Differences between seat, seat insert and seat ring.

[Newbie]

Greetings,

Can anyone kindly explain to me what are the differences between seat, seat insert and seat ring? Valves figures in API 6D show only seat ring and I got confused when I saw valve drawings with seat and seat insert.

 

[CKchi]

HI Jethrolawing,

Just take the Trunnion mounted ball valve for example, please see the attachment.

item 49 - is the seat insert (for example PTFE)
Item 45 - is the seat retainer or seat ring ( for example 316）

Hope this helps.

 

[Newbie]

Hi CKchi,

Thank you! Yes, I found that very helpful. On the other hand, I watched this video

https://www.youtube.com/watch?v=mWXjvVMvz6Q

which is an animation for valve assembly. If you watch this and see at 1:08 onward, did the video maker actually mistaken the seat insert with the seat?

 

[gerhardl]

No. Seat insert describes here the process of mounting (inserting) the seat ring, but before the seat (ring) is mounted you also see the 'seat insert -part' being mounted onto the seat ring and both parts moved animated as one unit into the body.

 

[Newbie]

Hi gerhardl,

Sorry for the very late reply. I appreciate your response. To summarize, seat insert is inserted into the seat ring, yes? And then again what is seat? Or does seat = seat insert + seat ring? Kindly explain.

Thanks!

 

[LocalCap]

Thank you for the question.
And thanks CKchi for clarification by drawing.
Can you please continue to let us know what are items 46 and 47 call.
What make it actually even more confusion is the seat o-ring.

And when we call the ball soft seated or metal seated?

 

[Ehzin]

Hello there,

I'd classify 46 as the seat o-ring which is more of a static seal meant to prevent leakage around the back side of the seat. It looks like item 47 could be a fire-proof gasket. The seat designs for API-6D valves can vary a decent bit by the features they include.

 

[gerhardl]

Hello LocalCap and Newbie:

1. A ball valve is metal seated when both main sealing surfaces (that prevent the flow when closing the valve) is metal.

2. Regarding names of different parts of a ball-valve sealing. As Ehzin states there is a lot of variations of details in ball-valves flow-sealing details. I am not sure there is a standard naming all details. On the other hand some standards refer to drawings and names various parts. If a valve is built to a named standard, nomenclature should be consistent with the names of parts given in the standard.

a) By common use the two main parts for a typical trunnion mounted ball valve (as discussed here) consists of the (seat) retainer also called seat retaining ring (or even a seat holding ring or seat clamping ring for other valve constructions). The other main part is the seat sealing itself which you insert into the retainer. This part (depending on producer and standard) is called seat sealing ring or seat insert ring, or shorted to seat. (Seat is sometimes unprecisly used for the complete assembly, just to confuse!)

As for the other parts (and naming of all parts in a technical drawing) the general advice is to name parts as close to describing the actual function as possible. I have often seen translations from German to English, where English do not have the single technical word describing the precise technical function given by one German word.

I feel that you guys are here searching for an exact English nomenclature, which perhaps does not exist for this product.