Ink handling systems: pumps, filters, and temperature management

Ink agitation refers to the process of stirring or mixing ink to ensure a uniform consistency and prevent settling or separation of its components.

Inks used in rotogravure and flexographic printing are “thixotropic” in nature. When kept in a stationary condition, the inks tend to thicken as against when agitated and circulated where they tend to thin out. It is just like a ketchup bottle – when the bottle is shaken, the ketchup tends to come out quickly as against trying to pour the ketch up from a bottle which was at rest for quite some time. Hence there is a continuous need to circulate ink between the print deck and the ink tank.

Valflow centrifugal pumps are best suited for ink circulating application as they help mixing and agitation of the ink and give an impeccable flow.

Valflow ink pumps require very low maintenance like cleaning the impeller once in a while. Standard operating and maintenance procedures are shared in our instructions manual.

Yes, you can order spares, accessories, and consumables separately.

Contaminants in the ink could be either metallic or non-metallic. Metallic contaminants are majorly the doctor blade worn outs which get into the ink through continuous circulation of ink between the tank and the tray. Non-metallic contaminants are generally in the form of undiluted pigments and dust in the air.

Valflow ink filters are very easy to maintain. The filter cartridge must be cleaned periodically depending on contaminants accumulated therein. However, a spare cartridge can be kept to quickly replace the dirty cartridge to ensure hassle free operation. Detailed operating and maintenance procedures are shared in our instructions manual.

The Valflow FC30 filter cartridge is non-disposable as it is made of SS. Only periodic cleaning is required. You may need to replace filter cartridge only if it is physically damaged.

Ink is a mixture of pigments and solvents. The solvents are volatile in nature and have a tendency to evaporate quickly. Solvent evaporation from ink in gravure and flexo presses occurs due to: • Rise in ambient temperature which triggers evaporation of solvents • Heat addition by film coming out of dryer getting in contact with ink • Friction between doctor blade and cylinder generates heat which is transferred to ink • Pressure of the anilox roll on the print cylinder generates heat The above factors also contribute to the increase in temperature of ink which promotes solvent evaporation.

Solvent evaporation: High temperature increases the rate of solvent evaporation. As the solvent evaporation increases, it results in, • Higher top up solvent consumption leading to increased operating costs • Under high temperature ink tends to thin out prompting the operator to add more fresh ink to get the desired print shade. This increases ink consumption. • Due to continuous solvent evaporation, there is a high concentration of solvents in air resulting in strong pungent solvent odour in shop floor. Poor print quality: Under high temperature, the ink in the gravure cells on the print cylinder tends to dry quickly before getting transferred onto the film. This causes missing dots resulting in poor print quality.

Valflow ink temperature stabiliser (ITS) is a shell and tube type heat exchanger. The warm ink passes through the inner tubes and chilled water circulates in the outer shell. The temperature of ink is continuously monitored by a temperature sensor. As the temperature increases more than the set value, the temperature controller operates a solenoid valve connected to the chilled water line. As the chilled water flows into the ink temperature stabiliser, the warm ink loses heat to chilled water.

By maintaining the ink temperature, solvent to pigment ratio can be maintained and hence the viscosity can be controlled to an extent. Since solvent evaporation happens even at an ink temperature of 25o C, viscosity variation happens even at this temperature. Hence it is suggested to install a Valflow ink temperature stabiliser and later install a viscosity control system if required.

No. Valence doesn’t supply chiller along with the Valflow ink temperature stabiliser. Valence can help with identifying the technical specifications of the chiller required for this particular application.

The maintenance of Valflow ink temperature stabilisers is very easy. The heat exchanger needs to be cleaned periodically. Also, it is necessary to ensure the usage of clean demineralised water in order to prevent the choking of solenoid valve. Standard operating and maintenance procedures are given in our instructions manual.

It is observed that by using Valflow ink temperature stabiliser, there is a saving of approximately 25 to 30% in the top up solvent consumption. These systems offer a very attractive payback of about 9-12 months.

Since printed web goes through heating process at each colour station, it is recommended to install one ITS per station.