Trunnion mounted or floating ball valve - Valve engineering - Eng-Tips

Hi people,
I'm familiar with design of ball (floating and trunnion mounted)valves. But, how can I decide which one should be used in specific situation? Which factors have main significance for such consideration?
Student Thank you Hush!!
I think both these valves are covered with API Spec 6D, but I don't have one. Where is the border between these two valves regarding the pressure and the ball size? Essentially they are used to prevent backflow. As an example they are used on wellheads where injection of steam or other fluid into the wellbore is required. The check valve prevents any wellbore fluids from flowing back into your injection line.

I have been asked to work on some trunnion valve requirements by my company. All our valves are with internal trunnions i.e. the trunnions are machined out of the ball casting/forging. In case of external trunnion this is not done and are relatively cheaper.
Can some one help on how the choice between either is done irrespective of rating part. My valve ratings are #150 & #300 with API 6D design.
ksg1,

I am not quite sure I understand your question correctly! Does your internal trunnion also have integrated trunnion blocks, that is no lower trunnion penetrating the body?

Any valve construction done after API 6D, and tested accordingly, will satisfy API 6D.

Apart from that any mechanical selecting process is of course and integrated anylysis of market/customers demands, technical solutions, production cost, maintaining cost and price/lifetime considerations.

Given more details and pointed questions it could possibly give you some tips, if you for instance are searching pros and cons for details in your construction, or tips on construction details.