120 psi Main Relief Valve not functioning

[Clifford]

We've been testing our pneumatics system and we've noticed that our relief valve isn't, well, relieving. We've pushed 120 to test it (140 once) but it isn't bleeding any air out of the system. We've tried two different valves (we've got two) in both A & B outlets. Nothing seems to be working, which is bad, because we'd really like to pass inspection.

Any input?

[dtengineering]

Okay... technically you aren't supposed to touch the relief valve, but since you've got two you could try this on your "non-competition" one and then figure things out from there. This is, after all, a safety issue and what you are doing will make your robot more safe.

The valve's release pressure can be adjusted by turning the "head" of the valve relative to the "body" of the valve after releasing the "lock nut" that keeps the head from vibrating loose.

Theoretically the valves come pre-set to 120psi, but at least once we have had a similar situation and corrected it to ensure that our tanks did not exceed 120 psi.

Congratulations on identifying a potential safety hazard and pro-actively taking steps to remedy the situation.

Jason

P.S. Also remember to set up the pressure switch and wire it in to your RC so that the compressor only turns on when needed. There are other threads on CD where you can find help with the (really, really simple) code needed to do that if you haven't programmed it in already.

[Clifford]

Thanks for the help. We'll look into it tomorrow, we were busy with other things today (like getting the electrical board back together). Is there anything we can do if neither work?

[ebarker]

Originally Posted by Clifford

We've been testing our pneumatics system and we've noticed that our relief valve isn't, well, relieving. We've pushed 120 to test it (140 once) but it isn't bleeding any air out of the system. We've tried two different valves (we've got two) in both A & B outlets. Nothing seems to be working, which is bad, because we'd really like to pass inspection.

Any input?

We noticed the same thing. During our 1st pneumatics test the relief failed to relieve itself and we shut the system down and purged it when it headed north of 140. Subsequent tests consistently did the same thing.

Robot Rules <R91> states the factory relief value is 125 psi.

Pneumatics manual page 3 states it is 120 psi.

From the factory the relief was well higher than 140.

So we were left with no choice but to lower the relief value to the correct value. Either the relief isn't calibrated correctly at the factory or the gauge isn't correct.

We set the relief to 120 according to the KOP gauges and the pressure switch didn't open until a little north of 120.

In light of all we have observed the relief needs to be set at 125 psi in my opinion just like the datasheet indicates.

But in the name of safety I think everyone needs to make sure that their relief isn't faulty. This is something inspection needs to look for.

Anyone have a NIST calibrated gauge ?

[Clifford]

I'm glad a I've got a few people saying the same thing. THis is what we'll do tomorrow. Thanks for the help.

[dtengineering]

No prob... that's what CD is for. When you get to the competition feel free to ask any of your neighbouring teams for help, too. I doubt you will find more helpful, courteous competitors in any other sport.

Jason

[Clifford]

I tweaked it today. It holds at 120 as it's supposed to. However, it can still go well over 140 with the compressor on. Should it bleed as slow as it does?

[ebarker]

It should 'popoff' and hold a steady 120 psi depending on which manual you refer to while the compressor is running full tilt.

[Clifford]

That's interesting, because it took ours about fifteen seconds to run back down to 120. I supposed I could try the other one we have and see if I get better results.

[ebarker]

It is important that this valve function correctly for safety reasons. I would definitely suggest going to a new valve.

I'm wondering if your valve is clogged with debris. It is always good to maintain good shop habits for a thousand reasons, FOD, foreign object debris is one of them. Especially you don't want to introduce FOD into a pneumatic or hydraulic system.

[Clifford]

I had thought of FOD, but the valves hav e been in their bags for ever. We really haven't had them out except for the last few days, and even then they were far away from where we machine. Unless someone's been sticking FOD (or food ) into it, I think it may just be faulty. Either way, we'll know tomorrow afternoon.