Class 150 Pressure Rating – Class 150 / 300 Flange Pressure Rating | ZECOdouble offset butterfly valve

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According to ASME B16.5, the steel flange has seven pressure ratings: Class 150-300-400-600-900-1500-2500, which is very clear. The Class 300 flange can withstand more pressure than the Class 150, because the Class 300 flange needs to be made of more material to withstand greater pressure. However, the pressure capacity of the flange depends on many factors. The pressure rating of the flange is expressed in pounds, and a pressure rating has a different representation. For example, 150Lb, 150Lbs, 150# and Class 150 mean the same.

Table of Contents

  • Examples of Pressure Rating
  • Examples of Pressure Temperature Rating
  • CARBON STEEL FLANGE RATING CHART
    • ANSI FLANGE ASTM A105, A350 Gr. LF2/LF6 Class 1
    • ANSI FLANGE ASTM A350 Gr. LF3, A350 LF6, Class 2
    • ANSI FLANGE ASTM A350 Gr. LF1 

Examples of Pressure Rating

The bearing capacity of flanges varies with temperature. As the temperature increases, the bearing capacity of the flange decreases. For example, the Class 150 flange has a pressure capacity of 270 PSIG at room temperature; has a pressure capacity of 180 PSIG at 400℉; has a pressure capacity of 150 PSIG at 600℉; has a pressure capacity of 75 PSIG at 800℉.

In other words, when pressure falls, temperature rises, and vice versa. Valve Flanges can be made of a variety of materials, such as stainless steel, cast iron, ductile iron, carbon steel, and so on, each with a different pressure rating. The following figure shows an example of a flange in NPS12. As you can see, the diameter of the flange inner hole and face is the same. However, the flange outside diameter, bolt hole center circle diameter, and bolt hole diameter increase with the increase of the pressure level. The number and diameter of bolt holes are: CL150 – 12 x 25.4 CL300 – 16 x 28.6 CL400 – 16 x 34.9 CL600 – 20 x 34.9 CL900 – 20 x 38.1 CL1500 – 16 x 54 CL2500 – 12 x 73

https://lugbutterflyvalve.top/wp-content/uploads/2024/04/20240409015508-66149ffc09872.jpg

Examples of Pressure Temperature Rating

The pressure-temperature rating means the maximum allowable working gauge pressure (pressure in Bar) of the material and class at the rated temperature (Celsius). The linear insertion method can be used to determine the intermediate temperature, but insertion between flange levels is not allowed. Flange joints can be suitable for pressure-temperature ratings if the bolts and gaskets of the flange joints meet the relevant limitations and the alignment and assembly of the flange joints are in accordance with standards.

The rated temperature corresponding to the rated pressure is the case temperature of the pressure vessel of the flange and the flange pipe. In general, this temperature is the same as the temperature of the stored fluid. When the temperature is – 29 ℃ (- 20 ℉), the following rating, shall be no greater than – 29 ℃ (- 20 ℉) rating.

CARBON STEEL FLANGE RATING CHART

ANSI FLANGE ASTM A105, A350 Gr. LF2/LF6 Class 1

The flange rating table shows the maximum pressure for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures  (Celsius or Fahrenheit) – in PSI

Temperature (in F°)150#300#400#600#900#1500#2500#
< 1002857409851480222037056170
2002606809051360203533955655
3002306558701310196532705450
4002006358451265190031705280
5001706058051205181030155025
6001405707551135170528404730
6501255507301100165027454575
7001105307101060159026554425
750955056751015152025354230
80080410550825123520553430
8506532042564095515952655
9005023030546069011501915
950351351852754106851145
10002085115170255430715
Hydrostatic Test Pressure (in Psig)450112515002225335055759275

The flange rating table shows the maximum pressure for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures  (Celsius or Fahrenheit) – in bars

Temperature in C°150#300#400#600#900#1500#2500#
   -29 / 3819.651.168.1102.1153.2255.3425.5
5019.250.166.8100.2150.4250.6417.7
10017.746.662.193.2139.8233388.3
15015.845.160.190.2135.2225.4375.6
20013.843.858.487.6131.4219365
25012.141.955.983.9125.8209.7349.5
30010.239.853.179.6119.5199.1331.8
3259.338.751.677.4116.1193.6322.6
3508.437.650.175.1112.7187.8313
3757.436.448.572.7109.1181.8303.1
4006.534.746.369.4104.2173.6289.3
4255.528.838.457.586.3143.8239.7
4504.62330.74669115191.7
4753.717.423.234.952.387.2145.3
5002.811.815.723.535.358.897.9

Notes:

  • ASTM A105: An extended exposure to temperatures above 425°C, converts the carbide phase of steel to graphite (therefore this material is not recommended for constant temperatures above this value.
  • ASTM A350 LF6: shall not be used for temperatures above 260 C°

ANSI FLANGE ASTM A350 Gr. LF3, A350 LF6, Class 2

The flange rating chart shows the maximum pressure for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures  (Celsius or Fahrenheit) – in PSI

Temperature in °F150#300#400#600#900#1500#2500#
-20 to 10029075010001500225037506250
20026075010001500225037506250
3002307309701455218536406070
4002007059401410211535305880
5001706658851330199533255540
6001406058051210181530255040
6501255907851175176529404905
7001105707551135170528404730
750955056701010151025204200
80080410550825123520603430
8506527035553580513402230
900501702303455158601430
95035105140205310515860
1000205070105155260430

ANSI FLANGE ASTM A350 Gr. LF1 

The flange rating table shows the maximum pressure for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures  (Celsius or Fahrenheit) — in PSI

Temperature °F150#300#400#600#900#1500#2500#
-20 to 1002356208251235185030851545
2002155607501125168528104680
3002105507301095164027354560
4002005307051060158526454405
500170500665995149524904150
600140455610915137022853805
650125450600895134522453740
700110450600895134522453740
75095445590885132522103685
80080370495740111018503085
8506527035553580513402230
900501702303455158601430
95035105140205310515860
1000205070105155260430

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