Indiana Administrative Code
Title 355 - STATE CHEMIST OF THE STATE OF INDIANA
Article 3 - AGRICULTURAL AMMONIA
Rule 8 - Refrigerated Storage
Section 8-5 - Pressure relief valves
Current through March 20, 2024
Authority: IC 15-16-1-6; IC 15-16-1-7
Affected: IC 15-16-1-10
Sec. 5.
(a) Pressure relief valves shall be set to start-to-discharge at a pressure not in excess of the design pressure of the tank and shall have a total relieving capacity sufficient to prevent a maximum pressure in a tank of more than one hundred twenty percent (120%) of the design pressure.
(b) The total relieving capacity shall be the larger requirement of the following:
Where: W = Weight of vapors to be relieved in pounds per hour at relieving conditions.
Qa = Air flow in cubic feet per minute at standard conditions (sixty (60) degrees Fahrenheit and fourteen and seven-tenths (14.7) psia).
F = Fireproofing credit. Use F = 1.0 except when an approved fireproofing material of recommended thickness is used, then use F = 0.2.
A = Total surface area in square feet up to twenty-five (25) feet above grade or to the equator of a sphere, whichever is greater.
Z = Compressibility factor of ammonia at relieving conditions (if not known, use Z = 1.0).
T = Temperature in degrees R (460 + temperature in degrees F of gas at relieving conditions).
M = Molecular weight = 17 for ammonia.
L = Latent heat of ammonia at relieving conditions.
C = Constant based on relation of specific heats. (C may be obtained from the following table.)
(If K is not known, use C = 315.)
K | C | K | C | K | C |
1.00 | 315 | 1.26 | 343 | 1.52 | 366 |
1.02 | 318 | 1.28 | 345 | 1.54 | 368 |
1.04 | 320 | 1.30 | 347 | 1.56 | 369 |
1.06 | 322 | 1.32 | 349 | 1.58 | 371 |
1.08 | 324 | 1.34 | 351 | 1.60 | 372 |
1.10 | 327 | 1.36 | 352 | 1.62 | 374 |
1.12 | 329 | 1.38 | 354 | 1.64 | 376 |
1.14 | 331 | 1.40 | 356 | 1.66 | 377 |
1.16 | 333 | 1.42 | 358 | 1.68 | 379 |
1.18 | 335 | 1.44 | 359 | 1.70 | 380 |
1.20 | 337 | 1.46 | 361 | 2.00 | 400 |
1.22 | 339 | 1.48 | 363 | 2.20 | 412 |
1.24 | 341 | 1.50 | 364 |
Where:
CP = Specific heat of vapor at constant pressure.
Cv = Specific heat of vapor at constant volume.
If the relieving capacity required for fire exposure is greater than that required by subdivision (1), the additional capacity may be provided by weak roof to shell seams in tanks operating at essentially atmospheric pressure and having an inherently weak roof to shell seam. The weak roof to shell seam is not to be considered as providing any of the capacity required by subdivision (1).
(c) All pressure relief devices shall comply with the following: