Mechanical seals, or sealing rings of mechanical seals respectively, are very sensitive to dry operation, i.e. without being flushed with a cooling medium. The cooling medium can be drinking or process water, or even steam, which must be transferred to the seal before the pump is turned on.

Only 2-3 seconds of dry operation are long enough to cause permanent damage to the sealing rings. Rings in such an operation are damaged by the heat and lose their ability to seal which leads to outflow of the pumped medium from the seal. The only possible remedy to such a situation is to exchange the sealing rings.

In order to avoid damaging the sealing rings by using them in dry operation, the control unit ASP 21 is included in the supply circuit of the pump (electric motor) and an armature is connected to the supply of the cooling medium to the seal.

When running the pump, ASP 21 first opens a solenoid (magnetic valve) cooling medium in the seal. Subsequently, a contact pressure gauge measures the pressure of the cooling medium entering the seal. If the pressure of the cooling medium is within the preset range, the electric motor of the pump will be turned on.

If the supply of the cooling medium fails, the contact pressure gauge notices the decrease in the pressure of the cooling medium and the pump will be turned off automatically which is visually indicated on the control panel of the control unit. The control unit is equipped with an outlet for connecting to external signalling. Once the cooling medium with the right pressure is being fed into the seal again, the pump will be turned on.

After the electric motor is disconnected from the power supply, the inflow of the cooling medium into the seal will be automatically closed.