BI-Lok Tube Fittings Tube Selection Guide
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    Home    >    Tube Selection Guide

Tube Selection Guide

Stainless Steel Tubing | Carbon Steel Tubing | Copper Tubing | System Temperatures | Pipe Thread Pressure Rating | SAE Straight Thread Pressure Rating | AN 37° Flare Pressure Rating

Proper tube selection and installation are essential elements in providing a reliable leak-free tubing system. The following tables are intended to assist the designer to properly select quality tubing for use with the BI-Lok Series D Dual Ferrule Instrument Tube Fittings. The pressure rating of a fitting assembly is a direct function of the tubing selected. Care should be taken to insure that all tubing OD surfaces are free of scratches and imperfections that could hinder the sealing capabilities of the BI-Lok Tube Fitting. Proper tube selection and installation is the ultimate responsibility of the system designer and user.

  Suggested Maximum Allowable Working Pressure for Stainless Steel Tubing

Table 1 PSI
STAINLESS STEEL TUBING
Tube OD inch Wall Thickness, inch
0.01 0.012 0.014 0.016 0.02 0.028 0.035 0.049 0.065 0.083 0.095 0.109 0.120
1/16 5600 6800 8100 9400 12000                
1/8           8500 10900            
3/16           5400 7000 10200          
1/4           4000 5100 7500 10230        
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


304 and 316 annealed seamless tubing per ASTM A-269 or equivalent working pressure are based on allowable stress of 20,000 psi between -20° F and 100° F (Reference: ANSI B31.3)

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  Suggested Maximum Allowable Working Pressure for Carbon Steel Tubing

Table 2 
CARBON STEEL TUBING
Tube OD inch Wall Thickness, inch
0.028 0.035 0.049 0.065 0.083 0.095 0.109 0.120
1/8 8000 10200            
3/16  5100  6600 9600         
1/4  3700  4800  7000 9600        
5/16    3700  5500  7500        
3/8    3100  4500  6200        
1/2    2300  3200  4500  5900      
5/8    1800  2600  3500  4600 5300     
3/4      2100  2900  3700  4300 5100   
7/8      1800  2400  3200  3700  4300  
1      1500  2100  2700  3200  3700 4100


Carbon steel tubing per ASTM A-179 or equivalent. Working pressures are based on allowable stress of 15,750 PSI between -70° F and 100° F (Reference: ANSI B31.3)
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  Suggested Maximum Allowable Working Pressure for Copper Tubing

Table 3  PSI
COPPER TUBING
Tube OD inch Wall Thickness, inch
0.01 0.012 0.014 0.016 0.02 0.028 0.035 0.049 0.065 0.083 0.095 0.109 0.120
1/16 1500 2100 2600 3100 4200     2900          
1/8           2700 3600 5100          
3/16           1800 2300 3400          
1/4           1300 1600 2500 3500        
5/16             1300 1900 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


Copper tubing per ASTM B-75 or equivalent. Working pressures are based on allowable stress of 6,000 PSI between -70° F and 100° F (Reference: ANSI B31.3)
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  System Temperature

Operating temperature is another factor in determining the proper tubing material and suggested maximum allowable working pressure of a fitting assembly. Temperature stress factors are used to calculate the suggested maximum allowable working pressures at elevated temperatures. Locate the correct factor in Table 4 and multiply this by the appropriate value in Tables 1-3 to obtain the elevated temperature working pressure.

Table 4
STRESS FACTORS
Temperature 304 Stainless Steel 316 Stainless Steel 1 Copper
°F °C
-325 - 100 -198 - 38 1.0 1.0 1.0
200 93 1.0 1.0 0.97
400 204 0.93 0.96 0.45
600 316 0.82 0.85  
800 427 0.76 0.79  
1000 537 0.69 0.76  
1 Maximum recommended usable temperature 300°F (150°C).

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  Pipe End Pressure Rating

Fittings with both Tube End and NPT/ISO threaded pipe end connections have different pressure ratings. When specifying these types of fittings, please refer to the chart for the maximum allowable pressure ratings. A thread sealant must always be used when using NPT/ISO connections.

Table 5 PSI
PIPE END PRESSURE RATINGS
NPT/ISO size 316 Stainless Steel Brass
Male Female Male Female
1/16 11000 6700 5500 3300
1/8 10000 6500 5000 3200
1/4 8000 6600 4000 3300
3/8 7800 5300 3900 2600
1/2 7700 4900 3800 2400
3/4 7300 4600 3600 2300
1 5300 4400 2600 2200
1-1/4 6000 5000 3000 2500
1-1/2 5000 4600 2500 2300
2 3900 3900 1900 1900

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  SAE Straight Thread End Pressure Rating

For the 2straight thread connection, refer to the table below for the allowable working pressure.

PSI
1SAE STUD END PRESSURE RATING
Thread size 316 stainless steel
Nonpositional Positional
5/16-24 4568 4568
3/8-24
7/16-20
1/2-20
9/16-18 3626
3/4-16
7/8-14 3626 2900
1-1/16-12
1-3/16-12 2900 2320
1-5/16-12
1 SAE J1926-3
2 Part number DCU, DCUZ, DCO, DCF, DLO, DHB and DHO

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  AN 37° Flared End Pressure Rating

For the 2AN 37° flare end connection, refer to the table below for the suggested maximum allowable working pressure.

PSI
1AN END PRESSURE RATING
Thread size 316 stainless steel Brass
5/16-24 3000  
7/16-20  
1/2-20  
9/16-18  
3/4-16  
7/8-14  
1-1/16-12  
1 SAE AS5174
2 Part number DAN, DHN, DLC, DUC, and DUE

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