At our district champs I was at the automation direct table and came across their mini pneumatic gauges with a small gauge, bleed valve, regulator, and 2nd small gauge all connected nice and cleanly with U tubes. The reps told me this was all we needed to run pneumatics on an FRC bot. We hadn’t spent our AutoDirect Voucher yet so I bought them once we got back.
We are now switching them out on our robot and having a small issue. The bleed valve is only releasing pressure from one side. When it is shut again it sends the pressure back into the other side where it can then be bled again. This creates a half life style system that never gets all of the pressure out.
Am I doing this wrong? I have it set up (at least I think I do) with everything AutoDirect had in their display.
@TFM110 has it right. You need a T or Y fitting to direct your bleed valve to atmosphere. Where you’ve got the valve, it won’t bleed the system.
Also be aware that the Automation Direct valves and regulators have arrows stamped in their housings. They must be plumbed so that air flows in the direction of the arrows, or they won’t work properly.
Yellow line is in from the compressor, blue is out to cylinders. We love how compact the set-up is. We join the parts with metal rods and 3d printed spacers. The metal rods were actually BBQ skewers we had on hand.
How do you ensure that first orange-knob isolation valve, between the regulator and the working pressure gauge, does not violate R813? (Note the word “any”)
It has to be the right kind of valve. It is called an isolation valve. When closed it vents pressure down stream of it. A regular stop valve will not do this. So opening the vent valve will always result in a vented system.
Will the GDCGame Design Committee consider it legal? You are going to have to ask them. It meets the intent of the rule of the vent valve fully dumping all pressure. I pass then unless my LRILead Robot Inspector or Q&A says I can’t. (Under current rule set)
A true rules lawyer will tell you it has to be down stream of the regulator since it is not a listed component allowed on the HP side.
The hvu14-3 will vent all downstream pressure when closed. It’s not just a typical ball valve. That being said the relief valve should be on the high pressure side, not the low pressure side when there is another valve in the middle.
The HPU14-3 is a 3 way valve. The 3rd port is the vent. It is not that clear in the description, that is the way it works in real life. The direction arrow is important. HPU14-2 is a conventual 2 way ball valve you are thinking of
WAIT… does HPU14-3 vent the downstream trapped pressure to atmosphere, or does it vent the downstream trapped pressure into the upstream circuit? That makes a difference as to how you’d meet R813.
I’m more worried about a student or mentor accidentally leaving that isolation valve closed, which would run your match. It seems like an opportunity for Murphy’s law. Why have it?
Our compressor feeds into our storage tanks and then goes through this system. The bottom valve allows us relive the pressure from our cylinders without draining our storage tank. This falls under R804-F and R804-G. The top valve meets the R813 requirements. The only reason we close the bottom valve is in between matches to allow us to safely work on the pneumatics without having to pressurize the tanks when done. We’ve run this setup for two seasons with no issues at inspection.
It is nice to be able to isolate the low pressure side to work on the robot without having to vent the accumulators. Especially if you have lots. The valve meets the requirements for LOTO. It should be on the field set up check list to check the valve. Everytime. You do use check list?
We do use checklists. We spend a lot of time thinking about robot performance risks. I prefer to eliminate a risk rather than mitigate it with procedure if possible.
Of course, if you go far down that line of thought you start wanting to eliminate the pneumatic system completely, but sometimes it’s still needed
[Edit] to give you credit, there’s a competing risk about not refilling the air tanks if you bleed the whole system. The “detectability” of both is about the same I guess if all you’re looking at is the gauges. Still, I can imagine a student accidentally turning the wrong valve and not noticing. I’m glad you’ve had good enough procedural controls to prevent that
I agree. Engineering the problem away is always best practice. But it not a lot different than leaving the vent valve open or forgetting to pull the safety retention pins. We try to design our robots to be able to start a match with 0 pressure. Which means using a minimum number of accumulators.
Accidently leaving the isolation valve closed is a valid concern. We are willing to take the risk because in the past we feel the benefit of not draining batteries or losing time to pressurize the system are more important. To ensure the isolation valve is close it is on our prematch checklist that we do in the pit and the prematch checklist that we run after placing the robot on the field.
Actually we have ran an isolation setup since 2019 with no issues. Initially we weren’t using the mini components from automation direct but functionally the same. We haven’t had a single match that we left a valve in the wrong position. Some of that is thorough checklists and some is habit at this point. Make sure people understand how this works because they don’t want to be working on pneumatics and discover there is pressure they didn’t know about.
Also remember to vent the air at the end of a day. Both for safety and to blow moisture out of the system. The moisture can collect and damage components if too much accumulates or sits too long.
