[Hallb-engineering] Fwd: Lesson Learned "ENG-16-0726- Shock Incident at the ARC1 Box Power Supply in the LERF- No Injuries"
tilles at jlab.org
Wed Sep 7 09:59:18 EDT 2016
----- Forwarded Message -----
From: "Tina Johnson" <cjohnson at jlab.org>
To: "Tina Johnson" <cjohnson at jlab.org>
Sent: Friday, September 2, 2016 3:00:08 PM
Subject: Lesson Learned "ENG-16-0726- Shock Incident at the ARC1 Box Power Supply in the LERF- No Injuries"
Jefferson Lab Lessons Learned : Print Lesson
ENG-16-0726- Shock Incident at the ARC1 Box Power Supply in the LERF- No Injuries
Statement of Lessons Learned
1. When an unexpected result/scenario is encountered; take time to stop the work and re-analyze the path forward.
2. When performing a design/operational review, made up of different components, make sure the system is reviewed as a whole.
Discussion of Activities
On July 26, 2016, two technicians were working under an approved work package to diagnose a magnet problem within the Low Energy Recirculating Accelerator Facility (LERF). The ARC 1 power supply for the magnet is in a top-side gallery, while the magnet/magnet string is located in the LERF vault. After applying a lock and tag to the 480 volt input on this particular magnet power supply, the voltage verification unit showed the power supply to be de-energized. One of the technicians was in the process of removing a direct current output conductor from the power supply cabinet when they received an electrical shock as their elbow brushed against the grounded cabinet frame. The work was promptly stopped and their Supervisor informed. The technician that received the shock was not injured, which was confirmed after evaluation by the onsite medical clinic. The technician has been medically released without restrictions. Based on post-event measurements, the unexpected voltage was measured to be 87 volts alternating current between the positive side output conductor and the power supply cabinet. The uncontrolled electrical power originated from an induced/coupled voltage from a trim card supply on a magnet coil which is embedded in the ARC1 dipole magnet. The trim card was a 30volt/10amp direct current (DC) output card. The cause of the trim card going into oscillation, producing an alternating current voltage at its output, was later determined to be the load impedance falling outside of the specification for the normally configured compensation loop. The standard practice for the CEBAF equipment is that the power supply and the magnet load are properly matched during the design and then this matching is followed up with an analysis of the magnet string. Work was halted until an amended work plan eliminating the risk of a repeated shock, was developed and implemented. Soon after the investigation process began, a short term action plan (see below) was put into to place and the suspension of the specific work activities was lifted.
The problem (incident event scenario) was not anticipated and therefore analysis of the systems hazards were not performed and mitigated. The cause of the trim card going into oscillation, producing an alternating current voltage at its output, was later determined to be the load impedance falling outside of the specification for the normally configured compensation loop.
C1 - Lack of sufficient operational/design review; review of a system as individual components and not as a whole complete operating system.
C2 - Lack of single point ownership/responsibility when it comes to a system that involves multiple interests from different groups. Each group has their own agenda and the optimization between the power supply and the magnet load is not always considered or looked at.
Extent of Condition: All equipment/system owners will review their magnet configurations and determine if they have magnets that have multiple coils driven by separate power supplies.
1. Evaluate the effectiveness of the �short term action plan� and implement any continuous improvements. Determine the final corrective action to prevent a recurrence of this type of incident. Implement improvements to work procedures and equipment specific training as deemed necessary.
2. Evaluate the need to improve on the process of an operational/design review when an end user makes a request for a power supply to be connected to their magnet/coil loads. This process should consider identifying a single system owner point of contact for analyzing any hazards and for optimization of the system and control/updating of documentation related to the system.
3. Evaluate the need to update the magnet configuration documentation at the LERF. Include in this opportunity the analysis of the magnet loads so as to best match a power supply to each load for better optimization of the whole system.
JLab Preventive Measures
9/2/2016 1:01:14 PM by Johnson, Tina
SME has reviewed and approved. Please review and share this event and lessons learned within your work group.
Summary Lesson ID: 964
Safety Related: NO
Originator: Johnson, Tina
Issued: 9/2/2016 12:21:29 PM
Approved By: Johnson, Tina
Approved On: 9/2/2016 1:01:14 PM
Source: TJNAF NE
Contact: Todd Kujawa
Queued Emails: 0
Sent Emails: 0
Viewings: 2 times Attachments
* 50V or Greater: De-energized Work
* 50V or Greater: Diagnostic Type Operations
* 50V or Greater: Repair or Construction of Energized Components and Systems
* SAF603: SAF603A FPA-70E BASIC ELECTRICAL TRAINING
* SAF603A: ELECTRICAL SAFETY AWARENESS
* SAF603N: NFPA-70E BASIC ELECTRICAL SAFETY
* SAF604: HIGH VOLTAGE IN R&D
* SAF603S: NFPA-70E for Supervisors
* SAF603M: NFPA-70E for Managers
* SAF603N1: ARC FLASH:LIVE to TELL! (ELE016EFV)
* SAF603N2: Electrical Safety:Beware of the Bite (ELE5EFV)
* SAF603N3: Electrical Safety for the Qualified Worker (ELECEFV)
* *Division Safety Officers (DSOs)
* *Safety Wardens
* *DOE Notification
* *ESH&Q Liaisons
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