One of our members wrote me this question:

“In hydraulic systems and in hydraulic components in particular, bolts are everywhere. Should we change bolts every time we open them, for example, on a hydraulic cylinder head joint? If not, how many times can bolts be re-torqued?”

Unlike bolts used on engine heads, most of the bolts used to assemble hydraulic … Read more

In chapter 13 of The Hydraulic Maintenance Handbook, I discuss the principle of engineering out issues that have the potential to cause recurring maintenance problems. Since maintenance occurs after the event, that is, after the machine is designed and built, this strategy is very much a retrospective one. Which means it’s desirable and preferable not to engineer in such … Read more

One of the key advantages of direct-acting relief valves, in comparison to their pilot-operated cousins, is fast response. And their fast response makes direct-acting reliefs the valve of choice in situations where pressure spikes are possible and must be minimized. Secondary relief valves in an actuator circuit and the ‘spike relief’ for a variable-displacement pump are common examples.

But as … Read more