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-   -   Legal Pneumatic Fittings - Nipples & Elbows? (http://www.chiefdelphi.com/forums/showthread.php?t=125411)

nuclearnerd 28-01-2014 22:41

Legal Pneumatic Fittings - Nipples & Elbows?
 
R77 of the 2014 game manual states "Pressure transducers, pressure gauges, flow control valves, and connecting fittings" are legal. Can I assume that means any connecting fittings (which are rated for the pressure)?

We're looking to use 1/4" nipples and elbows to connect a tank to a nearby (stationary) cylinder, rather than 0.16" ID tubing for better flow rate. It looks legal to me, (especially as many teams use manifolds and cylinders with 1/4" npt ports).

jmartin 28-01-2014 22:54

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Also according to R77 (e), any tubing used has to have an ID of 0.16". So I don't think using 1/4" NPT would be any more useful since you're still limited by the tubing.

Are you sure it isn't ports with 1/4" OD that you're thinking of? Because the 1/8" NPT ports we have fit 1/4" OD tubing. The 1/8" NPT ports have an ID of 1/8". It can be a bit confusing that the 1/8" NPT ports have labels on them saying 1/4.

theawesome1730 29-01-2014 00:01

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
We've done it in the past with no issue. You can always set it up with the fittings you want and fix it if it is not legal provided it is something you design to be easily changeable

nuclearnerd 29-01-2014 01:50

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Quote:

Originally Posted by jmartin (Post 1333987)
Also according to R77 (e), any tubing used has to have an ID of 0.16". So I don't think using 1/4" NPT would be any more useful since you're still limited by the tubing.

Are you sure it isn't ports with 1/4" OD that you're thinking of? Because the 1/8" NPT ports we have fit 1/4" OD tubing. The 1/8" NPT ports have an ID of 1/8". It can be a bit confusing that the 1/8" NPT ports have labels on them saying 1/4.

That's just it. Elbows and nipples are *not* tubing, so I am thinking that rule doesn't apply. We are planning to use 1/4" (nominal ID) pipe nipple to go into a 1/4" NPT port.

jmartin 29-01-2014 07:22

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
I see. I would be careful though, perhaps someone should ask about this on the q&a.

Al Skierkiewicz 29-01-2014 08:48

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Guys,
Can we agree that "we used it in the past" is not a response.
Thanks.

martin417 29-01-2014 09:09

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
There are very few restrictions on the use of "fittings", just be careful in defining a fitting. For example;

A quick exhaust valve is not a fitting, Nor is a check valve, but a 1/4" NPT close nipple is.

Also keep in mind that the 1/8" NPT restriction is for valves, not fittings. It is allowable to use fittings larger than 1/8" NPT, just not valves that have ports larger than 1/8" NPT.

FrankJ 29-01-2014 11:15

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
The question is do you consider a nipple a fitting or a tube. I would tend to consider a close (short) nipple a fitting (legal). At some point it would transition into a pipe, which it really is, which be closer to tubing (not legal)

Keep in mind I am not the one inspecting your robot.

nuclearnerd 29-01-2014 11:36

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Thanks for the input. I'm glad to get some backing on my interpretation.

Personally I'm not worried about a "pipe" being mistaken for "tubing". In this area, "tubing" usually means flexible (or at least, bendable). I'm guessing the rule is there to minimize damage if the vulnerable plastic tubing is cut or disengaged, which isn't a risk with hard pipe. I agree the question is probably worth a Q&A (I don't know how to do that though - I'm a first year mentor).

FrankJ 29-01-2014 12:01

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Quote:

Personally I'm not worried about a "pipe" being mistaken for "tubing".
In that case "pipe" is not a fitting & not on the list of approved items. You probably OK with short nipples, without a Q&A only your inspector knows for sure.

Al Skierkiewicz 29-01-2014 12:33

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
The rule was simplified this year as 0.160 ID tubing has the same flow restrictions as saying Cv of 0.32 or about the same flow as 1/8" NPT port diameter.

lcoreyl 05-02-2014 07:18

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1334257)
The rule was simplified this year as 0.160 ID tubing has the same flow restrictions as saying Cv of 0.32 or about the same flow as 1/8" NPT port diameter.

