Regarding the selection of wall thickness for the Sch series

It is possible to use the outer diameter of series II; it’s fine to require a wall thickness in line with series 1a. We often do this, for both pipes and pipe fittings.

Using standardization makes factory maintenance more troublesome

1. Strictly speaking, Sch refers to the wall thickness series; pipes of series II do not have such a designation as Sch, nor is it specified in the standards. Generally, for pipes of Series II, the wall thickness value is provided directly. But you can use this as a reference: the outer diameter should follow Series II, while the wall thickness should comply with Series 1a. As a result of this, you must specify it clearly in the procurement documents to avoid purchasing errors. 2. There is no difference in design between using Sch and directly specifying the wall thickness; it doesn’t matter which method is used. As long as the design meets the requirements for strength, stiffness, etc., it is sufficient. The advantage of Sch is standardization, which can reduce the workload related to design, manufacturing, construction, inspection, and maintenance.

I did the same thing, but when it came to procurement, they still preferred the wall thickness of Series II, and they told me that my approach caused a lot of trouble. But it’s easier for me to produce design files. ;P

I think it’s fine; the design meets all the requirements, and it even helps the client save money.

The situation is as follows: the design pressure for the main steam pipe of the boiler is 9.9 MPa, with a design temperature of 312°C. I chose a pipe with an outer diameter of 57 mm and a wall thickness of 5 mm, using material 20G. I didn’t determine the wall thickness based on SCH standards; if I had used those standards, the wall thickness would have been 8 mm. Now the client is asking why I chose 5 mm as the wall thickness. How should I respond? It’s because I didn’t consider SCH standards from the beginning. If I had followed those standards, then the choice of wall thickness would have been based on relevant specifications, which would be more reasonable. But since I decided on 5 mm, it seems there’s no standard or specification to support this choice

The situation is as follows: the design pressure for the main steam pipe of the boiler is 9.9 MPa, with a design temperature of 312°C. I chose a pipe with an outer diameter of 57 mm and a wall thickness of 5 mm, using material 20G. I didn’t determine the wall thickness based on SCH standards; if I had used those standards, the wall thickness would have been 8 mm. Now the client is asking why I chose 5 mm as the wall thickness. How should I respond? It’s because I didn’t consider SCH standards from the beginning. If I had followed those standards, then the choice of wall thickness would have been based on relevant specifications, which would be more reasonable. But since I decided on 5 mm, it seems there’s no standard or specification to support this choice

The situation is as follows: the design pressure for the main steam pipe of the boiler is 9.9 MPa, with a design temperature of 312°C. I chose a pipe with an outer diameter of 57 mm and a wall thickness of 5 mm, using material 20G. I didn’t determine the wall thickness based on SCH standards; if I had used those standards, the wall thickness would have been 8 mm. Now the client is asking why I chose 5 mm as the wall thickness. How should I respond? It’s because I didn’t consider SCH standards from the beginning. If I had followed those standards, then the choice of wall thickness would have been based on relevant specifications, which would be more reasonable. But since I decided on 5 mm, it seems there’s no standard or specification to support this choice

We didn’t ask them to make any changes when placing the order, so we just kept it as it was

The main issue is likely related to the welding of the weld flange to the pipe; if there is a large difference in thickness, the flange needs to have its edges trimmed