1. The problem statement, all variables and given/known data A valve is required to regulate the flow of natural gas. Details of the gas are given in table below. It can be assumed that the pipe size and the valve size are the same [i.e. piping geometry does not have to be allowed for]. The chosen valve type is the V250 rotary ball valve by Fisher Controls International I have this data sheet, it the chart it gives values for Cv, Kv, Fd, Fl, Xt 1) Determine the required valve size in inches from the range of sizes given in the data sheet [the data sheet gives a range of nominal pipe sizes (NPS) in inches]. 2) Estimate the percentage the chosen valve would have to be open to carry the required flow. required volumetric flow rate = 2.8x10^6 litre per min Density (@STP) = 0.724 kg/m^3 Specific heat ratio (y) = 1.31 inlet pressure = 20barg outlet pressure 6barg inlet temp 20degC 2. Relevant equations Kv=qm/31.6YSQRT(xp1P1) .........1 where kv is valve coefficient qm is mass flow in kg/h Y is expansion factor p1 density P1 inlet pressure Y=1-(x/(3FyXt)) ..........2 Fy = y/1.4 3. The attempt at a solution So, I think here I have to find the value of Kv, then use that to size the valve on the sheet. So to satisfy equation 1, I must find Y the issue is I am not given Xt. Xt features on the valve chart, so how can I specify this? Or am I off in the wrong direction?