When liquids are flowing through straight sections of pipes, friction is lost as a result of the internal forces of the viscous fluid. The friction losses depend on the pipe diameter, viscosity, speed, pipe type and are proportional to the length of the pipe. Additional losses arise from deformation of the velocity field due to a change in the pipe profile, direction etc. and these losses are referred to as local losses. The total losses are then equal to the sum of friction losses and local losses.
Due to their optimal stopping dimensions, the original construction of plastic FV PLAST ball valves use balls with only slightly smaller diameter of the closed hole than the inside diameter of the pipe. The new design of the plastic ball valves offers an inside diameter of the ball equal to the inside diameter of the pipe.
The following charts show similar pressure loss characteristics of both valve constructions compared to the loss in pipes without a valve and with a straight-way valve.