When I replace a file on my website, Safari does not show the updated file.

I have a chart which presents current data. I generate the chart, then ftp it to my website, replacing the previous chart. When I show the chart with Safari, it shows the old chart. After a delay, the new chart will be shown but the delay is between 5 minutes and a half hour. Chrome shows the new chart immediately. Do I have to switch to Chrome? I have tried clearing the cache without any success. I have no extensions enabled.

I'm using FileZilla. It shows the updated file on the server and using view/edit it shows the current file. It seems to be just Safari that doesn't get updated.