Products Solutions Services CT287. Hazardous Area Classifications and Protection Systems

Transcription

1 Products Solutions Services CT287 Hazardous Area Classifications and Protection Systems Slide 1

2 Topics covered Types of Hazardous Area classifications with focus on North America Types of hazardous protection systems Overview of Recognized National Testing Laboratories (NRTL), the National Electrical Code and OSHA Documentation and labeling Questions Slide 2

3 Types of Hazardous Area classifications with focus on North America Slide 3

4 What constitutes a Hazardous Location? In electrical engineering, a hazardous location is defined as a place where concentrations of flammable gases, vapors, or dusts occur. Electrical equipment that must be installed in such locations is especially designed and tested to ensure it does not initiate an explosion, due to arcing contacts or high surface temperature of equipment. In some cases the gas, ignitable vapor or dust is present all the time or for long periods; other areas would have a dangerous concentration of flammable substances only during process upsets, equipment deterioration between maintenance periods, or during an incident. These are then divided into areas of risk of release of gas, vapor or dust. The process of determining the type and size of these hazardous areas is called area classification. Slide 4

5 Solvent Recovery Tank Slide 5

6 Coal Conveyor Slide 6

7 Industrial Fire Slide 7

8 History Began with mine safety in the U.K. Low voltage concepts began early By 1913 a deadly explosion proved low voltage was not enough Slide 8

9 Ignition Triangle Three components are required to permit combustion, ignition, fire or explosion Oxygen Fuel Energy Slide 9

10 Sources of Ignition Flame Spark Heat Electrical energy Slide 10

11 Sources of Ignition Flame Spark Heat Electrical energy Slide 11

12 Classification Instrumentation specifications often designate the classification of the area where instrument will be used. We will address the Area classification system The Zone classification system is in place but is not common Slide 12

13 Area Classification hierarchy Class Division Group Slide 13

14 Area Classes Class I - Ignitable gases or vapors Class II - Ignitable dust Class III - Ignitable textile fibers NOTE: always in Roman numerals Slide 14

15 Three Classes Means Three Types of Materials Slide 15

16 Area Divisions Division 1 - Hazard constantly present, or occasionally present under normal operating conditions. Division 2 - Hazard present only under abnormal conditions. NOTE: always in Arabic numerals Slide 16

17 Abnormal Tank Conditions Slide 17

18 Boundaries Division Method Boundaries (Designated Areas) Vent Hatch Vent Key Division 1 Division 2 Dike Flammable Liquid Sump or trench Grade Slide 18

19 Gases and Vapors Slide 19

20 Area Groups: Gases Group A - Acetylene only B - Hydrogen + few select gases C - Ethylene, UDMH, etc. D - Hydrocarbons, alcohols, etc. Slide 20

21 Dusts Slide 21

22 Area Groups: Dusts Group E - Metal dusts F - Coal dusts (carbonaceous dusts) G - Non-conductive dusts Agricultural Plastics Slide 22

23 Typical North American Standard: Another consideration is Temperature: Temperature Class, or T-Class Definition: The temperature classes are used to designate the maximum operating temperatures on the surface of the equipment which should not exceed the ignition temperature of the surrounding atmosphere. Ignition temperature is the minimum temperature required, at normal atmospheric pressure and in the absence of a spark or flame, to set afire or cause self-sustained combustion independently of the heating or heated element. Slide 23

24 Typical North American Standard: Temperature (T) Class Values: Slide 24

25 Types of hazardous protection systems Slide 25

26 Achieving Safety Slide 26

27 Safety Approach: Terms Explosionproof Dust ignitionproof Intrinsically safe Non-incendive Associated apparatus Purged Slide 27

28 Explosionproof Applies to Class I Only (Gases) Containment Strategy - Assume gas will enter enclosure and the contained circuitry is capable of igniting it. BUT the system is sufficiently sealed and of sufficient strength to prevent ignition of outside atmosphere. Slide 28

29 Explosionproof enclosures Slide 29

30 Exploded Explosion-Proof Housing Slide 30

31 Dust Ignitionproof Applies to Class II and III Only (Dusts/Fibers) Containment Strategy - Assumes contained circuitry is capable of igniting dust. BUT enclosure is sufficiently sealed against entry of dust, and surface temperatures are too low to ignite settled dust on enclosure. Slide 31

