Flanged Ballvalve in oxygen service

Primarily, one "cleaned for oxygen service", i.e. NO grease! The type is going to depend upon the application.

Give more info, and you will probably get more specific answers. Is this going to be used as an isolation valve (on/off service), or is it going to be used as a modulating valve?

If it will be used as an isolation valve, the type doesn't matter so much; you just have to make sure that it has a good shutoff, and the seals are made of a material that won't degrade due to the oxygen. If it is a modulating valve, then the same is true, but you also have to consider accuracy. A full port, equal percentage V-ball would be my choice. Others may differ on that point.

Your best course is to contact your valve rep and get a recomendation. They are used to dealing with such requests, and will know what materials and prep needs to be done.

I would also question the mettalurgy of the body,ball etc.

Depending on the pressure I have seen both Stainless steel and Monel being specified.

Oxygen service valves are usually made of monel, and they should not only be degreased, but should be cleaned, then bagged and also tagged accordingly.