Detector Collimator Unit Replacement - Merc40

Prerequisites

Table 2. Tools and test equipment
Item	Quantity	Effectivity	Part number	Manufacturer
FE torque wrench kit	1	-	46-268445G1 or 5135228 or equivalent	-
5 and 6 mm Hex end sockets	(Field Supplied)	-	-	-

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.

Table 6. Required conditions
Condition	Reference	Effectivity
This procedure requires special technique and experience, do NOT work only field engineers.	-	-
Only trained service personnel should service the GE CT Scanner.	-	-
Static strap and monitor must be used when working inside the detector.	-	-

Overview

This procedure defines the necessary steps to Remove and Install the Detector Collimator Unit.

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.

Cover the Tube Collimator port to protect it against dropped tools or screws. (Cloth or any other available item)
Remove the Air Plenum as shown in Detector Air Plenum Removal/Installation.
Remove 3 detector modules (one is over the collimator unit and the others are on both sides of it) as shown in Detector Module Replacement.

Figure 1. Collimator Unit
Remove 4 long screws holding the collimator unit to the collimator rails. Aluminum tape needs to tear off.

Figure 2. 4 Long Screws
Hold both guide pins of the collimator unit, and carefully pull up the collimator unit.

Figure 3. Collimator Unit Removal

To prevent damage to collimator unit, do not touch the sides of collimator unit.

Hold both guide pins of the collimator unit, and put it on the collimator rails.

Collimator has its direction of top and bottom. Align the direction of top to gantry front.

Figure 4. Collimator Unit Installation
Push the collimator unit against the rear collimator rail, and tighten the 4 screws to fix the collimator unit to the collimator rails.

Table 7. Screw torque of collimator unit
2.3 N-m 1.7 lb-ft 20.4 lb-in 23.5 Kg-cm

Figure 5. Collimator Unit Fixing
Install the 3 detector modules as shown in Detector Module Replacement.
Check Aluminum tape condition. If Aluminum tape has been peeled off at the edge of carbon window, attach Aluminum tape to the area (Aluminum tape is provided with the FRU kit).
Install the air plenum as shown in Detector Air Plenum Removal/Installation.
Remove the cloth or any other item from the tube collimator port.

Make sure the Axial Drive, HVDC and 120 VAC switches on the gantry’s Service Switch Panel are OFF.
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.