Equipment Service - Gantry

All un-insulated electrical contacts, including the slipring, have secondary covers in place to protect service personnel from accidental contact. Removal of any secondary cover exposes service personnel to potentially deadly voltages (see Figure 1).

All secondary covers must be in place before primary covers are installed and during routine service.

Figure 1. CT Gantry Slip Ring Platter Covers

Un-insulated high voltage areas in the brush-block area include:

• High voltage DC for X-ray generation. Only measurement equipment isolated from ground can be used to measure HVDC on this system. Use of grounded measurement equipment can result in serious personal injury and/or equipment damage.

• 120VAC for power supplies.

If a secondary cover can be removed and it potentially exposes a service person to an uninsulated electrical hazard, a warning label is applied to or near the secondary cover. In the gantry, voltage hazards in excess of 120VAC have been labeled. However, the 120VAC present in the gantry also is capable of causing electrocution. See Figure 2 for some of the label types used in the gantry.

Figure 2. Gantry Electrical Hazard Lables

Special warning labels for a limited-access hazard are visible when the left-side cover is removed. See Figure 3.

Figure 3. Limited Access Warning Label

LAMPS & LEDS

There are a number of lamps/LEDs on the Service Switch Panel that indicate the functional state of the gantry. See Table 1 for a functional description.

The descriptions in the above table apply when the associated LED is lit.

A number of features have been provided as means of disabling hazards at particular points in the gantry, for ease of service. This and the next few sections will describe these features.

The E-Stop and Service outlets are located on both sides of the gantry on the stationary frame. The E-Stop is identified as a large red push button. The Service outlets are standard duplex 120VAC outlets. These are provided for ease of using AC powered test equipment near the gantry without requiring extension cords.

Figure 4. Gantry E-Stop and Service Outlets (Left Side of Gantry)

The service switches and circuit breakers described hereafter are not to be relied on as personal protection devices. They do not replace tag and lockout of main power to ensure personal safety. Switches and breakers are intended to only inhibit particular system functions and equipment operation. They do not eliminate or remove the electrical or mechanical hazards that exist. Because hardware can fail and defeat the functionality of these devices, only Lockout/Tagout ensures protection from unattended gantry rotation and electrocution. Be aware that not all power is removed on the gantry by use of these switches.

The Service switches are located on the right side of the gantry on the stationary base just above the rear cover cam latch. UP (enabled) is the normal operational position for these switches. The primary service safety switches are located across the top of the service switch panel.

Figure 5. Service Switch Panel Location

Power pan includes two parts (Simplified 120VAC Power Pan and Simplified HVDC Power Pan), located at the gantry base.

Figure 6. Power Pan

The gantry’s internal E-Stop performs the same function as the E-Stops mounted to the console and the gantry covers. See Figure 4.

Inside the Gantry are several hazards that can cause personal injury from:

• moving assemblies (rotational and tilt)

• assembly weights (tube and covers)

• chemicals (slip ring brush dust and oils {Tube, HV Tank and Tilt Drive Hydraulic Oil})

• heat sources (tube)

To prevent assembly and part separations from the rotating assembly, all fasteners must be torqued to their proper specification, using a calibrated torque wrench. The torque specification for a fastener is specified in its associated replacement procedure. For further information on torque, including a conversion factor chart, refer to Torque Wrench Information.

To prevent un-commanded or unintended motion of the rotating assembly, the rotational lock must be engaged anytime the rotating assembly is serviced.

Figure 7. Rotational Lock Assembly

The rotational lock is located on the rear right side of the gantry, near the top. It is positioned directly across from the teeth in the rotational assembly. To operate the lock:

• To Lock the gantry rotation, turn the handle clockwise until the teeth on the lock fully engage the teeth on the rotating assembly. If necessary, rock the rotating assembly slightly to align the teeth. Hand tighten until snug. Do not over-tighten. Visually verify that the teeth are engaged.

• To unlock the gantry rotation, turn the handle counter-clockwise until the lock is fully retracted away from the gantry teeth and the handle can no longer be turned counter-clockwise.

(For Performix Plus_LB Tube Only as below)

warning SEVERE PERSONAL INJURY MAY OCCUR. GANTRY ROTATES WHEN CAUTION MESSAGE IS CONFIRMED. WHEN you SEE THIS POPUP MESSAGE, MAKE SURE no personnel are CLOSE TO the GANTRY WHEN GANTRY COVERS ARE REMOVED.

notice Property damage may occur. Liquid Bearing (LB) rotor start/stop requires gantry rotation. If operation needs gantry rotation, please make sure there is no physical obstruction in the rotation track and the gantry lock pin is unlocked. If not, it may impact liquid bearing tube life.

Be careful when performing replacement or troubleshooting processes with a Liquid Bearing tube as the gantry will need to rotate in some conditions. Pay attention when you see the above popup message. To allow tube rotation, make sure the path of the rotation is clear and all personnel are away from the gantry before selecting Confirm.

warning Crush Hazard Use the appropriate procedure for hydraulic component replacement Do not use this procedure when replacing or servicing the Gantry Tilt Hydraulic Cylinders. The appropriate method for safely inhibiting gantry movement for that procedure is defined directly within the steps of the replacement procedure.

1. Position the gantry at zero degrees. Start on one side.

2. While holding the bracket in place (see Figure 8), secure the bracket to the stationary frame at locations 1 and 2. [Note: The two tilt brackets are identical.]

3. Next, secure the bracket to the pivoting frame at location 3.

4. Repeat these steps on the other side.

Figure 8. Tilt Locking Bracket (Right Side)

When the brackets and associated hardware are not in use, store them in the top compartment of the PDU.

Whenever the x-ray tube is removed or installed, a tube hoist must be used. With the help of the tube hoist, one (1) person can change an x-ray tube.

caution Potential for injury to service personnel. Service task requires personal evaluation. Proceed with an evaluation of how best to approach this service task. Apply ergonomics principles where necessary. Understand your physical limits with regards to the task and seek additional help if required.

The front and rear covers are designed to be safely removed by one (1) person, using the cover dollies supplied with your system. Because the weight of these covers could cause injury, these cover dollies must always be used. Both the installation manual and enclosure replacement procedures describe how to assemble and use cover dollies.