After importing the IGS file following the steps stated above, saving the file, it still is at 14Mb. After doing this you can then go through the steps doing the PLANTPARTCONVERT
Are you going to be using this valve multiple times or is it a one time use component. If you are going to be using this valve frequently, you WILL run into model size issues and performance issues. I highly recommend not using this for your modeling and instead build the valve in Plant 3D using existing valve components.
In 2013 you can use the IMPORT command. Just type it in the command line. A browser will pop up. Select IGES for the file type and browse to your igs-file. You don't need here the subscription advantage package.