Flexography and rotogravure

In the flexible packaging and printing industry there are two types of rotary machines that require a thermal oil heating process: flexographic and rotogravure machinery.

In both cases, thermal fluid boilers are used to dry the printing inks from the coils of polyester, polypropylene or other plastic material.

The thermal fluid is heated in the boiler by the combustion of gas or diesel. The thermal fluid is transported to the printing machine by the recirculation pump. Usually, this has several independent heating zones where the drying temperature can be selected. In each of these independent drying zones, there is an oil-air heat exchanger, like a unit heater. A fan sucks in air at room temperature and expels it as hot air, after it has passed through the heat exchangers consisting of finned tubes through which hot thermal fluid flows. An air temperature probe, a 3-way valve and a temperature regulator complete the control loop.

It is common in this type of machine for a certain amount of heat recovery; i.e. a recirculation of hot air by a certain percentage to increase the efficiency of the system.

In this application it is usual to find quite lengthy thermal fluid circuits. Consequently, the thermal oil system must be designed properly, bearing in mind that it is intended for future expansion, both in terms of printing presses and the number of boilers.

The drying capacity of the system as well as the power of the thermal oil boiler are determined according to the type of material, the ink to be dried and the printing speed.

Pirobloc has extensive experience in the printing machinery sector. Our thermal fluid solutions are highly adapted to the needs of this sector and have demonstrated great efficiency and reliability in the many facilities they have been used in.

The following image shows the classic scheme of the thermal oil circuit with a boiler and pump.