I'm having a heck of a time with spool valve configurations and their names. For example, a winch tech support guy told me I needed a 'motor spool' type directional control valve so that the work ports would be blocked when the valve is in the center, neutral position.

So, I find several valves described as 'open center, motor spool' and the descriptions state that the work ports connect to tank when in neutral to allow the motor to coast.

I find 'tandem center' described as a spool valve that allows pump-to-tank in neutral, but that blocks A and B (sounds like what the winch guy wanted me to use).

I see another online glossary with the following entry: "OPEN CENTER (TANDEM) VALVE", indicating they think open center and tandem are the same thing.

I think my Eaton book says open center is ALL ports to tank when in neutral.

It also doesn't help with I find a catalog that lists a Northman 4-way valve with a C3 spool as 'tandem center' (this is an open center config) AND it lists another 4-way with a C6 spool (A and B blocked, P to T) as 'tandem center'. So, I can't rely on catalogs, either.

Maybe what I'm not getting is the meaning of 'tandem'...I just now realized that all it may mean is that A and B do the same thing--and that it says nothing about what they do. Duh...there can be 'tandem blocked' and 'tandem to tank' then?

So...is there a reliable, accurate glossary available that also includes synonyms for the varous terms?

I'm going crazy.

This message has been edited. Last edited by: Bongo Boy,

Welcome to the real world of FLUID POWER????

I beleive you have found many of the explanations you cite in Fluid Power manufacturers literature since that is where the bulk of Fluid Power training literature comes from. All of this information is from falible persons who learned their terms from other falible persons who learned their terms from other falible persons ad-infinitum.

Since there is very few persons trained by the colleges and universities of the world and this usually is part of the Mechanical Engineering program I don't beleive you find any real changes in the near or distant future.

As one of those persons from the College of Hard Knocks who learned Fluid Power as a Salesman you can see my take on what I learned as common names for spool valve center conditions by looking at the basic book I wrote to teach Fluid Power at this site.

http://www.hydraulicspneumatics.com/200/eBooks/

Chapter 4 starting on page 11 shows the common centers and the following few pages go into other center conditions that may be named but still not any concensus on the names.

Chapter 10 is my take on Directional Controls and is again from my experience not necessarily how everyone would explain them.

The National Fluid Power Association, www.nfpa.com is one organization who has some standards that might help.

Someday I hope to see Fluid Power Engineeers and Fluid Power Maintenance persons who are trained in Fluid Power and have that discipline as their major work similar to how Mechanical and Electrical is handled at present. Until then plan to see confusing information when it comes to Fluid Power and how it can be applied.

Thanks so much, Bud. That's an incredible amount of work, there, and a great resource. I'll start digging in. I never thought I'd see a reference to 'ideal gas' again...it's been about 25 years.