The classification of is as follows:
1. The operating temperature of the valve t ＞ 425 ℃~550 ℃ (＞ 800 ℉~1022 ℉) is classified as high temperature I, referred to as P1.
2. The operating temperature of the valve t ＞ 550 ℃~650 ℃ (＞ 1022 ℉~1200 ℉) is classified as high temperature class II, referred to as class P II for short.
3. The operating temperature of the valve t ＞ 650 ℃~730 ℃ (＞ 1200 ℉~1346 ℉) is classified as high temperature class III, referred to as class P III.
4. The operating temperature of the valve t ＞ 730 ℃~816 ℃ (＞ 1346 ℉~1500 ℉) is classified as high temperature level IV, referred to as P Ⅳ.
5. The temperature zone where the operating temperature of the valve t is more than 816 ℃ (more than 1500 ℉) is called the higher temperature level, that is, high temperature level V, referred to as P V for short.
