Injection molding machine

Plant specifications:

  • Year of construction 2002
  • Clamping force: 31.500 kN
  • Oil type: Mobil DTE 25
  • Tank capacity: 6,000 liters
  • Cycle time: 98 to 120 seconds
  • Number of cycles: 720 to 881 per day

As a preventive measure against condensation water damage, GIEBEL adsorbers of the type DUO-VARIO 560-PA were installed on several plastic injection molding machines with servo hydraulics in May 2014. Not only the high purchase and maintenance costs of the system, but also the high number of cycles and thus the load of the hydraulic oil with humid air have prompted to implement this measure. The results speak for themselves and illustrate the added value of an aeration dryer on hydraulic units. The water content in the oil has fallen continuously after the adsorber has been used.

Examination date03.07.201424.07.201425.08.201418.06.201516.09.2015 20.10.2015
Oil changednonononoyesno
Silicon (Si [mg/kg])111165
Water K.F. [ppm]425409376347193167
Purity class (ISO 4406)15/14/1016/14/1214/12/1018/17/1317/16/1218/16/13

Table 1: Extract from laboratory reports to illustrate the development of the water content.
Adsorber mounted om May 20th 2014

The reason for sustainable oil and air drying in the tank is based on two effects:

Follow-up flow of dry air.

With each inflow of fresh, dry air, the internal tank air and the water molecules it contains are homogeneously mixed. This causes the humidity in the tank to drop permanently. The steadily drying air removes moisture from the oil by equilibrium excitation, but slowly. The drying of the internal tank air takes place quickly with a high number of cycles and is clearly visible in the water content of the laboratory reports.

Active drying of the air inside the tank

Silica gel has a highly hydrophilic surface and strongly attracts polar substances such as water (H2O). As a result, even when the system is not in operation, the moisture inside is adsorbed by the silica gel, thus drying the internal air. The adsorbers of the VARIO series are used as aerators and deaerators. This means that every time the cylinders are retracted, the air is forced out into the environment by the silica gel. If this air is dry, the silica gel is partially regenerated and the service life of the adsorber is extended many times over. However, if this air is moist, active drying takes place and thus discoloration of the adsorber from above (air flows out of the system into the environment). This can be seen very clearly when the adsorbers are used on the plastic injection molding machine.

Adsorber during assembly
Date: 20.05.2014

Adsorber nach 675 Betriebsstunden
Datum: 24.06.2014

Verfärbung im oberen Bereich.
Feuchtigkeit kommt aus dem Inneren des Tanks und wird damit getrocknet.

Im unteren Bereich des Adsorbers ist noch keine Verfärbung zu sehen.

Summary & added value

  • Water content in hydraulic oil is constantly low, even after oil change
  • Adsorber provides protection for the hydraulic unit against renewed entry of atmospheric moisture, thus reducing the risk of condensation water damage
  • Discoloration of the adsorber indicates active drying of the internal tank air
  • Existing internal air moisture is also permanently adsorbed and removed from the tank