MACS Monthly Newsletter - 2017 - OCT3

WHAT IS AN OIL SEPARATOR ANYWAY?

service information. It doesn't help much though,
and what it says really just adds to the confusion.
See Figure 2.
This factory information kind of goes against
some of what we've been taught about best service
practices, in saying that compressor oil drainage
is unnecessary. We learned (and MACS has been
preaching for years) that successful compressor replacement depends (in part) on performing a procedure called oil balancing. This is when you drain the
oil from both compressors, compare the amounts,
and then refill the replacement compressor with
new, clean oil of the same amount that was drained
from the old. It's important because it's the only
way we can ensure putting the correct amount of
oil back into the system, neither over nor undercharging it. Of course, this assumes we're not dealing with a flushed, dry system like we are here with
this CR-V (where balancing really isn't necessary),
but we'll cover that more in a future issue.
In our case, the technician decided to try and
drain the old compressor, and was able to remove
just 2 ounces of oil. If the separator was doing its
job, the label information is correct, and the compressor did have about 2.7 ounces of oil inside, that
would mean the remaining ¾ of an ounce is trapped
in the nooks and crannies of the inner workings,
which sounds about right.

US Patent Office

Many years ago, a retired engineer told me that
car makers have long had the technology and capability to install oil separators into each one of their
compressors, but that back in the day it was thought
to be too costly on a per vehicle basis, and so they
decided not to do it (even thought it would be one
of the best things they could do to help protect the
compressor from wearing prematurely).
Times have changed, and we now have stringent
environmental regulations that push manufacturers
towards building cleaner, more fuel-efficient cars
and trucks. One of the ways this is done is through
the EPA's CAFE credits program, where small improvements in vehicle subsystems can earn credits
for the manufacturer that are otherwise not measurable through typical drive cycle testing.
An example of these improvements is the oil separator itself, and there have been many different
types over the years. It's basically a small device
incorporated in the discharge area of the compressor that works to remove the oil from the refrigerant/oil mixture just before it leaves the compressor.
One design uses a specially shaped pipe that puts a
rotational sling on the mixture to centrifugally separate the oil. Another uses a spinning fan shape to
accomplish the same task. See Figures 3, 4.

Figure 3: This drawing shows the position of the oil separator installed along the right (rear) portion of a Sanden scroll compressor. As refrigerant and oil
enters the discharge chamber it encounters the separator which puts a spin on the mixture. This action works to sling oil out of the mixture so it can drip
down into a sump, while the refrigerant and a tiny amount of oil are allowed to exit.

October 2017

MACS Service Reports

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017