The grass always seems greener on the other side. Trust me it isn't. There is a common message from everyone of us who has responded. You must give it some time. You are not going to be placed in the position that you want with zero ability. Learn what is offered and use it to better...
ANSI Classs 150 flanges are rated to 280 psi water pressure at ambient temp & 300 ANSI are rated to 740 psi water. They are correct tht the 150 & 300 designations are for steam applications. THe ASME steam tables do a good job with this. Crane Vavles Flow of Fluids has a lot of good info on...
Depending on whether you need a ball or butterfly valve there are fluoropolymers that are lined with PTFE blends that hold up well and have better properties than PTFE or PFA. Look at valves with Dupont NXT or 3M TFM.
depending on the size of the valve and the gear box that is the manual operator it could be adapted in the field as an option. Several time we have adapted an electric actuaotr to the gear when the vale was very large in order to reduce the size of the electric actuator.
For this application you might alos consider the BFVs with Nylon coated disc. They ususally hold up ptetty well over epoxy. Bray, Sure Seal, and Tyco make these types.