To be continued from this chapter “Pipe pressure rating“, I’d like to introduce to you about the fitting pressure rating.

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Note:

Flanges, Gaskets, Valves, Weld fittings are designed as CLASS

Typically, there’re three type of Fitting CLASS rating:

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According to ASME B16.5, are made in seven primary Pressure Classes:

150 300 400 600 900 1500 2500

The concept of flange ratings likes clearly. A Class 300 flange can handle more pressure than a Class 150 flange, because a Class 300 flange are constructed with more metal and can withstand more pressure. However, there are a number of factors that can impact the pressure capability of a flange.

The Pressure Class or Rating for flanges will be given in pounds. Different names are used to indicate a Pressure Class.
For example: 150 Lb or 150 Lbs or 150# or Class 150, all are means the same.

Base on type of material group – see this topic, we can find out the temperature rating according to ASME B16.5  from PRESSURE TEMPERATURE RATING TABLE.

Example for Group 1.2

Maximum Allowable non-shock Pressure (psig) 
Temperature
(oF)
Pressure Class (lb)
150 300 400 600 900 1500 2500
Hydrostatic Test Pressure (psig) 
450 1125 1500 2225 3350 5575 9275
-20 to 100 290 750 1000 1500 2250 3750 6250
200 260 750 1000 1500 2250 3750 6250
300 230 730 970 1455 2185 3640 6070
400 200 705 940 1405 2110 3520 5865
500 170 665 885 1330 1995 3325 5540
600 140 605 805 1210 1815 3025 5040
650 125 590 785 1175 1765 2940 4905
700 110 555 740 1110 1665 2775 4630
750 95 505 675 1015 1520 2535 4230
800 80 410 550 825 1235 2055 3430
850 65 320 425 640 955 1595 2655
900 50 225 295 445 670 1115 1855
950 35 135 185 275 410 685 1145
1000 20 85 115 170 255 430 715

According to JIS B 2220/2239 containing all flange dimension, Pressure/temperature rating.

See JIS STANDARD PRESSURE RATING

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