the dryers has
reduced by a factor of 30%, in fact the results
of this single application alone paid for the
product within 18 months.”
As access restrictions were prohibiting the
potential benefits of monitoring internal
machine bearings, Bridge of Weir Leather is
investigating Kittiwake Holroyd’s remote
sensor range. These ‘match box sized’ sensors
integrate with the portable tools to ensure
measurements can be completed while the
plant continues its normal running.

Lang concludes: “As our understanding of
the capabilities of AE increases, so too does
the number of applications that it’s suited to,
many of which have proven difficult for
some other forms of condition monitoring to
address.”