View Full Version : HELP: Internal Solenoid Leaks Killed Us!
We went from a major contender to losing the semi-finals for our alliance when our robot ran out of air due to increasing severe air leaks through-out the day this past weekend. We have one more chance next weekend but obviously our robot is in quarantine . We had already seriously tightened all brass fittings to the point soapy water did not find any leaks. We have yet to see any "push in" air hose fittings leak. We had tightened all the pilot valve screws and the manifold screws. Our best guess is we had joint seal leaks and or internal valve air leaks. But that was hard to confirm with soapy water as the valves were vertically mounted immediately above the spikes which could not get wet.
We had a number of people at the regional say that they had suffered from (more than one )"blown" solenoids (implying seals) and or leaking porous castings.
What is everyone elses experiences ? Since we are operating these values close to 1/2 their rated pressure and they are largely brand new and have only an hour of use (ie pressured), I am surprised we are in this position.
Anyone know how waterproof the pilot values are ? We would love to be able to dunk the complete solenoids for 10 seconds in a water tank under pressure with capped output tubes and tubes on the exhaust valve in a way that water can run up them but leaks from them would be obvious. That way all possible leaks will clearly be visible.
Anyone have any experience with the Festo valves ?
Our plan is to come in with tested spares, a standalone test compressor (with no reserve tanks: shows leaks much faster), replacement gasket kits.
Any other suggestions ?
There is another thread on leaks but for some reason its closed.
If you're using the plastic festo valves, thats your problem. We had a MAJOR air leak at Waterloo this weekend because of one of those piles of crap. We hate them, and as a team that heavily utilizes pneumatics every year, their quality definitely leaves something to be desired. SMC all the way!
Ditch the Festos !!
Last year we had 50% failure rates.
This year it was OBF.
They are just annoying.
Indeed, the Festos are not worth the hassle. We tried to use then the year before last for our shifter, but after the first time it fired, it would not fire again. I know the spike was delivering power to them, and we had 2, and both did the same thing. I'm also not a fan of plastic for pneumatic parts. The Festos are too large as well.
Daniel_LaFleur
23-03-2008, 16:44
We went from a major contender to losing the semi-finals for our alliance when our robot ran out of air due to increasing severe air leaks through-out the day this past weekend. We have one more chance next weekend but obviously our robot is in quarantine . We had already seriously tightened all brass fittings to the point soapy water did not find any leaks. We have yet to see any "push in" air hose fittings leak. We had tightened all the pilot valve screws and the manifold screws. Our best guess is we had joint seal leaks and or internal valve air leaks. But that was hard to confirm with soapy water as the valves were vertically mounted immediately above the spikes which could not get wet.
We had a number of people at the regional say that they had suffered from (more than one )"blown" solenoids (implying seals) and or leaking porous castings.
What is everyone elses experiences ? Since we are operating these values close to 1/2 their rated pressure and they are largely brand new and have only an hour of use (ie pressured), I am surprised we are in this position.
Anyone know how waterproof the pilot values are ? We would love to be able to dunk the complete solenoids for 10 seconds in a water tank under pressure with capped output tubes and tubes on the exhaust valve in a way that water can run up them but leaks from them would be obvious. That way all possible leaks will clearly be visible.
Anyone have any experience with the Festo valves ?
Our plan is to come in with tested spares, a standalone test compressor (with no reserve tanks: shows leaks much faster), replacement gasket kits.
Any other suggestions ?
There is another thread on leaks but for some reason its closed.
First off, as an engineer from Parker (Festos competitor) I can tell you that the Festo valves are far better than what the posts above will lead you to believe.
Most leaks with the Festo have to do with the quick compression fittings. Thise fittings require that the tube be cut square to the side of the tube and straight. If they are not then they will leak and they tend not to be easy to spot (for those that don't have a LOT of experiance with them). I would suggest popping each tube out of the valves compression fitting and recutting the tubes, making sure they are cut square to the side of the tubing, and then reinsert into the festo valve compression fitting.
Now on to how to test for internal leak of the Festo valve.
With the valve deenergized:
Apply pressure to the common (supply) port, seal off the Normally open port, and seal the normally open dump port with your thumb. If you can feel pressure building against your thumb then there is an internal leak against the normally open seat ... and the valve is bad.
With the valve energized:
Apply pressure to the common (supply) port, seal off the Normally closed port, and seal the normally closed dump port with your thumb. If you can feel pressure building against your thumb then there is an internal leak against the normally closed seat ... and the valve is bad.
