Pressure at the downstream of valve in case of water hammer reduces to vapor pressure as the valve shuts down. As such the pressure difference between the adjacent elbows of the run would be (Operating pressure-Vapor pressure) hence, hammer force might be calculated as:

F= (DLF) x K x (Operating pressure-Vapor pressure) x (Cross sectional area of pipe)

But I doubt, what would happen in case of steam hammer as the medium is already in gaseous phase