Large cryo pumps (500mm - 1000 mm)
In optics, electronics and sensor technology, there are always cases where production coating systems have to meet particularly high vacuum requirements. A low water vapor partial pressure is usually the top priority here, but a low hydrocarbon level can also be important. These requirements can strictly only be met with cryogenic pumps, possibly in combination with a Meissner trap. For larger plants, cryogenic pumps of the 10,000 l/s class with 500 mm flange are often required.
Cryogenic pumps of this size often suffer from the fact that the cold head used is actually undersized. This makes the pump thermally sensitive, which is particularly evident in reactive processes with permanent high gas loads due to a corresponding temperature rise of the second stage. Even a brief gas surge, as always occurs in everyday production, can lead to an impermissibly high temperature. Normally, the maximum permissible temperature of the second stage is limited by the plant control system to 20-22 K in order to avoid an unintentional release of the lightest gases H2 and He. Such an unintentional release is basically a risk and must therefore be avoided. In such a case, the system control normally aborts the process and allows the cryopump to cool down again without gas loading.
Recently, SHI-APD Cryogenics launched the CH-210, a cold head that surpasses all its predecessors in performance. Based on this cold head, HSR Kryotechnik developed the Velco-500A cryopumps. Its external dimensions correspond to those of the former RZP501 model from Balzers and it can therefore be used in its place without any problems. However, by using the powerful CH-210 cold head, the Velco pumps exhibit exceptional thermal stability. This makes them ideal for cases in which, according to the above, special requirements are placed on the cryogenic pump.
The Velco pumps are equipped with a Si-diode for temperature measurement. As an option, a suitable temperature monitor with the two adjustable temperature trigger points required for control is available. Furthermore, the Velco pumps are supplied with a heater for faster regeneration on request.