Is 195 F Too Hot?
I work on various industrial equipment including gas turbines, lube oil systems, hydraulic systems, etc.
We generally use these days an ISO 32 hydraulic oil for the ambient conditions you have, or maybe an ISO 46. Sounds like you are using an ISO 46. The ISO and 32 or 46 designate the viscosity in centistokes at 104 F, i.e. 32 and 46 respectively.
Given the fluid temperature you have you could use ISO 68 oil. But I don't think you really need to.
As all of these oils heat up the viscosities of each come closer together, at hotter temperature. At 212 F the difference in viscosity from ISO 32 to ISO 46 to ISO 68 might be something like 5.4 to 6.8 to 8.7 centistokes; but it would depend on actual oil make up. Synthetics and mineral base oils do act a bit different, over wide ranges in temperature.
But as you can see the viscosity drops a lot as the temperature rises to 212 F, and the differences become less. Much less.
As a point of fact I do not use 'hydraulic oil' in my splitter, I use Mobil 1 synthetic ATF. I live in AK where it gets cold, as well as warm in summer. Mobil 1 synthetic ATF is a very good all around hydraulic oil, for most applications, and since it is a synthetic it can work well over a very wide range of temperatures.
Your reservoir is not really too small. One negative it has is that it is a square of sorts, thus the surface area is minimal for the amount of oil it holds. If it was long and narrow, there would be more surface area. The one you have thus does not afford much in the way for natural cooling.
On most of the equipment I work with we like any oil to be in say the 130 F range, before it enters bearings, pumps, and those sorts of components. If we use shutdowns for the high side, they are often in the 165 F area. We like the oil to flow easily, if it does it actually lubricates better. Thicker is not always better, in fact in my career thicker has been found to lead to failure more than the opposite. When the oil is loaded in films, as it goes through bearings, pumps and such, the peak temperature can get well over 200 F. Maybe even up to 300 F. About the hottest we allow babbit coated bearings to run at the surface is in the 260 F area, because this is where the babbit melt temperature is approached.
So is 195 F at the reservoir too hot? It is decently warm but I don't think it is going to lead to direct and immediate failure of any components. The items most suspect to degradation would be orings, seals and such. Some are made to take 195 F, but I would not know for sure what the ones you have are made of. Would in general doubt they were chosen to tolerate high temperatures. Assuming not they just won't last as long as they would if operated at cooler temperatures. Not really like a line that one crosses.
Many standard orings and seals are made of Buna N, it will take 195 F, but that is getting a bit high. Viton on the other hand is more high temperature tolerant.
If you want to make some improvements a larger reservoir would help, because you would increase the surface area for cooling. A poor mans method, if you only operated in warmer temps now and then, might be to run a garden hose and run water over your reservoir, but be sure you don't get water in your reservoir. Anther option might be to look for a small natural air fin type of cooler, and install on the return side. These are generally of SS tubing, with fins attached, with a single inlet and outlet. They can be oriented and made to get some decent cooling with just natural air convection type air flow.
One could make one as well, they really don't need to be that large.
I do not have a cooler on mine, my reservoir is long and narrow, has decent surface area. Most of time when I use mine it is cold out so never had any heating issues.
There are some charts at this link you might want to look at.
Hydraulic Fluid Chart Hydraulic Oil Table and Cross Reference
As a point of reference I figure I can hold my hand on 130 F. At 150 F, no too hot, really to the point of getting a burn. Maybe 140 F but that too would be pretty uncomfortable after a spell.
nspolar
