SA, Single Action and DA, Double Action

[AKKAMAAN]

Since SA and DA cylinders are a pretty common subject, I want to make this comment....
Some SA cylinders can look like a DA cylinder with two ports, but rod side port is always connected to return or straight to tank. Even if rod side is connected to the Control Valve port, there can be a spool SA valve spool, that makes the cylinder SA.
SA or DA is best determined by checking if there is "power down" or not.

[Willl]

but rod side port is always connected to return or straight to tank.

Is that to drain away any 'leak by' pass the piston seals ?

Even if rod side is connected to the Control Valve port, there can be a spool SA valve spool, that makes the cylinder SA.

With the piston side port piped to tank to do the same as above ?

[AKKAMAAN]

Is that to drain away any 'leak by' pass the piston seals ?

Yes...

If cylinder is a SA that's plumbed on a "DA" cylinder, the rod side can either be air vented with a filter fitting in the port, or hydr-vented with a hose.
I always prefer hydr-vented because it takes care of oil that by-passes the piston seal, and also keep air moist out of the cylinder.

With the piston side port piped to tank to do the same as above ?

Sorry Willl, I do not know what you mean here...."piston side"= capped or rod side??

See if I can find an example of a SA spool .....

[Willl]

Sorry Willl, I do not know what you mean here...."piston side"= capped or rod side??

My bad,,,capped side.

It be just the opposite of one piped in the first example.

[AKKAMAAN]

See if I can find an example of a SA spool .....

here are two drawing showing spool design for airvented alt hydr vented connected to CV work port...


This one looks like a DA connected cylinder but is actually SA, due to the spool design...

[Willl]

More questions,,,,



In your first example (OP), port C is plumbed to a SA output spool valve port and port R is plumbed to; return port on valve (1), or tank return (2), or vented to atmosphere(3).

Second example sounds just like the first except ports on cylinder are swapped. Correct ?

(1) If it's a SA spool valve, would there even be a return port on the valve ?

(2) If plumbed to tank (return), would it not 'suck' tank oil back to cylinder during retract mode ?

(3) Vented to air,,,like you said,,,moisture,,, but on a setup like a snow plow SA angle cylinders, you have no other choice but to vent to atmosphere. Correct ?

(4) Speaking of snow plows w/ SA cylinders, and more directly the dual SA angle cylinders, what's the correct plumbing ?, must it only be done with only a SA or DA spool valve ?

(5) Is there a difference between SA piston seals compared to DA ? (one would think so)

((sorry for all the ?'s, SA cylinders and spool valves have been a little cloudy for me.))

[Willl]

My questions are not limited towards AKKAMAAN specifically.

I'm not shy, I'll learn off anybody.

[AKKAMAAN]

In your first example (OP), port C is plumbed to a SA output spool valve port and port R is plumbed to; return port on valve (1), or tank return (2), or vented to atmosphere(3).

Thats Right!

Second example sounds just like the first except ports on cylinder are swapped. Correct ?

Thats right too, but I did not intend to swap ports, that came with the deal, "stealing" the drawing from Prince...LOL

(1) If it's a SA spool valve, would there even be a return port on the valve ?

Is I showed on my TWO (2) drawing, there can be two (2) different kinds of SA spools, one for PLUGGED PORT, and one for OPEN PORT (connected to rod side)

(2) If plumbed to tank (return), would it not 'suck' tank oil back to cylinder during retract mode ?

You got it!! Thats right!

(3) Vented to air,,,like you said,,,moisture,,, but on a setup like a snow plow SA angle cylinders, you have no other choice but to vent to atmosphere. Correct ? If there is a port, you can plumb a low pressure line to return or tank (below oil level)

(4) Speaking of snow plows w/ SA cylinders, and more directly the dual SA angle cylinders, what's the correct plumbing ?, must it only be done with only a SA or DA spool valve?

Anything simple and functional is most likely "correct"...Air venting is a way to safe hoses and lines, but will show external leaks and deal with potentioal moist/rust problem when storing....

(5) Is there a difference between SA piston seals compared to DA ? (one would think so)

Could be...a piston seal is usually two seals, and each seal from one direction....A "cheap" cylinder might only have one seal on capped side....

((sorry for all the ?'s, SA cylinders and spool valves have been a little cloudy for me.))

Do not be sorry for being organized when asking questions!! I wish ALL questions was this well organized....

[kennyd]

(4) Speaking of snow plows w/ SA cylinders, and more directly the dual SA angle cylinders, what's the correct plumbing ?, must it only be done with only a SA or DA spool valve ?

The correct way is with a DA valve, and one hose to each cylinder. The valve will see the two SA cylinders and one DA cylinder.