ISSUING AUTHORITY / AUTHOR / DATE / DOCUMENT ID / Page 1 of 6
Hall A / Stevens / 5/23/08 / A-08-043-P
1. Define the scope of work:
· Job Summary:
o This description of work will explain how to Lockout, Tagout and Try the Big Box power supply, then reverse its output polarity, and finally restore power and test the system.
· Affected systems:
o The Big Box power supply, and an area extending 4 feet out from it.
o The powered magnet (typically, the Big Bite magnet).
2. Analyze hazard
Task Hazard Analysis Worksheet
Task / Potential Hazards / Risk Code before mitigation / Safe Procedures/Practices/Controls / Risk Code after mitigationBig Box polarity reversal procedure / Electrical shock hazard
Electrical arc flash hazard / 4
4 / Lockout, Tagout and Try the power supply in accordance with Jlab Lock, Tag and Try regulations and this procedure.
Lockout, Tagout and Try the power supply in accordance with Jlab Lock, Tag and Try regulations and this procedure. / 1
1
3. Develop and implement hazard controls:
· List of PPE:
o Safety glasses or goggles, a rubber safety mat rated at least Class 0, 1000V and meets OSHA 1910.335 and complies with ASTM D-178 standard for type II matting, rubber high voltage (500V) Class 00 gloves which comply with ASTM D120, with leather outer gloves, long sleeved cotton or fire retardant shirt, long cotton or fire retardant pants, closed-toe shoes and a hardhat with attached Hazard Risk Category 2 Arc Flash Faceshield rated 15cal/cm.
· Identify danger zones:
o An area extending four feet out from the four sides of the Big Box power supply shall be cordoned off with yellow and black safety rope or tape, upon which shall be placed signs identifying the area as both the Electrical Shock Hazard Limited Approach Boundary and the Arc Flash Hazard Protection Boundary.
· Training required:
o Qualified electrical worker and equipment specific training
4. Perform work within controls:
· Number of people needed:
o Two qualified Hall A electrical workers; one will act as a safety observer.
· Training verification:
o Verify that the above training is completed and current for both workers
· List of materials:
o Grounding hook and probe complying with Jlab EH&S manual chapter 6240
o 3 Suitable shorting/grounding jumpers to earth/short out capacitor banks
o A pair of ¾” wrenches
· Procedure:
o Pre-job briefing and walkdown:
§ Discuss the following steps, and the task hazard analysis. Walk through the steps and ensure that current conditions on the floor will allow this procedure to be performed. (Ensure that 480VAC power is on or available to Big Box, there is no one working in the area around Big Box, and that the system is not being used for a critical test, etc.) Get permission to commence the procedure from the Technical Coordinator, or the Run Coordinator, as appropriate.
o Ramp the magnet current to 0 amps by using the Hall A control screen or the local controls on the power supply. Observe the power supply control panel. If the “Main Power” lamp is green, observe the display panel – “SET” should be all zeros. If it is not zeros, go to the Controls Interface Terminal next to the green steel block wall and select the Big Box power supply gui from the “Hall A General Tools” gui. Type in zeros into the “Setpoint” box, and press enter. Go back to the power supply control panel display. The “SET” and “ADC” (which reads in per cent – with .999999999 being the maximum) should read zeros, but a small amount of offset is normal in the “ADC” reading.
o On the Big Box control panel, push the “local/remote” button to extinguish the remote control lamp. The “Main Power” lamp should extinguish; if it does not, push the “Main Power Off” button.
