Eccentric Reducers!

I've never seen where they added a hole thru the gate! But I've seen where they add a hole thru the flapper on a check valve; I suspect the reason is the same. When there is a chance that you could trap a "slug" of liquid between to two stops (between two valves or a down stream of a check valve and a valve) and the temperature goes up, the trapped liquid expands and the pressure in this area goes up and could cause problems. To alleviate this issue you add a hole to avoid the thermo-stress in this section of line.

This is a steam line and the project I am currently working on is in the rotterdam region of holland, so it does not get "extremely" cold here but it can certainly get to -5 to -10 celcius in the winter.

Thanks again for your replies.