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How to choose the valve welding type by ASME B36.10M
- Thread starter ryanhu
- Start date
Someone will have determined the "Design Pressure" for the piping system. A Class rating is selected to ensure that the flanges and valves have a pressure rating greater than the design pressure. Using the design code (e.g., B31.3) the required wall thickness is calculated (either using the design pressure or the pressure rating of the flanges/valve class that has been selected).
Now you would order a butt weld valve that was the Class you required and that had butt weld ends that were the same schedule as the pipe that had been selected.
This would be the normal case when the steel used in the valves had the same allowable stress value (or greater) than the pipe. If the valves had a lower allowable stress value than the pipe then you would have a problem to sort out but this is very unusual. In this case, you might specify a thicker schedule for the valve ends and then you might need transition pieces to allow welding into the line.
Now you would order a butt weld valve that was the Class you required and that had butt weld ends that were the same schedule as the pipe that had been selected.
This would be the normal case when the steel used in the valves had the same allowable stress value (or greater) than the pipe. If the valves had a lower allowable stress value than the pipe then you would have a problem to sort out but this is very unusual. In this case, you might specify a thicker schedule for the valve ends and then you might need transition pieces to allow welding into the line.
- Thread starter
- #3
If you have a Class 2500 welding end valve you would choose the SCH160 or SCH XXS based on the pipe that the valve will be welded to.
For example, if the pipe materials has the same allowable stress value as the valve material, and the pipe is Sch 160 then the valve needs to be Sch 160. If the pipe is Sch XXS then the valve needs to be Sch XXS.
If you do not know what schedule of pipe is being used, you can not specify the valve.
NOTE: it is important that the above is only true if the pipe and the valve have the same allowable stress value. If the pipe is stronger than the valve then the valve needs to be thicker than the pipe.
I don't know what you mean by "contrast". Can you give me an example of how this is used or referred to?
For example, if the pipe materials has the same allowable stress value as the valve material, and the pipe is Sch 160 then the valve needs to be Sch 160. If the pipe is Sch XXS then the valve needs to be Sch XXS.
If you do not know what schedule of pipe is being used, you can not specify the valve.
NOTE: it is important that the above is only true if the pipe and the valve have the same allowable stress value. If the pipe is stronger than the valve then the valve needs to be thicker than the pipe.
I don't know what you mean by "contrast". Can you give me an example of how this is used or referred to?
- Thread starter
- #5
Hi rneill
I must say thankyou again.
I mean that what is the valve welding type, when the pipe
type is no determine.and I choose must be suitable General
situation.maybe a form such as flow:
valve class pipe type
2500lb sch160
1500lb sch80
900lb sch80
600lb sch40
... ...
I must say thankyou again.
I mean that what is the valve welding type, when the pipe
type is no determine.and I choose must be suitable General
situation.maybe a form such as flow:
valve class pipe type
2500lb sch160
1500lb sch80
900lb sch80
600lb sch40
... ...
I'm sorry but it really isn't clear what you're asking ?
I think you are saying if you don't know what pipe will be used, what would be a suitable general valve schedule.
The answer to this question would be this:
Obtain a copy of ASME B31.3, select a pipe material with the same allowable stress value as your valve, calculate what pipe wall thickness is required (you will have to assume some corrosion allowance) and then specify this as your valve schedule. If you have any concerns, make the valve schedule higher and the customer can always machine it down to match the pipe. They can't increase the thickness if it is to thin.
The required schedule will normally calculate out to a different Schedule for different diameters so different sizes will be different Schedules.
Sorry but I don't think anyone in the forum is going to do the calculations for you.
I think you are saying if you don't know what pipe will be used, what would be a suitable general valve schedule.
The answer to this question would be this:
Obtain a copy of ASME B31.3, select a pipe material with the same allowable stress value as your valve, calculate what pipe wall thickness is required (you will have to assume some corrosion allowance) and then specify this as your valve schedule. If you have any concerns, make the valve schedule higher and the customer can always machine it down to match the pipe. They can't increase the thickness if it is to thin.
The required schedule will normally calculate out to a different Schedule for different diameters so different sizes will be different Schedules.
Sorry but I don't think anyone in the forum is going to do the calculations for you.
- Thread starter
- #7
- Status
