Reduce bore ball valve

Reduce bore ball valve

What is a reduce bore ball valve

Reduced bore ball valve is also called one piece ball valve, is relatively inexpensive and generally are throw-away.

When is a reduced port ball valve a better choice?

Considering that pressure/energy loss is almost always undesirable, and the fact that they're not easily pigged, why and under what circumstances would a reduced port ball valve ever be a better choice than a full port valve? A well defined problem is half solved.

Full port cost more, and lots of applications don't need them. Installations like domestic water service (especially commercial & residential), many compressed air lines, isolation valves for steam traps, etc.

The reduced port style might be less expensive in smaller sizes, especially if the manufacturers are using the same casting for both types of balls and simply machining a larger bore in those that will be sold as full port. Valves in the sizes of  12" and up, manufacturers would save money by using two different castings (one for boring full ports, one for boring reduced ports), thereby saving on initial material and subsequent machining costs. 

Reduced port ball valve is the normal choice because of its less cost as compared to full port ball valves.When less pressure drop is desired (but not very critical) then we reduced port ball valves. I have seen the full port valves normally in inlet of PSVs( here the minimum the loss the better).Ball valves can be used for control purpose as the flow and pressure drop can be set in the range from full to completely closed. Is this possible with venturi.And ball valves are not only for control thay are used as block valves also (very often in gas service).

When only considering pressure drop and the ability to pig the line, there is no benefit or justification to use reduced bore ball valves.  The diameter of the hole through the ball determines the required OD in order to have full contact around the seat when shut.  Usually, the diameter of the waterway is around 60% of the ball OD.  So, the ball OD for full and reduced port valves cannot be the same size for a given valve size.  Said another way, the ball OD for a 3 inch full port is much larger than a 3 inch reduced port valve.  Because of this, manufactures cannot not use the same castings for full and reduced port.  A larger body is needed to enclosed a full port ball, so there is more material, more machining time, heavier valve, more cost.  In addition, the valve operating torque is a function of the ball diameter cubed.  So a larger, actuator is need for the full port valve.  The weight of a full port valve with actuator can be up to 600% more than a reduced bore valve.  The cost goes along with the weight increase.

Because of the cost difference, significantly more reduced port valves are sold than full port (by a factor of around 3:1).  This fact says a majority of valve applications can live with the increased pressure drop.