pic: In-Line Pneumatic Fittings

[rfolea]

Originally Posted by Oblarg

A good question that has never been adequately answered, especially given the fact that it's legal to just not put a fitting in one end of a dual-stroke cylinder and vent directly to atmosphere that way.

Some folks disallow quick exhaust valves because they are technically "Check Valves" (Only let air pass in one direction, other direction is vented) and anything that can keep a system pressurized (like a check valve) after the air has been vented to the atmosphere is illegal, since we don't want ANYTHING left pressurized when the system has been opened up, for obvious safety reasons.

The problem with this argument is the QUICK exhaust valves actually make the system SAFER in that they GUARANTEE the system won't be pressurized.

Yes, we are working on the wording of that one too ... Sometimes common sense HAS to win ...

BTW - all the solenoid valves folks use that have a center closed position are ALSO illegal under this rule (they can keep a system pressurized after venting), but no one seems to notice that ...

[Kevin Sevcik]

Originally Posted by rfolea

BTW - all the solenoid valves folks use that have a center closed position are ALSO illegal under this rule (they can keep a system pressurized after venting), but no one seems to notice that ...

Closed center solenoid valves would actually probably fall under R78(A):

Any pressure vent plug must be:
A. connected to the pneumatic circuit such that, when manually operated, it will vent to the atmosphere to relieve all stored pressure in a reasonable amount of time.

Whether they're legal or not depends on if you think the air inside them constitutes "stored" pressure, "working" pressure, stored pressure, or some other kind of pressure. The pneumatic rules use several different terms when talking about pressure on the robot, so I don't think it's clear if they want the the entire system at ~0 psig with the vent open, or if they just want the tanks at ~0 psig.

In other news, the pneumatics rules are kind of arcane and vague and could really use some revising to better clarify and enforce whatever the GDC's intent behind them is. There's some hint of an intent to limit actuator speeds and unintentional overpressure from external loads on cylinders, but it'd be better if they spelled that out up front.