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6420 Appendix T3 Engineering
and Administrative Controls for Magnetic and Radio Frequency – Including
Posting Requirements |
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Jefferson Lab recognizes that
magnets, and any associated external fringe static magnetic fields, may be
dangerous. It is therefore required that they be controlled and the designated
area provide warning of the potential hazards. This appendix defines Jefferson
Lab’s minimum engineering controls for this type of equipment; the
administrative controls – including area postings; and how these are updated,
repaired, and maintained.
The process steps for this procedure are performed in coordination with ES&H Manual Chapter 6420 Non-Ionizing Radiant Energy (i.e.: Radio Frequency (RF), Microwave, and Static Magnetic Fields.
NOTE: Management authority may be delegated to a task qualified Jefferson Lab employee at the discretion of the responsible manager.
· Request an equipment/area hazard evaluation from the Magnet Owner if compliance with these requirements is unclear.
·
Perform equipment/area hazard evaluation and
provide appropriate mitigation. Ensure it is in place and
functioning.
3.3
Supervisor/Subcontracting
Officer’s Technical Representative
(SOTR)/Sponsor
· Ensure controls are in place in accordance with requirements.
· Perform Magnetic Field Surveys and provide training and mitigation as required.
A superconducting magnet quenches
when most of its superconducting wire changes to and remains in the
non-superconducting state due to a rise in temperature or exposure to excessive
magnetic field. When called for by analysis, a system is installed to detect
the quench and trigger a lowering of the current and withdrawal of the stored
magnetic energy to preclude burnout of the conductor. Usually this system
includes isolation contactor(s) and a diode/dump resistor system. Quenches
usually cause cryogen boil-off and rapid current change, inducing voltages
higher than the normal magnet charging voltage.
How the quench protection system works and how hazards are mitigated are
documented within the magnet’s work control document. Refer to ES&H Manual 6420 Appendix
T2 Operational Safety Procedure for Qualifying Static Magnetic Fields.
Electromagnets at Jefferson Lab are designated by a red flashing warning light that turns on when the magnet is energized. Magnets that create strong static magnetic field are typically de-energized when personnel exposures could occur (i.e.: during lengthy down-times associated with accelerator operations). Circumstances that require the magnet to remain energized are considered a Risk Code >2 and require a Work Control Document. Refer to ES&H Manual 6420 Appendix T2 Operational Safety Procedure for Qualifying Static Magnetic Fields.
4.2.1
Magnetic
Field Hazard Controls
· Industrial Hygiene performs a magnetic field survey when necessary and provides hazard mitigation requirements to magnet owners. These include:
o Area Designation
(i.e. tape or rope indicating hazard zone)
o Posting Caution Signs - at work areas where the magnetic field exceeds 0.5 mT (5 G) for staff with medical implants, and 2 T (20,000 G) for those without medical implants. See Figure 1 and 2below for posting examples.
Figure
1: 5G Boundary for Bioelectronic Device
Figure 2: 20,000 G (2T) boundary; no entry permitted
4.2.2
Radio
Frequency (RF) Hazard Controls
· Industrial Hygiene performs a RF survey when necessary and provides hazard mitigation requirements to owners. These include:
o Area Designation
(i.e. tape or
rope indicating hazard zone)
o Posting
Caution Signs (See below)
Figure 4: RF posting
4.3 Update, Repair, or Maintenance to Warning Beacons and Labels
Anyone at Jefferson Lab may request new, update, repair, or maintenance to a magnetic field area hazard label.
· Contact the Magnet Owner and state the location of beacon or label needing review.
o If it is determined that the device is defective, the owner will rectify the situation.
o If no hazard is found – the owner informs the concerned party(ies) of the determination.
5.0
Revision Summary
Revision 1.2 – 01/22/18 – Updated to align with the updated Worker Safety & Health Plan
Revision 1.1 – 04/18/16 –
Periodic Review; minor edits with no substantive changes
Revision 1.0 – 07/16/12 – Updated
to reflect current laboratory operations
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ISSUING
AUTHORITY |
TECHNICAL POINT-OF-CONTACT |
APPROVAL
DATE |
REVIEW DATE |
REV. |
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ES&H Division |
01/22/18 |
01/22/23 |
1.2 |
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