Packed thermal oil boiler also called skid mounted thermal oil heater, the difference of normal thermal oil boiler as follows:

 
Shape: Boiler shape is the same, but packed thermal oil boiler is packed together and no need boiler pipe installed at site, it is a whole set. While the normal thermal oil boiler is installed by several pieces at site.
Shipment: Packed thermal oil boiler is difficult for shipment; the capacity in 3500kw can be shipped. Normal boiler is easy to ship. And shipping cost is cheaper.
Installation: Packed thermal oil heater can use directly after connect the user equipment, but the normal heater needs to install on site, some countries which labor cost is expensive is not economy. And it need professional person to install.
Price: Price for normal thermal oil heater is cheaper than the packed one, because the packed boiler has some more pipes and valves, however the normal one haven’t.
Size: Packed boiler has compact structure and small footprint. However, the normal one need more area.