Page 76 - D30003

76 Parker Hannifin Corporation
Instrumentation Products Division
Huntsville, AL USA
http://www.parker.com/ipdus
Gas Service
Special care must be taken when selecting tubing for gas service. In order to achieve a gas-tight seal, ferrules in instru-
ment fittings must seal any surface imperfections. This is accomplished by the ferrules penetrating the surface of the tubing.
Penetration can only be achieved if the tubing provides radial resistance and if the tubing material is softer than the ferrules.
Thick walled tubing helps to provide resistance. Tables 2-7 indicate the minimum acceptable wall thickness for various materi-
als in gas service. The ratings in white indicatecombination of diameter and wall thickness which are suitable for gas service.
Acceptable tubing hardness for general application is listed in Table 9. These values are the maximum allowed by ASTM. For
gas service, better results can be obtained byusing tubing well below thismaximum hardness. For example, a desirable hard-
ness of 80 Rb is suitable for stainless steel. The maximum allowed by ASTM is 90 Rb.
System Pressure
The system operating pressure is another important factor in determining the type, and more importantly, the size of tubing to
be used. In general, high pressure installations require strong materials such as steel or stainless steel. Heavy walled softer
tubing such as copper may be used if chemical compatibility exists with the media. However, the higher strength of steel or
stainless steel permits the use of thinner tubes without reducing the ultimate rating of the system. In any event, tube fitting
assemblies should never be pressurized beyond the recommended working pressure.
The following tables (2-7) list by material the maximum suggested working pressure of various tubing sizes. Acceptable tubing
diameters and wall thicknesses are those for which a rating is listed. Combinations, which do not have a pressure rating, are
not recommended for use with instrument fittings.
MAXIMUM ALLOWABLE WORKING PRESSURE TABLES
Table 2 316 or 304 STAINLESS STEEL (Seamless)
Tube
O.D.
Size
Wall Thickness
0.010 0.012 0.014 0.016 0.020 0.028 0.035 0.049 0.065 0.083 0.095 0.109 0.120 0.134 0.156 0.188
1/16 5600 6900 8200 9500 12100 16800
1/8 8600 10900
3/16 5500 7000 10300
1/4 4000 5100 7500 10300
5/16 4100 5900 8100
3/8 3300 4800 6600
1/2 2600 3700 5100 6700
5/8 3000 4000 5200 6100
3/4 2400 3300 4300 5000 5800
7/8 2100 2800 3600 4200 4900
1 2400 3200 3700 4200 4700
1-1/4 2500 2900 3300 3700 4100 4900
1-1/2 2400 2700 3000 3400 4000 4500
2 2000 2200 2500 2900 3200
Table 3 316 or 304 STAINLESS STEEL (Welded)
Tube
O.D.
Size
Wall Thickness
0.010 0.012 0.014 0.016 0.020 0.028 0.035 0.049 0.065 0.083 0.095 0.109 0.120 0.134 0.156 0.188
1/16 4800 5900 7000 8100 10300 14300
1/8 7300 9300
3/16 4700 6000 8700
1/4 3400 4400 6400 8700
5/16 3400 5000 6900
3/8 2800 4100 5600
1/2 2200 3200 4300 5700
5/8 2500 3400 4500 5200
3/4 2100 2800 3700 4200 4900
7/8 1800 2400 3100 3600 4200
1 2100 2700 3100 3600 4000
1-1/4 2100 2400 2800 3100 3500 4200
1-1/2 2000 2300 2600 2900 3400 4200
2 1700 1900 2100 2500 3000
D30003 76 5/12/05