nitrogen pipe sizing

[nitro]

need a calculation for sizing nitrogen piping with these parameters.

250 psig working pressure
11 cfm volume
-65 F temperature
418 ft. of run

also need info on pressure relief valves.

 

[socrates]

Nitro: The standard tables for air (nitrogen) don't go down to -65 deg F. However I noticed that they appeared fairly linear and made the assumption that they could be exprapolated down the necessary 25 deg's. Here are some of my results;

Q=0.1833 cft/sec Re= 4Q/(pi V D); Re = 28,010/D
v = 1.0 E-4 sq ft/s eps/D = 1.94 E-4
ro = 3.1 E-3 slugs/cft Delta P =( 8L ro Q2/pi2)(f/D5)
= 61(f/D5)
Calculate Re, eps/D, f, and delta p;
use D = 0.344 inch
eps/D = 1.95E-4
Re = 28,010/.344= 8.14E4
f = 0.02
So delta P = 61 (0.02/.344 5) = 253.3 psi// So: drawn tubing of appoximately 0.344 or 0.345 inch Diameter should give you your desired pressure. I could not find any sizes for drawn tubing so you will have to use some judgment in sizing your pipe or tube. The other thing that you must consider is the wall thickness and material so that the tube can withstand the pressure without bursting. I hope you find this of some help and best of luck.
Sincerely, Socrates