But then in Carbon Steel A105, at 25✬, it can work up to 255 bar, and at 250✬, only 209 bar. These ANSI classes have temperature pressure charts that correlate with the flange and/or valve ratings to determine the operating pressure at the corresponding operating temperature.įor example, a class 1500 valve in 316 stainless steel, at a temperature of 25✬, can withstand a pressure of 248 bar, while at 250✬, it can only withstand 166 bar. Important I will keep repeating … Do not confuse the rating number with the operating pressure value for the valve or flange connection. Class 4500 appears in ASME B16.34 but not in the flanged standard since no one will use a flanged valve at these pressures. It is an intermediate class between 600 and 900 and is usually rounded to PN140 or 2000 PSI.Ĭlass 4000, I believe, is not in any standard, but some manufacturers and commercial catalogs use it. In which standard are Class 800 valves listed? Class 800 is listed in API 602 and is equivalent to about 132.4 bar or 1920 psi pressure. Outside the API 6D standard but commercially used, we have the following classes: PN 140 Table of equivalences between PN (Nominal Pressure) and Class (ASME): PN According to EN 1092-1 or ISO-7268 The API 6D standard is the one that tells us the equivalence between PN and Class. The pressure rating (PN) or class (CL) of ASME classification is used to specification the pressure of a valve. Equivalences between PN and ANSI CLASS in pressure valves Thus, a PN250 valve works at 250 bar pressure, equivalent to 3,625 psi, and does not correspond to an ANSI class 250. This is why the valve pressure is indicated in bar. This is mainly used in the standard European system, including DIN, EN, BS, and ISO. Then we have the Nominal Pressure (PN), a type of classification that uses the operating pressure value to identify the valve, including the high-pressure valve. Working pressure 150 PSI (10 bar) is not the same as working pressure CL 150 (20 bar).įor example, Redfluid 3000 Series needle valves are not C元000 but are 3000 PSI (250 bar) equivalent to CL 1500. We must be clear if we are talking about pounds and, therefore, PSI (pressure unit) or ANSI Class. You can also see it in the ANSI blog that I leave HERE. The old 1973 nomenclature used LBS and was, for example, 150LBS or 150lb, and as the standard evolved, the correct name was CL. Many customers use LBS, LB, CL, or # interchangeably. It is defined as the maximum amount of pressure the flange or valve can withstand at increasing temperatures. The ANSI class is used primarily for flanged valves. Body static pressure requirements and pressure rating will be expressed in various ways depending on the manufacturer, standard, and type of valve. The rating refers to the total pressure the body and stem can withstand without leakage. It’s a matter of understanding it in a minute. It doesn’t sound straightforward, but it is not. RATING, ANSI CLASS, or Nominal Pressure (PN) in pressure valves This is why we have created standards and nomenclatures to refer to equipment pressures in the industrial world. The pressure that a valve, pipeline, or pressure equipment can withstand depends on other factors, such as the material of construction and the working temperature. So far, we have been talking about pressure units, but let’s complicate the subject a little more. The equivalence between bar and psi corresponds to 1 bar = 14.5 psi. BAR and PSI equivalence in pressure valves 1 bar is equivalent to 100,000 Pascals or 100 Kilopascals which is the same. In the industrial world, it is also one of the most used. In my opinion, it is the most famous unit in Europe and Spain. BARĪlthough in the international system (SI), the unit of pressure is the pascal (newton / square meter). It just helps to avoid confusion to use psig or psia as appropriate to be clear about what we are talking about. Sometimes, we write that as 44.7 psia (pounds per square inch, absolute) to remind us that we are talking about absolute pressure. Then the absolute pressure inside is 30 + 14.7 = 44.7 psi. Suppose the air pressure in the car tire is 30 PSIG. The absolute air pressure at sea level is approximately 14.7 psi. When we measure the tire pressure of a car or bike tire, the pressure gauge reads the difference in pressure between the air inside the tire and the air outside the tire. The “G” reminds us that we are discussing this pressure difference. It represents a measure of pressure relative to atmospheric pressure as read on the pressure gauge. The acronym PSIG refers to Pound per Square Inch Gauge.
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