32 Intrinsically Safe Applies to all Division 1 Areas (i.e. in all Classes and Groups) Circuitry Strategy - Circuits are designed to be incapable of an energy release sufficient to ignite the specified atmosphere, even with specific instances of circuitry failures. Slide 32

33 Intrinsically Safe System Slide 33

34 How is a Circuit Made Intrinsically Safe? First must define what atmospheres will be involved Refer to published ignition curves Slide 34

35 How is a Circuit Made Intrinsically Safe? First must define what atmospheres will be involved Refer to published ignition curves Max Allowable Current Group C Group B Max Operating Voltage Slide 35

36 How is a Circuit Made Intrinsically Safe? First must define what atmospheres will be involved Refer to published ignition curves Implement voltage and current limiting L1 device L2 hazardous safe Slide 36

37 How is a Circuit Made Intrinsically Safe? First must define what atmospheres will be involved Refer to published ignition curves Implement voltage and current limiting L1 device L2 hazardous safe Slide 37

38 How is a Circuit Made Intrinsically Safe? First must define what atmospheres will be involved Refer to published ignition curves Implement voltage and current limiting L1 device L2 hazardous safe Slide 38

39 How is a Circuit Made Intrinsically Safe? First must define what atmospheres will be involved Refer to published ignition curves Implement voltage and current limiting L1 device L2 hazardous safe Slide 39

40 How is a Circuit Made Intrinsically Safe? First must define what atmospheres will be involved Refer to published ignition curves Implement voltage and current limiting L1 device L2 hazardous safe Slide 40

41 How is a Circuit Made Intrinsically Safe? Max Allowable Current First must define what atmospheres will be involved Refer to published ignition curves Implement voltage and current limiting What are the practical limitations? Group C Group B Max Operating Voltage Slide 41

42 How is a Circuit Made Intrinsically Safe? First must define what atmospheres will be involved Refer to published ignition curves Implement voltage and current limiting What are the practical limitations? Installation Requirements Proper wiring connections Proper cable routing Attention to entity parameters Slide 42

43 Non-Incendive Applies to all Division 2 Areas Circuitry Strategy - Circuits are incapable of an energy release sufficient to ignite the specified atmosphere, under normal circuit operation. In this context normal includes user mis-wiring. Slide 43

44 Div. 2 Non-Incendive Installation Slide 44

45 Associated Apparatus Normally safe area equipment which affects the energy levels of intrinsically safe equipment in the hazardous area. Examples - Intrinsic Safety Barrier or I.S. Power Supply Slide 45

46 Purged Systems or devices are under positive pressure, to exclude hazardous atmospheres from the equipment interior. Extensive controls, interlocks may be required, depending upon specific areas involved. Slide 46

47 Purged Systems or devices are under positive pressure, to exclude hazardous atmospheres from equipment interior. Extensive controls, interlocks may be required, depending upon specific areas involved. Type X purging: reduces classification within enclosure from Div 1 to nonhazardous Type Y purging: reduces classification within enclosure from Div 1 to Div 2 Type Z purging: reduces classification within enclosure from Div 2 to nonhazardous Slide 47

48 Purged Systems or devices are under positive pressure, to exclude hazardous atmospheres from equipment interior. Extensive controls, interlocks may be required, depending upon specific areas involved. Escalating Severity Type X purging: reduces classification within enclosure from Div 1 to nonhazardous Type Y purging: reduces classification within enclosure from Div 1 to Div 2 Type Z purging: reduces classification within enclosure from Div 2 to nonhazardous Slide 48

49 Common Purge Systems Slide 49

50 Overview: Safety Techniques Slide 50

51 NEMA Ratings NEMA 4 = Outdoor, Weatherproof NEMA 4x = NEMA 4 + Corrosion Resistance NEMA 6 and 6P: Submersible NEMA 7 = Explosionproof NEMA 9 = Dust Ignitionproof Slide 51

