Change In Legality of Certain Solenoids?

pneumatics

#1

Has there been a change to the rules governing the specifications of what solenoids are legal this year? R84 C seems to suggest that solenoids with 1/4 in NPT, BSPP, or BSPT ports are illegal. Our team has been using this kind of solenoid for years. Is this new this year? If so, which solenoids should I be using?


#2

I think you meant R84 C:

Solenoid valves with a maximum ⅛ in. (nominal, ~3 mm) NPT, BSPP, or BSPT port diameter or integrated quick connect ¼ in. (nominal, ~6mm) outside diameter tubing connection

This is actually more flexible than the 2018 and 2017 rules, which didn’t allow integrated quick connect:

Solenoid valves with a maximum ⅛ in. (nominal) NPT, BSPP, or BSPT port diameter

Are you sure your solenoids are actually 1/4 in NPT?

SMC solenoids like those sold by VexPro are probably the most common ones used by teams.


#3

Yes. Based on some of the images of the example fittings on the vex products which are 1/4 press terminals, I can confidently say that the ports on our solenoids have a diameter of 1/4 in.


#4

Just to make sure, a 1/8 in NPT fitting has an outer diameter on the threads of around .4 inches and looks like about a 1/4" hole. A 1/4 in NPT fitting has an outer diameter of the threads of over .5 inches. https://en.wikipedia.org/wiki/National_pipe_thread#Standard_sizes


#5

Sounds to me like you’ve been getting away with illegal solenoid valves a while. 1/8" NPT was the largest allowed by the rules until this year explicitly added 1/4" push tubing terminals.


#6

So the spec of the port is a radius and not a diameter? The diameter of our fittings fits in to the solenoids, whose ports are about 1/4 in in diameter.


#7

It’s a pipe size. A 1/8" NPT fitting (female side) will look visually like about a 1/4" hole. Based on your description I think you’re okay. A part number of the solenoid would let us check for certain.

Another link: https://www.fairburyfastener.com/xdims_pipe_threads.htm


#8

Well, that’s certainly confusing at least. Thanks for the clarification. I currently have no way to get a part number for it, as I’m at home, but I’ll be sure to check it out if I do.


#9

NPT (National Pipe Thread) fitting sizes can sure be confusing! The size is based on a nominal inside diameter of a thick walled pipe, so the threads are much larger than the nominal size.


#10

Pipe and conduit sizes are based on (approximate) inside diameter and tubing size is based on (approximate) outside diameter. Both 1/8" NPT fittings and 1/4" plastic tubing mean that the airway is not much larger than 1/8" diameter.