What do Class I and Class II mean in heat exchangers?

Proposed for the accuracy grade of carbon steel pipes!

These are the container categories for heat exchangers, namely Class I, Class II, and Class III. The definitions are as follows: According to the New Safety Technical Regulations for Fixed Pressure Vessels (TSG 21-2016), Article 1.3 on scope of application states that these regulations apply to fixed pressure vessels that meet the following conditions simultaneously: (1) The operating pressure is greater than or equal to 0.1 Mpa (Note 1-2); (2) The product of the operating pressure and volume is greater than or equal to 2.5 MPa·L； (Note 1-3) (3) The medium contained is a gas, a liquefied gas, or a liquid whose maximum operating temperature is higher than or equal to its standard boiling point. (Note 1-4) Among them, ultra-high pressure vessels shall comply with the provisions of the \"Regulations on Safety Inspection of Ultra-High Pressure Vessels\", non-metallic pressure vessels shall comply with the provisions of the \"Regulations on Safety Inspection of Non-Metallic Pressure Vessels\", and simple pressure vessels shall comply with the provisions of the \"Regulations on Safety Inspection of Simple Pressure Vessels\". Note 1-2: Operating pressure refers to the highest pressure (gauge pressure) that may be reached at the top of the pressure vessel under normal operating conditions. Notes 1-3: Volume refers to the geometric volume of the pressure vessel, that is, calculated from the dimensions specified in the design drawings (without considering manufacturing tolerances) and rounded off. Generally, the volume of the internal components permanently attached inside the container should be deducted. Notes 1–4: When the medium inside the container is a liquid whose maximum operating temperature is below its standard boiling point, this regulation also applies if the product of the volume of the gas space and the operating pressure is greater than or equal to 2.5 MPa·L. (Note: 1. The current working pressure is actually the original maximum working pressure, and this applies to each pressure chamber. 2. The requirements of regulations such as the \"Safety Technical Inspection Regulations for Simple Pressure Vessels\" and the \"Safety Technical Inspection Regulations for Fixed Pressure Vessels\" cannot be satisfied simultaneously on the same design. 3. Regarding the “gas phase space”” ； If it has been determined that a vessel falls under the jurisdiction of the Code for Fixed Pressure Vessels, then when classifying it, the volume used to calculate its PV value should be the total volume of that vessel (pressure chamber), and not merely the volume of the gas phase space. (Q&A 1-5) 4. Regarding “medium”” ； For pressure vessels covered by the Fixed Capacity Regulations, when the gas phase and liquid phase consist of different media, the classification is determined based on the medium with the higher toxicity and explosion risk, regardless of whether the maximum operating temperature of the liquid-phase medium is higher than or equal to its standard boiling point. ）

Specifically, you need to consider the pressure, medium temperature, and type of medium; different operating conditions require different grades. The American container standard is ASME, while the European standards are PED/SPVD/TPED. You can check the relevant standards for more details

Are you referring to the “Ⅰ” and “Ⅱ” at the end of the standard heat exchanger specifications and models? If so, this indicates Grade I tube banks and Grade II tube banks.

What does a Grade 1 tube bundle mean? What are the criteria for being classified as Grade 1?

For details, see GB/T151-2014 P23

It refers to the pressure vessel classification, which is usually divided into: Class I pressure vessels, Class II pressure vessels, Class III pressure vessels, and vessels outside these categories.

The manufacturing requirements for related components differ between Class I tube bundles and Class II tube bundles.