52 Wiring containment Techniques: NEC Conduit Seals: Process seals: Slide 52

53 Overview of Recognized National Testing Laboratories (NRTL), the National Electrical Code and OSHA Slide 53

54 What s an NRTL? NRTL = Nationally Recognized Testing Laboratory The US Occupational Safety and Health Act (OSHA) accredits Nationally Recognized Testing Laboratories (NRTL). Canadian Standards Council of Canada (SCC) accredits Testing Organization and Certification Bodies (TOCB) Individual States are allowed to implement State Occupational Safety and Health Plans. OSHA approves and monitors State plans. Slide 54

55 What s an NRTL? NRTL = Nationally Recognized Testing Laboratory A Scope of recognition defines the specific safety test standards for which an NRTL applies for recognition, and that OSHA approves. OSHA does not specify which test standards an NRTL must use. Instead, when an organization applies for recognition, it submits a list of test standards for which it seeks recognition, and OSHA determines if these standards are "appropriate" as defined in 29 CFR An NRTL may only certify products to the specific product safety test standards included in its scope of recognition. Slide 55

56 National Electrical Code (NEC) and NRTL test standards The National Electrical Code (NEC) is the bible" of the Electrical Industry, and the primary source of reference for hazardous locations. The NEC is also the basis for OSHA standard , Hazardous (Classified) Locations. The NEC is approved as an American National Standard by the American National Standards Institute (ANSI) and formally identified as ANSI/NFPA 70 Slide 56

57 National Electrical Code (NEC) and NRTL test standards The National Fire Protection Association NFPA 70: National Electrical Code (NEC) publishes the Bible with the most recent the 2011 Edition (available Sept ) which is adopted in all 50 states NRTLs use safety test standards that OSHA determines are "appropriate" as defined in 29 CFR developed to assess that a device has been designed, manufactured, tested or inspected, and marked in accordance with requirements of the listing agency as recognized by the United States Department of Labor, Occupational Safety and Health Administration (OSHA) under the requirements of 29CFR Slide 57

58 Some NRTL History When first adopted, OSHA regulations gave two examples of approval organizations: Underwriters Laboratories (UL) and Factory Mutual Research Corporation (FMRC) In 1983, OSHA was ordered by a court to remove the specific references to UL and FMRC in a successful lawsuit brought by a private lab In 1988, OSHA revised its regulations to remove the references, and established the NRTL Program to recognize other organizations as NRTLs Slide 58

59 Some additional background on FM and UL Underwriters Laboratory (UL) is not only an NRTL but a function within the company also develops testing standards. Underwriters Laboratories is an independent, not-for-profit product safety certification organization that has been writing Standards for Safety, testing products and involved in conformity assessment for well over a century. Many of these standards are now open ANSI standards as well used by other organizations FM not only is an NRTL but a function within the company also develops testing standards. Many of these standards are now open ANSI standards as well used by other organizations. Another portion of FM has grown to be the largest independent insurance provider to industry. Each of the NRTL, standards setting and insurance portions of these organization are separate functions and are not supposed to be combined to the exclusion of others Slide 59

60 Documentation and labeling Slide 60

61 Documentation Certificates are issued by the cognizant NRTL Many Labs can issue combined certifications, such as for both US and Canada, as well as issuing separate certificates for multiple schemes simultaneously (such as ATEX and IECEx). Multiple certificates typically exist for any given device or model family, for multiple protection techniques as well as from multiple entities, in multiple countries. Copies of most certifications are available though the equipment vendor or via lifecycle management tools like the Endress+Hauser Web Asset Management system. Slide 61

62 Typical Equipment Marking In the US, we ll typically see a layout like this: Cl I Div 1 ABCD T4, Cl II Div1 EFG, Cl III So, what s it all mean? And what can we use for a given location? Slide 62

63 Typical Equipment Marking Let s break it down: Slide 63

64 Typical Equipment Marking Let s break it down: NRTL (FM, for both US and Canada) Hazard Class (Class I = Gas) Cl I Div 1 ABCD T4, Cl II Div 1 EFG, Cl III Gas Groups (All) Area Classification (Division 1) Temperature Class (T4: 135C) Dust Groups (All) Hazard Class (Class II = Dust) Hazard Class (Class III = Flyings) Slide 64

65 Products Solutions Services Any questions? Thanks very much! Slide 67