What to Look For When Hydraulic Spool Valves Stick

spool1Why do hydraulic spool valves sometimes stick? In a word: contamination. The radial clearance between the spool and bore in common, garden-variety directional control valves ranges between 3 and 13 microns. And in practice, perfectly round and straight bores are difficult to achieve. This is why servo and servo-proportional valves are fitted with a sleeve between the spool and bore-for … Read more

When NOT To Use Wire Reinforced Hydraulic Hose

hydraulic hoseA recent client engaged me to design the hydraulic steering system for a luxury motor yacht he was building. During installation, the installer questioned why I specified thermoplastic hose for the sections where stainless steel tube was not able to be used.

For those not familiar, thermoplastic hose (Synflex, Parflex, etc) is entirely reinforced with synthetic fibers. And this is … Read more

Hydraulic Filters: How to Compare Apples to Oranges

Filter used on a filter cartOne of our readers wrote me this question:

“We are evaluating filters for a contract and I had the suppliers give me the Beta ratios for the elements they propose to supply. The problem is one company has given me Beta ratios for 2 and 11 microns, and the other company, 6 and 20 microns, i.e.:

Company A’s filter is Read more