Pipeline pumps must be located outside the tank farm area, so that other tanks can be emptied to another location in the event of a fire. The separation distance is too far to get sufficient NPSH to the pipeline pumps, exactly as 1gibson said above. Can pumps are best when product vapor pressures are high (hot gasoline, etc.), due to their low NPSH requirements. Horizontal pumps will work for lower vapor pressure products (typically crudes, jet fuels and diesel).