Plenum Fan Replacement

Prerequisites

Table 5. Safety

CRUSH HAZARD.
UNEXPECTED GANTRY ROTATION CAN CAUSE SERIOUS INJURY.
Never service the gantry with the axial drive enabled. Use the gantry rotation lock to lock out gantry rotation. See safety menu of Service Document gui for appropriate procedures.

Overview

This procedure defines the necessary steps to Remove and Install the Plenum Fan Assembly.

Move table to home position, fully out and down.
Remove right side gantry cover.

Refer to Parts Replacement → Gantry → Enclosure → (Cover Removal Procedure).
Stop the rotor of X-ray tube in case of Liquid Bearing Tube before HVDC off. Refer to Liquid Bearing Tube Rotor stop procedure for details.
Turn OFF the Axial Drive and HVDC switches on the gantry’s Service Switch Panel.
Position the detector at 12 o'clock and lock gantry rotation.
Turn OFF the 120 VAC switch on the gantry’s Service Switch Panel.
Remove the gantry left side cover, top covers and front cover.

Disconnect a fan cable connector from the fan assembly.

Figure 1. Fan Cable Connector
Remove 4 screws holding the fan assembly to the plenum.

Figure 2. 4 Screws
Press the fluke (hook) on the safety pin to unlatch, and remove the fan assembly.

Figure 3. Plenum Fan Removal

Position the new fan assembly, and fix it to the plenum using the 4 screws.

Torque the M5 screws to the value shown in Table 7.

Table 7. M5 Screw Torque
4.6 N-m 3.4 lb-ft 40.9 lb-in 46.9 Kg-cm
Connect the fan cable connector.
Turn on the 120 VAC service switch at the service switch panel. Check to make sure all 3 fans are running. Use a piece of paper or similar object to make sure fans are pulling air into the plenum. A fan that is not running will still have the fan blades moving as air is pushed back out of the plenum through that fan port.

Turn off the 120 VAC service switch, release the gantry rotational lock and install gantry covers, all except the right side cover.

Refer to Replacement → Gantry → Enclosure → (Cover Removal Procedures).
Turn on the 120 VAC, HVDC and Axial drive service switches.
Install gantry right side cover.

If any calibrations were run with a fan not working (Fastcal or Detailed Calibration), those calibrations will need to be run after repair is complete.
Perform the Quality Assurance Test.
Perform a [Save State] operation if Detailed Calibrations were performed.