Valve body and flange material

[DANIAL AZIMI]

As mentioned the requirment of materials for equipment in standard and non standard material table(table no 5 in api 6a) body and bonnet can be 36 up to 75K for example in 5000 class but also indicated that integral end connection flanged shall be only 60,75K,
So if we want to select valve with flanged end and manufacture by forging or casting integrally, we have to use 60K for body and bonnet too, or flanges are from the body parts and can use 36K for 5000 and blow classes???

 

[SPDL310]

Your body would need to meet the integral flange requirement of 60K or 75K. Your bonnet can be 36K material as long as your design criteria is based upon a 36K yield material. That means that your allowable bonnet stress would be around 24K at working pressure. If you can spare the thickness for that then it is ok.

 

[DANIAL AZIMI]

[pre]But, in this situation, according to this table, BW valve can be 36k for 5000 class and flange valve sall be 60k in same class, what is the different between these 2 valve when we calculate minimume wall thickness in accordance with api 6a methods like vonn misses or asme sec 8 div 2 appendix 4 or etc,when we measured thickness for whole parts, it can occure at flange parts. I think that there is a bug in this standard because that in table 5 mentioned that only 45k material for weld neck flange in 2000 ,3000,5000 classes is permmited, but also i think that when we manufacture flange valve in solid shape and monolithic we can calculate thickness for flange with lower stenght material like 36k as well as body,
Is it true???
[/pre]

 

[SPDL310]

First off the quality requirements of Table 5 are not a misprint. I believe the rationale behind it is that API has design control over the flanges detailed in 6A.
They do not know the exact application and loading each piece will be subjected to. They thus create a high material requirement to cover all possible applications.
For a better understanding of API flange performance see API TR 6AF1.

If you are incorporating a flange not listed in API 6A such as a compact flange or an OEC you would refer to footnote C.)as specified by manufacturer. Then the specification is up to you.