If niether builds pressure then the valve is good.
One last thing, The Festo valves require 30 PSI to fire. If 30 PSI is not available on the supply port the spool within the valve will not move or worse, may move 1/2 way and cause a leak between the common and the dump ports. This could also be your issue if the pressure falls below 30 PSI during the valves operation.
Good luck.
We are talking about the plastic festo valve included in the kit of parts since 2004. Its only got 4 ports, a pressure, NO, NC, and exhaust. This limits its creative uses by creative exhausting, and we also have found that in the FIRST environment, they tend to work for a short time, and then leak. It does not appear to be an issue with the compression fittings, but I will agree that these are a common source of air leaks in a system, especially when the lines are not cut square.
Now on to how to test for internal leak of the Festo valve.
With the valve deenergized:
Apply pressure to the common (supply) port, seal off the Normally open port, and seal the normally open dump port with your thumb. If you can feel pressure building against your thumb then there is an internal leak against the normally open seat ... and the valve is bad.
With the valve energized:
Apply pressure to the common (supply) port, seal off the Normally closed port, and seal the normally closed dump port with your thumb. If you can feel pressure building against your thumb then there is an internal leak against the normally closed seat ... and the valve is bad.
I like the Festo valves when they work, but ....
Last year we had to go through 4 units to get 2 good units, using the above tests. And this year it was DOA. I was planning to buy some spares but gave up on the idea after the DOA.
Next year we will try again.
can anyone tell me how to wire up the smc double solenoids and how to put them together please, the festos we have are not working.
can anyone tell me how to wire up the smc double solenoids and how to put them together please, the festos we have are not working.
I personally haven't ever put one together, but I know there are 4 parts you need:
The screws
Top solenoid part
Bottom Inlet, Outlet part
Gasket
I imagine the easiest way would be to insert the screws into the top half, then put the gasket on, then place it on the bottom half, screw the screws in, and call it good. This may or may not be good, but I know with oil filters, you should put some oil on the rubber gasket part to seal it better, so adding a little oil to the gasket may help it seal better.
As for wiring, I do know how to do that! The attachment below shows a diagram I drew to help another team a while back. It has more information than you asked for, but it should still help you out.
EDIT:
From Daniel_LaFleur from a few posts down.
Don't add oil as some oils will attack the seals. Use a silicone grease like Krytox or a barium based grease like Parker O-Lube.
Amanda839
23-03-2008, 20:01
Rosie had a major pnuematics leak with our Norgren regulator, there made to handle 50psi but according to the manual we were allowed to set it to 60 psi, well didnt, we replaced it with the Monnier Regulator and our system works good. We further investigated why the Norgren had malfunction, and our conclusions were that this years regualtors were only hand tight and the outside was more of a 12 sided polygon than the many ridges of last years Norgin, anyway we replaced it to the Monnier and it works good
Tristan Lall
23-03-2008, 20:07
Rosie had a major pnuematics leak with our Norgren regulator, there made to handle 50psi but according to the manual we were allowed to set it to 60 psi, well didnt, we replaced it with the Monnier Regulator and our system works good. We further investigated why the Norgren had malfunction, and our conclusions were that this years regualtors were only hand tight and the outside was more of a 12 sided polygon than the many ridges of last years Norgin, anyway we replaced it to the Monnier and it works goodDid you follow <R98>, which requires a Norgren regulator before any Monniers?
Daniel_LaFleur
23-03-2008, 20:09
I personally haven't ever put one together, but I know there are 4 parts you need:
The screws
Top solenoid part
Bottom Inlet, Outlet part
Gasket
I imagine the easiest way would be to insert the screws into the top half, then put the gasket on, then place it on the bottom half, screw the screws in, and call it good. This may or may not be good, but I know with oil filters, you should put some oil on the rubber gasket part to seal it better, so adding a little oil to the gasket may help it seal better.
As for wiring, I do know how to do that! The attachment below shows a diagram I drew to help another team a while back. It has more information than you asked for, but it should still help you out.
Don't add oil as some oils will attack the seals. Use a silicone grease like Krytox or a barium based grease like Parker O-Lube.
Your wiring is correct of you want to use it to power 1 side or the other as long as your output to the spike is -1 or 1. Setting the spike to 0 will not move the spool and the valve will not change (this can be used to your advantage).
SMC valves also require 20 PSI for the spool move.
Use a silicone grease like Krytox or a barium based grease like Parker O-Lube.
Is the grease required ?
Is the grease required ?