If 1/8" NPT port diameter has a Cv of 0.32, then why would a solenoid with 1/8" NPT output advertise a Cv of 0.75? (mcmaster 6124K511)

IndySam 05-02-2014 07:37

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Quote:

Originally Posted by lcoreyl (Post 1337875)
If 1/8" NPT port diameter has a Cv of 0.32, then why would a solenoid with 1/8" NPT output advertise a Cv of 0.75? (mcmaster 6124K511)

The CV of a valve is a calculated number that includes the fitting size and the internal restriction of the valve and is basically just used for valves.

I think what Al was saying that using port size and hose ID is just a way of restricting flow like quoting a CV value.

Using CV can be pretty confusing because some valves give flow rate and some give CV which is not the same number. Eliminating the CV restriction and just using port size and hose ID is much easier to understand and inspect.

lcoreyl 05-02-2014 08:10

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Quote:

Originally Posted by IndySam (Post 1337877)
The CV of a valve is a calculated number that includes the fitting size and the internal restriction of the valve and is basically just used for valves.

I think what Al was saying that using port size and hose ID is just a way of restricting flow like quoting a CV value.

Using CV can be pretty confusing because some valves give flow rate and some give CV which is not the same number. Eliminating the CV restriction and just using port size and hose ID is much easier to understand and inspect.

(emphasis mine)

right, so if a solenoid has a 1/8 NPT port, and the Cv of the 1/8 NPT is 0.32, then how can the Cv of the solenoid which includes said port and internal restriction be 0.75?

FrankJ 05-02-2014 08:29

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Cv is the conductance of flow. (inverse of resistance.) It is a handy way of knowing how much a particular valve or fitting flows. The easiest example is with liquid. A valve with a Cv of 1 will flow 1 Gal/Min with a pressure drop of 1 PSI. Note the unit dependance. Cv with pneumatics is more difficult because the flow is referenced to standard conditions. (Cubic feet per min at 14.47 PSI at 32 F, or 60F or 68F or 70F). Lets not get started with metric definitions. Anyway Cvs determined with consistent standards with let you know the relative size without worrying about all the illogic & math behind it. Which is what standards are all about.

Any way no matter how free flowing a valve is, the restrictions in the 1/4 OD tube restrict the flow to something acceptable to the GDC. I think that was what Al was saying. You would have to know the length of tube to calculate the exact Cv for it.

Al Skierkiewicz 05-02-2014 08:34

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
I read the flow specification on the valve as without fittings for the exhaust ports. So a 1/8" port with no fittings ought to have a higher flow rate than the same port with fittings inserted.

lcoreyl 05-02-2014 18:13

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1337890)
I read the flow specification on the valve as without fittings for the exhaust ports. So a 1/8" port with no fittings ought to have a higher flow rate than the same port with fittings inserted.

well, this still strikes me as a "1080p" TV sold with only an s-video input.

thanks for the info on the Cv of tubing and fittings, based on reading CD threads about flow restriction, I had assumed past KOP solenoids were significantly* worse than tubing and fittings, but I guess not...

*maybe a Cv difference of at least 0.1, as opposed to 0.03

Levansic 05-02-2014 22:07

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Going back to the OP's question, I would suggest testing your setup with a nipple, and with the tubing. See if there is enough difference, or even good difference that would be worth risking the creation of a new rule.

One of our mentors had the same thought, and attached one of our higher Cv solenoids to an accumulator with a short brass nipple. Imagine our surprise, when the increased "performance" turned out to be detrimental to the actual performance of our catapult. Everything was promptly changed back.

Test your theory, and find out if you are just tilting at windmills with trying something that will attract attention from inspectors. You will at least satisfy your curiosity, and you may just find, as we did, that it isn't worth it.

fsgond 06-02-2014 13:33

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1334137)
Guys,
Can we agree that "we used it in the past" is not a response.
Thanks.

But Al, I have used that response in the past ;)

DonRotolo 06-02-2014 21:53

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Quote:

Originally Posted by fsgond (Post 1338563)
But Al, I have used that response in the past ;)

Best. Response. Ever.

Al Skierkiewicz 07-02-2014 07:33

Re: Legal Pneumatic Fittings - Nipples & Elbows?
 
Why do you guys to this to me?


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