• Discovery MR750 3.0T System Service Methods
  • 5690009-2EN Revision 4
  • Object ID: 00000018WIA3008C030GYZ
  • Topic ID: id_12374703 Version: 1.5
  • Date: Nov 27, 2019 10:21:28 AM

Body Coil Air Flow Functional Check

Prerequisites

Table 1. Personnel requirements
Required personsPreliminary requirementsProcedureFinalization
1-10-15 minutes for Section 4.1; 60 minutes including Sections 4.1 and 4.2-
Table 2. Safety
Table 3. Required conditions
ConditionReferenceEffectivity

System software must be booted.

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About this task

Overview

This test checks the functionality of the body coil air blower system, which cools the patient bore wall surfaces by forcing air between the gradient coil and the RF coil Figure 1. Air enters the RF coil through two rear air ports; therefore, the rear of the RF coil needs to have an air tight seal (foam and gasket) in order to maintain a sufficient pressure head to force air to flow. This helps to transfer heat away from the bore wall with convection. If there is not air tight seal (foam and gasket) in the rear of the RF coil, there will not be enough pressure to force air through the space between the gradient and RF coils.

The system currently has a configuration according to the block diagram shown in Figure 2. Air is pulled out of the magnet room and travels through the penetration wall and into the heat exchanger cabinet (HEC). This air is then cooled and sent back through the penetration wall and into the magnet room. This cooled air then travels from the penetration wall, splits into two air hoses, and into the back of the RF coil through tubing in the body coil. At the front of the magnet are two air sensors that capture an average airflow measurement and relay the information back to the HEC display. This airflow requires a measurement of greater than 500 feet per minute (fpm) during scanning operations. If the airflow measurement is less than 500 fpm, refer to Troubleshooting Body Coil Air Flow.

Figure 1. Air Flow System
Figure 2. Input/Output for DVMR Cooling Cabinet
Topic ID: id_SL2273131-1126648

Checking Body Coil Air Flow

About this task

This procedure consists of taking readings from the HEC display on the heat exchanger cabinet and determining if an error is occurring with the air flow system.

Procedure

  1. Go to the heat exchanger cabinet (HEC) and view the display.
  2. Select the following buttons from the main menu display in order to view the air flow set point and feedback readings:
    1. Note:

      Select ESC multiple times to return to the main menu display.

      Monitor (F3)
    2. Blower (F4)
  3. Confirm that the air flow set point corresponds to a measurement equal to or greater than 550 fpm.
  4. Confirm that the air flow feedback corresponds to a measurement greater than 500 fpm.
    1. If the feedback is lower than 500 fpm, refer to Troubleshooting Body Coil Air Flow to troubleshoot the body coil air flow.
    2. If the feedback is greater than or equal to the Normal mode set point, the system is functioning properly.
Topic ID: id_SL2272801-1126648

Troubleshooting Body Coil Air Flow

About this task

The air flow fpm should always be greater than 500 fpm. In situations where the fpm falls under 500 fpm, follow the checklist for troubleshooting below. After each checklist task, look at the HEC control panel to see if the air flow fpm is 500 fpm or greater.

Procedure

  1. Note:

    If the air flow fpm is between 450 fpm and 500 fpm, the system will be able to complete a scan, but unable to initiate a scan. If the air flow falls under 450 fpm, the scan control system will automatically shut down.

    Verify that the farthest right blower variable frequency drive (VFD) display is reading 60 Hz.
    Figure 3. VFD Blower Display in HEC
  2. Check the hose connections at the top of the HEC.
  3. Check the air filter on the secondary penetration wall (SPW).
  4. Check the hose connections on the SPW from both the equipment room and the scan room sides.
  5. Check the hose connections at the rear of the RF body coil.
  6. Check that the connections are properly attached at the “Y” junction. This “Y” junction is in the cable tray splitting the 4 inch hose to two smaller diameter hoses.
  7. Check for any gaps between the rear end bell and the RF coil as well as the front end bell to the RF coil.
  8. Remove the right front cover to do the following (see Front Cover Removal and Installation):

    • Check the orientation of the sensors. The sensor head should be in the center of the cutout and the orientation of the sensor head should be perpendicular to air flow (i.e., the flat surface of the sensor should be perpendicular to air flow).

    • Check that there is no cable routing obstructing the air flow.

      Figure 4. Front End Bell Sensors

    • Check that the air flow sensors are completely below the edge of the front end bell. The bracket position can be adjusted without removing the front end bell.

      Figure 5. Sensor Locations
  9. Remove the front end bell to check the gap between the RF coil and the gradient coil. Ensure that nothing is stuck in between them.