Hi Mostafa,

The wedge material of Trim 8 should usually come with Stellite to avoid galling between the seats and wedge.

The term "WCB + 13%Cr" usually means WCB carbon steel with 13%Cr overlay, which is not common unless the service is corrosive and the size of the wedge gate valve is huge.

The recommended pairing should be:
Wedge Material: A216 WCB + Stellite
Seat Material: A105 + Stellite

I don't agree with @wornandwound, Trim 8 should be a combination trim, the seating surface should be 13% on one side, and Hardfacing on the otherside. For gate valve NPS 2 and above, the most common selection is:
Wedge material: A216 WCB + 13Cr
Seat material: A105 + Stellite 6

Of course, you can specify the wedge material to be solid A217 CA15 (casting material equivalent to 13Cr), then again the price is much higher.

James Chan

Hello, Mostafa,

Please realize that:
According to API 600, the seating surface (hard faced coating) material for wedge and seat shall be 13Cr or Co-Cr alloy.
The standard does not say the wedge/seat ring material shall be 13 Cr.


Regards

TZL

The standard say that the base material of the trim should be minimal equal to the body material, so A105 or WCB is accepted.
One of the surfaces (seat or wedge in case of a gate) needs to be hard and there needs to be aminimum and a difference. Don't think there is a requirement how the hardness should be made.

JChanMe

Gave the right answer IMHO

luis

I agree with JchanMe as well. Wedge material is a fair bit higher if you use solid A217 CA15 for the valve

Just FYI. A217 CA15 is "acceptable" replacement for WCB with 13CR overlay. for smaller valves, this is much easier to manufacture.

I say this because when's the last time you've seen an A217 CA15 PT rating?

Luke | Valve Hax | https://valvehax.com/

API Trim Number 8
Nominal Trim
410 - Hard faced
Trim code
F6HFS
Stem and other trim parts
410 (13Cr) (200-275 HBN)
Disc/wedge
410 (13Cr) (250 HBN min)
Seat surface 410+St Gr6 (CoCr Alloy) (350 HBN min)
Trim Material Grade
13Cr-0.75Ni-1Mn/1/2Co-Cr-A
Service
Universal trim for general service requiring long service life up to 593°C. As trim 5 for moderate pressure and more corrosive service. Steam, gas and general service to 540°C. Standard trim for gate valves.

I cannot tell a lie, I lifted this sometime ago. Shamelessly submitted without attribution.

The trim8 mean wedge sealing surface overlaying 13Cr, not the whole wedge 13Cr. Just like the seat ring stellite, not the whole seat stellite material.Moreover, casting material code of 13Cr is CA15.

Bruce | https://www.ntgdvalve.com