We used to have the Hahn and Clay unheading device on our drums and now have Delta Valves on top and bottom. As for as maintainence we have cleaned our hydraulic tank and coolant tank once in over 2 years. Adjusted the packing on the rams once and that is all we have had to do to our system. And if you are management the safety of your personel outways the cost of these valves. I have 20 years experience operating cokers and after we installed these valves my life expectancy increased dramatically.