How can you figure the optimum control line size for controlling a R12/R14 relay valve given the line distance needed? I am replumbing a machine and need to determine the optimum line size for 30'-35' of control line for both the service and spring brake relay valves. I was thinking either 1/4" or 3/16" i.d. for quickest relay response. There ought to be a chart for this. The engineers would have a formula that they would use for this. Thanks for your response in advance.
I am assuming you are working with air pressure and the line will be for supply to the valve and not pilot making it work. It sounds almost like you are plumbing the air system to a yarder for drum brakes and maybe not trailer brakes. What is the volume of air you need to work the accessory? Let us know a little more info and maybe we can help.
John, Control and pilot are one in the same and that is what I am concerned with what line size given that distance would provide me with the quickest air relay control/pilot signal to the R-12/R-14. The supply is going to be from a tank mounted alongside the relay valve. The supply tank will feed (supply) the valve with a 5/8" line the valve will then deliver (delivery) the air via 5/8" line to a pair of type 36 Maxibrakes (later on I may replace with type 50 Maxibrakes) that are very near the relay valve. I will use the R-12 for the release of the spring brakes and the R-14 for the service brakes having the R-14 set up for anti-compounding. My only question is concerning the control/pilot line size given a distance of 30'-35' feet.
I don't do much with air anymore but I'm thinking since this is just a pilot line and the valve only has to feel pressure to make it release, 1/4" should be big enough. I don't think there is much if any line loss when there is so little flow necessary to make the valve trip.