I have a water system with a large manifold feeding 10 3 inch pipes.  Each pipe off the header has one 3" ball valve, about 1 ft of pipe and a nozzle. During normal operation we bleed water through the valves and nozzles and then close the valves.  The system is pressurized to 180 psig and when needed, all the valves are commanded open. When complete the valves are commanded closed under full flow conditions.  This is the second valve we have damaged in a short time and the seat damage is in the same exact location on both valves.  The damaged seat is on the inlet side and is the part of the seat that is exposed when the valve is approx. 90% closed/open.  Each nozzle is sized to flow about 500 GPM.  See attached picture.  Any ideas on what is causing this would be greatly appreciated.

So what we're seeing is the O-ring extruded through the clearance on the seat OD, correct?  Is that seat bent inward?  It sort of appears so.  Or is it worn thin there?

What is the seat material?  Looks like PTFE or Nylon, or I guess it could be UHMW.  What brand of valve is it?  What pressure class / rating are they?

Thinking out loud here . . . when the ball turns so that its spherical OD moves off the seat and the bore is over that area, there is no longer a physical restraint holding the seat in place.

The problem MIGHT be that the o-rings are of too low a durometer and when the seat deflects a little, the o-ring is pushed through.  Nah, that doesn't seem likely at only 180 psi.  Do you know what the o-ring material is?  And its durometer?

The seat might not be physically strong enough and is deflecting due to the pressure under/behind it at the brief time period when the ball bore is over it but the spherical OD is still in contact with the very outer portion of the seat, i.e., prior to breaking the seal and relieving the differential.  It could be deflecting enough to allow the o-ring to be pushed up, and then when the bore moves over the seat's outer edge, things just pop out of place.  Without knowing the materials and the dimensions/clearances, I'm just speculating.

There might just be too much clearance around the OD of the seat, but from the picture, it doesn't look like that is the case.

How often are these operated?  If it is a softer thermoplastic seat material, you might be getting "stick-slip" where the seat is adhering to the ball as it sits, then as the ball begins to turn it "smooshes" the seat out of shape.  People sometimes refer to this problem by saying "it's trying to pop the seat out of the pocket".  That might be what I'm seeing in the photo when I asked if it is bent inward.

I'm assuming this is a "floating ball" valve, it looks to be.  Perhaps it is just dimensionally incorrect and when closed allows that upstream seat to move too far out of its pocket.  Is it a Chinese valve?

Well, there are a few ideas and things I've seen before.  Without more detailed information, I can't be more definite, so:
-soft/very weak o-ring
-too large of a clearance
-weak seat due to wrong material or improper design
-plastic-to-metal adhesion leading to deformation
-improperly designed/manufactured valve assembly

Commonly restrictions through solenoid valves or vents on actuators could be restrictive: better to use a solenoid valve with high cv and then restrict (within allowable limits on the solenoid valve) with throttle valve on the solenoid, or incorporated in solenoid in/out pipelines.

(Remember that a 1/4" solenoid valve could have an actual through-bore from (normally) about 0,8mm up to 4-5mm, which would mean a lot of difference).

Better to have real and faster on/off with ball-valves than change to BFL. BFL could give more problems and could more easy stick and give higher torques than ball-valves.

Regulating valves, as stated before, gives the ideal solution.

Apart from a suspectively long opening/closing time that indicates higher torque or more restrictive air supply than
ideal, (or too small/weak  actuators) the high temperature will add to sealing 'floating' problems.

Carbon reinforced sealing materials possible? Check valvetypes and constructions for steam/condensate purposes!

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