No, but it reduces the chance that you will have a leak.
just wondering, what team number?
We had some issues with the Festo valves this year. One worked fine, but the other had an open relay coil. The valve wouldn't fire.
We picked up 2 more from the FIRST spare parts table and they also had an open relay coil.
Finally a team donated one to us and it worked.
It weight isn't an issue, go with the SMC valves. They will be more reliable and easier to repair if something does go wrong.
team number 1310
All SMC hardware. (not Festo). Got the SMC engineers on it. However, the leak rate could be the norm in industrial environments and we are expecting too much using a 12v compressor that has to be off for 5+ minutes between when the robot is placed on the field and when the balls are randomized and announcer finally finishes his lengthy intros in the round robin matches. By then 1/2 the air may be gone with the leaks !!!
Thats why I'm looking for input on teams that have used SMC solenoids for years in non-trival pneumatics on their robots. We have 8 cylinders but with careful design (use gravity a lot to retract cylinders) and our initial minimal leak practise days, we had enough air to be very competitive.
Thanks for the heads up about potential leaks in the regulator.
It wasn't your guys fault we lost... Feces Occurs
Get it fixed up for GTR and we'll take down 1114.
If you need any help conserving air Ive been known to come up with some fairly nuts ideas.
- Bochek
Chris Fultz
24-03-2008, 22:51
We have used a significant number of pneumatics for several years, with very few problems, but this year we have replaced several of the SMC double solenoids. (we also failed a regulator last year.)
The SMC valves seemed to leak around the seals (between the top and bottom) and also 2 had some sort of internal issue where one exhaust port stayed in a venting mode and let the system pressure drop. We replaced 2 valves before shipping the robot, and at least one at each competition so far.
The replacement valves SMC sold us seem to be less reliable than the ones in the kit. the kit part numbers were sold out everywhere - this is a slightly better valve, but has not performed as good as the less expensive ones in the KOP.
As far as the overal system, you should be able to get all connections such that you lose less than 5 or 10 psi in 30 minutes.
Mark McLeod
25-03-2008, 07:58
We've always used pneumatics, with both Festo and SMC solenoid valves.
It does help to have a supply you can swap out suspect parts with (older robots end up with any leaky parts).
Our system this year holds pressure seemingly indefinitely, I'll have to send you our pneumatics lead. I think he'll fit in a crate...
At one time or another I've seen just about every possible part arrive with a manufacturing flaw: regulators, pressure release valves, solenoids, pressure sensor, damaged actuators, damaged fittings. It helps of course to assemble your pneumatics system outside the robot first making it easier to locate leaking sections, but it's probably too late for that unless you have a lot of spare parts.
Square tube cuts (there's a special cutter for this), also rough, scratched tubing ends won't seal well either
Use as few fittings as possible (I wouldn't follow the Pneumatics Manual example layout)
Check for SMC gasket damage or flaws
Push the tubing all the way in until it's firmly seated
Don't use teflon tape twice. If you unscrew a fitting at all then completely remove the old tape and replace with fresh
Debris such as flakes of teflon tape (don't ever wrap threads all the way to the tip) will lodge inside the solenoid valves to cause a leaky valve
Check for barely visible nicks in long (and short) lengths of tubing
Look for damaged threads from cross-threading, leaving them to rattle around in a large bag of loose metal parts
Push-on fittings can be damaged by yanking the tube out by force, rough tube endsIsolate the pneumatics system a section at a time working from upstream to downstream and eliminate all leaks in each section before moving on. Just temporarily dead-end the tubing with a plugged brass fitting or a loopback T-fitting. You should be able to isolate the problem to a specific part that way.
1075 has had issues in the past with a SMC valve jamming because of very small flecks of aluminum that found their way into the air system... Not really sure if we ever got those out of that robot...
ayeckley
25-03-2008, 08:52
At the Buckeye Regional we went through three (3!) brand new, in-the-box Festo valves and did not find a single one that worked. We had good LED indications, and sufficient pilot valve pressure, but we never got a single stroke out of them. I'm confident it wasn't user error - our 2007 KOP Festo worked just fine in the same installation. If it weren't for a more favorable Cv from the Festo, we'd have gone right to the SMC valves in the initial design. Ultimately that's what we wound up doing anyhow. In the future we'll just save ourselves the hassle and go right to the SMC.
Sometimes new valves wont work unless you manually cycle them a couple times first.
ayeckley
25-03-2008, 09:00
Sometimes new valves wont work unless you manually cycle them a couple times first.
Tried that also, I'm afraid...
