[Vwdiesel] Risks of Hydraulic Heating?

[Val Christian]

> flyweights thrashing in the diesel fuel. My experience in working with
> hydraulically-powered industrial machinery has taught me that the easiest
> way to find a malfunctioning valve or a cylinder that is leaking internally
> is by using an infrared pyrometer or even just your hands to seek out the
> hottest part of the system. Don't underestimate the heating potential of oil
> under high pressure passing to an area of low pressure without performing
> any work. The energy put into pressurizing the oil has to come out
> somewhere, you know...
> 
> Lee
> Oo-v-oO
> PP-ASEL
> KB1GNI


Lee, Thanks for the good thoughts.  There area a few points I can speak to.
First, the heating of hydraulic oil when transitioning from a high pressure
area to a low pressure area is from the friction of the oil past the 
"orifice", whether it's a cylinder or a bypass.  No doubt that the oil
gets real hot doing that.  I don't know how hot, but localized heating
more micro than a passive radiometer will detect, could be on the order
of 800F (WAG), then rapidly cooling down as it mixes with other fluid.
Factors would include how turbulent the flow is, etc.  I'll have to see
if I can get a fluid dynamicist to give me some better ideas on that.
Second, the hydraulic system doesn't really have to get to 220F.  If it's
real cold, the partial pressure of water will be real low, and it will 
more readily vaporize at lower temps.  The downside of that, is in my 
hydraulic system, there is little air circulation.  The system mostly 
is vented from a breather cap, hidden under the seat.  

The good news is that a couple of heavy, warm, lake effect snows, help,
because I end up using the loader and when I'm pushing, it's at higher 
power settings, consequently, the oil gets quite warm, and the case can 
get as warm as about 120F with an air temp of 30F.  That helps.

I like your idea of installing a new loop, which has a regulator, orifice,
or whatever, to get the oil warmed, even if only at the begining of the 
season.  The tractor lives outdoors, and I suspect the moisture of fall,
and the lack of use, create much of the problem.

Val