Stanier - hollow jet valves (Howell Bunger Valves) are usually used as high pressure outlet valves cavitation is avoided by discharge to atmosphere and aeration at the rim of the valve. There are several manufactures in business. (eg Alstom, Rodney Hunt etc. ). But, you need a stilling basin downstrwam of the valve (USBR have a standard design) and this can be costly. There are probably several better valves for your application, giving lower overall costs, such as submerged discharge valves. It depends on the range of head loss that you are trying to accommodate. An in-line needle valve with an anti cavitation gage or sleeve valve will likely give you a lower cost solution. If you can locate the valve in a depression in the pipeline to provide a back pressure and reduce cavitation then you can reduce costs even more.