Basic Service Documentation. Copyright General Electric Company.
Object ID: 00000018WHA30DA72GYZ
Topic ID: id_2001693 Version: 14.1
Date: Jun 23, 2021 11:29:19 AM
Electrical Safety
You must follow all recommended safety procedures when servicing and working near energy sources.
MR RAC Reference: 1.100.10, 1.100.20, 1.200.10, 1.200.20; PPE hazard class requirements are found in NFPA 70E (per EHS).
DANGER
Electrical Shock
The MR system operates at high voltages that will shock or kill you if appropriate safety precautions are not taken. When performing any service in or around an MR system, always make sure you adhere to the following requirements.
If any of these requirements are unclear or in conflict, do not begin work or immediately stop work and contact your supervisor, this site safety officer, or your GE Healthcare service representative for guidance.
Follow all electrical safety and LOTO procedures in this manual, the MR service documentation, or any other applicable service manual.
Refer to the appropriate MR employee health and safety (EHS) or your equivalent employee electrical safety training for general LOTO information.
Understand and follow all site-specific electrical safety protocols.
After LOTO is applied, always verify the power is removed before starting any work.
Always wear appropriate electrical personal protective equipment (PPE).
Never defeat any safety interlock.
Never scan with covers or other safety interlocks removed.
Always ensure all safety interlocks and covers are properly installed before turning over the MR system to the customer.
DANGER
Arc Flash
The MR system operates at high voltages that can cause arc flash. Arc flash can shock, burn, or kill you. When performing any service in or around a component with the potential for arc flash, always wear appropriate PPE.
Arc flash hazard
Arc flash is not a common event but can be extremely dangerous when it occurs. All arc flash precautions must be followed even if you have worked on energized electrical equipment in the past and never encountered arc flash.
Arc flash is a high-energy discharge of highly-conductive plasma.
Arc flash PPE is required when working on live electrical components (50 to 480 volts).
Note: Some tasks, such as servicing the Main Disconnect Panel (MDP) or Power Distribution Unit (PDU), are not permitted by GE Healthcare service personnel even if appropriate PPE is worn.
Arc flash PPE must be worn inside the flash protection boundary (48 inches [122 cm] minimum).
Arc flash PPE is required during the zero-energy verification step when performing LOTO. All electrical circuits must be considered energized with the potential for an arc flash until verification with a voltmeter is completed.
The arc flash PPE listed in this chapter is a minimum requirement. Your site may have additional or stricter requirements.
Follow all site-specific arc flash safety requirements. Your site may have arc flash labels on components or require a risk assessment before performing tasks with the potential for arc flash.
Follow all GE Healthcare EHS (or equivalent) arc flash training.
Electrical installation and servicing
All MR system electrical work must comply with applicable electrical codes.
Electrical service must be completed by qualified service personnel.
The Main Disconnect Panel (MDP) and Power Distribution Unit (PDU) must be installed and serviced (including tightening nuts, changing fuses, or replacing batteries) by a licensed or certified electrician with the exception noted below:
Note:
MR service personnel may perform live electrical calibration, testing, or troubleshooting on a PDU or GE MDP if all of the following conditions are met:
Live electrical calibration, testing, or troubleshooting is permitted by local code or regulation.
The FE has completed arc flash and LOTO training.
The FE is wearing Level 2 arc flash PPE.
The FE has the approved calibration, troubleshooting, and test tools.
Electrical connection between the PDU and other applicable equipment must be a installed by a licensed or certified electrician.
Other electrical connections, calibrations, or testing may be completed by qualified service personnel.
All applicable LOTO procedures must be followed when doing electrical service.
PPE hazard class levels
The following table is for reference only. Some PPE listed below may have specific ratings. Refer to your EHS (or equivalent) training and site requirements for detailed PPE instructions.
GE Healthcare provides PPE as an orderable kit.
