Your question is vague; however, I will make an assumption based on where you posted this question.
Do you need to size a fuel oil line from a tank to a boiler or furnace?
You will need to look at the requirements of the fuel pump to size the line. Take a look at the technical info at suntecpumps.com. They have some information for the piping requirements for their pumps. The fuel oil piping requirements often are included with the boiler/furnace installation manual.
Are you sizing for a day tank with a gravity overflow back to the bulk storage tank?
Are you sizing lines for inner-tank transfers for multiple bulk storage tanks?
Give a little more information and someone should be able to give you the information you need.
The website has many useful charts and information. They also have some simple software and a VERY valuable design guide that accompanies it "DESIGN CONSIDERATIONS for OIL SYSTEMS SIZING". It has been my experience that their reps are also able to help you answer mostly any question, either through their own experience or through contacting the factory.
CRG
I will not use a Tiger Loop in industrial systems. You should not eliminate the return on industrial systems, otherwize the recirculated oil will keep on heating up as it gets pumped and repumped by the burner pump to the hot burner. Returning the fuel oil to the tank would cool it down.
