Discovery MR750 3.0T System Service Methods
5690009-2EN Revision 4
Object ID: 00000018WIA3036D630GYZ
Topic ID: id_19633183 Version: 5.2
Date: Feb 14, 2022 4:10:22 PM

Applying LOTO - PGR PDU/Gradient Subsystem

Prerequisites


Personnel requirements
Required persons	Preliminary requirements	Procedure	Finalization
1	-	10 minutes	-


Tools and test equipment
Item	Quantity	Part number	Manufacturer
RED Logout Tagout Lock with Each Lock Uniquely Keyed	1	5451778	-
Multi-Locking Device (if multiple service personnel are involved)	1	46-194427P313	-
Red Warning LOTO Tag	1	46-194427P322	-
Digital Voltmeter (DVM)	1	46-194427P284	-


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.

Warning

Electrocution hazard

High voltage present.

Use proper LOTO procedures before servicing and/or maintaining.

CAUTION

Coolant under pressure

Coolant lines going to the gradient amplifiers, gradient amplifier power supplies, and RF amplifiers are under pressure.

Before disconnecting any of these coolant lines, lock out/tag out power to the Heat Exchanger Cabinet (HEC). Refer to LOTO for Heat Exchanger Cabinet (HEC).

About this task

The PGR cabinet contains the Power Distribution Unit (PDU) and eXtreme Gradient Amplifier (XGA). The XGA is part of the eXtreme Gradient Driver (XGD) subsystem. Prior to servicing and/or maintenance work on the PGR PDU or any element of the XGD, the steps in this Lock Out / Tag Out (LOTO) procedure must be completed by a LOTO-authorized GE Field Engineer. Completing all the steps in this procedure ensures a safe environment and avoids equipment damage when working on these parts.

Note: GE Healthcare supplies two types of MDPs (GE and teal) and two types of PDUs (5140621 and 5343114). The LOTO steps are the same, but the physical components are slightly different. Customers have the option of supplying their own MDPs.

MR750w systems have only the teal MDP (if the MDP is supplied by GE Healthcare) and PDU 5343114.


Affected by LOTO
Name of equipment	Number of locks	Titles of employees authorized to perform LOTO	Titles of affected employees	How to notify
All MR equipment	1 per GE field engineer (FE)	GE Field Engineers	Hospital personnel	Verbal, posted signs

Note: The following table describes the type, location, and magnitude of energy to be LOTO’d.


Energy Source	Yes	No	Location of Energy Isolating Means	Magnitude of Energy
Electrical	x		PGR PDU circuit breaker panel, Main Disconnect Panel (MDP) circuit breaker panel	208 VAC, 420 VAC, 380-480 VAC
Pneumatic		x
Hydraulic		x
Gas/Water/Steam		x
Chemical		x
Mechanical Motion		x
Gravity		x
Springs		x
Thermal		x
Stored Energy	x		Time discharge of internal capacitors	208 VAC, 420 VAC
Air Under Pressure		x
Oil Under Pressure		x
Water Under Pressure	x		Heat Exchanger Cabinet (HEC), PGR Pump Circuit Breaker (PPMPCB) and RF amp quick disconnect	5.0 Bar (80 psi)
Gas Under Pressure		x
Steam		x
Other		x

Topic ID: id_SL1770157-1162791

Types of equipment and/or methods selected to dissipate or isolate stored energy

About this task

Time method for dissipation of stored energy – five minutes.

Topic ID: id_SL1770158-1162791

Type(s) of equipment and/or method(s) used to ensure disconnection(s)

About this task

A personal lock and tag per Field Engineer (FE) at the site working on the de-energized equipment at the time of LOTO.
Voltmeter to read voltage for verification that energy has dissipated in the PDU.

Procedure

Notify affected personnel that LOTO will be applied.
At the Operator Workspace, shut down the Host PC.
Locate and turn off the PGR PDU main breaker on the Main Disconnect Panel (MDP) that feeds the PGR cabinet.

Note: If the system uses a customer-supplied MDP, see the MDP manual for information about how to lock out/tag out the PDU breaker.
Lock Out/Tag Out the PDU breaker on the MDP.

Figure 1. PDU breaker on an GE MDP

Figure 2. PDU breaker on teal MDP
Make sure all energy has been dissipated. Use a voltmeter to measure the line-to-line voltage between each INPUT phase voltage test point on the PDU.
The PDU main breaker must be in the ON position to read accurate voltage on the test points.
Note: The test points are 100:1 ratio (480 VAC = 4.80 VAC, 208 VAC = 2.08 VAC). Therefore, a low voltage reading still indicates the presence of high voltage. Your voltage reading for each of the three phases must be 0 VAC before proceeding.
- Input Voltage Range: 380 - 480 VAC = 3.8 - 4.8 VAC
- Output Voltage Range: 208 VAC = 2.08 VAC
Figure 3. PDU test points (PDU 5140621)
Figure 4. PDU test points (PDU 5343114)