thanks. That's a nice reference. BTW, the lubricant is used in circulating system over a period of 20 years, will I have to designate the FU to be in flow rate or the total volume that is circulated in 20 years? say the quantity of lubricant in the entire system is 2000 litres at any given instant and the circulated quantity is 500 lpm, so throughout 20 years of lifetime, total lubricant circulated would be 4.7 billion litres. I'm a little confused on this. If you would, I'd like a clarification. Appreciate it!!