Design requirements for the main circulating pump of the electrophoresis tank

With the popularization of electrophoretic paint, electrophoretic coating lines have been erected one after another.
However, in the supply of many electrophoretic paint equipment, technically professional and experienced suppliers often have higher construction costs, and equipment manufacturers who have just entered the industry have low prices.
Intervention, because it is not professional enough, there are often defects in the design of many details.
The electrophoresis line equipment process determines the quality of the paint film.
If the congenital deficiency is difficult to make up in the future, it must be paid attention to
.

The main circulation system is mainly composed of pumps, valves, filters, pipes, nozzles,
etc.
In order to keep the bath liquid uniform and prevent precipitation, the electrophoresis tank must be equipped with a main circulation system and the pump should run continuously for 24 hours.
If the fault stops, it needs to be repaired immediately.
The stop time should not exceed 2 hours to prevent the tank liquid from precipitation and cause pipeline blockage and poor coating
.

The flow direction of the electrophoresis bath is consistent with the direction of the workpiece
.
The flow rate of the electrophoresis liquid is generally 2~4 times of the running speed of the workpiece; the flow rate of the liquid surface is not less than 0.
2m/s; the flow rate of the bottom of the tank is not less than 0.
4m/s; Only then can the solids of the electrophoresis liquid be prevented from precipitating in the pipeline, which has strict requirements on the selection of the size and quantity of the circulating pump
.

Types of circulating pumps

In the electrophoresis tank liquid circulation system, horizontal or vertical centrifugal pumps are generally used
.
The split horizontal type requires the use of double mechanical seals and liquid sealing equipment needs to be added
.
Usually, clean ultrafiltrate or deionized water liquid seal is used, the pressure is 3~5kgf/cm, and the rotation speed of the pump is 1450-1470r/min
.
The vertical pump is usually installed on the auxiliary tank, and the suction port of the pump should extend not less than 1.
5 times the pipe diameter from the bottom of the tank to minimize the eddy current and maximize the evacuation of the tank liquid when cleaning the tank body
.
All pumps shall be fitted with protective devices to prevent foreign particles from damaging the impeller and pump casing
.
Vertical pumps are equipped with a double-layer removable steel mesh installed on the pump head (suction port) and coated with an insulating coating
.

Why not use a high speed circulating pump?

① High rotation speed will cause the local temperature of the tank liquid in the pump to be too high.
Long-term operation will lead to the easy aging of the coating resin.
Different chemical components in the resin will be separated and precipitated.
Shrinkage and other problems, while the physical and chemical properties of the paint film are significantly reduced
.

② The high shear force of the rotating speed increases, and the high shear force easily causes the emulsion particles of the paint to be demulsified, and the inorganic pigment and filler components are peeled off and precipitated from the organic resin components.

.

 The author of this article: Li Shanhai, Haolisen Application Engineering Center