Alex Cormier
25-03-2008, 09:02
At the Buckeye Regional we went through three (3!) brand new, in-the-box Festo valves and did not find a single one that worked. We had good LED indications, and sufficient pilot valve pressure, but we never got a single stroke out of them. I'm confident it wasn't user error - our 2007 KOP Festo worked just fine in the same installation. If it weren't for a more favorable Cv from the Festo, we'd have gone right to the SMC valves in the initial design. Ultimately that's what we wound up doing anyhow. In the future we'll just save ourselves the hassle and go right to the SMC.
I also suggest to check them out on what voltage they run. I have noticed numerous 24 volt valves laying around the 1930 shop. and we actually put one on the robot by accident. So, check them out to see if they are the supplied 24v or 12v. I don't have a clue why they actually send us 24V ones anyway.
ayeckley
25-03-2008, 09:15
So, check them out to see if they are the supplied 24v or 12v. I don't have a clue why they actually send us 24V ones anyway.
I know SMC sends us some 24V solenoids, but I was unaware that Festo did the same. Is there a way to tell from the P/N on the valve body? I verified that we had a good 12V input to the solenoid pins.
Sorry to hijack the thread away from the internal leak issue...
Alex Cormier
25-03-2008, 09:16
I know SMC sends us some 24V solenoids, but I was unaware that Festo did the same. Is there a way to tell from the P/N on the valve body? I verified that we had a good 12V input to the solenoid pins.
Sorry to hijack the thread away from the internal leak issue...
It states right on the solenoid what voltage it takes.
Tried that also, I'm afraid...
I find it very difficult to believe that three brand new one were bad right out of the box? Festo makes great products that many teams use with great success, including us. After three I would question my installation. How were you switching them + to - or on and off?
I am not just trying to defend Festo, my dad retired from SMC.
ayeckley
25-03-2008, 09:48
I find it very difficult to believe that three brand new one were bad right out of the box?
I do too, which is why the problem was so consternating. Usually a pattern like that points to user error (translation: my error), but I just haven't been able to figure out what we could have done wrong, especially given that we did have one working Festo, albeit from the 2007 KOP. There's just not that much that we could have done wrong, and I think we've worked through all the possibilities other than infant mortality.
My initial guess when we identified the first problem was that we'd somehow overtorqued the mounting screws and distorted the plastic case, causing the pilot to bind, but we rejected that theory after we had the same problems with the unmounted replacement valves.
If we'd wired up things wrong electrically, then we shouldn't have had a good LED indication, nor should we have had a good 12V measurement on pins 1 and 2. The silkscreening on the valve body indicated that it was a 12V part, not a 24V part, so I think we have to reject that theory as well, unless it was mislabeled.
If we'd plumbed things wrong pneumatically, then we should have had the same issue with the 2007 KOP Festo, but we didn't. When the valves were swapped, the problem followed the valves.
If the infant mortality rate of the Festos in the 2008 KOP really is 50% (which it honestly seems to be, based on the reports I'm reading from other teams) then it isn't really surprising that we'd get three bad ones in a row from the parts desk at the regional. The real question is how could the IMR be that high? The most obvious possibility is that the 2008 KOP valves were units that had issues on the production line, and rather than scrapping them they were donated. I'm not prepared to make that assertion just yet since it has some pretty negative connotations, but right now it's the best explanation I've got.
If the infant mortality rate of the Festos in the 2008 KOP really is 50% (which it honestly seems to be, based on the reports I'm reading from other teams) then it isn't really surprising that we'd get three bad ones in a row from the parts desk at the regional. The real question is how could the IMR be that high? The most obvious possibility is that the 2008 KOP valves were units that had issues on the production line, and rather than scrapping them they were donated. I'm not prepared to make that assertion just yet since it has some pretty negative connotations, but right now it's the best explanation I've got.
Unfortunately that thought has crossed more than a couple of peoples minds.
Mark McLeod
25-03-2008, 10:15
If the infant mortality rate of the Festos in the 2008 KOP really is 50% (which it honestly seems to be, based on the reports I'm reading from other teams) then it isn't really surprising that we'd get three bad ones in a row from the parts desk at the regional. The real question is how could the IMR be that high?
It could likely be that teams return non-working valves to the Spare Parts desk at a Regional and then they get handed out to the next person in line, or at the next Regional where the new parts person doesn't know there was a problem with them. Spare Parts may become a collecting point for malfunctioning parts. Spare Parts has no test rig to verify that teams didn't have something else wrong. Go for the ones in original, still sealed, boxes. They probably didn't have metal filings dropped into them at the last Regional.
