四、 Classified by boiler outlet working pressure
								 		
		1. Low pressure boiler: general pressure is less than 1.275MPa; 
2. medium pressure boiler: general pressure is 3.825MPa; 
3. high pressure boiler: general pressure is 9.8MPa; 
4. ultra high pressure boiler: general pressure is 13.73MPa; 
5. subcritical Pressure boiler: general pressure is 16.67MPa; 
6. supercritical pressure boiler: general pressure is 22.13MPa.