R07-100-RNEA regulator outlet pressure

[Caleb Sykes]

FIRST recommends in the blue box beneath R71 that teams use one of the following regulators:

Norgren regulator P/N: R07-100-RNEA or Monnier P/N: 101-3002-1 recommended.

We are currently using the R07-100-RNEA on our robot. As I was looking up the specifications on this product, I realized that the intended adjustable outlet pressures for this product are 5 to 50 psi. Here is the webpage that contains this information.

Now, I understand that manufacturers often are conservative in their estimates for things like this, but even so, shouldn't we be using regulators that are specified to handle up to 60 psi? Norgren sells a very similar model, the R07-100RNKA, which has the output adjustable from 5 to 100psi. Here is that product's webpage. At the moment, both of these cost $23.50, so why doesn't FIRST recommend that teams use this regulator?

[JesseK]

That may be an artifact from the old days of pneumatics, and the manufacturer changed the spec afterwards? There are plenty of pneumatics with similar scenarios, and I think the only thing we can do is recommend modern alternatives, like you've done. I'm sure there are other parts & rules which are based upon what was available 8+ years ago. The GDC has done a great job modernizing the rules, and we as a community can continue to keep them on their toes .

For example, Festo makes some great 90 & 180-degree rotary pneumatics with an awesome form factor, but they're all only rated for 8 bars of pressure. I'm willing to bet it's 8 bars only because they rounded down from the actual safe value. This is 116 psi, therefore illegal in 2015. After Champs, I plan to write a letter to FIRST asking about the reasoning behind the number of 125 psi for all pneumatic parts. I bet it's because of this regulator you've listed - if it fails, then 110 psi goes to all parts downstream. Yet what if we were allowed to only store 105 or 110 psi of air for pneumatics - would that alleviate the safety concerns?

[cgmv123]

Originally Posted by JesseK

After Champs, I plan to write a letter to FIRST asking about the reasoning behind the number of 125 psi for all pneumatic parts.

Because 125 psi is the maximum pressure that should be experienced on an FRC robot, assuming the pressure switch and/or the relief valve are working correctly.

[Jon Stratis]

Originally Posted by JesseK

That may be an artifact from the old days of pneumatics, and the manufacturer changed the spec afterwards? There are plenty of pneumatics with similar scenarios, and I think the only thing we can do is recommend modern alternatives, like you've done. I'm sure there are other parts & rules which are based upon what was available 8+ years ago. The GDC has done a great job modernizing the rules, and we as a community can continue to keep them on their toes .

For example, Festo makes some great 90 & 180-degree rotary pneumatics with an awesome form factor, but they're all only rated for 8 bars of pressure. I'm willing to bet it's 8 bars only because they rounded down from the actual safe value. This is 116 psi, therefore illegal in 2015. After Champs, I plan to write a letter to FIRST asking about the reasoning behind the number of 125 psi for all pneumatic parts. I bet it's because of this regulator you've listed - if it fails, then 110 psi goes to all parts downstream. Yet what if we were allowed to only store 105 or 110 psi of air for pneumatics - would that alleviate the safety concerns?

That would necessitate a different pressure switch. The reason the rule is 125 PSI is because The pressure switch maxes out at 120 and the relief valve is supposed to be set to 125. That way if something goes wrong the relief valve will open before anything explodes.

Sure, we could have different standards. I'm sure FIRST could find a pressure switch that opperates at a lower pressure, and require the relief valve to open at a lower pressure, and thus allow more items to be used in the system. Do that, though, and a bunch of teams will scream about how they just "lost" available storage by having to store at a lower pressure, and how they now have to add more tanks to make up the volume difference, etc.

[JesseK]

I'm not asking that every team be forced into lower storage, but rather, the GDC allows teams to be able to make the choice by providing an alternative pressure switch part #. It may put more pressure on RI's though (no pun intended).

While I agree the relief valve is supposed to be set to 125 psi, every inspection I've ever been apart of has led to the relief valve being set to 120-122 psi so that the max pressure caps out at under 124psi with the compressor running. Maybe that's just how this region does it (we usually get the same RI in DC since we inspect so early)? Champs has never commented on it because it was already set lower than required.

We certainly would have made the tradeoff a couple of years ago if it meant having a good rotary.

[Jon Stratis]

Maybe instead of playing with the storage pressure rules, we could take a rule staring from the rulebook and suggest it be adapted for other items. R66 D states "Solenoid valves that are rated for a maximum working pressure that is less than 125 psi rating mandated above are permitted, however if employed, an additional pressure relief valve must be added to the low pressure side of the main regulator. The additional relief valve must be set to a lower pressure than the maximum pressure rating for the solenoid valve,"

Why limit that just to solenoid valves (other than the fact the rules have that limit imposed)?. Do some research. Find the difference in available selection for the rotary pneumatic actuators you describe, sorted into "legal" and "illegal", and if you can, suggest that this rule be extended to include those actuators as well. The presence of an additional relief valve could very easily be argued to make these actuators safe for use, I would think, and if a team isn't using them then it won't affect them.

[Nate Laverdure]

These relief valves are not precision devices:
-- They have a specified repeatability of +/-20% of the setpoint
-- They don't reach full flow until the inlet pressure is approximately 120% of the setpoint
-- They'll reach equilibrium with a notional 1.05 CFM compressor flow rate at approximately 110% of the setpoint