A collegue told me that Lift Plug valves are, in some processes, good alternatives for ball or gate valves as they are full bore, pressure tight and do not wear whilst being turned. I know it is hard to determine how pressure tight a valve is in all conditions, but these are said to shut off better than gate valves.

Anyone experienced with these lift plug valves or knows in which industries/process they are commonly used? Most website argue their lift plug valves are applicable in all severe circumstances, which I think is not a complete unbiased statement...

I believe you are talking about double eccentric plug valves. The closing element 'plug' is a curved plug segment, closing the full bore opening in shut position. Spindle is positioned sligtly off centre pipeline and off centre circle curve of inner housing wall. This will have a lifting and freeing movement of the segment in the first 2-3 degrees of opening turning, and by 90 degrees the element will give a full open port.

This is similar to what is happening in double eccentric ball valves. Except that here the the closing element is a full bore ball, with seat sealing ring mounted on the ball itself. In full open position the sealing is turned 90 degrees away from main flow, and the ball has both a full port and in addition a flow around the ball against the wall to get grit away.

The eccentric plug valve is a available on the market, althoug not that common, the use mainly restricted by sealing properties and cost. The soft sealings will have good and waterthight properties, when metal poorer.

Mostly other types of quality valves will be selected as 'good enough' and cheaper. The price of the valves will often be above other types of valves.

One segment of use is large valves for waste water with large gate valves or knife-gate valves as competitors.

The plug valve will cost considerably more, but will have (in top quality) a very long standtime.

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