PPE hazard class levels
PPE
Class 1
Class 2
Hearing protection
X
X
Safety glasses
X
X
Hard hat
X
-
Arc-rated helmet with face shield (rated 4 cal/cm2) with chin/neck protector
X
-
Arc-rated helmet with face shield (rated 8 cal/cm2) with chin/neck protector
-
X
Leather gloves
X
-
Class 0 rated gloves with leather protectors
-
X
Flame-resistant pants and long-sleeve shirt (ATPV arc rating minimum 4 cal/cm2) or coveralls
X
-
Flame-resistant pants and long-sleeve shirt (ATPV arc rating minimum 8 cal/cm2) or coveralls
-
X
Cotton underwear (short-sleeve shirt and briefs/shorts)
X
X
Safety shoes
X
X
Task PPE requirements for GE Healthcare FE
The table below lists the minimum PPE required for MR system electrical tasks performed by GE Healthcare FEs.
All tasks may not be listed. Always follow site safety requirements or check with your supervisor if unsure.
Task PPE requirements
Task
PPE
Energizing or de-energizing circuit breakers or switched fuse operation (with system covers on)
Class 1
Working on energizing components (50 to 240 volts)
Class 1
Working on energizing components above 240 volts
Class 2
Verifying zero energy in components above 240 volts
Class 2
Live electrical calibration, testing, or troubleshooting on a GE MDP or PDU
Not permitted
RF amplifier electrical hazards
The RF amplifier operates at extremely high voltages and current levels.
Before working on the ISC, RF amplifiers or any associated circuitry or cabling, make sure proper LOTO is in place and cabinet power cords are disconnected.
Always wait at least five minutes for filter capacitors to discharge before performing any service procedure or removing any module covers.
Interlock switches are provided on the covers of power supply and amplifier decks. Never defeat the interlock switches to work on energized components. Even if an interlock switch is disengaged, always use a voltmeter to verify circuits are de-energized.
Use a voltmeter to verify RF amplifier circuits are de-energized.
Specific component LOTO procedures
The following tables contain specific LOTO procedures for removing power to the system and system components. If your system is not listed, refer to the Safety section in your service documentation for appropriate LOTO procedures.
GOC LOTO energy source details
Energy source
Yes
No
System PDU circuit breaker panel
Magnitude of energy
Electrical
X
-
PDU circuit breaker panel
120 VAC
Pneumatic
-
X
-
-
Hydraulic
-
X
-
-
Gas/water/steam
-
X
-
-
Chemical
-
X
-
-
Mechanical motion
-
X
-
-
Gravity
-
X
-
-
Springs
-
X
-
-
Thermal
-
X
-
-
Stored energy
-
X
-
-
Air under pressure
-
X
-
-
Oil under pressure
-
X
-
-
Water under pressure
-
X
-
-
Gas under pressure
-
X
-
-
Steam
-
X
-
-
Other
-
X
-
-
MDP LOTO energy source details
Energy source
Yes
No
Location of energy-isolating means
Magnitude of energy
Electrical
X
-
MDP circuit breaker
380/400/415/480 VAC per output of MDP or facility PDU
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
Air under pressure
-
X
-
-
Oil under pressure
-
X
-
-
Water under pressure
-
X
-
-
Gas under pressure
-
X
-
-
Steam
-
X
-
-
Other
-
X
-
-
Heat exchanger energy source details
Energy source
Yes
No
Location of energy-isolating means
Magnitude of energy
Electrical
X
-
Main disconnect panel (MDP) or circuit breaker panel
380 to 480 VAC
Pneumatic
-
X
-
-
Hydraulic
-
X
-
-
Gas/water/steam
-
X
-
-
Chemical
-
X
-
-
Mechanical motion
-
X
-
-
Gravity
-
X
-
-
Springs
-
X
-
-
Thermal
-
X
-
-
Stored energy
-
X
-
-
Air under pressure
-
X
-
-
Oil under pressure
-
X
-
-
Water under pressure
X
-
Facility water valves at top of HEC and MDP Circuit Breaker Panel
6.0 Bar (87 psi) Input
5.7 Bar (82.8 psi) Output Gradient Coil (GC)
5.0 Bar (80 psi) Output Power, Gradient, and RF (PGR) Cabinet
Gas under pressure
X
-
Valves on ends of cryocooler helium lines – valves close automatically when disconnected.
-
Steam
-
X
-
-
Other
-
X
-
-
PGR PDU gradient system energy source details
Energy source
Yes
No
Location of energy-isolating means
Magnitude of energy
Electrical
X
-
Power Distribution Unit (PDU) in the Power Gradient RF Cabinet (PGR) or the main disconnect panel (MDP) circuit breaker panel