2017 NWHA TECHNICAL SEMINAR. Arc Flash Hazard Awareness MIKE BRENDLE LLC

Transcription

1 2017 NWHA TECHNICAL SEMINAR Arc Flash Hazard Awareness

2 WHAT IS ARC FLASH Arc Flash is a short circuit that flashes from one exposed live part to another, or to ground The result is ionized air that creates electrically conductive super heated plasma that can reach temperatures that are hotter than the surface of the sun. ( F) This explosion produces a brilliant light, intense heat, and a pressure blast traveling over 700 mph, over 2000 PSI. 2

3 3

4 4

5 Electrical Safety 1995 was the first publication of NFPA 70E arc flash was recognized as an electrical hazard edition of NFPA 70E, a broad consensus was established that determined incident energy as an acceptable way to categorize the arc flash hazard. 5

6 NFPA-70E-2015 NFPA The Informational Note 1 references the 2012 edition of NFPA 70-E as the standard to follow for assistance in determining the hazards. NFPA 70E 2015 is the most current standard that is enforced by OSHA 6

7 NFPA 70 E Compliance Compliance with NFPA 70E will assure compliance with the OSHA requirement. In the event of an injury or death due to an electrical accident, and if OSHA determines that compliance with 70E would have prevented or lessened the injury, OSHA may cite the employer under the general duty clause. In a 2003 Standards Interpretation letter OSHA stated 70E can be used as evidence of whether the employer acted reasonably. 7

8 2003 OSHA Standards Interpretation Letter 8

9 NUMBER OF INJURIES ANNUALLY DUE TO ARC FLASH Arc Flash Incidents 30,000 Burn Injuries 7000 Hospitalizations 2000 Workers sent to burn centers 2000 Fatalities 400 That s more than one per day in the United States. 80% due to burns, not shock 9

10 Cost of Arc Flash Hazard Events $1.5 M average for medical treatment 8-12 months lost time, may not return to work $10-15M average for litigation for general industry accident 10

11 WHAT FACTORS EFFECT ARC FLASH HAZARDS (AFH) Current How much current is allowed to flow during event. Arcing current can be as low as 40% bolted fault current. Time How long before the current is interrupted. An AFH with lower current and higher interrupting time can have very high results. 480 V AFH often greater than medium volt. 11

12 12

13 13

14 14

15 15

16 16

17 LOWERING AFH VS. COORDINATION NEC requires coordination of overcurrent devices. In some cases coordination has been given up for lower AFH results. If an AFH occurs the plant or process will be shutdown. Coordination doesn t matter. 17

18 PERSONAL PROTECTIVE EQUIPMENT (PPE) Can only protect for AFH < 40 cal/cm 2. Higher AFH will result in death due to crushing by arc blast. Clothing is readily available today. Some jeans are rated 25 cal/cm 2. Many jackets are rated cal/cm 2. 18

19 PERSONAL PROTECTIVE EQUIPMENT (PPE) Many companies choose 8 or 12 cal/cm 2 for daily dress. Depends on AFH for common tasks. 19

20 PERSONAL PROTECTIVE EQUIPMENT (PPE) Metering is considered PPE. Metering is part of lockout tagout (LOTO). Only the highest quality devices should be purchased and should be third party tested annually. 20

21 Types of Personal Protective Equipment Voltmeters Head Protection Eye & Face Protection Footwear Ground Fault Interrupters Overcurrent Devices Gloves & Blankets Clothing 21

22 PERSONAL PROTECTIVE EQUIPMENT (PPE) Overcurrent devices are considered PPE. They should be tested and maintained per the manufacturers instructions, or per NFPA 70B. The settings on overcurrent devices should be treated as PPE. If the settings are changed after an AFH study and labelling, then the labels are void. 22

23 Clothing Selecting clothing for an ARC Fault can be complex. The clothing is required to limit the thermal energy to 1.2 calories per square centimeter Limit burns to second degree 23

24 Clothing NFPA 70E has set levels of protection required based upon hazard. They also have what is called a simplified method. This is to protect the worker to less than 12 cal/cm 2 as an everyday standard. 24

25 Clothing Need to keep clean & dry. Follow the care label. Some clothing has maximum washes. Oil contamination will destroy AFH rating. Oil can t be washed out. Must take out of service and replace. The cal/cm 2 rating of clothing is the 50 percentile rating due to testing. 25

26 LEVEL <1.2 cal/cm 2 FR shirt & pants or FR coveralls Safety glasses, Hearing protection Heavy duty leather gloves Leather Safety Boots 26

27 Level 1.2 to 12 cal/cm 2 FR shirt & pants or FR coveralls Hard Hat, Safety Glasses, Hearing protection Face Shield Balaclava >4 cal/cm2 Heavy duty leather gloves 27

28 Level 12 to 40 cal/cm 2 FR shirt & pants and FR coverall or 2 FR coveralls. Layering must be approved by the manufacturer. FR rated flash hood, Arc rated gloves Hard Hat, Safety Glasses, hearing protection Leather Safety Boots 28

29 Clothing Levels Remember, these ratings are only a minimum standard to stop a second degree burn. You may want to add additional layers for more protection. Clothing ratings are 50 percentile of testing. Some clothing breaks through at higher and lower ratings. 29

