I know, you are not my robot inspector, and rules are subject to change, yadda yadda. With those caveats aside, help me decide about the legality of this setup:
I’m looking for cheaper, lighter, and easier mounted solenoid valves for the 2018 season. McMaster-Carr and Automation direct sell some really nice plastic-bodied valves for less than $50 ea.
They’re meant to plug into a $25 plastic manifold, but the only manifold that fits has 3/8" push-to-connect fittings. Last years’s rules say that solenoid valves must have “a maximum ⅛ in. (nominal) NPT, BSPP, or BSPT port diameter” (R82.D). Furthermore any connecting tubing must have “a maximum 0.165 in. (nominal) inside diameter” (R82.E). The rules work for the valves (both inlets and outlets), but not the manifold inlet.
I’m wondering whether the manifold is still legal (there is no rule afaik about manifold ID afaik), and whether the tubing connection could be made legal by installing a push-to-connect insert reducer to bring the inlet back down to 1/4".
Probably not. The size of the ports and tubing are designed to limit the speed of activity taking place; if a solenoid valve (or its manifold) has larger ports, the internals can larger and still be effective. As far as how it would be implemented:
The tubing is too large at one point.
The rules specify the fittings as part of the solenoid valve. In nearly any solenoid valve I’ve seen used in FRC, the fittings are actually on an adapter. In your setup, the manifold is that adapter, and is therefore “part of” the solenoid valve.
I would say that the OPs logic almost right; however the solenoid valve restriction(Per-R82D) means the valve itself would not be allowed. The valve noted, BVS-4251-24D, have a port size of 1/4" and is therefore just too big port wise under the current rules. The limit is 1/8"port size. As noted by GeeTwo that restriction is done to keep flow rates regulated. We do this instead of trying to rate Cv because many manufacturers don’t have a standard test setup for Cv making comparison and data acquisition hard.
If the valves were 1/8"(or smaller) on their own, they would be allowed. The kind of valves described can stand alone, but are 1/4" ports. I concur with GeeTwo that adapters on the solenoid valve do not change the valve legality under the current wording.
I should point out the way R82-F is currently worded, there is no connector size restriction on manifolds or connectors/adapters themselves. So a manifold could have a larger than 1/8" input, if an adapter is used directly to pair it down to the required tube size. This last bit is important because some compressors and tanks out in the FIRST community do not fit the 1/8" port rule.
If you want cheaper, though they are identical weight spec, my teams will buy SMC valve manifold filled with used valves on ebay. They are the same as the vex products, though they tend to be 24V, but are far cheaper. You still end up paying full price for manifolds, blanking plates. You also might also get some duds, but under $100 for 8 double solenoid valves is a good deal.
Hmm. I see this logic, but I’m not convinced. First, the limit is 1/8" NPT. That pipe thread size is actually more than 3/8" ID! Even 1/8 schedule 40 pipe is over 1/4" ID. By contrast, the 1/4" push-to-connect fitting has the same ID as the bore of the (legal) tube.
Second, I can’t see the GDC intending to force teams to use a threaded fitting on the inlet just for the sake of it (although the rule does read that way). Push-to-connect fittings are much more rookie-friendly, and NPT fittings may be hard to find overseas.
I have definitely used solenoids with 1/4" push to connect ports integrated into them without them being called illegal. That accepts tubing of the maximum legal size. I would interpret the holes as being smaller than “1/8” NPT" which could theoretically have an ID around 3/8" if you had a comically thin wall (certainly 1/4" is possible). I’m an inspector, but not necessarily a very good one at this particular intersection of the rules. I’ve honestly never run into anybody using valves that differ from the standard or look questionably illegal, so this hasn’t come up for me.
No comment on the manifold itself - the larger holes on those don’t look great for this purpose… You would need 3/8" OD, .165" ID tubing to stand a chance there, right?
Let’s see if we can clarify things a little (I work at AutomationDirect)
The OP refers to a manifold BVM-436 - That has 10mm ports - not 3/8
The 3/8 equivalent is BVM-4325
Those really do take 3/8" tubing - that is not 3/8 NPT
Since the rules require using 1/4 tubing, you would need a reducer.
This reducer would do the trick, and keep you legal (IMHO). It takes 1/4 tubing and adapts it to 3/8" hole.
As an option, consider using this manifold - it has all the control wiring in one place (D-Sub connector) and it uses 1/4 tubing fittings - no reducers required. There is a 4 and 8 slot version.
Notice that the BVM series valves come in 24V, 12V, 5V and 3V versions - which means you could actually run them off of a digital output!
And don’t forget that AutomationDirect puts a $35 voucher in the KOP (Instructions in TIMS) that you can use to buy what ever you want from their 22,000 part inventory … and 2-day standard shipping is free if you order over $49 (over the free stuff, of course). Here is last year’s instructions for reference.
That’s a good looking manifold, but unless I’m mistaken it is only compatible with BVS-3 valves, not the BVS-4 valves. The BVS-3 valves are smaller, having only a 4mm tube outlet (and a 10x smaller Cv).
Thanks for mentioning the Automation Direct voucher, and thanks for supporting FIRST!
Yeah, that is a different series valve but if you just need to control a shiftier, etc they are really great.
FYI - I see you are in Canada - Shipping to Canada is REALLY fast from AutomationDirect. We get comments all the time from Canadian teams on how they prefer to order from us because they get parts FASTER then from their local distributors.
You make an excellent point. I was reading the 1/8" NPT rule and applying it to push-to-connect fittings. This does not make sense to do. It looks to me like the rule was not designed to apply to this solenoid valve type. I would think the rule should be reworded to better suit both existing SMC like valves and this style valve with push-to-connect fittings.
If this were in the middle of the season I would Q&A it,which would be a mixed bag of results. But now I would hope some of the key lead inspectors read this and suggest a rewording of the rules for 2018. I think these valves should be allowed. We have used ones in the past like it, the Festo VPLE18-M5H-4/2-1/4(http://www.team358.org/files/pneumatic/). And you make a good point that this wouldn’t increase flow rate anymore than the tubing already allows.
After posting I was going to look up that old Festo, not realizing it was 1/4" ports. About 7 years ago one of my teams invested in some plastic Mead valves that looked identical. We used them for a year or two. We stopped using them because kids would forget how to plug them in right, and SMC manifolds are great for keeping plumbing concise. But that is true of any manifold.
On a different note, I love the AutomationDirect vouchers. I just want to buy too much from there. The tiny regulators, gauges, quick exhaust valves, flow regulators, and even ferrules, so much I want and so little robot budget I can spend.
You’re right, the Mead valves are identical. I have a huge pet peeve against retailers who don’t list the OEM, so you can’t get first-party information.
I’m looking at you McMaster Carr, Automation Direct, and too many others >:(
I have a huge pet peeve against retailers who don’t list the OEM, so you can’t get first-party information. I’m looking at you McMaster Carr, Automation Direct, and too many others >
I hear your frustration - but please keep in mind that it’s not always the ‘retailer’ that makes that decision.
At Automation Direct we strive to post the most comprehensive documentation possible for ALL our products, regardless of the source.
A side note that we also offer “control distribution blocks” for use with those BVS-4 series valves. These allow the use of a single cable from a bank of valves back to your controller.