Purpose of off-board Vent Plug?

[rich2202]

If you have an off-board compressor, per R89, and pictures in R85 and R86, the off-board compressor setup must have a pressure vent plug.

What is the purpose of the off-board pressure vent plug?

Without the off-board plug, if the compressor is disconnected from the robot, the system never builds pressure - which is ok.

If the compressor is connect to the robot, the on-board pressure vent plug is redundant to an off-board vent plug.

[Richard Wallace]

What if the off board compressor is pumping into a closed system without a pressure switch? I suppose one might connect the off-board compressor to the robot's pneumatic system and forget to open the on board shutoff valve.

[rich2202]

Originally Posted by Richard Wallace

What if the off board compressor is pumping into a closed system without a pressure switch?

If the on-board system does not have a pressure switch, then the pressure switch is on the off-board side. So the compressor will cycle properly. The more interesting case is if the pressure switch is on the on-board side, and the vent plug is closed. ...

I suppose one might connect the off-board compressor to the robot's pneumatic system and forget to open the on board shutoff valve.

Same problem as not opening the off-board vent plug. In either case, the Pressure Relief Valve on the compressor side would prevent excessive pressure buildup.

[FrankJ]

Realizing the pneumatic rules have an over abundance of caution, but they are still the rules. When the off board compressor is connected as shown in the diaphragm, the on board vent will not vent the system necessitating the vent valve on the off board side.

[Al Skierkiewicz]

The object of the off board valve is to relieve pressure when disconnecting the two systems. Yes you can obtain the relief by disconnecting the hose, however, have you ever seen a hose whip around with pressure on it? I would rather relieve the pressure and then disconnect the hose.

[rich2202]

Originally Posted by Al Skierkiewicz

I would rather relieve the pressure and then disconnect the hose.

That would make sense if there were a way to relieve the pressure. The way the diagrams have it plumbed is the output of the two vent plugs are plumbed together trapping pressurized air between them.

I was thinking that the off-board vent plug would reduce the amount of air that would vent at the time of disconnection, but in the example, there is minimal air trapped behind the vent plug vs the tubing between the two vent plugs.

Now, if they required the off-board vent plug to vent to the atmosphere, and the off-board components are connected via a T connector, that would make sense. Close the on-board vent plug, open the off-board vent plug, and then safely disconnect the hosing. But, that is not what is described.

[Jon Stratis]

Originally Posted by rich2202

That would make sense if there were a way to relieve the pressure. The way the diagrams have it plumbed is the output of the two vent plugs are plumbed together trapping pressurized air between them.

I was thinking that the off-board vent plug would reduce the amount of air that would vent at the time of disconnection, but in the example, there is minimal air trapped behind the vent plug vs the tubing between the two vent plugs.

Now, if they required the off-board vent plug to vent to the atmosphere, and the off-board components are connected via a T connector, that would make sense. Close the on-board vent plug, open the off-board vent plug, and then safely disconnect the hosing. But, that is not what is described.

Are we looking at the same picture? Figured 4-16 and 4-17 have the vent valve located on a T, with the other sides going to the compressor and across to the robot. It does vent to atmosphere.

[rich2202]

Originally Posted by Jon Stratis

Are we looking at the same picture? Figured 4-16 and 4-17 have the vent valve located on a T, with the other sides going to the compressor and across to the robot. It does vent to atmosphere.

My bad. I didn't look closely enough at the picture. I didn't see the T, and thought it was in-line.

Thanks.

[Al Skierkiewicz]

Rich....
Are you going to be at Duluth this year, hmmmm?

[rich2202]

Originally Posted by Al Skierkiewicz

Rich....
Are you going to be at Duluth this year, hmmmm?

No. My team didn't make it. They are going to Kansas City instead this year.

I applied to be a Ref and RI in KC, but have not heard back. I'm guessing I was too late since we did not know we were going until the end of January.

[Al Skierkiewicz]

That's OK, I know people in KC too.

[Jon Stratis]

How do you connect the cocompressor to the system? Most teams that I've inspected use their one on-board vent plug, meaning when the compressor is connected, without a second vent plug somewhere, either in the robot or off, there isn't one available to vent the air.

Edit: my bad, I was thinking of the manual release valve. What Richard said.