Loader appears while using the slider revolution

Try adding the following lines in style.css:

body .tp-loader.spinner1 {
  display: none;
  visibility: hidden;
}

Just change the .spinner1 to the spinner number that is chosen in the Revolution Slider Settings.

Update:

The CSS for spinners are defined in the following location:

plugins\revslider\rs-plugin\css\settings.css

As you can see, the spinner selectors all have .tp-loader class:

.tp-loader.spinner3{
...
}

.tp-loader.spinner5{
...
}

You could try to directly edit that settings.css file to see if it works.