(1) Table A - Rate of Discharge.

TABLE A - RATE OF DISCHARGE

Minimum required rate of discharge in cubic feet per minute (CFM) of air for safety relief valves. Discharge measured at 60 degrees F and atmospheric pressure (14.7 pounds per square inch) .

Surface

Area

Sq. Ft.
  CFM
Surface

Area

Sq. Ft.
   CFM
Surface

Area

Sq. Ft
   CFM

20
   258
185
1,600
   900
5,850

25
   310
190
1,640
   950
6,120

30
   360
195
1,670
1,000
6,380

35
   408
200
1,710
1,050
6,640

40
   455
210
1,780
1,100
6,900

45
   501
220
1,850
1,150
7,160

50
   547
230
1,920
1,200
7,410

55
   591
240
1,980
1,250
7,660

60
   635
250
2,050
1,300
7,910

65
   678
260
2,120
1,350
8,160

70
   720
270
2,180
1,400
8,410

75
   762
280
2,250
1,450
8,650

80
   804
290
2,320
1,500
8,900

85
   845
300
2,380
1,550
9,140

90
   885
310
2,450
1,600
9,380

  95
   925
320
2,510
1,650
9,620

100
   965
330
2,570
1,700
9,860

105
1,010
340
2,640
1,750
10,090

110
1,050
350
2,700
1,800
10,330

115
1,090
360
2,760
1,850
10,560

120
1,120
370
2,830
1,900
10,800

125
1,160
380
2,890
1,950
11,030

130
1,200
390
2,950
2,000
11,260

135
1,240
400
3,010
2,050
11,490

140
1,280
450
3,320
2,100
11,720

145
1,310
500
3,620
2,150
11,950

150
1,350
550
3,910
2,200
12,180

155
1,390
600
4,200
2,250
12,400

160
1,420
650
4,480
2,300
12,630

165
1,460
700
4,760
2,350
12,850

170
1,500
750
5,040
2,400
13,080

175
1,530
800
5,300
2,450
13,300

180
1,570
850
5,590
2,500
13,520

Surface area = Total outside surface area of container in square feet. When the surface area is not stamped on the name plate or when the marking is not legible, the area can be calculated by using one of the following formulas:

(a) Cylindrical container with hemispherical heads area = (overall length in feet times outside diameter in feet times 3.1416).

(b) Cylindrical container with semi-ellipsoidal heads. Area = (overall length in feet plus 0.3 outside diameter in feet) times diameter in feet times 3.1416.

(c) Spherical Container. Area = Outside diameter in

Flow Rate SCFM Air = Cubic feet per minute of air required at standard conditions, 60 degrees F and atmospheric pressure (14.7 psia).

The rate of discharge may be interpolated for intermediate values of surface area. For container with total outside surface area greater than 2,000 sq. ft., the required flow rate can be calculated using the formula, Flow Rate SCFM Air = 22.11A degrees .82, where A = Outside surface area of the container in square feet.

(2) Table B - Guide for Selection of Materials for Refrigerated Ammonia Storage Tanks.

TABLE B - GUIDE FOR SELECTION OF MATERIALS

FOR REFRIGERATED AMMONIA STORAGE TANKS

(a) Materials for shell and bottom for tanks of all design pressures shall have ductility at low temperatures equal to or superior to those listed in Table C.

(b) When austenitic steels or non-ferrous materials are used, the code shall be used as a guide for temperature requirements.

(c) Materials for nozzles, attached flanges, structural members which are in tension, and other such critical elements shall be selected for the design temperature. This selection shall be based on impact test requirements, or on probabilities such as used for the plate materials listed in Table C.

(3) Table C - Minimum Material Requirements for Shells and Bottoms of Refrigerated Storage Tanks for Various Temperatures and Thicknesses.

