Relationship between the operating pressure and design pressure of the drum
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Is there any standard regarding the relationship between the operating pressure and the design pressure of a steam drum?
The design pressure of the drum is based on the rated pressure; for saturated steam or hot water boilers, the design pressure of the drum equals the rated pressure, while for superheated steam boilers, the drum pressure is 1.1 times the rated pressure； The operating pressure of the steam drum is related to actual operation, with the operating pressure being lower than the rated pressure.
The operating pressure of the steam drum must be lower than the design pressure
In terms of containers, according to GB150-1998 \"Steel Pressure Vessels\", the operating pressure of a steam drum is designed at a low pressure level. In terms of boilers, according to the terms and definitions section in GB/T9222-2008 \"Calculation of Strength of Pressure Components in Water-Tube Boilers\", pressure is generally divided into operating pressure, rated pressure, and calculated pressure; design pressure is not considered. The determination of the operating pressure is carried out in accordance with Clause 6.3 of GB/T9222-2008 \"Calculation of Strength for Pressured Components in Water Tubular Boilers\"; in some boilers, the actual operating pressure is lower than the rated pressure. I think that by studying the GB/T9222-2008 standard \"Calculation of Strength for Pressured Components in Water Tubular Boilers\" carefully, this issue will become very clear.
There is a connection: in the boiler industry, the design pressure is not generally mentioned; instead, the rated pressure, operating pressure, and calculated pressure of the boiler are used. These values depend on the structure of the boiler. For shell-type boilers, the GB/T16508-1996 standard applies. The formula is as follows: P = Pe + ΔP + ΔPz + ΔPSZ, where P represents the calculated pressure, Pe is the rated pressure of the boiler (or its operating pressure), and ΔP is the additional pressure, which is 0.02 MPa when the rated pressure is less than 1.2 MPa. When the rated pressure is not less than 1.2 MPa, ΔP = 0.04 (Pe + ΔPsz + ΔPSZ). ΔPz represents the pressure drop between the component under consideration and the boiler outlet at maximum flow rate, while ΔPSZ denotes the hydrostatic pressure exerted by the water column on that component. If ΔPSZ < 3% of (Pe + ΔP + ΔPz), it can be taken as zero. For water-tube boiler structures, the specific requirements are as follows: P = Pg + ΔPa, where Pg = Pe + ΔP + ΔPz; Pg represents the operating pressure, with the other values as defined above. ΔPa is the design additional pressure, which is calculated as follows: when Pe ≤ 0.8 MPa, ΔPa = 0.03 MPa; when 0.8 MPa < Pe ≤ 5.9 MPa, ΔPa = 0.04Pe; and when Pe > 5.9 MPa, ΔPa = 0.05Pe. For the boiler drum used on cylinder partitions or smoke hoods, when a safety valve is installed in accordance with container design standards, the design pressure is generally 1.15 times the maximum operating pressure, mainly to take into account the impact of the safety valve.
The operating pressure of the steam drum need not exceed the design pressure
The design pressure of the steam drum is 1.05 to 1.1 times the operating pressure
The boiler and pressure vessel section of the ASME standards can be consulted
Set pressure, control pressure, rated pressure, nominal pressure, safety pressure, start-up pressure, return pressure – who can distinguish them?
It’s not exactly 1.1 times； It must be below the design pressure, and a safety valve should be installed as protection against overpressure
The pressure in the drum of a superheated steam boiler is set at 1.1 times the rated pressure. Which standard or manual specifies this? ?