friction loss in weld clad pipe

[mathias28]

I need to calculate the friction loss in a flow loop made of 4" ID weld clad pipe. As the inner surface is not machined after cladding, anybody knows how to estimate fricton loss in such irregular surface?
I have just two bends and one gate valve, as this line must be piggable.

The clad is made by TIG process. Pipe Material is API X70, clad material is Inconel 625. The fluid is produced oil and water at 76ºC.

Thanks