• Topic ID: id_2011680
  • Version: 4.1
  • Date: Sep 23, 2019 3:48:38 PM

Doing a compressor pressure check

Do a check of the cryocooler compressor supply pressure.

Prerequisites

Personnel requirements
Required persons Preliminary requirements Procedure Finalization
1 - 5 minutes -
Safety

Before working in any GE Healthcare MR suite or performing any GE Healthcare service procedure, you must:

  • Have read and understood all hazard conditions and safety requirements in the latest revision of the GE Healthcare MR Service Safety Manual (5452735).
  • Have successfully completed all relevant GE Healthcare Environmental Health and Safety (EHS) courses (or for non-GE employees, equivalent workplace training courses).
  • Comply with all site-specific training and workplace safety requirements.

If you have any safety concerns at any time, do not begin work or immediately stop work and move to a safe location. Immediately contact your supervisor or site safety officer for instructions on how to proceed.

Procedure

  1. Make sure the cryocooler system is at equilibrium (coldhead at approximately 4.2 K from Magnet Monitor 3).
    note: Do not do a check of the operating (dynamic high-side) pressure if the cryocooler system is not at equilibrium (coldhead is not at approximately 4.2 K). It will not be accurate.
  2. Do a check of the operating (dynamic high-side) pressure of the cryocooler system and compare the pressure to the specifications below.

    Figure 1. Gauge for RDK-408A3 and RDK-408A2

    note: The supply pressure gauge displays static pressure when the compressor is off and high-side dynamic pressure when the compressor is on. The table below shows the applicable compressor operating (dynamic high-side) pressure range for the compressor and coldhead combination.
    Table 1 Acceptable compressor operating pressure range
    Compressor model Compressor operating (dynamic high-side) pressure, MPa (approximate)
    F50H and F50L 1.90 to 2.20
    CSA-71A and CSW-71D 2.00 to 2.20
    If the dynamic high-side pressure is within the acceptable range, the task is complete.
  3. If the dynamic high-side pressure is outside the acceptable range:
    1. Turn the cryocooler system off.
    2. Let the system stabilize.
    3. Do a check of the static pressure and compare the pressure to the specifications below.
      Table 2 Compressor pressure specifications
      Coldhead model Compressor static gas pressure at 20°C (68°F), MPa (approximate)
      RRDK-408 4K two-stage coldhead 1.60 to 1.65
      RDK-408, RDK-408A2, RDK-408A3 4K coldhead 1.60 to 1.65
      RDK-408T, RDK-400 1.45 to 1.50
      • If both the dynamic and static pressures are within the acceptable range, the task is complete.
      • If both the dynamic and static pressures are out of range, continue on with the next steps for Adjusting the static pressure on the compressor.