API 610 - Machined and Studded connections on pump casing 2

[Henrique Orlandini]

Hello!

Our engineering team is developing a "API 610 guide for beginners", in which we're trying to make it even easier for someone new to this area to understand the standard's requirements.

One point that got us confused were items 6.4.2.1 and 6.4.3.6 (from API 610 12th ed), which says about pump nozzles and auxiliary connections being machined and studded. Our understanding was that a "machined and studded" connection was a alternative to directly welded pipes to the pump casing. I've attached a image of a positive displacement pump we use that we believe to have the "machined and studded" connection.

Basically I would like to know the opinion of other professionals in this area to verify whether out interpretation of API 610 was correct or not.

Thanks in advance.

 

[Mech5656]

Henrique Orlandini:

In my opinion, the difference is in the way the material is formed to make the pump casing. In this case, two options are mentioned. Forged case (made by hammering and press) Vs case made from casting (molten metal poured in certain made shape). In paragraph 6.4.2.1 of API 610, it says that the pump case made from castings should have flanged connections and not studded machined connections. If the pump case is made from forged material then it can be either flanged or machined studded connection (any of them will work in forged material case). Does it make sense? Does this align with the research you have done?

 

[Henrique Orlandini]

Thansk for your answer! The requirement from 6.4.2.1 actually slipped from us (will make sure to include that), but my original post was more about the actual definition of "machined and studded connections" for pump casings, since it's not our bread and butter configuration.

 

[SB1976]

[pre]
Henrique,
I am not quite sure what exactly your question is. Anyway, I would like to answer you in the way I thought might help you.

First, let us understand what is the difference between stud and bolt. Refer the picture below which is self explanatory. As can be seen, through bolting has better leak tightness and containment measures when compared to stud.

Second, pumps compliant with API 610 need to have suction and discharge nozzles with bolted connections OR studded connections for forged nozzles. I agree with Mech5656 about why studded connections are preferred in case of forgings. That's because they can be formed.

Third, from general engineering judgement, unless pressures are low, we should not be using studded connection interfaces.

Trust this helps.

[/pre]

 

[Henrique Orlandini]

Thanks Mech5656 and S. Barman, your contributions were of great help!