Relationship between the thickness of the tube sheet and the flange thickness in fixed-tube-sheet heat exchangers
Thread Content
I’m a complete novice when it comes to pressure vessels, and I have some questions I’d like to ask the experts here. For a fixed-tube-sheet heat exchanger, the tube box flanges are calculated to be standard FM1100-1.6 flanges with a thickness of 62 mm. The nominal thickness of the tube sheet, as calculated, is 37 mm, while the thickness of the shell-side flanges on the tube sheet is 22 mm. There’s a significant difference between the 22 mm thickness of the tube sheet flanges and the 62 mm thickness of the tube box flanges. If the shell-side flanges or the tube box flanges cannot be designed with a thickness of 22 mm, can the relevant thicknesses of the tube sheet still be determined using this calculated value? I would appreciate it if the experts could provide some guidance.
In the design of fixed-tube-sheet heat exchangers, the thicknesses of the tube sheet, the tube box flanges, and the shell-side flanges indeed have different calculation requirements and safety standards. The thickness of the tube sheet is primarily influenced by factors such as the pressure and temperature in the tube side, as well as corrosion. The thickness of the tube box flanges and shell side flanges, on the other hand, must also take into account the structural stability of the connections and the requirements for flange sealing. Since the thickness of the flange on the shell side, which you mentioned is 62 mm, is significantly greater than the thickness of the tube sheet (37 mm) and the shell-side flange (22 mm), this is usually because the loads acting on the flange area—such as the clamping force and the internal pressure within the shell—require greater strength and rigidity. If the shell-side flanges and tube box flanges do not meet the requirements when calculated with a thickness of 22 mm, their design thickness should remain at the originally calculated value or be increased to meet safety standards. Regarding your question, “Can the relevant thickness of the tube sheet be manufactured according to the calculated result?” Yes, as long as the thickness of the tube sheet meets the operating pressure it must withstand and other design conditions, it can be manufactured according to the calculated results. It is important to ensure that the strength, sealing, and long-term stability of all components meet the requirements of the design specifications. It is recommended to verify the design parameters against relevant pressure vessel standards once again or consult a professional pressure vessel design engineer before proceeding with implementation. .
Is your calculation correct? If it is, that’s great; I don’t see your work though
This post was last edited by bluishice on 2024-8-6 10:01. In fact, if the calculations are correct, then it’s acceptable, unless there are errors in the calculation parameters. For flanges, the main requirement is stiffness, which ensures that the sealing surface does not deform, thereby preventing seal failure. For tube box flanges, it is the flange itself that provides stiffness. In the case of tube sheet flanges, in addition to the flange itself, the tube sheet also contributes to providing stiffness; as a result, tube sheet flanges actually need to be much thinner. The thickness of the tube sheet is primarily determined by the pressure difference between the tube side and the shell side, as well as by the heat exchange tubes; as long as it is sufficient, that’s enough. However, there used to be a statement that the thickness of the tube sheet should be no less than 60% of the thickness of the shell flange, but I couldn’t find its source.
The thickness calculations are all within acceptable limits. I’m just concerned that when the shell side flanges are under pressure in the tube sheet, the difference in thickness between the two flanges is so large that I’m hesitant to make a decision
From the perspective of the minimum relative stiffness of the bolted connection, the two flanges should not differ too much; this is why, as specified in standard 151, the difference must not be less than 60%