Image Processing - Removing grid lines from graph image

Hi,

I`m not very experienced with image analysis. I have some graphs like the one below and I`m seeking to automatically get tabular values for the lines. My main problem is getting rid of the grid lines to keep only the data lines in the graph so I can work with them. I did some searching and tried bothat and hough transformation but did not got good results, probably for bad use of the filters. Anyone can provide some guidance?