Cryomech CPA289C, Инструкция по установке и эксплуатации

Страница: 47 / 64

Operation
7-2
7.2 Normal operation behavior
7.2.1 Normal pressures
On startup, a pressure differential should be noticed immediately between the high and low
pressure gauges. This differential will decrease as the cold head temperature decreases.
The typical pressure differential is approximately 220 psi to 250 psi (15.2 bar to 17.2 bar) with
a range of 5 psi to 10 psi (.34 bar to 0.7 bar) on the pressure gauge needles.
7.2.2 Normal sounds
When operating properly, the cryocooler will emit a rhythmic sound (squeak or chirp). This
noise is an indication that there is proper flow of helium gas within the system
7.2.3 Cool down time
Refer to Section 5 for the cool down time of an unloaded cold head with no additional mass
on the heat exchanger(s). If the cold head is exposed to a heat load or additional mass is
attached, the cool down time will increase
7.2.4 Normal temperatures
Refer to Section 5 for the minimum no load temperature rating of the cold head.
This temperature will vary depending on the quality of the vacuum, the quality of the super
insulation, and the heat load brought in by the instrumentation leads.
7.3 Use of the PLC
Status and error messages will be shown on the PLC screen. The status messages, error
messages, and set points at which error conditions will occur are listed in Section 7.7.
The screen normally shown on the display is referred to as the run time screen. The messages
described in Section 7.7 are displayed on the top line of the run time screen. The bottom line
displays the number of hours the helium compressor package has run.
Please refer to the CPA User Guide (separate document) for detailed instructions on the
capabilities of the helium compressor package display panel.
7.4 Shutdown procedure
Press the helium compressor package OFF button on the front panel of the helium compressor
package, this will switch off the system. Switch off the front panel mounted circuit breaker to
remove power from the helium compressor package’s electrical panel
7.5 Recommended routine procedures
Cryomech, Inc. recommends keeping daily logs of system temperatures and pressures to
detect changes in performance. This can include ambient air temperature, in and out cooling
water temperatures, helium temperature and, high and low helium pressure fluctuation in
performance could signify a problem that requires attention.
7.5.1 High and low pressure
Changes in the high and low pressure readings on the helium compressor package gauges
are used for diagnosing several different types of problems. It is important to know whether
changes are sudden or gradual and to know how the high and low pressures are changing
relative to each other.
The high and low pressures should be monitored daily.