If you're a hydraulic machine owner, or responsible for the same, one sure way of transferring a scary amount of dinero from your bank account to your hydraulic supplier's is to allow your hydraulic machines to run hot, as this exchange I had with one of our members illustrates:
Member: "The hydraulic systems on my customer's underground machines are running at 148°C. I have replaced the NBR 90-shore o-rings with Viton 75 shore o-rings on the SAE flanges but they are still failing."
BC: "You need to get that operating temperature down. Without doing so everything else you do will be in vain."
Member: "Yes, I understand that but I only supply the hydraulic hose, fittings and o-rings."
BC: "In that case, keep on supplying them. Your customer's ignorance and/or inaction is going to make you rich. But in terms of your seal options for the SAE flanges, for high pressures, 90-shore o-rings are a better choice than 70/75-shore. And even though Viton has a temperature rating of 200°C, it does NOT mean it's longevity is unaffected by extreme operating temperatures.
You should also consider that being underground, the machines will likely be running some type of fire-resistant hydraulic fluid. Viton is compatible with all fire-resistant fluids, except HFC fluids, so you need to confirm what type of fluid is being used so that compatibility is not an issue.
As already stated, you're really up against it with the machines' sky-high operating temperature. It means whatever fix you offer to this customer will only be a Band-Aid measure it best. The only lasting solution is to get the machine's operating temperature down to below 85°C."
The moral of this story is: allowing a hydraulic machine to run too hot is the most costly mistake a hydraulic equipment owner can make. And to discover six other costly mistakes you want to be sure to avoid with your hydraulic equipment, get "Six Costly Mistakes Most Hydraulics Users Make... And How You Can Avoid Them!" available for FREE download here.