Cryomech PT415, Инструкция по установке, эксплуатации и текущему обслуживанию

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Specifications
5-4
Section 7 for further detail. The safety devices listed below are not monitored by the
compressor control panel.
High-Pressure Relief Valve
The compressor package high-pressure relief valve is set at 420 ± 5 PSIG (29 ± .34 bar) .
At pressures above 420 PSIG (29 bar), the relief valve will open automatically and
relieve pressure to the atmosphere.
Internal Motor Overload Switch
A motor overload switch, located inside the compressor module, protects the system by
sensing excessive current draw and temperature. This switch automatically resets itself
after the compressor module cools to an acceptable level.
Cold Head High Pressure Relief Valve
The cold head high-pressure relief valve is set at 425 ± 5 PSIG (29.3 ± .34 bar) . At
pressures above 425 PSIG (29.3 bar), the valve will open automatically and relieve
pressure to the atmosphere.
5.3 Description of the Helium Reliquefier
It has been standard practice in the design of liquid helium dewars/cryostats to use the
liquid helium boil off to cool the cryostat neck, intermediate radiation shield, current
leads, insert assembly, and other components of the cryostat that connect room
temperature to the liquid helium. This practice is necessary to the overall efficiency of
the cryostat. The Reliquefier condenses the helium boil off after it leaves the cryostat
and then re-fills the cryostat through the existing fill port, turning the open cycle cryostat
into a closed cycle system with no helium leaving the system.
The Pulse Tube Cryorefrigerator supplies the cooling to liquefy the helium. The complete
cryorefrigerator consists of two major components: the Helium Compressor Package and
the Pulse Tube Cold Head. The Helium Compressor Package supplies high and low
pressure helium gas to the Pulse Tube Cold Head. The High Pressure helium is
expanded inside the Cold Head to the low pressure, dropping in temperature to below
4K. The heat load can then be transferred into the Pulse Tubes 4K heat exchanger and
returned to the Compressor Package, where it is removed into the cooling water. Two
flexible stainless steel lines and a motor cord connect the Pulse Tube and the
Compressor Package.
The Pulse Tube Cold Head is mounted into a vacuum insulated condensing chamber,
referred to as the Reliquefier Main Assembly, as shown in Figure 5-3. The room
temperature helium gas/vapor returning from the cryostat dewar enters into the
condensing chamber through the KF16 flange on the Reliquefier Main Assembly. As the
warm helium comes in contact with the Cold Head, its heat is absorbed into the heat
exchangers on the Pulse Tube. This reduces its temperature, increasing its density,
dropping it lower inside the condensing chamber; until it contacts the 4K condensing
surface, where it condenses.
The Liquid helium is funneled into the Liquid helium Return Line which connects the
bottom of the condensing chamber to the cryostat.
The return line is delicate and
must be handled with care.
Other components of the Helium Reliquefier are a temperature controller, electrical
feedthrough, silicon diode, and heater assembly as well as a pressure relief valve and a
vacuum port.