Sudden hose failure has been a major
potential problem for fluid power applications since hydraulic hose was first
introduced decades ago. Sudden failures can lead to safety issues, environmental
concerns and downtime that in extreme cases, such as offshore oil rigs, have
been estimated to cost as much as $500,000 a day.
But now using a real-time monitoring system
that senses changes in the electrical resistance within a hose, Eaton Corp.'s new LifeSense hose monitoring
system provides a way to avoid costly hose assembly failures.
"The uniqueness of LifeSense technology is that
it truly monitors the condition of the hydraulic hose as opposed to systems
that predict hose failure basically using a time-based replacement process,"
says Doug Jahnke, Eaton product marketing manager.
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Jahnke says it's impossible to tell when a
hose is failing because it fails from the inside out. Most hydraulic hoses have
a rubber elastomeric cover, a rubber tube and wire reinforcement. During its
life, the fatigue of consistent hydraulic surges eventually wears out the hose.
"There's been no way in the past to monitor
the condition of the hose and identify symptoms of failure as they are
occurring," says Jahnke. "The idea is to identify these conditions prior to
failure and with enough time that you can replace the hose prior to failure."
Eaton's
new LifeSense hose is very similar to two-wire braid hydraulic hose and was
developed in conjunction with Purdue University and the Purdue Research
Foundation's Office of Technology Commercialization. The goal is to
continuously monitor the health of hydraulic hose assemblies and alert users
when an assembly approaches the end of its useful life.
"Most hydraulic maintenance programs are
designed to avoid hose failures by replacing assemblies at regular intervals,
using a schedule based on usage data or past experience," says Jahnke.
As a result, a large number of hydraulic
hose assemblies can be discarded long before the end of their useful life out
of fear that they might fail. LifeSense hose allows the user to utilize the
useful life of a hydraulic hose assembly, which is 50 percent longer than most
hoses are left in service today, according to Eaton's lab testing.
"A hose is basically part of a hydraulic
circuit, and what we've done with LifeSense technology is also make it part of
an electrical circuit," says Jahnke. "A very low voltage signal is going
through the entire length and circumference of the hose and, using feedback
from the electrical signal to measure resistance, we can determine if the hose
is nearing the end of its life."
"We've proven very clearly in the lab that
it consistently reports certain feedback that lets us know it's close to the
end of its life," he adds.
The LifeSense monitor uses a wired
connection with wires running from one end of the hose to a microprocessor and
software in the monitoring device. Whenever the equipment is on, it provides a
continuous monitoring process measuring electrical feedback using contacts on
the hose.
Right now, each monitor can be connected to
up to eleven hoses. Any number of hoses can be monitored using multiple
monitors wired into either a 12 or 24V system, so it can be used on mobile or
industrial equipment. A converter for 110V operation is also available, and Eaton
is actively working on a new wireless conection system as well.
The initial LifeSense hose offering includes
widely used -8, -12 and -16 two-wire hose assemblies. It offers performance
equal to industry standard 2SN pressure-rated hose, and is certified to the
same industry specifications as conventional hydraulic hose products. The
technology is also currently available for trial with factory-made assemblies
including straight JIC swivel fittings.
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