During a recent conversation with a client, the issue of testing hydraulic pump rebuilds came up. As I explain in Insider Secrets to Hydraulics, it is essential that all hydraulic components are properly tested after rebuild. Ensuring a repaired component will perform the way it should when it’s installed on the machine BEFORE it leaves the shop, instills confidence in the customer and the repairer. And this is especially important for hydraulic pumps.
But this conversation was about testing BIG pumps. For example, Rexroth A7VSL1000 and A4VSO1000 (1000 cc/rev). Any purchasing officer who has been around a while understands … continue reading »
I was recently consulted about a situation where the glass-reinforced nylon, rod guide-bush in a hydraulic cylinder was scratching the hard chrome plated rod. So in effect, the guide-bush was harder than the hard chrome plating. And this should NOT be the case. In other words the hard chrome plating on the rod was soft. Or more correctly, not hard enough. The hardness of the chrome plating should be Rockwell C (Rc) 65 minimum, and preferably higher.
So how can the hard chrome plating end up not being hard enough? This can happen when the surface area of the cylinder … continue reading »
Pipe threads are a lot like suction strainers in that they have no place in a modern, properly designed hydraulic system. HOWEVER, pipe threads are a legacy item, and as such, are still a feature of many (too many) hydraulic systems still in operation today. So every hydraulics professional needs to know about them.
National Pipe Tapered (NPT – U.S.) and British Standard Pipe Tapered (BSPT – UK) were originally designed for water pipe plumbing (60 psi rating). Both NPT and BSPT thread forms engage on the sides (flanks) of the threads. This leaves a spiral leak path at the … continue reading »