SMC Solenoid bank air control issues

Hi All,
Solenoid bank controls air to 8 cylinders. We used to able to move cylinder up and down by hand no problem but now there is a small amount of air going to those cylinders when they are not energized(retract position). We are going through lot of cylinders on this line in comparison to other similar lines. Please help.

EX250-SEN1 module.

You most likely have blow by on the solenoid. Meaning that the valve is not fully shut when de energized.

Is the air supply lubricated, often without lubrication the seals dry out and pass air, Try putting a little lube into the air supply to the valve & stroke it a few times. You can also do the same for the cylinders. In the food industry you must use food safe lubricants.

check this out

Not sure I have all your info needed to trouble shoot, but if cylinder retracted then air is normally on one side of cylinder, if you have air leaking out exhaust it could be as said above valve is leaking by in de-energized state or it could also be that cylinder seal is leaking by

The cylinders are replaced biweekly and I dont this all eight cylinders leaking but I ll check the exhaust mufflers this week. I 've seen those get dirty which is what might be not exhausting air completely. I ll get back to you with a fix. Thank you all.

I am not a fan of valve banks, one bad valve puts backpressure on all the rest, and the fact that by the time you go to replace several valves they have been discontinued and you are forced to upgrade everything or go to eBay. I know its easier to design when building a machine and probably more cost effective and space saving. But on the maintenance side at 2am its a pain not having the correct valve to install. I have always mounted individual valves for ease of replacement and found the MAC valves so reliable I always use them, with over 250 of them operating on everything imaginable in the dirtiest places.