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Pressure Ratings For Tubing and Threaded End Connections

Generally, SSP tube fittings, adapters and components (fittings) are rated for pressures equal to the maximum allowable working pressures of the tubing, hose or pipe recommended for use with the fittings. However, it is important to note that many specially designed fittings, bored-through fittings and fittings having SAE/AN, O-Ring boss and SAE/MS integral ends may have lower pressure ratings than that of the tubing.

Stainless Steel Tubing Pressure Ratings Fractional Sizes)

Notes: 1) Shaded areas indicate tubing that is not suitable for gas service. 2) For welded and drawn tubing, a derating factor must be utilized. For double welded tube, multiply the below pressure rating by .85; and for single welded tube by .80 (ANSI B 31, Table A-1B).

Specifing Stainless Steel Tubing for Tube Fitting and Welding

Specify the outside diameter and wall thickness of annealed, seamless or welded and drawn 316 or 304 stainless steel tubing of ASTM A-269, A-249, A-213 or equivalent. Also specify high quality tubing to be free of scratches, and suited for bending with material hardness not to exceed Rb 90.Calculation Basis: Annealed, seamless 304 or 316 stainless steel tubing ASTM A-269 or equivalent. System temperatures between -20°F and 100°F with allowable stress of 20,000 psi. Ultimate tensile strength of 75,000 psi. Reference: ANSI B 31.3 Code. (For more specific working pressure information regarding a particular tubing, consult with the actual manufacturer of the tubing).

Tube O.D.Size (Inches)  Wall Thickness of Tube (inches)             
 .010 .012 .014 .016 .020 .028 .035 .049 .065 .083 .095 .109 .120 .134 0156 .188
Working Pressure, psig
1/16 5600 6800 8100 9400 12100                      
1/8           8500 10900                  
3/16           5400 7000 10200                
1/4           4000 5100 7500 10200              
5/16             4000 5800 8000              
3/8             3300 4800 6500              
1/2             2600 3700 5100 6700            
5/8               2900 4000 5200 6000          
3/4               2400 3300 4200 4900 5800        
7/8               2000 2800 3600 4200 4800        
1                 2400 3100 3600 4200 4700      
1-1/4                   2400 2800 3300 3600 4100 4900  
1-1/2                     2300 2700 3000 3400 4000 4900
2                       2000 2200 2500 2900 3600

 

Stainless Steel Tubing Pressure Ratings - Metric Sizes 

 Tube OD
(mm) 

Walll Thickness (mm) 
0.8 1.0 1.2 1.5 1.8 2.0 2.2 2.5 2.8 3 3.5 4 4.5 5
Working Pressure (bar)
3 670                          
6 310 420 540 710                    
8   310 390 520                    
10   240 300 400 510 582                
12   200 250 330 410 470                
14   160 200 270 340 380 430              
15   150 190 250 310 360 400              
16     170 230 290 330 370 400            
18     150 200 260 290 320 370            
20     140 180 230 260 290 330 380          
22     140 160 200 230 260 300 240          
25         180 200 230 260 290 320        
28           180 200 230 260 280 330      
30           170 180 210 240 260 310      
32           160 170 200 220 240 290 330    
38             140 160 190 200 270 270 310  
50                   150 210 210 240 270

Copper Tubing Pressure Ratings

Maximum Allowable Working Pressure (PSIG)

Calculation Basis: Annealed (Temper 060), seamless copper tubing ASTM B-75 or equivalent. System temperatures between -20°F and 100°F with allowable stress of 6000 psi. Ultimate tensile strength of 30,000 psi. Reference: ANSI B 31.3 Code. (For more specific working pressure information regarding a particular tubing, consult with the actual manufacturer of the tubing.)

Tube O.D.
in.

