PTA Control Valves

[DeeDee]

Dear All,

we're experiencing severe errosion on some PTA control valves. The most severe is on the pump recirculation valves which see ~100 pressue drop over the seat with 23% solids content in the slurry flow. These valves are installed on the line after the booster pumps to recirculate flow to the pump when the process line has been switched. Valve trim materials such as Hastelloy, Ti-nitrided st.st. and ceramic have only managed up-times of ~6 months to date. Anyone have positive experience with alternative materials/surface treatments?

Help would be appreciated.
DD.

 

[valvetech]

Depending on the type of valve that you have taking the pressure drop you could have two problems. the first being cavitaion and the second being the particulate in the slurry. Combined you have a valving nightmare.
Very few valves are good at operating with particulate going through them under pressure.
I would make sure that you do not have any cavitation ( or are even close to incipient cavitation and then find the best material that is caompatible with the media you are flowing. But there is little that you can do to avoid the particulate eating away the wetted parts surface, it is just a matter of how long you can put off the having to replace the valve. Look for something that has the largest bore with the straightest flow pattern and as few parts in the flow pattern you can find. That is about all you can do if you process must have a large amount of particulate in it. It may also help to reduce the amount of pressure drop you are taking across the valve.

 

[tmtresearch]

We have used Boron diffusion alloys coatings to protect against solid particles in control valves with great success. See

http://www.tmtresearch.com

or contact me directly (matt.hinckley@tmtresearch.com) for more info.