30 ELECTRICAL SAFETY CULTURE CHANGE We need to shift the bias from routinely accepting the risk of electrical injury to viewing the risk as unacceptable. Per NFPA 70E written permission from management is required before working on anything that is energized. 30

31 RECOGNITION AND REWARDS Just as enforcement policies are important, so is the recognition and rewards programs. An effective program will reduce the number of injuries; thereby, reducing costs. 31

32 EQUIPMENT OPERATORS Equipment operators who open a door to reset an overload relay are also at risk of injury. No longer allowed. Risk of injury is not related to work assignment. 32

33 CAUSES OF INJURIES & INCIDENTS Failure to recognize the hazard Lack of necessary skills, knowledge and ability Previous performance of the same task many times without incident Pressure to finish the task 33

34 CAUSES OF INJURIES & INCIDENTS Performance of a familiar task without thinking Distraction due to a personal issue or other employee Lack of familiarity with some unique aspect of the equipment Incomplete or inaccurate reference drawings Failure to follow the company procedure 34

35 Electrical diagrams All drawings should be current or be marked up to depict the actual installation The work procedure should identify all drawings and diagrams that depict the installation as it exists 35

36 Equipment Details The work procedure should caution the workers to any special conditions that exist, such as interlocks, special latches or other components. 36

37 Sketches/Picture of Unique Features When an installation is complicated, the use of photos and sketches will help jog the workers memories to the task at hand. 37

38 Reference material & Manufacturer s data Any reference material or data, such as set points provided by the equipment manufacturer, should be identified in the procedure. The procedure should specify where such information can be found. 38

39 Head Protection American National Standard (ANSI Z-89.1) Protective Headwear for Industrial Workers addresses impact and bumping, but does not address Arc Flash. It does address electrical shock protection. 39

40 Head Protection A plastic hat will melt when exposed to an arcing fault. When worn inside of the arc-flash boundary, hard hats and bump caps should always be covered by a switchman s hood 40

41 Footwear Safety shoes should always be worn in an industrial site. Avoid wearing any shoes which may have a conductive sole. Avoid carbon-impregnated rubber soles or soles with nails or screws. There are E rated shoes which use nonconductive materials for the arch as well as for the toe protection. 41

42 Ground Fault Interrupters GFICs work by limiting the amount of allowed current flow through the ground conductor from 5 to 7 ma. When using portable hand tools a GFIC should always be used, unless a tested & maintained grounding program is in place. All outside contractors and vendors should be required to use GFICs when on site. 42

43 Gloves & Blankets All electrical safety gloves and blankets are rated for a MAX voltage. Be sure you have the correct equipment for the job Gloves & blankets need to be third party tested annually 43

44 Gloves & Blankets Experience shows that heavy-duty leather gloves provide adequate thermal protection for most exposures. There is an a new ANSI standard for gloves. Rubber protective equipment should be based on the voltage of the conductor that will be approached. 44

45 Degree of Arc Flash Hazard NFPA 70E has some tables which identify several work tasks and then assigns a hazard category. Table 130.7(C) (8) Calculations of the ARC FLASH Hazard can also be done, which will assign a category that fits the specific hazard. 45

46 ! WARNING Arc Flash and Shock Hazard Appropriate PPE Required 46

47 47

48 AFH Study This is one piece of an Electrical Safety Program. 48

49 AFH Study Data Gathering Utility short circuit impedance in all switching modes. Transformer nameplate data. Cable size, type, length. Be accurate! Conduit size, type, length. Breaker, fuse, protective relay data. 49

50 AFH Study Build the One Line Use data collected. Gather missing data. Confirm questionable data. Review the one line. 50

51 AFH Study Analyze and Review Investigate unusual results. Create Time Current Curves (TCC) to justify results in key areas. Investigate changes to lower AFH. Discuss changes with customer. Will changes be done now, or in the future after the study? 51

52 AFH Study Create Report Scope and Details. Drawings. Short Circuit and Equipment Duty Reports. AFH One Lines, Summary. TCCs of key equipment showing as found and recommended changes to lower AFH. Print and apply labels. 52

53 10 Pitfalls to Avoid While Developing an Arc Flash Safety Program 1. Relying on PPE tables instead of arc flash calculations. 2. Failing to perform a protective device coordination study. 3. Estimating equipment data instead of collecting it from the field. 4. Labeling for work tasks instead of equipment "worst case" scenarios. 53

54 10 Pitfalls to Avoid While Developing an Arc Flash Safety Program 5. Assuming AF labeling makes you NFPA 70E compliant. 6. Failing to train electricians that changing protective device trip times affect the arc flash hazard. 7. Lacking a detailed safety program and safe work practices. 54

55 10 Pitfalls to Avoid While Developing an Arc Flash Safety Program 8. Not implementing safety training for all workers. 9. Failing to keep your one-lines up-to-date. 10.Not implementing a work permit requirement and job planning/briefing for all electrical work. 55

56 Arc Flash Event 480 V Swgr Hot work was done on a Sunday night to replace a TVSS that had failed. Phone center customer didn t want to take an outage. During disassembly, a tool went line to line. 750 KVA Xfmr protected by fuses on the pole. The substation breaker tripped and reclosed before lock out. 56

57 57

58 58

59 59

60 60

61 61

62 62

63 63

64 64

65 65

66 66

67 67

68 68

69 69

70 70

71 71

72 72