o
Establish the Arc Flash Hazard Boundary and an Electrical Shock Hazard Boundary. The Arc Flash Hazard Boundary for this power supply has been calculated to be 15 inches. The Electrical Shock Hazard Limited Approach Boundary is 42 inches. These boundaries, and the associated PPE requirements, were determined in an Arc Flash Hazard Analysis performed by the Vansant and Gusler Company, under contract to Facilities Management, using SKM Power Tools software. This information is contained in the equipment specific WARNING label attached to the Big Box power supply Door 1. Both the Arc Flash and Electric Shock Limited Approach Personnel Boundaries will be established using a set of safety cones of the type at least 3 feet tall, with yellow and black boundary tape or rope stretched between them. This rope boundary will be placed around the Big Box power supply at a comfortable distance for the personnel working within it, but at a minimum distance of 4 feet, or the surface of the adjacent permanently installed equipment. Attach signs which read “DANGER – ELECTRICAL SHOCK HAZARD – LIMITED APPROACH BOUNDARY - AUTHORIZED PERSONNEL ONLY – PPE REQUIRED” and “DANGER – ARC FLASH HAZARD – FLASH PROTECTION BOUNDARY – AUTHORIZED PERSONNEL ONLY – PPE REQUIRED”
Only authorized and qualified personnel (or an authorized trainee) with the proper PPE and the permission of the person performing the procedure may enter this area.
o Don PPE:
§ Safety glasses or goggles, rubber high voltage (500V) Class 00 gloves which comply with ASTM D120, with leather outer gloves, long sleeved cotton or fire retardant shirt, long fire retardant pants, closed-toe shoes and a hardhat with attached Hazard Risk Category 2 Arc Flash Faceshield rated 15cal/cm. Put the rubber safety mat rated at least Class 0, 1000V and meets OSHA 1910.335 and complies with ASTM D-178 standard for type II matting, behind the Big Box under the left door (facing the back of Big Box).
o Attach the grounding hook grounding clamp to the Hall earth ground cable
§ located inside the electronics rack immediately adjacent to the rubber mat you just put down. It is a large gauge bare copper stranded conductor in the bottom of the rack.
o Locate the Big Box safety disconnect switch located immediately left of the front of Big Box. Observe the Voltage Verification Unit on top of the switch. Ensure all three phases of 480VAC are present. Check phase to phase and phase to neutral.
o Turn off the safety disconnect switch
§ and lock and tag it out in accordance with Jlab Lock Tag and Try regulations. Immediately use the Voltage Verification Unit to verify the absence of all three phases of 480VAC power, testing both phase to phase and phase to neutral.
o Attempt to turn on Big Box
§ from its control panel. The power supply should be completely “dead”.
o Open the left rear door of the power supply.
§ Using the grounded shorting hook, short out and earth the power supply output (at the top of the doorway). Then locate and short out and earth each of three sets of capacitors. These are located behind the transistor pass bank. Install grounding jumpers across each capacitor set.
o PPE may now be removed.
§ Locate the output wiring at the top of the doorway. There are a total of four 535MCM lugs/cables, two positive and two negative. Locate the nylon cable locators where the cables penetrate the cabinet. These cable locators will have to be loosened to allow their movement in the polarity swap. Loosen the lug fasteners and swap the pairs of cables/lugs. Make note of their new configuration (normal or reverse polarity). Tighten the lug fasteners. Tighten the cable locator fasteners.
o Check the area
§ for loose tools or parts, etc. Remove the grounding jumpers. Close and latch the power supply door.
o Minimum PPE required for this step:
§ Safety glasses, long sleeved cotton or fire retardant shirt, rubber high voltage (500V) Class 00 gloves which comply with ASTM D120, with leather outer gloves. Unlock and restore power to Big Box. PPE may now be removed.
o Turn on Big Box
§ and check for normal operation.
o Make a HAlog entry
§ announcing the new configuration of Big Box.
o Post-job briefing and clean up:
§ Put away PPE and grounding hook/probe. Put away the barricade and cones. Discuss any changes that need to be made to this procedure, and document them.
5. Provide feedback and continuous improvement:
· If there are any mistakes, corrections or recommended changes to this procedure, provide documentation to the Hall A Technical Coordinator, and the Hall A Electronics Coordinator.
This document is controlled as an on line file. It may be printed but the print copy is not a controlled document. It is the user’s responsibility to ensure that the document is the same revision as the current on line file. This copy was printed on 5/23/2008.