How to Prevent Entraped Solids causing damage to Ball and seat 4

[bmoorthy]

Valve: Ball Valves (Some are actuated type and some are manual operated type)
Application: can tolerate Leakage to the level given in API 6D for metal seated valves (Not more than that/ On Off type (Not for Throttling)
Service (Severity): Once in one month
Fluid: Sour Liquid/Gas mixture and Has Solid Suspensions (less than 100 PPM of soilds).
Size of the particulate: Maximum size 1 cubic mm.
Hardness of the particulate: Not known.
Erosion by the virtue of impingement not envisaged.

Balls and the seats are Tungsten carbide coated (Ball material 31254 (SMO 254))

Fear/Concern: Entrapped solid particulates (between seat and Ball) may damage the seating surface during opening or closing the valve there by causing leakage during subsequent operation.


Question:

1) Is Tungsten Carbide coated material resistant to Scratch/Peel effect (That may occur when the valve is being opened or closed, due to entrapped solid pieces, may be i am not using the correct property terminology for scratch resistance)

2) Will the valve be better with out Tungsten Carbide application

3) Are there better material or coating that may address the concern/Fear

4) Is soft seated valve better in the above application instead of hard seated valve

5) Can on apply tungsten carbide coating on one side and leave the other side un coated, so tat one can take advantage of both

6) Can one apply Tungsten Carbide only on seat ring and leave the ball with out coating?

 

[BigInch]

Have you actually had problems with your valves with an operation frequency of 1 action per month? If so, I think you need to get that particulate matter over to the lab and find out exactly what the heck it is.

http://virtualpipeline.spaces.msn.com

 

[bmoorthy]

We are not users, we are EPC contracotrs.

We need to select valves that are workable and the same time cost effective, with out compromising on the application and safety.

At this juncture i am not sure whether coating will aid leakage or whether it will stop leakage by the virtue of entrapped solid particles.

There are sensibe arguments for and agains coating and am weighing the pros and cons.

One thing that occurs to me is to conduct a demonstration, that is take fluid with solid suspensions and force it through valve and open and close say ( 120 times) and then record the leakage rate for coated valves and uncoated valves and if the results are not all that different then chose uncoated valve.

If this kind of data is already available or answer to my questions are already availabel then i would not venture out to an expriment.

 

[JimCasey]

The best trick I know to reduce scratching is to install the ball with the axis of rotation horizontal.
The ball should customarily rotate CCW to open. Therefore the stem should be on the left when looking downstream.

When the valve is closed, the solids drop out of suspension and lie along the bottom of the pipe. Rotating the ball CCW tends to lift and dislodge any particles that might be at the ball/seat interface, so they don't get ground into the seat, but get flushed away as soon as flow begins.

Also, with the horizontal rotation, the body cavity gets flushed every cycle. Conversely with a vertical axis, the body cavity might accumulate debris and the ball will be sitting in a pile of grit.

This trick works for butterfly valves also.

Just because the pictures in the catalogs show the valve with a vertical stem, does not mean that they HAVE to be installed that way.

 

[BigInch]

Star for the very practical advice.

http://virtualpipeline.spaces.msn.com

 

[NGiLuzzu]

bmoorthy,
may be I'm a little "off-topic" (and tactless, too), but I try to ask you anyway: is it mandatory to use ball valves?
If yes, why (e.g.: do they need to be "piggable")?
If not, did you consider other valve types?

Thanks, 'NGL

 

[Ashereng]

A star for very good advise.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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