Multiple pressure regulators

[FRCTeam2906]

We are looking at using many pistons and solenoids this season and don't want them all to work (but some of them) at 60psi, more like 20psi or 30psi. If we were to have a pressure regulator controlling the overall working pressure at 60psi can we then have multiple downstream controlling the pressure going to one or more solenoids at a lower pressure say 25psi, then a higher pressure regulator at 50psi and another working at the original 60psi? Let us know if this is legal.

FRC Team 2906

[rich2202]

R82 allows "pressure regulators" (note the plural).

R88 limits what is on the High Pressure side. Nothing limits R82 parts on the low pressure side.

The interesting question would be: Can you have multiple pressure regulators, each regulating high pressure down to various working pressures. R88 seems to assume only one regulator on the high pressure side.

[ShIfTiNgBoT]

Yes, multiple regulators are allowed, so long as they comply with the pneumatic standards. They can also be placed anywhere.

Although, you may not want to use a pressure regulator. If you're worried about breaking your robot or the field in some fashion, there are alternatives. We've had great success with flow regulators, which limit the flow of air into a piston, slowing it down, but not limiting the overall force. This would slow down the entire movement of the piston, but would probably be similar to running the pistons at a lower pressure (speed wise).

You can also look into using adjustable cushion pistons. I know that most Bimba pistons have no dampening or partial plastic dampeners at the end of each stroke. Festo pistons have many options for cushioning, ranging from automatically adjusting air cushions, soft plastic internal cushions, or even manually adjustable air cushions.

This year, we opted to get the manually adjustable air cushions. I believe that they use an internal check valve that cushions the piston in one direction at each end. basically, when going from in to out, the speed is not slowed down at the beginning and the middle of the stroke, and is slowed as it reaches the end. But at the same time, it does not dampen the movement as it moves inward from the extended position, and only cushions as it approaches the fully inward position.

The manually adjustable cushions are controlled by a set screw, recessed in the piston housing. Turning this will change the overall strength of the cushion and its effective dampening distance within the internal stroke.

From my understanding, Festo pistons are one of the only such customizable pistons readily available to FRC teams. Standard configurations include many strokes and bores and include all dampening options except no dampener. Pistons also have an optional internal position sensor (effectively a linear potentiometer), but I can divulge further at a different time.

Standard configs usually ship in 1-2 days, custom one's ship at a similar schedule from Germany.

Sorry if it's coming off like I'm one of their reps or something, I'm just a senior who loves their quality products

[D_Price]

Also be sure to note how much air you are using for each of the pistons and solenoids and also try to run the the full 2:30 match using pistons/solenoids to make sure you can handle a match for the whole duration.

[Nuttyman54]

Originally Posted by ShIfTiNgBoT

Yes, multiple regulators are allowed, so long as they comply with the pneumatic standards. They can also be placed anywhere.

Although, you may not want to use a pressure regulator. If you're worried about breaking your robot or the field in some fashion, there are alternatives. We've had great success with flow regulators, which limit the flow of air into a piston, slowing it down, but not limiting the overall force. This would slow down the entire movement of the piston, but would probably be similar to running the pistons at a lower pressure (speed wise).

Flow regulators will limit speed, but don't limit air usage or force, since the air cylinder will still eventually develop 60psig occupying the same volume. The most common reasons I've seen for multiple different pressures is either to reduce air usage (if an air cylinder only needs to run at 20psig, you'll use 1/3 the air as the same cylinder operating at 60psig) or reduce force. Likewise, the flow regulator does not limit final force, so a cylinder that moves slower but still is running at 60psig will develop significantly more force than at 20psig at the stops (not a linear relationship on this one, do the math).

If you're looking at running air cylinders at lower pressures, my first question would by why not use a smaller bore cylinder? That is effectively the same as running at lower pressure (smaller volume of air, less force). I realize air cylinders are expensive, so wanting to use existing parts is a totally valid reason. Another good reason is because you have a very force-specific application and want to be able to tune the final force applied, which can only be done with a regulator.

[GeeTwo]

Do take note of R87 (emphasis mine):

“Working” air pressure on the ROBOT must be no greater than 60 psi (~413 kPa) and must be provided through a single primary adjustable, relieving, pressure regulator.

That is, to do what you're proposing, put a primary regulator adjusted to 60psi, and put your lower pressure regulators downstream of the primary. Watch out for minimum pressure required to work piloted solenoid valves!

[Mark McLeod]

Another caution is that piloted pneumatic solenoids like FRC teams typically use, must have a certain minimal air pressure to work reliably or at all.
Usually this minimum pressure will be between 20 and 25psi. It should be in the manufacturers notes.

Pressure dips in the low-pressure regulated system may also drop you below that minimum momentarily, so activating one set of solenoids may momentarily disrupt the operation of another set.
Just test all possible conditions and firing combinations so you are aware.

[Al Skierkiewicz]

Please note that the additional regulators musts be downstream from the one primary regulator set to 60 psi. Please be sure to check the specifications for the solenoid valves you are using as Mark has pointed out. Many piloted valves do not work reliably below 40 psi. Valves that came in the KOP years ago would not work at all below 45 psi.

[Ari423]

Originally Posted by Mark McLeod

Another caution is that piloted pneumatic solenoids like FRC teams typically use, must have a certain minimal air pressure to work reliably or at all.
Usually this minimum pressure will be between 20 and 25psi. It should be in the manufacturers notes.

There are solenoids that can work at very low pressures. In 2015, we used solenoids rated for 15psi minimum at 12psi without a problem. Just make sure the solenoids you are using are within (or close to) spec.

[ShIfTiNgBoT]

Originally Posted by Nuttyman54

Flow regulators will limit speed, but don't limit air usage or force, since the air cylinder will still eventually develop 60psig occupying the same volume.

Right, that's absolutely true. I just brought it up because it's possible that OP was wanting the results that may be achieved with a flow regulator or different dampeners. Many teams often aren't aware of the different options, and I haven't checked how experienced OP's is.

[scca229]

Also make sure that whatever you do end up using that R94 is still being met:

R94. 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, and
B. placed on the ROBOT so that it is visible and easily accessible.

[Kevin Thorp]

The free cylinders Bimba offers FRC teams don't have cushions, but they do sell cylinders with cushions: Link.

But in many cases a mechanism will hit an external stop before a cylinder's piston hits its internal cushion. You can add foam tape or rubber bumpers to these external hard stops.