We have had several gearboxes supplied from the
manufacturer with a breather that is basically a
pipe plug with a hole drilled in it. Every once
in a while, a less experienced craftsman rebuilds
a gearbox and switches the drain plug with the breather
plug. The result is always an oil leak mess and
an unsatisfied customer. On many gearboxes we've
started to replace these orifice breathers with
particulate filter breathers. On gearboxes where
we still have the pipe plug breather we've painted
the breather plug a different color so that it is
easy to see. This helps ensure that the plugs are
in the correct locations. (Submitted by Bill Jacobyansky,
Maintenance Manager, Guardian Industries. Thanks
Bill!)
From the book "Fluid Contamination
Control"
Pressure-line filters might be essential in protecting
components downstream. However, without auxiliary
filters, the pump is exposed to all the contaminant
that ingresses the system before it can be taken
out. A problem even more acute is that a pressure-line
filter is subjected to large variations in pressure
(fluid compression and decompression) and flow (valve
actuation, pump volume control and pump speed),
which cause particles to be constantly desorbed
and re-entrained.
| Q
& A: How to Get Water Contamination Out |
"What is the industry "best practice"
for removing water from the oil reservoir of a piece
of equipment? For example, routine oil analysis reveals
3,000 ppm of water in a gearbox oil reservoir of 15
gallons." - Keith Swearingen, Lubrication Coordinator,
Exelon Corp
Several technologies exist for removing water from
oil, including vacuum dehydration, centrifugal separators,
jet-dry devices, headspace dehumidification, aggregate
adsorption media and hygroscopic polymer impregnated
filter media.
The oil type, volume of water, size
of the reservoir and several other factors dictate
what technology should be employed for a given situation.
At ~0.30% water in a 15 gallon sump,
you have approximately five to six ounces of water
either dissolved and/or emulsified in the oil. Given
the application, I would either use a portable vacuum
dehydrator or a hygroscopic polymer impregnated media
filter.
Filter the machine offline, preferably
while it is operating (be sure that the plumbing in
your decontamination rig is full of new oil - the
type used in the gearbox). Before filtering, open
the drain valve to get rid of any FW (undissolved
and unseparated water that can settle to the bottom
of the sump). If you have some FW in the bottom of
sump, you will need to estimate the volume of FW and
add it to the estimate of five to six ounces.
You can do this by estimating the volume
in the sump below the lowest point of the drain port
(L x W x H). If the drain port is at the lowest point
in the reservoir, the volume will be zero. However,
most gearbox drain valves are set slightly above the
bottom. If you employ hygroscopic polymer media elements,
you need enough water-holding capacity to get rid
of the dissolved and emulsified water, plus the FW
that will become suspended during decontamination.
You will probably be drawing from the
drain port, so this will suspend the water, plus drying
the oil will lead to FW being pulled into the dry
oil via osmosis.
Of course, in addition to removing
the water, perform root cause analysis to find its
source. Breathers, seals and new oil are common culprits.
To reward the lubrication and
reliability community for its participation in the
Noria Message
Boards, we've started the Post
of the Week award. Every week, we award one lucky
member $50.
"I am currently involved in a
project installing mini-mess sample ports in the gearboxes
at the plant I work at. Each unit has to be looked
at to determine the best location for the sample port.
But for most applications, I place the valve in the
drain port. I am using the type with a swivel tube
which extends to place the end of the tube into an
active area where oil splashes around inside the gearbox.
By bending the tube slightly away from the bottom
of the gearcase, we are not sampling the sludge which
collects there. On circulating systems, you ideally
want to place the sample ports in return lines before
any filters or the reservoir." See
the entire post.