TABLE C - MINIMUM MATERIAL REQUIREMENTS FOR SHELLS AND BOTTOMS OF REFRIGERATED STORAGE TANKS FOR VARIOUS TEMPERATURES AND THICKNESSES

Design Temperature Thickness Material Spec. Qualifications to be Added to the Basic Specification

65 F to 25 F,
Incl.

(See Note 1)
Up to 1/2", Incl. Any approved steel with specified min.T.S. not exceeding 60,000 psi
None

Over 1/2" to 1", Incl. A-131B (or C)
None

Case 1256
None

A-201 A & B
FGP (Fine Grain Practice)

Over 1" to 1 3/8",
Incl. A-131C, Case 1256
None

A-201 A&B
None

FGP

Over 1 3/8" A-131C
Normalized

Case 1256
Normalized

A-201 A & B
FGP, Normalized

Below 25 F to

5 F, Incl.

(See Note 2)
Up to 1/2", Incl. Case 1256
None

A-201 A & B
None

Over 1/2" to 1 3/8", Incl. A-131B (to 1" max)
FGP

A-131C
FGP

Case 1256
FGP

A-201 A & B (to 1" max)
FGP, High Mang.*

A-201 A & B (over 1")
FGP, High Mang., Normalized

Over 1 3/8" A-131C
Normalized

Case 1256
Normalized

A-201 A & B
FGP, High Mang., Normalized

Below -5F to -30F

(See note 3)
Up to 1/2" Incl. Case 1256
FGP

A-201 A & B
FGP, High Mang.

Over 1/2" to 1 3/8" Incl. A-131B (to 1" max)
FGP, Normalized

A-131C
Normalized

Case 1256
FGP, Normalized

A-201 A & B
FGP, High Mang., Normalized

Over 1 3/8" A-300 Class 1
A-201 A & B Only

*Manganese content of 0.70% to 1.0% is preferred in lieu of usual content of 0.80% maximum.

Note 1: The design temperature shall be taken as the lower of the following:

(a) The minimum temperature to which the tank contents will be refrigerated.

(b) The minimum estimated tank shell temperature due to atmospheric temperatures,

considering effectiveness of the insulation in keeping shell temperatures above

expected minimum atmospheric temperature (if expected to be below the

refrigerated temperature) .

Note 2: For the thickness, temperature category approved steels include all of those listed in the

API 12-C and API 620. Materials for vessels must comply with the requirements of the code and

any additional requirements of the code and any additional requirements of this table. A-131 steel

is not approved by ASME and some code cases have not been approved by local jurisdictions.

All specific materials listed in table are satisfactory for all designs based on API 12-C or API 620.

Note 3: For vessels constructed under the code with a design temperature below -20F.,

the impact requirements shall comply with Table B.

(4) Table D - Repair Welding.

TABLE D - REPAIR WELDING

(a)

All containers, piping and appurtenances which have contained or have been in direct contact with nitrogen fertilizer solutions containing ammonium nitrate must be thoroughly cleaned and washed with water (or steam) to eliminate all solid ammonium nitrate before welding or torch cutting may be attempted: Extreme caution should be taken before attempting to weld or torch cut any container when. ammonium nitrate could be trapped, for example, in the area between tank shell and a reinforcing plate.

(b)

All containers, piping, and appurtenances which have contained aqua ammonia (ammonium hydroxide) must be thoroughly vented and thoroughly washed with large quantities of water. After washing, they shall be filled with water to a level higher than area to be welded or repaired.

(c) All containers shall be welded in accordance with the code.

(5) Table E - Safety Pressure Relief Valves.

TABLE E - SAFETY PRESSURE RELIEF VALVES

(a)

The rate of discharge shall be stamped on the safety relief valve in cubic feet of air per minute at:
(1) 60 degrees F,
(2) 14.7 pounds per square inch absolute, and
(3) 120 percent of the stamped start-to-discharge setting.

(b)

Safety pressure relief valves in systems utilizing air compressors for the transfer of nitrogen fertilizer solutions shall have a minimum rate of discharge in cubic feet per minute of air of 120 percent of the compressor manufacturer's maximum rated capacity.

(c)

Safety pressure relief valves in systems utilizing pumps for transfer of nitrogen fertilizer solutions shall have a minimum rate of discharge of 120 percent of the liquid inflow rate. This can be computed as follows: Liquid pump maximum rated capacity in GPM times 0.16 equals vapor flow in CFM.

History: 80-10-503, MCA; IMP, 80-10-503, MCA; NEW, 1986 MAR p. 1820. Eff. 10/31/86; AMD, 2024 MAR p. 128, Eff. 1/27/24.