Wall Thickness of Tube (inches)             
.028 .030 .035 .049 .065 .083 .095 .109 .120 0.134
Working Pressure (psig)
1/8 2700 3000 3600              
3/16 1800 1900 2300 3400            
1/4 1300 1400 1600 2700 3500          
5/16     1300 2200 2700          
3/8     1000 1600 2200          
1/2     800 1100 1600 2100        
5/8       900 1200 1600 1900      
3/4       700 1000 1300 1500 1800    
7/8       600 800 1100 1300 1500    
1       500 700 900 1100 1300 1500  
1 1/8         600 800 1000 1100 1300 1400

 

Alloy 400 Tubing Pressure Ratings

Maximum Allowable Working Pressure (PSIG)

Calculation Basis: Annealed, seamless Monel Alloy 400 tubing ASTM B-165 or equivalent. System temperatures between -20°F and 100°F with allowable stress of 18,700 psi. Ultimate tensile strength of 70,000 psi. Table values are per the ANSI/ASME B 31.3 Code for temperatures from -325°F to only 100°F. Monel derates fast at elevated temperatures. (For more specific working pressure information regarding a particular tubing, consult with the actual manufacturer of the tubing.) Suggested Tube Ordering Information: Specify the outside diameter and wall thickness of annealed, seamless Monel Alloy 400 tubing of ASTM B-165 or equivalent specification. Also specify high quality tubing to be free of scratches, and suited for bending with material hardness not to exceed Rb 75.

Tube O.D.
(in.)

Wall Thickness of Tube (inches)             
.028 .035 .049 .065 .083 .095 .109 .120
Working Pressure (psig)
1/8 7900 10100            
1/4 3700 4800 7000 9500        
5/16   3700 5400 7300        
3/8   3100 4400 6100        
1/2   2300 3200 4400        
3/4     2200 3000 4000 4600    
1       2200 2900 3400 3900 4300
 
 

NPT Pipe End Pressure Ratings, ANSI/ASME B 31.3

 Material 316 Stainless Steel  Brass  Carbon Steel
NPT/ISO
Nominal
Pipe Size

Fitting
Size

Male Female Male  Female  Male  Female
    psig bar psig bar psig bar psig bar psig bar
1/16" 1 11,050 760 6,750 460 3,350 230 11,050 760  6,750 460 
1/8" 2 10,050 690 6,550 450 3,250 220 10,050 690 6,550  450 
1/4" 4 8,050 550 6,650 460 3,350 230 8,050 5500 6,650  460 
3/8" 6 7,850 540 5,350 370 2,650 180 7,850 540 5,350  370 
1/2" 8 7,750 530 4,950 340 2,450 170 7,750 530 4,950  340 
3/4" 12 7,350 510 4,650 320 2,350 160 7,350 510 4,650  320 
1" 16 5,350 370 4,450 310 2,250 150 5,350 370 4,450  310 
1-1/4" 20 6,000 410 5,000 350 2,500 170 6,000 410 5,000  350 
1-1/2" 24 5,000 340 4,600 310 2,300 150 5,000 340 4,600  310 
2" 32 3,900 270 3,900 270 1,900 130 3,900 270 3,900  270 
Reference: bar = .0690 X psig  To obtain ANSI/ASME B 31.1 values, multiply ANSI/ASME B 31.3 values by .94

 

Pressure-Temperature Derating Table

Stress Factors for Determining Tube Pressure Ratings at Elevate Temperatures

Instructions

To determine maximum allowable working pressures for tubing at elevated temperatures, multiply the applicable tube’s maximum allowable working pressure from Tubing Allowable Work Pressure Tables  by the corresponding temperature stress factor from Pressure-Temperature Derating Table below.

SSP tube fittings function reliably in applications ranging from cryogenic temperatures to high temperature bake out with the tube fitting material as the limiting factor. It is important to note that elevated temperatures will reduce the maximum working pressure capability of the tubing system. (For more information regarding the effects of temperature on tubing pressure ratings, refer to Table 5 regarding temperature stress factors in SSP’s Selection Guide for Instrumentation Fittings and Tubing).

Temperature Stainless Steel   CarbonSteel   Copper  Monel®400
°F °C 304SS 316SS      
    100
38
    1.00
    1.00
            1.00
     1.00
1.00
200 93 1.00 1.00 .96 .80 .88
300 149 1.00 1.00 .90 .78 .82
400 200 .94 .97 .86 .50 .79
500 260 .88 .90 .82 n/a .79
600 316 .82 .85 .77 - .79
700 371 .80 .82 .73 - .79
800 427 .76* .80* .59 - .76
900 482 .73* .78* .41 - .43
1000 538 .69* .73* .16 - n/a
1200 649 .30* .37 n/a - n/a

* The precipitation of chromium carbides potentially resulting in intergranular corrosion may occur when exposed to operating temperatures above 800°F. Consult the factory for further information.