Stellite Hardfaced Valve trim

[Rusty211167]

Hello,

Subject: stellite 6 trim on Gate valves

I'd like to know if galling prevention is better achieved on full stellite trim (wedge and seat area) or half stellite trim (seat only)for wedge type gate valves?

Thanks in advance

Rusty211167

 

[Danlap]

Whats the base material?
Whats the size and service? Full stellite overlay shall not done properly (especially for big sizes) will overheat the 'soft' wedges and then bent.
Nature of operation? Operates frequently, NO, NC?
Why do you need full stellite if: 1. Most of the time the wedge (non sealing area) not in contact with abbrasive medium (steam, cat cracker, etc.). 2. Wedge design supposedly prevent friction for non sealing area side against the seat.

If you are tyring to control the flow by Gate valve, then it would be different case. But then it is questionable why you choose such type for controlling flow function.
Unless you have solid case, manufacturers most likely is reluctant for full stellite overlay

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[Rusty211167]

The valves are 2" class 800# gates valves, Body is Astm a350 lf2, the wedge and seat ring are 316SS with satellite 6 overlay, the media is refrigerant gas at minus 46deg c, isolation valves only.
[pre][/pre]The spec does not define between full or half hard faced trim.
The valve supplier has offered full hard faced trim valves and my concern is whether that trim will cause galling.
I've read elsewhere that satellite 6 on satellite 6 is okay, just looking for confirmation.

 

[Danlap]

I would say its also ok. Stellite 6 against stellite 6 is generally ok (galling may not be expected due to 'small' friction between this two parts without considering other factors)
Shall in doubt, choose the part which easier to be repaired (or replaced). For instance wedge against welded in seat. Then logically speaking shall the wedge is stellite 6 then the welded seat supposed to be at least st. 6 or higher (st. 12, etc).

In addition to that, yes smaller wedge may often offered as full stellite. Some manufacturer prefer to apply stellite overlay in one go for relativy small valves.

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments