Discovery MR750w and SIGNA™ Architect T 3.0T System Service Methods
5690002-2EN Revision 4
Object ID: 00000018WIA30BBE030GYZ
Topic ID: id_12374592 Version: 5.1
Date: Oct 11, 2021 3:47:40 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
Brass Master Padlock with Brass Shackle	1	46-194427P320	-
Red LOTO Personal Lock Wrap	1	2393068	-
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	-

About this task

DANGER

ELECTROCUTION HAZARD!

HIGH VOLTAGE PRESENT.

USE PROPER LOCK OUT / TAG OUT PROCEDURES BEFORE servicing and/or maintaining.

Overview

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 (FE). Completing all the steps in this procedure ensures a safe environment and avoids equipment damage when working on these parts.

Table 1. Affected by LOTO
Name of Equipment	Number of Locks	Titles of Employees Authorized to perform LOTO	Titles of Affected Employees	How to Notify
eXtreme Gradient Amplifier (XGA) eXtreme Power Supply (XPS) Power, Gradient, RF Cabinet Power Distribution Unit (PGR PDU) Gradient Filter	1 per GE FE	GE FEs	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_SL1770157-910100

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

About this task

Time method for dissipation of stored energy: 5 minutes.

Topic ID: id_SL1770158-910100

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

Procedure

One personal lock and tag per 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.

Topic ID: id_SL1770159-910100

Applying LOTO

Procedure

To prepare for shutdown of equipment, notify affected personnel working in the area the LOTO is being performed.
At the Operator Workspace, shut down the host PC.
Locate and turn off the PGR PDU main breaker on the MDP that feeds the PGR cabinet.

Lock Out/Tag Out the PDU breaker on the MDP.

Figure 1. PDU breaker on new style 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 2. New style PDU test points