PetroStreet

We are going to install a remote block valve at our natural gas transmission line. It would be a 16" line and ~ 15 Km long. What would be the minimum time to operate the RBV, from fully open position to fully close, to avoid any surge due to sudden flow stoppage. Can anyone direct me to the evaluation / equation for that.

Rough calculations can be made either using the Joukowsky equation, or more accurate ones using the method of characteristics. The pressure profile of the water hammer pulse can be calculated from the Joukowsky equation.
Instant valve closure; compressible fluid the maximum magnitude of the water hammer pulse is:
ΔP = ρaΔC,
where ΔP is the magnitude of the pressure wave (Pa), ρ is the density of the fluid (kgm−3), a is the speed of sound in the fluid (ms−1), and ΔC is the change in the fluid's velocity (ms−1).
For further details you should go through the following topic in wikipedia http://en.wikipedia.org/wiki/Water_hammer. For your reference an elaborative paper on the said subject is attached.