Anecdotal reports are not statistically significant.
Think about how you'd conduct a real engineering study...
I dont know about IMR, but 1075 has found that the plastic festo valves dont last long, even if they DO work properly out of the box. They leak in relatively short order... I can however report that the one we got from Spare Parts at Waterloo was good to go.
ayeckley
25-03-2008, 10:45
Go for the ones in original, still sealed, boxes. They probably didn't have metal filings dropped into them at the last Regional.
I believe I stated earlier that the replacement valves were sealed, new-in-the-box units. My direct experience is that the 2008 KOP Festo values had a 100% failure rate, so I believe I was being somewhat conciliatory in estimating a 50% rate. If anything, I have relied on anecdotal evidence to refute rather than affirm my hypothesis. That said, I'm still very much open to the idea that we/I somehow damaged the valves or installed them incorrectly. All I can tell you is that we installed and attempted to use them in accordance with the technical documentation available from the 2008 Pneumatics Manual and the online installation instructions.
Since the spare parts process at a regional is based on exchanges, we don't have a statistically significant sample size of valves with which to do a proper investigation (nor do we have the financial resources, etc.). If Festo would like to have our lone remaining [apparently] defective valve for their own engineering evaluation, we'd be happy to sent it in for analysis.
I believe I stated earlier that the replacement valves were sealed, new-in-the-box units. My direct experience is that the 2008 KOP Festo values had a 100% failure rate, so I believe I was being somewhat conciliatory in estimating a 50% rate. If anything, I have relied on anecdotal evidence to refute rather than affirm my hypothesis. That said, I'm still very much open to the idea that we/I somehow damaged the valves or installed them incorrectly. All I can tell you is that we installed and attempted to use them in accordance with the technical documentation available from the 2008 Pneumatics Manual and the online installation instructions.
Since the spare parts process at a regional is based on exchanges, we don't have a statistically significant sample size of valves with which to do a proper investigation (nor do we have the financial resources, etc.). If Festo would like to have our lone remaining [apparently] defective valve for their own engineering evaluation, we'd be happy to sent it in for analysis.
I'll second that. We have a new valve they can have for evaluation also.
I know we totally disassembled one of our SMC valves before, when it jammed up, and found an aluminum shaving in it. We had to do this a few times, but it always fixed the valve... we've had many festos that just started leaking through the plastic casing, pouring air out the exhaust port, or any number of other issues... open relay coils... no led's... actually, the one with no led still functions fine, just no light. other ones get a light but dont actually switch, and we've wired/plumbed them all the same way.
fi: Here's some postmortum info on our SMC leaks
- only ever had one push-on plastic tube joint leak. Oddly enough, it was the very last push-on we did. All the leaks were from fittings using brass.
- high pressure leaks would be solved, then reappear again in the next day
- some leaks could not be solved by tightening the brass fitting or taking the brass fitting out, replacing the teflon tape and reinstalling. We had to put in a new fitting.
- the leak that killed us was solved by finally swapping out the manifold on one SMC solenoid valve. One port had a brass "stopper" installed and we never were able to solve leaks around it even with new stoppers. Close inspection showed aluminum shavings in the threads of the port and aluminum fused onto the thread of the brass stopper near the leading edge. Clearly either the teflon tape was not applied close enough to the leading edge of the thread to protect it from galling (students scared of tape fragments getting in the air system), or more tape was required. Tightening it just cut into the aluminum threads of the manifold.
My recommendations now are
1) apply 2 wraps of teflon to darn close to the start of the first thread but absolutely no overhanging tape
2) leave the complete air system at full pressure as long as possible with air cylinders both extended and then retracted to try to get leaks to occur sooner than later.
3) Check every single low and high pressure joint with soapy water (we used dollar store childrens bubble liquid) during the Thursday with the air cylinder both extended and retracted.
4) Buy some port plugs and pipe caps so you can isolate each pneumatic circuit for testing
5) You can see evidence of air leaks very quickly if you bypass the reserve tanks and watch the 120 psi gauge. It will drop very quickly with the slightest leak if there are no reserve tanks connected. But don't forget to test the reserve tanks. Ours leaked repeatedly.
By the end, we had a totally leak-proof robot. But we regularly left it energized and watched the 120 pSI gauge for 15 minutes every 3rd match anyway.
vBulletin® v3.6.4, Copyright ©2000-2017, Jelsoft Enterprises Ltd.